lib/ruby2js/filter/functions.rb

require 'ruby2js'

require 'regexp_parser/scanner'

module Ruby2JS
  module Filter
    module Functions
      include SEXP

      # require explicit opt-in to to class => constructor mapping
      Filter.exclude :class, :call

      VAR_TO_ASSIGN = {
        lvar: :lvasgn,
        ivar: :ivasgn,
        cvar: :cvasgn,
        gvar: :gvasgn
      }

      def initialize(*args)
        @jsx = false
        super
      end

      def on_send(node)
        target, method, *args = node.children
        return super if excluded?(method) and method != :call

        if [:max, :min].include? method and args.length == 0
          if target.type == :array
            process S(:send, s(:const, nil, :Math), node.children[1],
              *target.children)
          elsif node.is_method?
            process S(:send, s(:const, nil, :Math), node.children[1],
              s(:splat, target))
          else
            return super
          end

        elsif method == :call and target and 
          (%i[ivar cvar].include?(target.type) or not excluded?(:call))

          S(:call, process(target), nil, *process_all(args))

        elsif method == :keys and args.length == 0 and node.is_method?
          process S(:send, s(:const, nil, :Object), :keys, target)

        elsif method == :[]= and args.length == 3 and
          args[0].type == :regexp and args[1].type == :int

          index = args[1].children.first

          # identify groups
          regex = args[0].children.first.children.first
          tokens = Regexp::Scanner.scan(regex)
          groups = []
          stack = []
          tokens.each do |token|
            next unless token[0] == :group
            if token[1] == :capture
              groups.push token.dup
              return super if groups.length == index and not stack.empty?
              stack.push groups.last
            elsif token[1] == :close
              stack.pop[-1]=token.last
            end
          end
          group = groups[index-1]

          # rewrite regex
          prepend = nil
          append = nil

          if group[4] < regex.length
            regex = (regex[0...group[4]] + '(' + regex[group[4]..-1] + ')').
              sub(/\$\)$/, ')$')
            append = 2
          end

          if group[4] - group[3] == 2
            regex = regex[0...group[3]] + regex[group[4]..-1]
            append = 1 if append
          end

          if group[3] > 0
            regex = ('(' + regex[0...group[3]] + ')' + regex[group[3]..-1]).
              sub(/^\(\^/, '^(')
            prepend = 1
            append += 1 if append
          end

          regex = process s(:regexp, s(:str, regex), args[0].children.last)

          # 
          if args.last.type == :str
            str = args.last.children.first.gsub('$', '$$')
            str = "$#{prepend}#{str}" if prepend
            str = "#{str}$#{append}" if append
            expr = s(:send, target, :replace, regex, s(:str, str))
          else
            dstr = args.last.type == :dstr ? args.last.children.dup : [args.last]
            if prepend
              dstr.unshift s(:send, s(:lvar, :match), :[], s(:int, prepend-1))
            end
            if append
              dstr << s(:send, s(:lvar, :match), :[], s(:int, append-1))
            end

            expr = s(:block,
              s(:send, target, :replace, regex),
              s(:args, s(:arg, :match)),
              process(s(:dstr, *dstr)))
          end

          if VAR_TO_ASSIGN.keys.include? target.type
            S(VAR_TO_ASSIGN[target.type], target.children.first, expr)
          elsif target.type == :send
            if target.children[0] == nil
              S(:lvasgn, target.children[1], expr)
            else
              S(:send, target.children[0], :"#{target.children[1]}=", expr)
            end
          else
            super
          end

        elsif method == :merge
          args.unshift target

          if es2018
            process S(:hash, *args.map {|arg| s(:kwsplat, arg)})
          else
            process S(:assign, s(:hash), *args)
          end

        elsif method == :merge!
          process S(:assign, target, *args)

        elsif method == :delete and args.length == 1
          if not target
            process S(:undef, args.first)
          elsif args.first.type == :str
            process S(:undef, S(:attr, target, args.first.children.first))
          else
            process S(:undef, S(:send, target, :[], args.first))
          end

