nodes.coffee

Error.stackTraceLimit = Infinity

{Scope} = require './scope'
{isUnassignable, JS_FORBIDDEN} = require './lexer'

{compact, flatten, extend, merge, del, starts, ends, some,
addLocationDataFn, locationDataToString, throwSyntaxError} = require './helpers'

exports.extend = extend
exports.addLocationDataFn = addLocationDataFn

YES     = -> yes
NO      = -> no
THIS    = -> this
NEGATE  = -> @negated = not @negated; this

exports.CodeFragment = class CodeFragment
  constructor: (parent, code) ->
    @code = "#{code}"
    @locationData = parent?.locationData
    @type = parent?.constructor?.name or 'unknown'

  toString:   ->
    "#{@code}#{if @locationData then ": " + locationDataToString(@locationData) else ''}"

fragmentsToText = (fragments) ->
  (fragment.code for fragment in fragments).join('')

exports.Base = class Base

  compile: (o, lvl) ->
    fragmentsToText @compileToFragments o, lvl

  compileToFragments: (o, lvl) ->
    o        = extend {}, o
    o.level  = lvl if lvl
    node     = @unfoldSoak(o) or this
    node.tab = o.indent
    if o.level is LEVEL_TOP or not node.isStatement(o)
      node.compileNode o
    else
      node.compileClosure o

  compileClosure: (o) ->
    if jumpNode = @jumps()
      jumpNode.error 'cannot use a pure statement in an expression'
    o.sharedScope = yes
    func = new Code [], Block.wrap [this]
    args = []
    if (argumentsNode = @contains isLiteralArguments) or @contains isLiteralThis
      args = [new ThisLiteral]
      if argumentsNode
        meth = 'apply'
        args.push new IdentifierLiteral 'arguments'
      else
        meth = 'call'
      func = new Value func, [new Access new PropertyName meth]
    parts = (new Call func, args).compileNode o
    if func.isGenerator or func.base?.isGenerator
      parts.unshift @makeCode "(yield* "
      parts.push    @makeCode ")"
    parts

  cache: (o, level, isComplex) ->
    complex = if isComplex? then isComplex this else @isComplex()
    if complex
      ref = new IdentifierLiteral o.scope.freeVariable 'ref'
      sub = new Assign ref, this
      if level then [sub.compileToFragments(o, level), [@makeCode(ref.value)]] else [sub, ref]
    else
      ref = if level then @compileToFragments o, level else this
      [ref, ref]

  cacheToCodeFragments: (cacheValues) ->
    [fragmentsToText(cacheValues[0]), fragmentsToText(cacheValues[1])]

  makeReturn: (res) ->
    me = @unwrapAll()
    if res
      new Call new Literal("#{res}.push"), [me]
    else
      new Return me

  contains: (pred) ->
    node = undefined
    @traverseChildren no, (n) ->
      if pred n
        node = n
        return no
    node

  lastNonComment: (list) ->
    i = list.length
    return list[i] while i-- when list[i] not instanceof Comment
    null

  toString: (idt = '', name = @constructor.name) ->
    tree = '\n' + idt + name
    tree += '?' if @soak
    @eachChild (node) -> tree += node.toString idt + TAB
    tree

  eachChild: (func) ->
    return this unless @children
    for attr in @children when @[attr]
      for child in flatten [@[attr]]
        return this if func(child) is false
    this

  traverseChildren: (crossScope, func) ->
    @eachChild (child) ->
      recur = func(child)
      child.traverseChildren(crossScope, func) unless recur is no

  invert: ->
    new Op '!', this

  unwrapAll: ->
    node = this
    continue until node is node = node.unwrap()
    node

  children: []

  isStatement     : NO
  jumps           : NO
  isComplex       : YES
  isChainable     : NO
  isAssignable    : NO
  isNumber        : NO

  unwrap     : THIS
  unfoldSoak : NO

  assigns: NO

  updateLocationDataIfMissing: (locationData) ->
    return this if @locationData
    @locationData = locationData

    @eachChild (child) ->
      child.updateLocationDataIfMissing locationData

  error: (message) ->
    throwSyntaxError message, @locationData

  makeCode: (code) ->
    new CodeFragment this, code

  wrapInBraces: (fragments) ->
    [].concat @makeCode('('), fragments, @makeCode(')')

  joinFragmentArrays: (fragmentsList, joinStr) ->
    answer = []
    for fragments,i in fragmentsList
      if i then answer.push @makeCode joinStr
      answer = answer.concat fragments
    answer

exports.Block = class Block extends Base
  constructor: (nodes) ->
    @expressions = compact flatten nodes or []

  children: ['expressions']

  push: (node) ->
    @expressions.push node
    this

  pop: ->
    @expressions.pop()

  unshift: (node) ->
    @expressions.unshift node
    this

  unwrap: ->
    if @expressions.length is 1 then @expressions[0] else this

  isEmpty: ->
    not @expressions.length

  isStatement: (o) ->
    for exp in @expressions when exp.isStatement o
      return yes
    no

  jumps: (o) ->
    for exp in @expressions
      return jumpNode if jumpNode = exp.jumps o

  makeReturn: (res) ->
    len = @expressions.length
    while len--
      expr = @expressions[len]
      if expr not instanceof Comment
        @expressions[len] = expr.makeReturn res
        @expressions.splice(len, 1) if expr instanceof Return and not expr.expression
        break
    this

  compileToFragments: (o = {}, level) ->
    if o.scope then super o, level else @compileRoot o

  compileNode: (o) ->
    @tab  = o.indent
    top   = o.level is LEVEL_TOP
    compiledNodes = []

    for node, index in @expressions

      node = node.unwrapAll()
      node = (node.unfoldSoak(o) or node)
      if node instanceof Block

        compiledNodes.push node.compileNode o
      else if top
        node.front = true
        fragments = node.compileToFragments o
        unless node.isStatement o
          fragments.unshift @makeCode "#{@tab}"
          fragments.push @makeCode ";"
        compiledNodes.push fragments
      else
        compiledNodes.push node.compileToFragments o, LEVEL_LIST
    if top
      if @spaced
        return [].concat @joinFragmentArrays(compiledNodes, '\n\n'), @makeCode("\n")
      else
        return @joinFragmentArrays(compiledNodes, '\n')
    if compiledNodes.length
      answer = @joinFragmentArrays(compiledNodes, ', ')
    else
      answer = [@makeCode "void 0"]
    if compiledNodes.length > 1 and o.level >= LEVEL_LIST then @wrapInBraces answer else answer

  compileRoot: (o) ->
    o.indent  = if o.bare then '' else TAB
    o.level   = LEVEL_TOP
    @spaced   = yes
    o.scope   = new Scope null, this, null, o.referencedVars ? []

    o.scope.parameter name for name in o.locals or []
    prelude   = []
    unless o.bare
      preludeExps = for exp, i in @expressions
        break unless exp.unwrap() instanceof Comment
        exp
      rest = @expressions[preludeExps.length...]
      @expressions = preludeExps
      if preludeExps.length
        prelude = @compileNode merge(o, indent: '')
        prelude.push @makeCode "\n"
      @expressions = rest
    fragments = @compileWithDeclarations o
    return fragments if o.bare
    [].concat prelude, @makeCode("(function() {\n"), fragments, @makeCode("\n}).call(this);\n")

  compileWithDeclarations: (o) ->
    fragments = []
    post = []
    for exp, i in @expressions
      exp = exp.unwrap()
      break unless exp instanceof Comment or exp instanceof Literal
    o = merge(o, level: LEVEL_TOP)
    if i
      rest = @expressions.splice i, 9e9
      [spaced,    @spaced] = [@spaced, no]
      [fragments, @spaced] = [@compileNode(o), spaced]
      @expressions = rest
    post = @compileNode o
    {scope} = o
    if scope.expressions is this
      declars = o.scope.hasDeclarations()
      assigns = scope.hasAssignments
      if declars or assigns
        fragments.push @makeCode '\n' if i
        fragments.push @makeCode "#{@tab}var "
        if declars
          fragments.push @makeCode scope.declaredVariables().join(', ')
        if assigns
          fragments.push @makeCode ",\n#{@tab + TAB}" if declars
          fragments.push @makeCode scope.assignedVariables().join(",\n#{@tab + TAB}")
        fragments.push @makeCode ";\n#{if @spaced then '\n' else ''}"
      else if fragments.length and post.length
        fragments.push @makeCode "\n"
    fragments.concat post

  @wrap: (nodes) ->
    return nodes[0] if nodes.length is 1 and nodes[0] instanceof Block
    new Block nodes

exports.Literal = class Literal extends Base
  constructor: (@value) ->

  isComplex: NO

  assigns: (name) ->
    name is @value

  compileNode: (o) ->
    [@makeCode @value]

  toString: ->
    " #{if @isStatement() then super else @constructor.name}: #{@value}"

exports.NumberLiteral = class NumberLiteral extends Literal

exports.InfinityLiteral = class InfinityLiteral extends NumberLiteral
  compileNode: ->
    [@makeCode '2e308']

exports.NaNLiteral = class NaNLiteral extends NumberLiteral
  constructor: ->
    super 'NaN'

  compileNode: (o) ->
    code = [@makeCode '0/0']
    if o.level >= LEVEL_OP then @wrapInBraces code else code

exports.StringLiteral = class StringLiteral extends Literal

exports.RegexLiteral = class RegexLiteral extends Literal

exports.PassthroughLiteral = class PassthroughLiteral extends Literal

exports.IdentifierLiteral = class IdentifierLiteral extends Literal
  isAssignable: YES

exports.PropertyName = class PropertyName extends Literal
  isAssignable: YES

exports.StatementLiteral = class StatementLiteral extends Literal
  isStatement: YES

  makeReturn: THIS

  jumps: (o) ->
    return this if @value is 'break' and not (o?.loop or o?.block)
    return this if @value is 'continue' and not o?.loop