        elsif method == :to_s
          process S(:call, target, :toString, *args)

        elsif method == :Array and target == nil
          if es2015
            process S(:send, s(:const, nil, :Array), :from, *args)
          else
            process S(:send, s(:attr, s(:attr, s(:const, nil, :Array),
              :prototype), :slice), :call, *args)
          end

        elsif method == :to_i
          process node.updated :send, [nil, :parseInt, target, *args]

        elsif method == :to_f
          process node.updated :send, [nil, :parseFloat, target, *args]

        elsif method == :to_json
          process node.updated :send, [s(:const, nil, :JSON), :stringify, target, *args]

        elsif method == :sub and args.length == 2
          if args[1].type == :str
            args[1] = s(:str, args[1].children.first.gsub(/\\(\d)/, "$\\1"))
          end
          process node.updated nil, [target, :replace, *args]

        elsif [:sub!, :gsub!].include? method
          method = :"#{method.to_s[0..-2]}"
          if VAR_TO_ASSIGN.keys.include? target.type
            process S(VAR_TO_ASSIGN[target.type], target.children[0],
              S(:send, target, method, *node.children[2..-1]))
          elsif target.type == :send
            if target.children[0] == nil
              process S(:lvasgn, target.children[1], S(:send,
                S(:lvar, target.children[1]), method, *node.children[2..-1]))
            else
              process S(:send, target.children[0], :"#{target.children[1]}=",
                S(:send, target, method, *node.children[2..-1]))
            end
          else
            super
          end

        elsif method == :scan and args.length == 1
          arg = args.first
          if arg.type == :str
            arg = arg.updated(:regexp,
              [s(:str, Regexp.escape(arg.children.first)), s(:regopt)])
          end

          if arg.type == :regexp
            pattern = arg.children.first.children.first
            pattern = pattern.gsub(/\\./, '').gsub(/\[.*\]/, '')

            gpattern = arg.updated(:regexp, [*arg.children[0...-1],
              s(:regopt, :g, *arg.children.last)])
          else
            gpattern = s(:send, s(:const, nil, :RegExp), :new, arg, s(:str, 'g'))
          end

          if arg.type != :regexp or pattern.include? '('
            if es2020
              # Array.from(str.matchAll(/.../g), s => s.slice(1))
              s(:send, s(:const, nil, :Array), :from,
                s(:send, process(target), :matchAll, gpattern),
                s(:block, s(:send, nil, :proc), s(:args, s(:arg, :s)),
                  s(:send, s(:lvar, :s), :slice, s(:int, 1))))
            else
              # (str.match(/.../g) || []).map(s => s.match(/.../).slice(1))
              s(:block, s(:send,
                s(:or, s(:send, process(target), :match, gpattern), s(:array)),
                :map), s(:args, s(:arg, :s)),
                s(:return, s(:send, s(:send, s(:lvar, :s), :match, arg),
                :slice, s(:int, 1))))
            end
          else
            # str.match(/.../g)
            S(:send, process(target), :match, gpattern)
          end

        elsif method == :gsub and args.length == 2
          before, after = args
          if before.type == :regexp
            before = before.updated(:regexp, [*before.children[0...-1],
              s(:regopt, :g, *before.children.last)])
          elsif before.type == :str and not es2021
            before = before.updated(:regexp,
              [s(:str, Regexp.escape(before.children.first)), s(:regopt, :g)])
          end
          if after.type == :str
            after = s(:str, after.children.first.gsub(/\\(\d)/, "$\\1"))
          end

          if es2021
            process node.updated nil, [target, :replaceAll, before, after]
          else
            process node.updated nil, [target, :replace, before, after]
          end

        elsif method == :ord and args.length == 0
          if target.type == :str
            process S(:int, target.children.last.ord)
          else
            process S(:send, target, :charCodeAt, s(:int, 0))
          end

        elsif method == :chr and args.length == 0
          if target.type == :int
            process S(:str, target.children.last.chr)
          else
            process S(:send, s(:const, nil, :String), :fromCharCode, target)
          end