  compileNode: (o) ->
    [@makeCode "#{@tab}#{@value};"]

exports.ThisLiteral = class ThisLiteral extends Literal
  constructor: ->
    super 'this'

  compileNode: (o) ->
    code = if o.scope.method?.bound then o.scope.method.context else @value
    [@makeCode code]

exports.UndefinedLiteral = class UndefinedLiteral extends Literal
  constructor: ->
    super 'undefined'

  compileNode: (o) ->
    [@makeCode if o.level >= LEVEL_ACCESS then '(void 0)' else 'void 0']

exports.NullLiteral = class NullLiteral extends Literal
  constructor: ->
    super 'null'

exports.BooleanLiteral = class BooleanLiteral extends Literal

exports.Return = class Return extends Base
  constructor: (@expression) ->

  children: ['expression']

  isStatement:     YES
  makeReturn:      THIS
  jumps:           THIS

  compileToFragments: (o, level) ->
    expr = @expression?.makeReturn()
    if expr and expr not instanceof Return then expr.compileToFragments o, level else super o, level

  compileNode: (o) ->
    answer = []

    answer.push @makeCode @tab + "return#{if @expression then " " else ""}"
    if @expression
      answer = answer.concat @expression.compileToFragments o, LEVEL_PAREN
    answer.push @makeCode ";"
    return answer

exports.YieldReturn = class YieldReturn extends Return
  compileNode: (o) ->
    unless o.scope.parent?
      @error 'yield can only occur inside functions'
    super

exports.Value = class Value extends Base
  constructor: (base, props, tag) ->
    return base if not props and base instanceof Value
    @base       = base
    @properties = props or []
    @[tag]      = true if tag
    return this

  children: ['base', 'properties']

  add: (props) ->
    @properties = @properties.concat props
    this

  hasProperties: ->
    [email protected]

  bareLiteral: (type) ->
    not @properties.length and @base instanceof type

  isArray        : -> @bareLiteral(Arr)
  isRange        : -> @bareLiteral(Range)
  isComplex      : -> @hasProperties() or @base.isComplex()
  isAssignable   : -> @hasProperties() or @base.isAssignable()
  isNumber       : -> @bareLiteral(NumberLiteral)
  isString       : -> @bareLiteral(StringLiteral)
  isRegex        : -> @bareLiteral(RegexLiteral)
  isUndefined    : -> @bareLiteral(UndefinedLiteral)
  isNull         : -> @bareLiteral(NullLiteral)
  isBoolean      : -> @bareLiteral(BooleanLiteral)
  isAtomic       : ->
    for node in @properties.concat @base
      return no if node.soak or node instanceof Call
    yes

  isNotCallable  : -> @isNumber() or @isString() or @isRegex() or
                      @isArray() or @isRange() or @isSplice() or @isObject() or
                      @isUndefined() or @isNull() or @isBoolean()

  isStatement : (o)    -> not @properties.length and @base.isStatement o
  assigns     : (name) -> not @properties.length and @base.assigns name
  jumps       : (o)    -> not @properties.length and @base.jumps o

  isObject: (onlyGenerated) ->
    return no if @properties.length
    (@base instanceof Obj) and (not onlyGenerated or @base.generated)

  isSplice: ->
    [..., lastProp] = @properties
    lastProp instanceof Slice

  looksStatic: (className) ->
    @base.value is className and @properties.length is 1 and
      @properties[0].name?.value isnt 'prototype'

  unwrap: ->
    if @properties.length then this else @base

  cacheReference: (o) ->
    [..., name] = @properties
    if @properties.length < 2 and not @base.isComplex() and not name?.isComplex()
      return [this, this]  # `a` `a.b`
    base = new Value @base, @properties[...-1]
    if base.isComplex()  # `a().b`
      bref = new IdentifierLiteral o.scope.freeVariable 'base'
      base = new Value new Parens new Assign bref, base
    return [base, bref] unless name  # `a()`
    if name.isComplex()  # `a[b()]`
      nref = new IdentifierLiteral o.scope.freeVariable 'name'
      name = new Index new Assign nref, name.index
      nref = new Index nref
    [base.add(name), new Value(bref or base.base, [nref or name])]

  compileNode: (o) ->
    @base.front = @front
    props = @properties
    fragments = @base.compileToFragments o, (if props.length then LEVEL_ACCESS else null)
    if props.length and SIMPLENUM.test fragmentsToText fragments
      fragments.push @makeCode '.'
    for prop in props
      fragments.push (prop.compileToFragments o)...
    fragments

  unfoldSoak: (o) ->
    @unfoldedSoak ?= do =>
      if ifn = @base.unfoldSoak o
        ifn.body.properties.push @properties...
        return ifn
      for prop, i in @properties when prop.soak
        prop.soak = off
        fst = new Value @base, @properties[...i]
        snd = new Value @base, @properties[i..]
        if fst.isComplex()
          ref = new IdentifierLiteral o.scope.freeVariable 'ref'
          fst = new Parens new Assign ref, fst
          snd.base = ref
        return new If new Existence(fst), snd, soak: on
      no

exports.Comment = class Comment extends Base
  constructor: (@comment) ->

  isStatement:     YES
  makeReturn:      THIS

  compileNode: (o, level) ->
    comment = @comment.replace /^(\s*)#(?=\s)/gm, "$1 *"
    code = "/*#{multident comment, @tab}#{if '\n' in comment then "\n#{@tab}" else ''} */"
    code = o.indent + code if (level or o.level) is LEVEL_TOP
    [@makeCode("\n"), @makeCode(code)]

exports.Call = class Call extends Base
  constructor: (@variable, @args = [], @soak) ->
    @isNew    = false
    if @variable instanceof Value and @variable.isNotCallable()
      @variable.error "literal is not a function"

  children: ['variable', 'args']

  updateLocationDataIfMissing: (locationData) ->
    if @locationData and @needsUpdatedStartLocation
      @locationData.first_line = locationData.first_line
      @locationData.first_column = locationData.first_column
      base = @variable?.base or @variable
      if base.needsUpdatedStartLocation
        @variable.locationData.first_line = locationData.first_line
        @variable.locationData.first_column = locationData.first_column
        base.updateLocationDataIfMissing locationData
      delete @needsUpdatedStartLocation
    super

  newInstance: ->
    base = @variable?.base or @variable
    if base instanceof Call and not base.isNew
      base.newInstance()
    else
      @isNew = true
    @needsUpdatedStartLocation = true
    this

  unfoldSoak: (o) ->
    if @soak
      if this instanceof SuperCall
        left = new Literal @superReference o
        rite = new Value left
      else
        return ifn if ifn = unfoldSoak o, this, 'variable'
        [left, rite] = new Value(@variable).cacheReference o
      rite = new Call rite, @args
      rite.isNew = @isNew
      left = new Literal "typeof #{ left.compile o } === \"function\""
      return new If left, new Value(rite), soak: yes
    call = this
    list = []
    loop
      if call.variable instanceof Call
        list.push call
        call = call.variable
        continue
      break unless call.variable instanceof Value
      list.push call
      break unless (call = call.variable.base) instanceof Call
    for call in list.reverse()
      if ifn
        if call.variable instanceof Call
          call.variable = ifn
        else
          call.variable.base = ifn
      ifn = unfoldSoak o, call, 'variable'
    ifn

  compileNode: (o) ->
    @variable?.front = @front
    compiledArray = Splat.compileSplattedArray o, @args, true
    if compiledArray.length
      return @compileSplat o, compiledArray
    compiledArgs = []
    for arg, argIndex in @args
      if argIndex then compiledArgs.push @makeCode ", "
      compiledArgs.push (arg.compileToFragments o, LEVEL_LIST)...

    fragments = []
    if this instanceof SuperCall
      preface = @superReference(o) + ".call(#{@superThis(o)}"
      if compiledArgs.length then preface += ", "
      fragments.push @makeCode preface
    else
      if @isNew then fragments.push @makeCode 'new '
      fragments.push @variable.compileToFragments(o, LEVEL_ACCESS)...
      fragments.push @makeCode "("
    fragments.push compiledArgs...
    fragments.push @makeCode ")"
    fragments

  compileSplat: (o, splatArgs) ->
    if this instanceof SuperCall
      return [].concat @makeCode("#{ @superReference o }.apply(#{@superThis(o)}, "),
        splatArgs, @makeCode(")")

    if @isNew
      idt = @tab + TAB
      return [].concat @makeCode("""
        (function(func, args, ctor) {
        #{idt}ctor.prototype = func.prototype;
        #{idt}var child = new ctor, result = func.apply(child, args);
        #{idt}return Object(result) === result ? result : child;
        #{@tab}})("""),
        (@variable.compileToFragments o, LEVEL_LIST),
        @makeCode(", "), splatArgs, @makeCode(", function(){})")

    answer = []
    base = new Value @variable
    if (name = base.properties.pop()) and base.isComplex()
      ref = o.scope.freeVariable 'ref'
      answer = answer.concat @makeCode("(#{ref} = "),
        (base.compileToFragments o, LEVEL_LIST),
        @makeCode(")"),
        name.compileToFragments(o)
    else
      fun = base.compileToFragments o, LEVEL_ACCESS
      fun = @wrapInBraces fun if SIMPLENUM.test fragmentsToText fun
      if name
        ref = fragmentsToText fun
        fun.push (name.compileToFragments o)...
      else
        ref = 'null'
      answer = answer.concat fun
    answer = answer.concat @makeCode(".apply(#{ref}, "), splatArgs, @makeCode(")")

exports.SuperCall = class SuperCall extends Call
  constructor: (args) ->
    super null, args ? [new Splat new IdentifierLiteral 'arguments']

    @isBare = args?