        elsif method == :empty? and args.length == 0
          process S(:send, S(:attr, target, :length), :==, s(:int, 0))

        elsif method == :nil? and args.length == 0
          process S(:send, target, :==, s(:nil))

        elsif [:start_with?, :end_with?].include? method and args.length == 1
          if es2015
            if method == :start_with?
              process S(:send, target, :startsWith, *args)
            else
              process S(:send, target, :endsWith, *args)
            end
          else
            if args.first.type == :str
              length = S(:int, args.first.children.first.length)
            else
              length = S(:attr, *args, :length)
            end

            if method == :start_with?
              process S(:send, S(:send, target, :substring, s(:int, 0),
                length), :==, *args)
            else
              process S(:send, S(:send, target, :slice,
                S(:send, length, :-@)), :==, *args)
            end
          end

        elsif method == :clear and args.length == 0 and node.is_method?
          process S(:send, target, :length=, s(:int, 0))

        elsif method == :replace and args.length == 1
          process S(:begin, S(:send, target, :length=, s(:int, 0)),
             S(:send, target, :push, s(:splat, node.children[2])))

        elsif method == :include? and args.length == 1
          while target.type == :begin and target.children.length == 1
            target = target.children.first
          end

          if target.type == :irange
            S(:and, s(:send, args.first, :>=, target.children.first),
              s(:send, args.first, :<=, target.children.last))
          elsif target.type == :erange
            S(:and, s(:send, args.first, :>=, target.children.first),
              s(:send, args.first, :<, target.children.last))
          else
            if es2016
              process S(:send, target, :includes, args.first)
            else
              process S(:send, S(:send, target, :indexOf, args.first), :!=,
                s(:int, -1))
            end
          end

        elsif method == :respond_to? and args.length == 1
          process S(:in?, args.first, target)

        elsif method == :each
          process S(:send, target, :forEach, *args)

        elsif method == :downcase and args.length == 0
          process s(:send, target, :toLowerCase)

        elsif method == :upcase and args.length == 0
          process s(:send, target, :toUpperCase)

        elsif method == :strip and args.length == 0
          process s(:send, target, :trim)

        elsif node.children[0..1] == [nil, :puts]
          process S(:send, s(:attr, nil, :console), :log, *args)

        elsif method == :first
          if node.children.length == 2
            process S(:send, target, :[], s(:int, 0))
          elsif node.children.length == 3
            process on_send S(:send, target, :[], s(:erange,
              s(:int, 0), node.children[2]))
          else
            super
          end

        elsif method == :last
          if node.children.length == 2
            if es2022
              process S(:send, target, :at, s(:int, -1))
            else
              process on_send S(:send, target, :[], s(:int, -1))
            end
          elsif node.children.length == 3
            process S(:send, target, :slice,
              s(:send, s(:attr, target, :length), :-, node.children[2]),
              s(:attr, target, :length))
          else
            super
          end


        elsif method == :[] and target == s(:const, nil, :Hash)
          s(:send, s(:const, nil, :Object), :fromEntries, *process_all(args))

        elsif method == :[]
          # resolve negative literal indexes
          i = proc do |index|
            if index.type == :int and index.children.first < 0
              if es2022
                return process S(:send, target, :at, index)
              else
                process S(:send, S(:attr, target, :length), :-,
                  s(:int, -index.children.first))
              end
            else
              index
            end
          end

          index = args.first

          if not index
            super

          elsif index.type == :regexp
            if es2020
              process S(:csend,
                S(:send, process(target), :match, index),
                :[], args[1] || s(:int, 0))
            else
              process S(:send,
                s(:or, S(:send, process(target), :match, index), s(:array)),
                :[], args[1] || s(:int, 0))
            end

          elsif node.children.length != 3
            super

          elsif index.type == :int and index.children.first < 0
            process S(:send, target, :[], i.(index))

          elsif index.type == :erange
            start, finish = index.children
            if not finish
              process S(:send, target, :slice, start)
            elsif finish.type == :int
              process S(:send, target, :slice, i.(start), finish)
            else
              process S(:send, target, :slice, i.(start), i.(finish))
            end

          elsif index.type == :irange
            start, finish = index.children
            if finish and finish.type == :int
              final = S(:int, finish.children.first+1)
            else
              final = S(:send, finish, :+, s(:int, 1))
            end

            # No need for the last argument if it's -1
            # This means take all to the end of array
            if not finish or finish.children.first == -1
              process S(:send, target, :slice, start)
            else
              process S(:send, target, :slice, start, final)
            end

          else
            super
          end

        elsif method == :reverse! and node.is_method?
          # input: a.reverse!
          # output: a.splice(0, a.length, *a.reverse)
          process S(:send, target, :splice, s(:int, 0),
            s(:attr, target, :length), s(:splat, S(:send, target,
            :reverse, *node.children[2..-1])))

        elsif method == :each_with_index
          process S(:send, target, :forEach, *args)

        elsif method == :inspect and args.length == 0
          S(:send, s(:const, nil, :JSON), :stringify, process(target))

        elsif method == :* and target.type == :str
          if es2015
            process S(:send, target, :repeat, args.first)
          else
            process S(:send, s(:send, s(:const, nil, :Array), :new,
              s(:send, args.first, :+, s(:int, 1))), :join, target)
          end

        elsif [:is_a?, :kind_of?].include? method and args.length == 1
          if args[0].type == :const
            parent = args[0].children.last
            parent = :Number if parent == :Float
            parent = :Object if parent == :Hash
            parent = :Function if parent == :Proc
            parent = :Error if parent == :Exception
            parent = :RegExp if parent == :Regexp
            if parent == :Array
              S(:send, s(:const, nil, :Array), :isArray, target)
            elsif [:Arguments, :Boolean, :Date, :Error, :Function, :Number,
                :Object, :RegExp, :String].include? parent
              S(:send, s(:send, s(:attr, s(:attr, s(:const, nil, Object),
                :prototype), :toString), :call, target), :===,
                s(:str, "[object #{parent.to_s}]"))
            else
              super
            end
          else
            super
          end

        elsif target && target.type == :send and target.children[1] == :delete
          # prevent chained delete methods from being converted to undef
          S(:send, target.updated(:sendw), *node.children[1..-1])

        elsif es2017 and method==:entries and args.length==0 and node.is_method?
          process node.updated(nil, [s(:const, nil, :Object), :entries, target])

        elsif es2017 and method==:values and args.length==0 and node.is_method?
          process node.updated(nil, [s(:const, nil, :Object), :values, target])

        elsif es2017 and method==:rjust
          process node.updated(nil, [target, :padStart, *args])

        elsif es2017 and method==:ljust
          process node.updated(nil, [target, :padEnd, *args])

        elsif es2019 and method==:flatten and args.length == 0
          process node.updated(nil, [target, :flat, s(:lvar, :Infinity)])

        elsif es2019 and method==:to_h and args.length==0
          process node.updated(nil, [s(:const, nil, :Object), :fromEntries,
            target])

        elsif method==:rstrip
          if es2019
            process node.updated(nil, [target, :trimEnd, *args])
          else
            node.updated(nil, [process(target), :replace,
              s(:regexp, s(:str, '\s+\z') , s(:regopt)), s(:str, '')])
          end

        elsif method==:lstrip and args.length == 0
          if es2019
            process s(:send, target, :trimStart)
          else
            node.updated(nil, [process(target), :replace,
              s(:regexp, s(:str, '\A\s+') , s(:regopt)), s(:str, '')])
          end

        elsif method == :index and node.is_method?
          process node.updated(nil, [target, :indexOf, *args])

        elsif method == :rindex and node.is_method?
          process node.updated(nil, [target, :lastIndexOf, *args])

        elsif method == :class and args.length==0 and not node.is_method?
          process node.updated(:attr, [target, :constructor])