  superReference: (o) ->
    method = o.scope.namedMethod()
    if method?.klass
      {klass, name, variable} = method
      if klass.isComplex()
        bref = new IdentifierLiteral o.scope.parent.freeVariable 'base'
        base = new Value new Parens new Assign bref, klass
        variable.base = base
        variable.properties.splice 0, klass.properties.length
      if name.isComplex() or (name instanceof Index and name.index.isAssignable())
        nref = new IdentifierLiteral o.scope.parent.freeVariable 'name'
        name = new Index new Assign nref, name.index
        variable.properties.pop()
        variable.properties.push name
      accesses = [new Access new PropertyName '__super__']
      accesses.push new Access new PropertyName 'constructor' if method.static
      accesses.push if nref? then new Index nref else name
      (new Value bref ? klass, accesses).compile o
    else if method?.ctor
      "#{method.name}.__super__.constructor"
    else
      @error 'cannot call super outside of an instance method.'

  superThis : (o) ->
    method = o.scope.method
    (method and not method.klass and method.context) or "this"

exports.RegexWithInterpolations = class RegexWithInterpolations extends Call
  constructor: (args = []) ->
    super (new Value new IdentifierLiteral 'RegExp'), args, false

exports.TaggedTemplateCall = class TaggedTemplateCall extends Call
  constructor: (variable, arg, soak) ->
    arg = new StringWithInterpolations Block.wrap([ new Value arg ]) if arg instanceof StringLiteral
    super variable, [ arg ], soak

  compileNode: (o) ->

    o.inTaggedTemplateCall = yes
    @variable.compileToFragments(o, LEVEL_ACCESS).concat @args[0].compileToFragments(o, LEVEL_LIST)

exports.Extends = class Extends extends Base
  constructor: (@child, @parent) ->

  children: ['child', 'parent']

  compileToFragments: (o) ->
    new Call(new Value(new Literal utility 'extend', o), [@child, @parent]).compileToFragments o

exports.Access = class Access extends Base
  constructor: (@name, tag) ->
    @soak  = tag is 'soak'

  children: ['name']

  compileToFragments: (o) ->
    name = @name.compileToFragments o
    node = @name.unwrap()
    if node instanceof PropertyName
      if node.value in JS_FORBIDDEN
        [@makeCode('["'), name..., @makeCode('"]')]
      else
        [@makeCode('.'), name...]
    else
      [@makeCode('['), name..., @makeCode(']')]

  isComplex: NO

exports.Index = class Index extends Base
  constructor: (@index) ->

  children: ['index']

  compileToFragments: (o) ->
    [].concat @makeCode("["), @index.compileToFragments(o, LEVEL_PAREN), @makeCode("]")

  isComplex: ->
    @index.isComplex()

exports.Range = class Range extends Base

  children: ['from', 'to']

  constructor: (@from, @to, tag) ->
    @exclusive = tag is 'exclusive'
    @equals = if @exclusive then '' else '='

  compileVariables: (o) ->
    o = merge o, top: true
    isComplex = del o, 'isComplex'
    [@fromC, @fromVar]  =  @cacheToCodeFragments @from.cache o, LEVEL_LIST, isComplex
    [@toC, @toVar]      =  @cacheToCodeFragments @to.cache o, LEVEL_LIST, isComplex
    [@step, @stepVar]   =  @cacheToCodeFragments step.cache o, LEVEL_LIST, isComplex if step = del o, 'step'
    @fromNum = if @from.isNumber() then Number @fromVar else null
    @toNum   = if @to.isNumber()   then Number @toVar   else null
    @stepNum = if step?.isNumber() then Number @stepVar else null

  compileNode: (o) ->
    @compileVariables o unless @fromVar
    return @compileArray(o) unless o.index

    known    = @fromNum? and @toNum?
    idx      = del o, 'index'
    idxName  = del o, 'name'
    namedIndex = idxName and idxName isnt idx
    varPart  = "#{idx} = #{@fromC}"
    varPart += ", #{@toC}" if @toC isnt @toVar
    varPart += ", #{@step}" if @step isnt @stepVar
    [lt, gt] = ["#{idx} <#{@equals}", "#{idx} >#{@equals}"]

    condPart = if @stepNum?
      if @stepNum > 0 then "#{lt} #{@toVar}" else "#{gt} #{@toVar}"
    else if known
      [from, to] = [@fromNum, @toNum]
      if from <= to then "#{lt} #{to}" else "#{gt} #{to}"
    else
      cond = if @stepVar then "#{@stepVar} > 0" else "#{@fromVar} <= #{@toVar}"
      "#{cond} ? #{lt} #{@toVar} : #{gt} #{@toVar}"

    stepPart = if @stepVar
      "#{idx} += #{@stepVar}"
    else if known
      if namedIndex
        if from <= to then "++#{idx}" else "--#{idx}"
      else
        if from <= to then "#{idx}++" else "#{idx}--"
    else
      if namedIndex
        "#{cond} ? ++#{idx} : --#{idx}"
      else
        "#{cond} ? #{idx}++ : #{idx}--"

    varPart  = "#{idxName} = #{varPart}" if namedIndex
    stepPart = "#{idxName} = #{stepPart}" if namedIndex

    [@makeCode "#{varPart}; #{condPart}; #{stepPart}"]

  compileArray: (o) ->
    known = @fromNum? and @toNum?
    if known and Math.abs(@fromNum - @toNum) <= 20
      range = [@fromNum..@toNum]
      range.pop() if @exclusive
      return [@makeCode "[#{ range.join(', ') }]"]
    idt    = @tab + TAB
    i      = o.scope.freeVariable 'i', single: true
    result = o.scope.freeVariable 'results'
    pre    = "\n#{idt}#{result} = [];"
    if known
      o.index = i
      body    = fragmentsToText @compileNode o
    else
      vars    = "#{i} = #{@fromC}" + if @toC isnt @toVar then ", #{@toC}" else ''
      cond    = "#{@fromVar} <= #{@toVar}"
      body    = "var #{vars}; #{cond} ? #{i} <#{@equals} #{@toVar} : #{i} >#{@equals} #{@toVar}; #{cond} ? #{i}++ : #{i}--"
    post   = "{ #{result}.push(#{i}); }\n#{idt}return #{result};\n#{o.indent}"
    hasArgs = (node) -> node?.contains isLiteralArguments
    args   = ', arguments' if hasArgs(@from) or hasArgs(@to)
    [@makeCode "(function() {#{pre}\n#{idt}for (#{body})#{post}}).apply(this#{args ? ''})"]

exports.Slice = class Slice extends Base

  children: ['range']

  constructor: (@range) ->
    super()

  compileNode: (o) ->
    {to, from} = @range
    fromCompiled = from and from.compileToFragments(o, LEVEL_PAREN) or [@makeCode '0']

    if to
      compiled     = to.compileToFragments o, LEVEL_PAREN
      compiledText = fragmentsToText compiled
      if not (not @range.exclusive and +compiledText is -1)
        toStr = ', ' + if @range.exclusive
          compiledText
        else if to.isNumber()
          "#{+compiledText + 1}"
        else
          compiled = to.compileToFragments o, LEVEL_ACCESS
          "+#{fragmentsToText compiled} + 1 || 9e9"
    [@makeCode ".slice(#{ fragmentsToText fromCompiled }#{ toStr or '' })"]

exports.Obj = class Obj extends Base
  constructor: (props, @generated = false) ->
    @objects = @properties = props or []

  children: ['properties']

  compileNode: (o) ->
    props = @properties
    if @generated
      for node in props when node instanceof Value
        node.error 'cannot have an implicit value in an implicit object'
    break for prop, dynamicIndex in props when (prop.variable or prop).base instanceof Parens
    hasDynamic  = dynamicIndex < props.length
    idt         = o.indent += TAB
    lastNoncom  = @lastNonComment @properties
    answer = []
    if hasDynamic
      oref = o.scope.freeVariable 'obj'
      answer.push @makeCode "(\n#{idt}#{oref} = "
    answer.push @makeCode "{#{if props.length is 0 or dynamicIndex is 0 then '}' else '\n'}"
    for prop, i in props
      if i is dynamicIndex
        answer.push @makeCode "\n#{idt}}" unless i is 0
        answer.push @makeCode ',\n'
      join = if i is props.length - 1 or i is dynamicIndex - 1
        ''
      else if prop is lastNoncom or prop instanceof Comment
        '\n'
      else
        ',\n'
      indent = if prop instanceof Comment then '' else idt
      indent += TAB if hasDynamic and i < dynamicIndex
      if prop instanceof Assign
        if prop.context isnt 'object'
          prop.operatorToken.error "unexpected #{prop.operatorToken.value}"
        if prop.variable instanceof Value and prop.variable.hasProperties()
          prop.variable.error 'invalid object key'
      if prop instanceof Value and prop.this
        prop = new Assign prop.properties[0].name, prop, 'object'
      if prop not instanceof Comment
        if i < dynamicIndex
          if prop not instanceof Assign
            prop = new Assign prop, prop, 'object'
        else
          if prop instanceof Assign
            key = prop.variable
            value = prop.value
          else
            [key, value] = prop.base.cache o
            key = new PropertyName key.value if key instanceof IdentifierLiteral
          prop = new Assign (new Value (new IdentifierLiteral oref), [new Access key]), value
      if indent then answer.push @makeCode indent
      answer.push prop.compileToFragments(o, LEVEL_TOP)...
      if join then answer.push @makeCode join
    if hasDynamic
      answer.push @makeCode ",\n#{idt}#{oref}\n#{@tab})"
    else
      answer.push @makeCode "\n#{@tab}}" unless props.length is 0
    if @front and not hasDynamic then @wrapInBraces answer else answer

  assigns: (name) ->
    for prop in @properties when prop.assigns name then return yes
    no

exports.Arr = class Arr extends Base
  constructor: (objs) ->
    @objects = objs or []

  children: ['objects']

  compileNode: (o) ->
    return [@makeCode '[]'] unless @objects.length
    o.indent += TAB
    answer = Splat.compileSplattedArray o, @objects
    return answer if answer.length