        elsif method == :new and target == s(:const, nil, :Exception)
          process S(:send, s(:const, nil, :Error), :new, *args)

        elsif method == :block_given? and target == nil and args.length == 0
          process process s(:lvar, "_implicitBlockYield")

        elsif method == :abs and args.length == 0
          process S(:send, s(:const, nil, :Math), :abs, target)

        elsif method == :round and args.length == 0
          process S(:send, s(:const, nil, :Math), :round, target)

        elsif method == :ceil and args.length == 0
          process S(:send, s(:const, nil, :Math), :ceil, target)

        elsif method == :floor and args.length == 0
          process S(:send, s(:const, nil, :Math), :floor, target)

        elsif method == :rand and target == nil
          if args.length == 0
            process S(:send!, s(:const, nil, :Math), :random)
          elsif %i[irange erange].include? args.first.type
            range = args.first
            multiplier = s(:send, range.children.last, :-, range.children.first)
            if range.children.all? {|child| child.type == :int}
              multiplier = s(:int, range.children.last.children.last - range.children.first.children.last)
              multiplier = s(:int, multiplier.children.first + 1) if range.type == :irange
            elsif range.type == :irange
              if multiplier.children.last.type == :int
                diff = multiplier.children.last.children.last - 1
                multiplier = s(:send, *multiplier.children[0..1], s(:int, diff))
                multiplier = multiplier.children.first if diff == 0
                multiplier = s(:send, multiplier.children[0], :+, s(:int, -diff)) if diff < 0
              else
                multiplier = s(:send, multiplier, :+, s(:int, 1))
              end
            end
            raw = s(:send, s(:send, s(:const, nil, :Math), :random), :*, multiplier)
            if range.children.first != s(:int, 0)
              raw = s(:send, raw, :+, range.children.first)
            end
            process S(:send, nil, :parseInt, raw)
          else
            process S(:send, nil, :parseInt,
              s(:send, s(:send, s(:const, nil, :Math), :random),
              :*, args.first))
          end

        elsif method == :sum and args.length == 0
          process S(:send, target, :reduce, s(:block, s(:send, nil, :proc),
            s(:args, s(:arg, :a), s(:arg, :b)),
            s(:send, s(:lvar, :a), :+, s(:lvar, :b))), s(:int, 0))

        elsif method == :method_defined? and args.length >= 1
          if args[1] == s(:false)
            process S(:send, s(:attr, target, :prototype), :hasOwnProperty, args[0])
          elsif args.length == 1 or args[1] == s(:true)
            process S(:in?, args[0], s(:attr, target, :prototype))
          else
            process S(:if, args[1], s(:in?, args[0], s(:attr, target, :prototype)),
              s(:send, s(:attr, target, :prototype), :hasOwnProperty, args[0]))
          end

        elsif method == :alias_method and args.length == 2
          process S(:send, s(:attr, target, :prototype), :[]=, args[0],
            s(:attr, s(:attr, target, :prototype), args[1].children[0]))

        elsif method == :new and args.length == 2 and target == s(:const, nil, :Array)
          if es2015
            s(:send, S(:send, target, :new, args.first), :fill, args.last)
          else
            super
          end

        elsif method == :chars and args.length == 0
          if es2015
            S(:send, s(:const, nil, :Array), :from, target)
          else
            super
          end

        else
          super
        end
      end

      def on_block(node)
        call = node.children.first
        method = call.children[1]
        return super if excluded?(method)

        if [:setInterval, :setTimeout, :set_interval, :set_timeout].include? method
          return super unless call.children.first == nil
          block = process s(:block, s(:send, nil, :proc), *node.children[1..-1])
          on_send call.updated nil, [*call.children[0..1], block,
            *call.children[2..-1]]

        elsif [:sub, :gsub, :sub!, :gsub!, :sort!].include? method
          return super if call.children.first == nil
          block = s(:block, s(:send, nil, :proc), node.children[1],
            s(:autoreturn, *node.children[2..-1]))
          process call.updated(nil, [*call.children, block])