    answer = []
    compiledObjs = (obj.compileToFragments o, LEVEL_LIST for obj in @objects)
    for fragments, index in compiledObjs
      if index
        answer.push @makeCode ", "
      answer.push fragments...
    if fragmentsToText(answer).indexOf('\n') >= 0
      answer.unshift @makeCode "[\n#{o.indent}"
      answer.push @makeCode "\n#{@tab}]"
    else
      answer.unshift @makeCode "["
      answer.push @makeCode "]"
    answer

  assigns: (name) ->
    for obj in @objects when obj.assigns name then return yes
    no

exports.Class = class Class extends Base
  constructor: (@variable, @parent, @body = new Block) ->
    @boundFuncs = []
    @body.classBody = yes

  children: ['variable', 'parent', 'body']

  defaultClassVariableName: '_Class'

  determineName: ->
    return @defaultClassVariableName unless @variable
    [..., tail] = @variable.properties
    node = if tail
      tail instanceof Access and tail.name
    else
      @variable.base
    unless node instanceof IdentifierLiteral or node instanceof PropertyName
      return @defaultClassVariableName
    name = node.value
    unless tail
      message = isUnassignable name
      @variable.error message if message
    if name in JS_FORBIDDEN then "_#{name}" else name

  setContext: (name) ->
    @body.traverseChildren false, (node) ->
      return false if node.classBody
      if node instanceof ThisLiteral
        node.value    = name
      else if node instanceof Code
        node.context  = name if node.bound

  addBoundFunctions: (o) ->
    for bvar in @boundFuncs
      lhs = (new Value (new ThisLiteral), [new Access bvar]).compile o
      @ctor.body.unshift new Literal "#{lhs} = #{utility 'bind', o}(#{lhs}, this)"
    return

  addProperties: (node, name, o) ->
    props = node.base.properties[..]
    exprs = while assign = props.shift()
      if assign instanceof Assign
        base = assign.variable.base
        delete assign.context
        func = assign.value
        if base.value is 'constructor'
          if @ctor
            assign.error 'cannot define more than one constructor in a class'
          if func.bound
            assign.error 'cannot define a constructor as a bound function'
          if func instanceof Code
            assign = @ctor = func
          else
            @externalCtor = o.classScope.freeVariable 'ctor'
            assign = new Assign new IdentifierLiteral(@externalCtor), func
        else
          if assign.variable.this
            func.static = yes
          else
            acc = if base.isComplex() then new Index base else new Access base
            assign.variable = new Value(new IdentifierLiteral(name), [(new Access new PropertyName 'prototype'), acc])
            if func instanceof Code and func.bound
              @boundFuncs.push base
              func.bound = no
      assign
    compact exprs

  walkBody: (name, o) ->
    @traverseChildren false, (child) =>
      cont = true
      return false if child instanceof Class
      if child instanceof Block
        for node, i in exps = child.expressions
          if node instanceof Assign and node.variable.looksStatic name
            node.value.static = yes
          else if node instanceof Value and node.isObject(true)
            cont = false
            exps[i] = @addProperties node, name, o
        child.expressions = exps = flatten exps
      cont and child not instanceof Class

  hoistDirectivePrologue: ->
    index = 0
    {expressions} = @body
    ++index while (node = expressions[index]) and node instanceof Comment or
      node instanceof Value and node.isString()
    @directives = expressions.splice 0, index

  ensureConstructor: (name) ->
    if not @ctor
      @ctor = new Code
      if @externalCtor
        @ctor.body.push new Literal "#{@externalCtor}.apply(this, arguments)"
      else if @parent
        @ctor.body.push new Literal "#{name}.__super__.constructor.apply(this, arguments)"
      @ctor.body.makeReturn()
      @body.expressions.unshift @ctor
    @ctor.ctor = @ctor.name = name
    @ctor.klass = null
    @ctor.noReturn = yes

  compileNode: (o) ->
    if jumpNode = @body.jumps()
      jumpNode.error 'Class bodies cannot contain pure statements'
    if argumentsNode = @body.contains isLiteralArguments
      argumentsNode.error "Class bodies shouldn't reference arguments"

    name  = @determineName()
    lname = new IdentifierLiteral name
    func  = new Code [], Block.wrap [@body]
    args  = []
    o.classScope = func.makeScope o.scope

    @hoistDirectivePrologue()
    @setContext name
    @walkBody name, o
    @ensureConstructor name
    @addBoundFunctions o
    @body.spaced = yes
    @body.expressions.push lname

    if @parent
      superClass = new IdentifierLiteral o.classScope.freeVariable 'superClass', reserve: no
      @body.expressions.unshift new Extends lname, superClass
      func.params.push new Param superClass
      args.push @parent

    @body.expressions.unshift @directives...

    klass = new Parens new Call func, args
    klass = new Assign @variable, klass, null, { @moduleDeclaration } if @variable
    klass.compileToFragments o

exports.ModuleDeclaration = class ModuleDeclaration extends Base
  constructor: (@clause, @source) ->
    @checkSource()

  children: ['clause', 'source']

  isStatement: YES
  jumps:       THIS
  makeReturn:  THIS

  checkSource: ->
    if @source? and @source instanceof StringWithInterpolations
      @source.error 'the name of the module to be imported from must be an uninterpolated string'

  checkScope: (o, moduleDeclarationType) ->
    if o.indent.length isnt 0
      @error "#{moduleDeclarationType} statements must be at top-level scope"

exports.ImportDeclaration = class ImportDeclaration extends ModuleDeclaration
  compileNode: (o) ->
    @checkScope o, 'import'
    o.importedSymbols = []

    code = []
    code.push @makeCode "#{@tab}import "
    code.push @clause.compileNode(o)... if @clause?

    if @source?.value?
      code.push @makeCode ' from ' unless @clause is null
      code.push @makeCode @source.value

    code.push @makeCode ';'
    code

exports.ImportClause = class ImportClause extends Base
  constructor: (@defaultBinding, @namedImports) ->

  children: ['defaultBinding', 'namedImports']

  compileNode: (o) ->
    code = []

    if @defaultBinding?
      code.push @defaultBinding.compileNode(o)...
      code.push @makeCode ', ' if @namedImports?

    if @namedImports?
      code.push @namedImports.compileNode(o)...

    code

exports.ExportDeclaration = class ExportDeclaration extends ModuleDeclaration
  compileNode: (o) ->
    @checkScope o, 'export'

    code = []
    code.push @makeCode "#{@tab}export "
    code.push @makeCode 'default ' if @ instanceof ExportDefaultDeclaration

    if @ not instanceof ExportDefaultDeclaration and
       (@clause instanceof Assign or @clause instanceof Class)

      if @clause instanceof Class and not @clause.variable
        @clause.error 'anonymous classes cannot be exported'

      code.push @makeCode 'var '
      @clause.moduleDeclaration = 'export'

    if @clause.body? and @clause.body instanceof Block
      code = code.concat @clause.compileToFragments o, LEVEL_TOP
    else
      code = code.concat @clause.compileNode o

    code.push @makeCode " from #{@source.value}" if @source?.value?
    code.push @makeCode ';'
    code

exports.ExportNamedDeclaration = class ExportNamedDeclaration extends ExportDeclaration

exports.ExportDefaultDeclaration = class ExportDefaultDeclaration extends ExportDeclaration

exports.ExportAllDeclaration = class ExportAllDeclaration extends ExportDeclaration

exports.ModuleSpecifierList = class ModuleSpecifierList extends Base
  constructor: (@specifiers) ->

  children: ['specifiers']

  compileNode: (o) ->
    code = []
    o.indent += TAB
    compiledList = (specifier.compileToFragments o, LEVEL_LIST for specifier in @specifiers)

    if @specifiers.length isnt 0
      code.push @makeCode "{\n#{o.indent}"
      for fragments, index in compiledList
        code.push @makeCode(",\n#{o.indent}") if index
        code.push fragments...
      code.push @makeCode "\n}"
    else
      code.push @makeCode '{}'
    code

exports.ImportSpecifierList = class ImportSpecifierList extends ModuleSpecifierList

exports.ExportSpecifierList = class ExportSpecifierList extends ModuleSpecifierList

exports.ModuleSpecifier = class ModuleSpecifier extends Base
  constructor: (@original, @alias, @moduleDeclarationType) ->

    @identifier = if @alias? then @alias.value else @original.value

  children: ['original', 'alias']

  compileNode: (o) ->
    o.scope.find @identifier, @moduleDeclarationType
    code = []
    code.push @makeCode @original.value
    code.push @makeCode " as #{@alias.value}" if @alias?
    code

exports.ImportSpecifier = class ImportSpecifier extends ModuleSpecifier
  constructor: (imported, local) ->
    super imported, local, 'import'

  compileNode: (o) ->

    if @identifier in o.importedSymbols or o.scope.check(@identifier)
      @error "'#{@identifier}' has already been declared"
    else
      o.importedSymbols.push @identifier
    super o

exports.ImportDefaultSpecifier = class ImportDefaultSpecifier extends ImportSpecifier

exports.ImportNamespaceSpecifier = class ImportNamespaceSpecifier extends ImportSpecifier

exports.ExportSpecifier = class ExportSpecifier extends ModuleSpecifier
  constructor: (local, exported) ->
    super local, exported, 'export'

exports.Assign = class Assign extends Base
  constructor: (@variable, @value, @context, options = {}) ->
    {@param, @subpattern, @operatorToken, @moduleDeclaration} = options

  children: ['variable', 'value']

  isStatement: (o) ->
    o?.level is LEVEL_TOP and @context? and (@moduleDeclaration or "?" in @context)

  checkAssignability: (o, varBase) ->
    if Object::hasOwnProperty.call(o.scope.positions, varBase.value) and
       o.scope.variables[o.scope.positions[varBase.value]].type is 'import'
      varBase.error "'#{varBase.value}' is read-only"

  assigns: (name) ->
    @[if @context is 'object' then 'value' else 'variable'].assigns name

  unfoldSoak: (o) ->
    unfoldSoak o, this, 'variable'