        elsif method == :select and call.children.length == 2
          call = call.updated nil, [call.children.first, :filter]
          node.updated nil, [process(call), process(node.children[1]),
            s(:autoreturn, *process_all(node.children[2..-1]))]

        elsif method == :any? and call.children.length == 2
          call = call.updated nil, [call.children.first, :some]
          node.updated nil, [process(call), process(node.children[1]),
            s(:autoreturn, *process_all(node.children[2..-1]))]

        elsif method == :all? and call.children.length == 2
          call = call.updated nil, [call.children.first, :every]
          node.updated nil, [process(call), process(node.children[1]),
            s(:autoreturn, *process_all(node.children[2..-1]))]

        elsif method == :find and call.children.length == 2
          node.updated nil, [process(call), process(node.children[1]),
            s(:autoreturn, *process_all(node.children[2..-1]))]

        elsif method == :find_index and call.children.length == 2
          call = call.updated nil, [call.children.first, :findIndex]
          node.updated nil, [process(call), process(node.children[1]),
            s(:autoreturn, *process_all(node.children[2..-1]))]

        elsif method == :index and call.children.length == 2
            call = call.updated nil, [call.children.first, :findIndex]
            node.updated nil, [process(call), process(node.children[1]),
              s(:autoreturn, *process_all(node.children[2..-1]))]

        elsif method == :map and call.children.length == 2
          node.updated nil, [process(call), process(node.children[1]),
            s(:autoreturn, *process_all(node.children[2..-1]))]

        elsif [:map!, :select!].include? method
          # input: a.map! {expression}
          # output: a.splice(0, a.length, *a.map {expression})
          method = (method == :map! ? :map : :select)
          target = call.children.first
          process call.updated(:send, [target, :splice, s(:splat, s(:send,
            s(:array, s(:int, 0), s(:attr, target, :length)), :concat,
            s(:block, s(:send, target, method, *call.children[2..-1]),
            *node.children[1..-1])))])

        elsif node.children[0..1] == [s(:send, nil, :loop), s(:args)]
          # input: loop {statements}
          # output: while(true) {statements}
          S(:while, s(:true), node.children[2])

        elsif method == :delete
          # restore delete methods that are prematurely mapped to undef
          result = super

          if result.children[0].type == :undef
            call = result.children[0].children[0]
            if call.type == :attr
              call = call.updated(:send,
                [call.children[0], :delete, s(:str, call.children[1])])
              result = result.updated(nil, [call, *result.children[1..-1]])
            else
              call = call.updated(nil,
                [call.children[0], :delete, *call.children[2..-1]])
              result = result.updated(nil, [call, *result.children[1..-1]])
            end
          end

          result

        elsif method == :downto
          range = s(:irange, call.children[0], call.children[2])
          call = call.updated(nil, [s(:begin, range), :step, s(:int, -1)])
          process node.updated(nil, [call, *node.children[1..-1]])

        elsif method == :upto
          range = s(:irange, call.children[0], call.children[2])
          call = call.updated(nil, [s(:begin, range), :step, s(:int, 1)])
          process node.updated(nil, [call, *node.children[1..-1]])

        elsif \
          method == :each and call.children[0].type == :send and
          call.children[0].children[1] == :step
        then
          # i.step(j, n).each {|v| ...}
          range = call.children[0]
          step = range.children[3] || s(:int, 1)
          call = call.updated(nil, [s(:begin,
            s(:irange, range.children[0], range.children[2])),
            :step, step])
          process node.updated(nil, [call, *node.children[1..-1]])

        elsif \
          # (a..b).each {|v| ...}
          method == :each and
          call.children[0].type == :begin and
          call.children[0].children.length == 1 and
          [:irange, :erange].include? call.children[0].children[0].type and
          node.children[1].children.length == 1
        then
          process s(:for, s(:lvasgn, node.children[1].children[0].children[0]),
            call.children[0].children[0], node.children[2])