  compileNode: (o) ->
    if isValue = @variable instanceof Value
      return @compilePatternMatch o if @variable.isArray() or @variable.isObject()
      return @compileSplice       o if @variable.isSplice()
      return @compileConditional  o if @context in ['||=', '&&=', '?=']
      return @compileSpecialMath  o if @context in ['**=', '//=', '%%=']
    if @value instanceof Code
      if @value.static
        @value.klass = @variable.base
        @value.name  = @variable.properties[0]
        @value.variable = @variable
      else if @variable.properties?.length >= 2
        [properties..., prototype, name] = @variable.properties
        if prototype.name?.value is 'prototype'
          @value.klass = new Value @variable.base, properties
          @value.name  = name
          @value.variable = @variable
    unless @context
      varBase = @variable.unwrapAll()
      unless varBase.isAssignable()
        @variable.error "'#{@variable.compile o}' can't be assigned"
      unless varBase.hasProperties?()

        if @moduleDeclaration
          @checkAssignability o, varBase
          o.scope.add varBase.value, @moduleDeclaration
        else if @param
          o.scope.add varBase.value, 'var'
        else
          @checkAssignability o, varBase
          o.scope.find varBase.value

    val = @value.compileToFragments o, LEVEL_LIST
    @variable.front = true if isValue and @variable.base instanceof Obj
    compiledName = @variable.compileToFragments o, LEVEL_LIST

    if @context is 'object'
      if fragmentsToText(compiledName) in JS_FORBIDDEN
        compiledName.unshift @makeCode '"'
        compiledName.push @makeCode '"'
      return compiledName.concat @makeCode(": "), val

    answer = compiledName.concat @makeCode(" #{ @context or '=' } "), val
    if o.level <= LEVEL_LIST then answer else @wrapInBraces answer

  compilePatternMatch: (o) ->
    top       = o.level is LEVEL_TOP
    {value}   = this
    {objects} = @variable.base
    unless olen = objects.length
      code = value.compileToFragments o
      return if o.level >= LEVEL_OP then @wrapInBraces code else code
    [obj] = objects
    if olen is 1 and obj instanceof Expansion
      obj.error 'Destructuring assignment has no target'
    isObject = @variable.isObject()
    if top and olen is 1 and obj not instanceof Splat

      defaultValue = null
      if obj instanceof Assign and obj.context is 'object'

        {variable: {base: idx}, value: obj} = obj
        if obj instanceof Assign
          defaultValue = obj.value
          obj = obj.variable
      else
        if obj instanceof Assign
          defaultValue = obj.value
          obj = obj.variable
        idx = if isObject

          if obj.this
            obj.properties[0].name
          else
            new PropertyName obj.unwrap().value
        else

          new NumberLiteral 0
      acc   = idx.unwrap() instanceof PropertyName
      value = new Value value
      value.properties.push new (if acc then Access else Index) idx
      message = isUnassignable obj.unwrap().value
      obj.error message if message
      value = new Op '?', value, defaultValue if defaultValue
      return new Assign(obj, value, null, param: @param).compileToFragments o, LEVEL_TOP
    vvar     = value.compileToFragments o, LEVEL_LIST
    vvarText = fragmentsToText vvar
    assigns  = []
    expandedIdx = false

    if value.unwrap() not instanceof IdentifierLiteral or @variable.assigns(vvarText)
      assigns.push [@makeCode("#{ ref = o.scope.freeVariable 'ref' } = "), vvar...]
      vvar = [@makeCode ref]
      vvarText = ref
    for obj, i in objects
      idx = i
      if not expandedIdx and obj instanceof Splat
        name = obj.name.unwrap().value
        obj = obj.unwrap()
        val = "#{olen} <= #{vvarText}.length ? #{ utility 'slice', o }.call(#{vvarText}, #{i}"
        if rest = olen - i - 1
          ivar = o.scope.freeVariable 'i', single: true
          val += ", #{ivar} = #{vvarText}.length - #{rest}) : (#{ivar} = #{i}, [])"
        else
          val += ") : []"
        val   = new Literal val
        expandedIdx = "#{ivar}++"
      else if not expandedIdx and obj instanceof Expansion
        if rest = olen - i - 1
          if rest is 1
            expandedIdx = "#{vvarText}.length - 1"
          else
            ivar = o.scope.freeVariable 'i', single: true
            val = new Literal "#{ivar} = #{vvarText}.length - #{rest}"
            expandedIdx = "#{ivar}++"
            assigns.push val.compileToFragments o, LEVEL_LIST
        continue
      else
        if obj instanceof Splat or obj instanceof Expansion
          obj.error "multiple splats/expansions are disallowed in an assignment"
        defaultValue = null
        if obj instanceof Assign and obj.context is 'object'

          {variable: {base: idx}, value: obj} = obj
          if obj instanceof Assign
            defaultValue = obj.value
            obj = obj.variable
        else
          if obj instanceof Assign
            defaultValue = obj.value
            obj = obj.variable
          idx = if isObject

            if obj.this
              obj.properties[0].name
            else
              new PropertyName obj.unwrap().value
          else

            new Literal expandedIdx or idx
        name = obj.unwrap().value
        acc = idx.unwrap() instanceof PropertyName
        val = new Value new Literal(vvarText), [new (if acc then Access else Index) idx]
        val = new Op '?', val, defaultValue if defaultValue
      if name?
        message = isUnassignable name
        obj.error message if message
      assigns.push new Assign(obj, val, null, param: @param, subpattern: yes).compileToFragments o, LEVEL_LIST
    assigns.push vvar unless top or @subpattern
    fragments = @joinFragmentArrays assigns, ', '
    if o.level < LEVEL_LIST then fragments else @wrapInBraces fragments

  compileConditional: (o) ->
    [left, right] = @variable.cacheReference o

    if not left.properties.length and left.base instanceof Literal and
           left.base not instanceof ThisLiteral and not o.scope.check left.base.value
      @variable.error "the variable \"#{left.base.value}\" can't be assigned with #{@context} because it has not been declared before"
    if "?" in @context
      o.isExistentialEquals = true
      new If(new Existence(left), right, type: 'if').addElse(new Assign(right, @value, '=')).compileToFragments o
    else
      fragments = new Op(@context[...-1], left, new Assign(right, @value, '=')).compileToFragments o
      if o.level <= LEVEL_LIST then fragments else @wrapInBraces fragments

  compileSpecialMath: (o) ->
    [left, right] = @variable.cacheReference o
    new Assign(left, new Op(@context[...-1], right, @value)).compileToFragments o

  compileSplice: (o) ->
    {range: {from, to, exclusive}} = @variable.properties.pop()
    name = @variable.compile o
    if from
      [fromDecl, fromRef] = @cacheToCodeFragments from.cache o, LEVEL_OP
    else
      fromDecl = fromRef = '0'
    if to
      if from?.isNumber() and to.isNumber()
        to = to.compile(o) - fromRef
        to += 1 unless exclusive
      else
        to = to.compile(o, LEVEL_ACCESS) + ' - ' + fromRef
        to += ' + 1' unless exclusive
    else
      to = "9e9"
    [valDef, valRef] = @value.cache o, LEVEL_LIST
    answer = [].concat @makeCode("[].splice.apply(#{name}, [#{fromDecl}, #{to}].concat("), valDef, @makeCode(")), "), valRef
    if o.level > LEVEL_TOP then @wrapInBraces answer else answer

exports.Code = class Code extends Base
  constructor: (params, body, tag) ->
    @params      = params or []
    @body        = body or new Block
    @bound       = tag is 'boundfunc'
    @isGenerator = [email protected] (node) ->
      (node instanceof Op and node.isYield()) or node instanceof YieldReturn

  children: ['params', 'body']

  isStatement: -> !!@ctor

  jumps: NO

  makeScope: (parentScope) -> new Scope parentScope, @body, this

  compileNode: (o) ->

    if @bound and o.scope.method?.bound
      @context = o.scope.method.context

    if @bound and not @context
      @context = '_this'
      wrapper = new Code [new Param new IdentifierLiteral @context], new Block [this]
      boundfunc = new Call(wrapper, [new ThisLiteral])
      boundfunc.updateLocationDataIfMissing @locationData
      return boundfunc.compileNode(o)

    o.scope         = del(o, 'classScope') or @makeScope o.scope
    o.scope.shared  = del(o, 'sharedScope')
    o.indent        += TAB
    delete o.bare
    delete o.isExistentialEquals
    params = []
    exprs  = []
    for param in @params when param not instanceof Expansion
      o.scope.parameter param.asReference o
    for param in @params when param.splat or param instanceof Expansion
      for p in @params when p not instanceof Expansion and p.name.value
        o.scope.add p.name.value, 'var', yes
      splats = new Assign new Value(new Arr(p.asReference o for p in @params)),
                          new Value new IdentifierLiteral 'arguments'
      break
    for param in @params
      if param.isComplex()
        val = ref = param.asReference o
        val = new Op '?', ref, param.value if param.value
        exprs.push new Assign new Value(param.name), val, '=', param: yes
      else
        ref = param
        if param.value
          lit = new Literal ref.name.value + ' == null'
          val = new Assign new Value(param.name), param.value, '='
          exprs.push new If lit, val
      params.push ref unless splats
    wasEmpty = @body.isEmpty()
    exprs.unshift splats if splats
    @body.expressions.unshift exprs... if exprs.length
    for p, i in params
      params[i] = p.compileToFragments o
      o.scope.parameter fragmentsToText params[i]
    uniqs = []
    @eachParamName (name, node) ->
      node.error "multiple parameters named #{name}" if name in uniqs
      uniqs.push name
    @body.makeReturn() unless wasEmpty or @noReturn
    code = 'function'
    code += '*' if @isGenerator
    code += ' ' + @name if @ctor
    code += '('
    answer = [@makeCode(code)]
    for p, i in params
      if i then answer.push @makeCode ", "
      answer.push p...
    answer.push @makeCode ') {'
    answer = answer.concat(@makeCode("\n"), @body.compileWithDeclarations(o), @makeCode("\n#{@tab}")) unless @body.isEmpty()
    answer.push @makeCode '}'

    return [@makeCode(@tab), answer...] if @ctor
    if @front or (o.level >= LEVEL_ACCESS) then @wrapInBraces answer else answer

  eachParamName: (iterator) ->
    param.eachName iterator for param in @params

  traverseChildren: (crossScope, func) ->
    super(crossScope, func) if crossScope

exports.Param = class Param extends Base
  constructor: (@name, @value, @splat) ->
    message = isUnassignable @name.unwrapAll().value
    @name.error message if message
    if @name instanceof Obj and @name.generated
      token = @name.objects[0].operatorToken
      token.error "unexpected #{token.value}"

  children: ['name', 'value']

  compileToFragments: (o) ->
    @name.compileToFragments o, LEVEL_LIST

  asReference: (o) ->
    return @reference if @reference
    node = @name
    if node.this
      name = node.properties[0].name.value
      name = "_#{name}" if name in JS_FORBIDDEN
      node = new IdentifierLiteral o.scope.freeVariable name
    else if node.isComplex()
      node = new IdentifierLiteral o.scope.freeVariable 'arg'
    node = new Value node
    node = new Splat node if @splat
    node.updateLocationDataIfMissing @locationData
    @reference = node

  isComplex: ->
    @name.isComplex()

  eachName: (iterator, name = @name)->
    atParam = (obj) -> iterator "@#{obj.properties[0].name.value}", obj

    return iterator name.value, name if name instanceof Literal

    return atParam name if name instanceof Value
    for obj in name.objects ? []

      if obj instanceof Assign and not obj.context?
        obj = obj.variable

      if obj instanceof Assign

        if obj.value instanceof Assign
          obj = obj.value
        @eachName iterator, obj.value.unwrap()

      else if obj instanceof Splat
        node = obj.name.unwrap()
        iterator node.value, node
      else if obj instanceof Value

        if obj.isArray() or obj.isObject()
          @eachName iterator, obj.base

        else if obj.this
          atParam obj

        else iterator obj.base.value, obj.base
      else if obj not instanceof Expansion
        obj.error "illegal parameter #{obj.compile()}"
    return

exports.Splat = class Splat extends Base

  children: ['name']

  isAssignable: YES

  constructor: (name) ->
    @name = if name.compile then name else new Literal name

  assigns: (name) ->
    @name.assigns name

  compileToFragments: (o) ->
    @name.compileToFragments o

  unwrap: -> @name

  @compileSplattedArray: (o, list, apply) ->
    index = -1
    continue while (node = list[++index]) and node not instanceof Splat
    return [] if index >= list.length
    if list.length is 1
      node = list[0]
      fragments = node.compileToFragments o, LEVEL_LIST
      return fragments if apply
      return [].concat node.makeCode("#{ utility 'slice', o }.call("), fragments, node.makeCode(")")
    args = list[index..]
    for node, i in args
      compiledNode = node.compileToFragments o, LEVEL_LIST
      args[i] = if node instanceof Splat
      then [].concat node.makeCode("#{ utility 'slice', o }.call("), compiledNode, node.makeCode(")")
      else [].concat node.makeCode("["), compiledNode, node.makeCode("]")
    if index is 0
      node = list[0]
      concatPart = (node.joinFragmentArrays args[1..], ', ')
      return args[0].concat node.makeCode(".concat("), concatPart, node.makeCode(")")
    base = (node.compileToFragments o, LEVEL_LIST for node in list[...index])
    base = list[0].joinFragmentArrays base, ', '
    concatPart = list[index].joinFragmentArrays args, ', '
    [..., last] = list
    [].concat list[0].makeCode("["), base, list[index].makeCode("].concat("), concatPart, last.makeCode(")")

exports.Expansion = class Expansion extends Base

  isComplex: NO

  compileNode: (o) ->
    @error 'Expansion must be used inside a destructuring assignment or parameter list'

  asReference: (o) ->
    this

  eachName: (iterator) ->

exports.While = class While extends Base
  constructor: (condition, options) ->
    @condition = if options?.invert then condition.invert() else condition
    @guard     = options?.guard

  children: ['condition', 'guard', 'body']

  isStatement: YES

  makeReturn: (res) ->
    if res
      super
    else
      @returns = not @jumps loop: yes
      this

  addBody: (@body) ->
    this

  jumps: ->
    {expressions} = @body
    return no unless expressions.length
    for node in expressions
      return jumpNode if jumpNode = node.jumps loop: yes
    no

  compileNode: (o) ->
    o.indent += TAB
    set      = ''
    {body}   = this
    if body.isEmpty()
      body = @makeCode ''
    else
      if @returns
        body.makeReturn rvar = o.scope.freeVariable 'results'
        set  = "#{@tab}#{rvar} = [];\n"
      if @guard
        if body.expressions.length > 1
          body.expressions.unshift new If (new Parens @guard).invert(), new StatementLiteral "continue"
        else
          body = Block.wrap [new If @guard, body] if @guard
      body = [].concat @makeCode("\n"), (body.compileToFragments o, LEVEL_TOP), @makeCode("\n#{@tab}")
    answer = [].concat @makeCode(set + @tab + "while ("), @condition.compileToFragments(o, LEVEL_PAREN),
      @makeCode(") {"), body, @makeCode("}")
    if @returns
      answer.push @makeCode "\n#{@tab}return #{rvar};"
    answer

exports.Op = class Op extends Base
  constructor: (op, first, second, flip ) ->
    return new In first, second if op is 'in'
    if op is 'do'
      return @generateDo first
    if op is 'new'
      return first.newInstance() if first instanceof Call and not first.do and not first.isNew
      first = new Parens first   if first instanceof Code and first.bound or first.do
    @operator = CONVERSIONS[op] or op
    @first    = first
    @second   = second
    @flip     = !!flip
    return this

  CONVERSIONS =
    '==':        '==='
    '!=':        '!=='
    'of':        'in'
    'yieldfrom': 'yield*'

  INVERSIONS =
    '!==': '==='
    '===': '!=='

  children: ['first', 'second']

  isNumber: ->
    @isUnary() and @operator in ['+', '-'] and
      @first instanceof Value and @first.isNumber()

  isYield: ->
    @operator in ['yield', 'yield*']

  isUnary: ->
    not @second

  isComplex: ->
    not @isNumber()

  isChainable: ->
    @operator in ['<', '>', '>=', '<=', '===', '!==']

  invert: ->
    if @isChainable() and @first.isChainable()
      allInvertable = yes
      curr = this
      while curr and curr.operator
        allInvertable and= (curr.operator of INVERSIONS)
        curr = curr.first
      return new Parens(this).invert() unless allInvertable
      curr = this
      while curr and curr.operator
        curr.invert = !curr.invert
        curr.operator = INVERSIONS[curr.operator]
        curr = curr.first
      this
    else if op = INVERSIONS[@operator]
      @operator = op
      if @first.unwrap() instanceof Op
        @first.invert()
      this
    else if @second
      new Parens(this).invert()
    else if @operator is '!' and (fst = @first.unwrap()) instanceof Op and
                                  fst.operator in ['!', 'in', 'instanceof']
      fst
    else
      new Op '!', this

  unfoldSoak: (o) ->
    @operator in ['++', '--', 'delete'] and unfoldSoak o, this, 'first'

  generateDo: (exp) ->
    passedParams = []
    func = if exp instanceof Assign and (ref = exp.value.unwrap()) instanceof Code
      ref
    else
      exp
    for param in func.params or []
      if param.value
        passedParams.push param.value
        delete param.value
      else
        passedParams.push param
    call = new Call exp, passedParams
    call.do = yes
    call

  compileNode: (o) ->
    isChain = @isChainable() and @first.isChainable()

    @first.front = @front unless isChain
    if @operator is 'delete' and o.scope.check(@first.unwrapAll().value)
      @error 'delete operand may not be argument or var'
    if @operator in ['--', '++']
      message = isUnassignable @first.unwrapAll().value
      @first.error message if message
    return @compileYield     o if @isYield()
    return @compileUnary     o if @isUnary()
    return @compileChain     o if isChain
    switch @operator
      when '?'  then @compileExistence o
      when '**' then @compilePower o
      when '//' then @compileFloorDivision o
      when '%%' then @compileModulo o
      else
        lhs = @first.compileToFragments o, LEVEL_OP
        rhs = @second.compileToFragments o, LEVEL_OP
        answer = [].concat lhs, @makeCode(" #{@operator} "), rhs
        if o.level <= LEVEL_OP then answer else @wrapInBraces answer

  compileChain: (o) ->
    [@first.second, shared] = @first.second.cache o
    fst = @first.compileToFragments o, LEVEL_OP
    fragments = fst.concat @makeCode(" #{if @invert then '&&' else '||'} "),
      (shared.compileToFragments o), @makeCode(" #{@operator} "), (@second.compileToFragments o, LEVEL_OP)
    @wrapInBraces fragments

  compileExistence: (o) ->
    if @first.isComplex()
      ref = new IdentifierLiteral o.scope.freeVariable 'ref'
      fst = new Parens new Assign ref, @first
    else
      fst = @first
      ref = fst
    new If(new Existence(fst), ref, type: 'if').addElse(@second).compileToFragments o

  compileUnary: (o) ->
    parts = []
    op = @operator
    parts.push [@makeCode op]
    if op is '!' and @first instanceof Existence
      @first.negated = not @first.negated
      return @first.compileToFragments o
    if o.level >= LEVEL_ACCESS
      return (new Parens this).compileToFragments o
    plusMinus = op in ['+', '-']
    parts.push [@makeCode(' ')] if op in ['new', 'typeof', 'delete'] or
                      plusMinus and @first instanceof Op and @first.operator is op
    if (plusMinus and @first instanceof Op) or (op is 'new' and @first.isStatement o)
      @first = new Parens @first
    parts.push @first.compileToFragments o, LEVEL_OP
    parts.reverse() if @flip
    @joinFragmentArrays parts, ''