        elsif \
          [:each, :each_value].include? method
        then
          if es2015 or @jsx
            if node.children[1].children.length > 1
              process node.updated(:for_of,
                [s(:mlhs, *node.children[1].children.map {|child|
                  s(:lvasgn, child.children[0])}),
                node.children[0].children[0], node.children[2]])
            elsif node.children[1].children[0].type == :mlhs
              process node.updated(:for_of,
                [s(:mlhs, *node.children[1].children[0].children.map {|child|
                  s(:lvasgn, child.children[0])}),
                node.children[0].children[0], node.children[2]])
            else
              process node.updated(:for_of,
                [s(:lvasgn, node.children[1].children[0].children[0]),
                node.children[0].children[0], node.children[2]])
            end
          else
            process node.updated(nil, [s(:send, call.children[0],
              :forEach), *node.children[1..2]])
          end

        elsif \
          method == :each_key and
          [:each, :each_key].include? method and
          node.children[1].children.length == 1
        then
          process node.updated(:for,
            [s(:lvasgn, node.children[1].children[0].children[0]),
            node.children[0].children[0], node.children[2]])

        elsif es2015 and method == :inject
          process node.updated(:send, [call.children[0], :reduce,
            s(:block, s(:send, nil, :lambda), *node.children[1..2]),
            *call.children[2..-1]])

        elsif method == :each_pair and node.children[1].children.length == 2
          if es2017
            # Object.entries(a).forEach(([key, value]) => {})
            process node.updated(nil, [s(:send, s(:send,
            s(:const, nil, :Object), :entries, call.children[0]), :each),
            node.children[1], node.children[2]])
          else
            # for (key in a). {var value = a[key]; ...}
            process node.updated(:for, [s(:lvasgn,
              node.children[1].children[0].children[0]), call.children[0],
              s(:begin, s(:lvasgn, node.children[1].children[1].children[0],
              s(:send, call.children[0], :[], 
              s(:lvar, node.children[1].children[0].children[0]))),
              node.children[2])])
          end

        elsif method == :scan and call.children.length == 3
          process call.updated(nil, [*call.children, s(:block,
            s(:send, nil, :proc), *node.children[1..-1])])

        elsif method == :yield_self and call.children.length == 2
          process node.updated(:send, [s(:block, s(:send, nil, :proc),
            node.children[1], s(:autoreturn, node.children[2])),
            :[], call.children[0]])

        elsif method == :tap and call.children.length == 2
          process node.updated(:send, [s(:block, s(:send, nil, :proc),
            node.children[1], s(:begin, node.children[2],
            s(:return, s(:lvar, node.children[1].children[0].children[0])))),
            :[], call.children[0]])

        elsif method == :define_method and call.children.length == 3
          process node.updated(:send, [s(:attr, call.children[0], :prototype), :[]=,
            call.children[2], s(:deff, nil, *node.children[1..-1])])

        else
          super
        end
      end

      def on_class(node)
        name, inheritance, *body = node.children
        body.compact!

        body.each_with_index do |node, i|
          if node.type == :send and node.children[0..1] == [nil, :alias_method]
            body[i] = node.updated(:send, [name, *node.children[1..-1]])
          end
        end

        if inheritance == s(:const, nil, :Exception)
          unless
            body.any? {|statement| statement.type == :def and
            statement.children.first == :initialize}
          then
            body.unshift s(:def, :initialize, s(:args, s(:arg, :message)),
              s(:begin, s(:send, s(:self), :message=, s(:lvar, :message)),
              s(:send, s(:self), :name=, s(:sym, name.children[1])),
              s(:send, s(:self), :stack=, s(:attr, s(:send, nil, :Error,
              s(:lvar, :message)), :stack))))
          end

          body = [s(:begin, *body)] if body.length > 1
          S(:class, name, s(:const, nil, :Error), *body)
        else
          body = [s(:begin, *body)] if body.length > 1
          super S(:class, name, inheritance, *body)
        end
      end
    end

    DEFAULTS.push Functions
  end
end