  compileYield: (o) ->
    parts = []
    op = @operator
    unless o.scope.parent?
      @error 'yield can only occur inside functions'
    if 'expression' in Object.keys(@first) and not (@first instanceof Throw)
      parts.push @first.expression.compileToFragments o, LEVEL_OP if @first.expression?
    else
      parts.push [@makeCode "("] if o.level >= LEVEL_PAREN
      parts.push [@makeCode op]
      parts.push [@makeCode " "] if @first.base?.value isnt ''
      parts.push @first.compileToFragments o, LEVEL_OP
      parts.push [@makeCode ")"] if o.level >= LEVEL_PAREN
    @joinFragmentArrays parts, ''

  compilePower: (o) ->

    pow = new Value new IdentifierLiteral('Math'), [new Access new PropertyName 'pow']
    new Call(pow, [@first, @second]).compileToFragments o

  compileFloorDivision: (o) ->
    floor = new Value new IdentifierLiteral('Math'), [new Access new PropertyName 'floor']
    second = if @second.isComplex() then new Parens @second else @second
    div = new Op '/', @first, second
    new Call(floor, [div]).compileToFragments o

  compileModulo: (o) ->
    mod = new Value new Literal utility 'modulo', o
    new Call(mod, [@first, @second]).compileToFragments o

  toString: (idt) ->
    super idt, @constructor.name + ' ' + @operator

exports.In = class In extends Base
  constructor: (@object, @array) ->

  children: ['object', 'array']

  invert: NEGATE

  compileNode: (o) ->
    if @array instanceof Value and @array.isArray() and @array.base.objects.length
      for obj in @array.base.objects when obj instanceof Splat
        hasSplat = yes
        break

      return @compileOrTest o unless hasSplat
    @compileLoopTest o

  compileOrTest: (o) ->
    [sub, ref] = @object.cache o, LEVEL_OP
    [cmp, cnj] = if @negated then [' !== ', ' && '] else [' === ', ' || ']
    tests = []
    for item, i in @array.base.objects
      if i then tests.push @makeCode cnj
      tests = tests.concat (if i then ref else sub), @makeCode(cmp), item.compileToFragments(o, LEVEL_ACCESS)
    if o.level < LEVEL_OP then tests else @wrapInBraces tests

  compileLoopTest: (o) ->
    [sub, ref] = @object.cache o, LEVEL_LIST
    fragments = [].concat @makeCode(utility('indexOf', o) + ".call("), @array.compileToFragments(o, LEVEL_LIST),
      @makeCode(", "), ref, @makeCode(") " + if @negated then '< 0' else '>= 0')
    return fragments if fragmentsToText(sub) is fragmentsToText(ref)
    fragments = sub.concat @makeCode(', '), fragments
    if o.level < LEVEL_LIST then fragments else @wrapInBraces fragments

  toString: (idt) ->
    super idt, @constructor.name + if @negated then '!' else ''

exports.Try = class Try extends Base
  constructor: (@attempt, @errorVariable, @recovery, @ensure) ->

  children: ['attempt', 'recovery', 'ensure']

  isStatement: YES

  jumps: (o) -> @attempt.jumps(o) or @recovery?.jumps(o)

  makeReturn: (res) ->
    @attempt  = @attempt .makeReturn res if @attempt
    @recovery = @recovery.makeReturn res if @recovery
    this

  compileNode: (o) ->
    o.indent  += TAB
    tryPart   = @attempt.compileToFragments o, LEVEL_TOP

    catchPart = if @recovery
      generatedErrorVariableName = o.scope.freeVariable 'error', reserve: no
      placeholder = new IdentifierLiteral generatedErrorVariableName
      if @errorVariable
        message = isUnassignable @errorVariable.unwrapAll().value
        @errorVariable.error message if message
        @recovery.unshift new Assign @errorVariable, placeholder
      [].concat @makeCode(" catch ("), placeholder.compileToFragments(o), @makeCode(") {\n"),
        @recovery.compileToFragments(o, LEVEL_TOP), @makeCode("\n#{@tab}}")
    else unless @ensure or @recovery
      generatedErrorVariableName = o.scope.freeVariable 'error', reserve: no
      [@makeCode(" catch (#{generatedErrorVariableName}) {}")]
    else
      []

    ensurePart = if @ensure then ([].concat @makeCode(" finally {\n"), @ensure.compileToFragments(o, LEVEL_TOP),
      @makeCode("\n#{@tab}}")) else []

    [].concat @makeCode("#{@tab}try {\n"),
      tryPart,
      @makeCode("\n#{@tab}}"), catchPart, ensurePart

exports.Throw = class Throw extends Base
  constructor: (@expression) ->

  children: ['expression']

  isStatement: YES
  jumps:       NO

  makeReturn: THIS

  compileNode: (o) ->
    [].concat @makeCode(@tab + "throw "), @expression.compileToFragments(o), @makeCode(";")

exports.Existence = class Existence extends Base
  constructor: (@expression) ->

  children: ['expression']

  invert: NEGATE

  compileNode: (o) ->
    @expression.front = @front
    code = @expression.compile o, LEVEL_OP
    if @expression.unwrap() instanceof IdentifierLiteral and not o.scope.check code
      [cmp, cnj] = if @negated then ['===', '||'] else ['!==', '&&']
      code = "typeof #{code} #{cmp} \"undefined\" #{cnj} #{code} #{cmp} null"
    else

      code = "#{code} #{if @negated then '==' else '!='} null"
    [@makeCode(if o.level <= LEVEL_COND then code else "(#{code})")]

exports.Parens = class Parens extends Base
  constructor: (@body) ->

  children: ['body']

  unwrap    : -> @body
  isComplex : -> @body.isComplex()

  compileNode: (o) ->
    expr = @body.unwrap()
    if expr instanceof Value and expr.isAtomic()
      expr.front = @front
      return expr.compileToFragments o
    fragments = expr.compileToFragments o, LEVEL_PAREN
    bare = o.level < LEVEL_OP and (expr instanceof Op or expr instanceof Call or
      (expr instanceof For and expr.returns)) and (o.level < LEVEL_COND or
        fragments.length <= 3)
    if bare then fragments else @wrapInBraces fragments

exports.StringWithInterpolations = class StringWithInterpolations extends Parens

  compileNode: (o) ->

    unless o.inTaggedTemplateCall
      return super

    expr = @body.unwrap()

    elements = []
    expr.traverseChildren no, (node) ->
      if node instanceof StringLiteral
        elements.push node
        return yes
      else if node instanceof Parens
        elements.push node
        return no
      return yes

    fragments = []
    fragments.push @makeCode '`'
    for element in elements
      if element instanceof StringLiteral
        value = element.value[1...-1]

        value = value.replace /(\\*)(`|\$\{)/g, (match, backslashes, toBeEscaped) ->
          if backslashes.length % 2 is 0
            "#{backslashes}\\#{toBeEscaped}"
          else
            match
        fragments.push @makeCode value
      else
        fragments.push @makeCode '${'
        fragments.push element.compileToFragments(o, LEVEL_PAREN)...
        fragments.push @makeCode '}'
    fragments.push @makeCode '`'

    fragments

exports.For = class For extends While
  constructor: (body, source) ->
    {@source, @guard, @step, @name, @index} = source
    @body    = Block.wrap [body]
    @own     = !!source.own
    @object  = !!source.object
    @from    = !!source.from
    @index.error 'cannot use index with for-from' if @from and @index
    source.ownTag.error "cannot use own with for-#{if @from then 'from' else 'in'}" if @own and not @object
    [@name, @index] = [@index, @name] if @object
    @index.error 'index cannot be a pattern matching expression' if @index instanceof Value and not @index.isAssignable()
    @range   = @source instanceof Value and @source.base instanceof Range and not @source.properties.length and not @from
    @pattern = @name instanceof Value
    @index.error 'indexes do not apply to range loops' if @range and @index
    @name.error 'cannot pattern match over range loops' if @range and @pattern
    @returns = false

  children: ['body', 'source', 'guard', 'step']

  compileNode: (o) ->
    body        = Block.wrap [@body]
    [..., last] = body.expressions
    @returns    = no if last?.jumps() instanceof Return
    source      = if @range then @source.base else @source
    scope       = o.scope
    name        = @name  and (@name.compile o, LEVEL_LIST) if not @pattern
    index       = @index and (@index.compile o, LEVEL_LIST)
    scope.find(name)  if name and not @pattern
    scope.find(index) if index and @index not instanceof Value
    rvar        = scope.freeVariable 'results' if @returns
    if @from
      ivar = scope.freeVariable 'x', single: true if @pattern
    else
      ivar = (@object and index) or scope.freeVariable 'i', single: true
    kvar        = ((@range or @from) and name) or index or ivar
    kvarAssign  = if kvar isnt ivar then "#{kvar} = " else ""
    if @step and not @range
      [step, stepVar] = @cacheToCodeFragments @step.cache o, LEVEL_LIST, isComplexOrAssignable
      stepNum   = Number stepVar if @step.isNumber()
    name        = ivar if @pattern
    varPart     = ''
    guardPart   = ''
    defPart     = ''
    idt1        = @tab + TAB
    if @range
      forPartFragments = source.compileToFragments merge o,
        {index: ivar, name, @step, isComplex: isComplexOrAssignable}
    else
      svar    = @source.compile o, LEVEL_LIST
      if (name or @own) and @source.unwrap() not instanceof IdentifierLiteral
        defPart    += "#{@tab}#{ref = scope.freeVariable 'ref'} = #{svar};\n"
        svar       = ref
      if name and not @pattern and not @from
        namePart   = "#{name} = #{svar}[#{kvar}]"
      if not @object and not @from
        defPart += "#{@tab}#{step};\n" if step isnt stepVar
        down = stepNum < 0
        lvar = scope.freeVariable 'len' unless @step and stepNum? and down
        declare = "#{kvarAssign}#{ivar} = 0, #{lvar} = #{svar}.length"
        declareDown = "#{kvarAssign}#{ivar} = #{svar}.length - 1"
        compare = "#{ivar} < #{lvar}"
        compareDown = "#{ivar} >= 0"
        if @step
          if stepNum?
            if down
              compare = compareDown
              declare = declareDown
          else
            compare = "#{stepVar} > 0 ? #{compare} : #{compareDown}"
            declare = "(#{stepVar} > 0 ? (#{declare}) : #{declareDown})"
          increment = "#{ivar} += #{stepVar}"
        else
          increment = "#{if kvar isnt ivar then "++#{ivar}" else "#{ivar}++"}"
        forPartFragments = [@makeCode("#{declare}; #{compare}; #{kvarAssign}#{increment}")]
    if @returns
      resultPart   = "#{@tab}#{rvar} = [];\n"
      returnResult = "\n#{@tab}return #{rvar};"
      body.makeReturn rvar
    if @guard
      if body.expressions.length > 1
        body.expressions.unshift new If (new Parens @guard).invert(), new StatementLiteral "continue"
      else
        body = Block.wrap [new If @guard, body] if @guard
    if @pattern
      body.expressions.unshift new Assign @name, if @from then new IdentifierLiteral kvar else new Literal "#{svar}[#{kvar}]"
    defPartFragments = [].concat @makeCode(defPart), @pluckDirectCall(o, body)
    varPart = "\n#{idt1}#{namePart};" if namePart
    if @object
      forPartFragments = [@makeCode("#{kvar} in #{svar}")]
      guardPart = "\n#{idt1}if (!#{utility 'hasProp', o}.call(#{svar}, #{kvar})) continue;" if @own
    else if @from
      forPartFragments = [@makeCode("#{kvar} of #{svar}")]
    bodyFragments = body.compileToFragments merge(o, indent: idt1), LEVEL_TOP
    if bodyFragments and bodyFragments.length > 0
      bodyFragments = [].concat @makeCode("\n"), bodyFragments, @makeCode("\n")
    [].concat defPartFragments, @makeCode("#{resultPart or ''}#{@tab}for ("),
      forPartFragments, @makeCode(") {#{guardPart}#{varPart}"), bodyFragments,
      @makeCode("#{@tab}}#{returnResult or ''}")

  pluckDirectCall: (o, body) ->
    defs = []
    for expr, idx in body.expressions
      expr = expr.unwrapAll()
      continue unless expr instanceof Call
      val = expr.variable?.unwrapAll()
      continue unless (val instanceof Code) or
                      (val instanceof Value and
                      val.base?.unwrapAll() instanceof Code and
                      val.properties.length is 1 and
                      val.properties[0].name?.value in ['call', 'apply'])
      fn    = val.base?.unwrapAll() or val
      ref   = new IdentifierLiteral o.scope.freeVariable 'fn'
      base  = new Value ref
      if val.base
        [val.base, base] = [base, val]
      body.expressions[idx] = new Call base, expr.args
      defs = defs.concat @makeCode(@tab), (new Assign(ref, fn).compileToFragments(o, LEVEL_TOP)), @makeCode(';\n')
    defs

exports.Switch = class Switch extends Base
  constructor: (@subject, @cases, @otherwise) ->

  children: ['subject', 'cases', 'otherwise']

  isStatement: YES

  jumps: (o = {block: yes}) ->
    for [conds, block] in @cases
      return jumpNode if jumpNode = block.jumps o
    @otherwise?.jumps o

  makeReturn: (res) ->
    pair[1].makeReturn res for pair in @cases
    @otherwise or= new Block [new Literal 'void 0'] if res
    @otherwise?.makeReturn res
    this

  compileNode: (o) ->
    idt1 = o.indent + TAB
    idt2 = o.indent = idt1 + TAB
    fragments = [].concat @makeCode(@tab + "switch ("),
      (if @subject then @subject.compileToFragments(o, LEVEL_PAREN) else @makeCode "false"),
      @makeCode(") {\n")
    for [conditions, block], i in @cases
      for cond in flatten [conditions]
        cond  = cond.invert() unless @subject
        fragments = fragments.concat @makeCode(idt1 + "case "), cond.compileToFragments(o, LEVEL_PAREN), @makeCode(":\n")
      fragments = fragments.concat body, @makeCode('\n') if (body = block.compileToFragments o, LEVEL_TOP).length > 0
      break if i is @cases.length - 1 and not @otherwise
      expr = @lastNonComment block.expressions
      continue if expr instanceof Return or (expr instanceof Literal and expr.jumps() and expr.value isnt 'debugger')
      fragments.push cond.makeCode(idt2 + 'break;\n')
    if @otherwise and @otherwise.expressions.length
      fragments.push @makeCode(idt1 + "default:\n"), (@otherwise.compileToFragments o, LEVEL_TOP)..., @makeCode("\n")
    fragments.push @makeCode @tab + '}'
    fragments

exports.If = class If extends Base
  constructor: (condition, @body, options = {}) ->
    @condition = if options.type is 'unless' then condition.invert() else condition
    @elseBody  = null
    @isChain   = false
    {@soak}    = options

  children: ['condition', 'body', 'elseBody']

  bodyNode:     -> @body?.unwrap()
  elseBodyNode: -> @elseBody?.unwrap()

  addElse: (elseBody) ->
    if @isChain
      @elseBodyNode().addElse elseBody
    else
      @isChain  = elseBody instanceof If
      @elseBody = @ensureBlock elseBody
      @elseBody.updateLocationDataIfMissing elseBody.locationData
    this

  isStatement: (o) ->
    o?.level is LEVEL_TOP or
      @bodyNode().isStatement(o) or @elseBodyNode()?.isStatement(o)

  jumps: (o) -> @body.jumps(o) or @elseBody?.jumps(o)

  compileNode: (o) ->
    if @isStatement o then @compileStatement o else @compileExpression o

  makeReturn: (res) ->
    @elseBody  or= new Block [new Literal 'void 0'] if res
    @body     and= new Block [@body.makeReturn res]
    @elseBody and= new Block [@elseBody.makeReturn res]
    this

  ensureBlock: (node) ->
    if node instanceof Block then node else new Block [node]

  compileStatement: (o) ->
    child    = del o, 'chainChild'
    exeq     = del o, 'isExistentialEquals'

    if exeq
      return new If(@condition.invert(), @elseBodyNode(), type: 'if').compileToFragments o

    indent   = o.indent + TAB
    cond     = @condition.compileToFragments o, LEVEL_PAREN
    body     = @ensureBlock(@body).compileToFragments merge o, {indent}
    ifPart   = [].concat @makeCode("if ("), cond, @makeCode(") {\n"), body, @makeCode("\n#{@tab}}")
    ifPart.unshift @makeCode @tab unless child
    return ifPart unless @elseBody
    answer = ifPart.concat @makeCode(' else ')
    if @isChain
      o.chainChild = yes
      answer = answer.concat @elseBody.unwrap().compileToFragments o, LEVEL_TOP
    else
      answer = answer.concat @makeCode("{\n"), @elseBody.compileToFragments(merge(o, {indent}), LEVEL_TOP), @makeCode("\n#{@tab}}")
    answer

  compileExpression: (o) ->
    cond = @condition.compileToFragments o, LEVEL_COND
    body = @bodyNode().compileToFragments o, LEVEL_LIST
    alt  = if @elseBodyNode() then @elseBodyNode().compileToFragments(o, LEVEL_LIST) else [@makeCode('void 0')]
    fragments = cond.concat @makeCode(" ? "), body, @makeCode(" : "), alt
    if o.level >= LEVEL_COND then @wrapInBraces fragments else fragments

  unfoldSoak: ->
    @soak and this

UTILITIES =

  extend: (o) -> "
    function(child, parent) {
      for (var key in parent) {
        if (#{utility 'hasProp', o}.call(parent, key)) child[key] = parent[key];
      }
      function ctor() {
        this.constructor = child;
      }
      ctor.prototype = parent.prototype;
      child.prototype = new ctor();
      child.__super__ = parent.prototype;
      return child;
    }
  "

  bind: -> '
    function(fn, me){
      return function(){
        return fn.apply(me, arguments);
      };
    }
  '

  indexOf: -> "
    [].indexOf || function(item) {
      for (var i = 0, l = this.length; i < l; i++) {
        if (i in this && this[i] === item) return i;
      }
      return -1;
    }
  "

  modulo: -> """
    function(a, b) { return (+a % (b = +b) + b) % b; }
  """

  hasProp: -> '{}.hasOwnProperty'
  slice  : -> '[].slice'

LEVEL_TOP    = 1  # ...;
LEVEL_PAREN  = 2  # (...)
LEVEL_LIST   = 3  # [...]
LEVEL_COND   = 4  # ... ? x : y
LEVEL_OP     = 5  # !...
LEVEL_ACCESS = 6  # ...[0]

TAB = '  '

SIMPLENUM = /^[+-]?\d+$/

utility = (name, o) ->
  {root} = o.scope
  if name of root.utilities
    root.utilities[name]
  else
    ref = root.freeVariable name
    root.assign ref, UTILITIES[name] o
    root.utilities[name] = ref

multident = (code, tab) ->
  code = code.replace /\n/g, '$&' + tab
  code.replace /\s+$/, ''

isLiteralArguments = (node) ->
  node instanceof IdentifierLiteral and node.value is 'arguments'

isLiteralThis = (node) ->
  node instanceof ThisLiteral or
    (node instanceof Code and node.bound) or
    node instanceof SuperCall

isComplexOrAssignable = (node) -> node.isComplex() or node.isAssignable?()

unfoldSoak = (o, parent, name) ->
  return unless ifn = parent[name].unfoldSoak o
  parent[name] = ifn.body
  ifn.body = new Value parent
  ifn