class Sass::Script::Funcall

def _perform(environment)
  args = @args.map {|a| a.perform(environment)}
  splat = @splat.perform(environment) if @splat
  if fn = environment.function(@name)
    keywords = Sass::Util.map_hash(@keywords) {|k, v| [k, v.perform(environment)]}
    return perform_sass_fn(fn, args, keywords, splat)
  end
  ruby_name = @name.tr('-', '_')
  args = construct_ruby_args(ruby_name, args, splat, environment)
  unless Functions.callable?(ruby_name)
    opts(to_literal(args))
  else
    local_environment = Environment.new(environment.global_env, environment.options)
    opts(Functions::EvaluationContext.new(local_environment).send(ruby_name, *args))
  end
rescue ArgumentError => e
  message = e.message
  # If this is a legitimate Ruby-raised argument error, re-raise it.
  # Otherwise, it's an error in the user's stylesheet, so wrap it.
  if Sass::Util.rbx?
    # Rubinius has a different error report string than vanilla Ruby. It
    # also doesn't put the actual method for which the argument error was
    # thrown in the backtrace, nor does it include `send`, so we look for
    # `_perform`.
    if e.message =~ /^method '([^']+)': given (\d+), expected (\d+)/
      error_name, given, expected = $1, $2, $3
      raise e if error_name != ruby_name || e.backtrace[0] !~ /:in `_perform'$/
      message = "wrong number of arguments (#{given} for #{expected})"
    end
  elsif Sass::Util.jruby?
    if Sass::Util.jruby1_6?
      should_maybe_raise = e.message =~ /^wrong number of arguments \((\d+) for (\d+)\)/ &&
        # The one case where JRuby does include the Ruby name of the function
        # is manually-thrown ArgumentErrors, which are indistinguishable from
        # legitimate ArgumentErrors. We treat both of these as
        # Sass::SyntaxErrors even though it can hide Ruby errors.
        e.backtrace[0] !~ /:in `(block in )?#{ruby_name}'$/
    else
      should_maybe_raise = e.message =~ /^wrong number of arguments calling `[^`]+` \((\d+) for (\d+)\)/
      given, expected = $1, $2
    end
    if should_maybe_raise
      # JRuby 1.7 includes __send__ before send and _perform.
      trace = e.backtrace.dup
      raise e if !Sass::Util.jruby1_6? && trace.shift !~ /:in `__send__'$/
      # JRuby (as of 1.7.2) doesn't put the actual method
      # for which the argument error was thrown in the backtrace, so we
      # detect whether our send threw an argument error.
      if !(trace[0] =~ /:in `send'$/ && trace[1] =~ /:in `_perform'$/)
        raise e
      elsif !Sass::Util.jruby1_6?
        # JRuby 1.7 doesn't use standard formatting for its ArgumentErrors.
        message = "wrong number of arguments (#{given} for #{expected})"
      end
    end
  elsif e.message =~ /^wrong number of arguments \(\d+ for \d+\)/ &&
      e.backtrace[0] !~ /:in `(block in )?#{ruby_name}'$/
    raise e
  end
  raise Sass::SyntaxError.new("#{message} for `#{name}'")
end

def children
  res = @args + @keywords.values
  res << @splat if @splat
  res
end

def construct_ruby_args(name, args, splat, environment)
  args += splat.to_a if splat
  # If variable arguments were passed, there won't be any explicit keywords.
  if splat.is_a?(Sass::Script::ArgList)
    kwargs_size = splat.keywords.size
    splat.keywords_accessed = false
  else
    kwargs_size = @keywords.size
  end
  unless signature = Functions.signature(name.to_sym, args.size, kwargs_size)
    return args if @keywords.empty?
    raise Sass::SyntaxError.new("Function #{name} doesn't support keyword arguments")
  end
  keywords = splat.is_a?(Sass::Script::ArgList) ? splat.keywords :
    Sass::Util.map_hash(@keywords) {|k, v| [k, v.perform(environment)]}
  # If the user passes more non-keyword args than the function expects,
  # but it does expect keyword args, Ruby's arg handling won't raise an error.
  # Since we don't want to make functions think about this,
  # we'll handle it for them here.
  if signature.var_kwargs && !signature.var_args && args.size > signature.args.size
    raise Sass::SyntaxError.new(
      "#{args[signature.args.size].inspect} is not a keyword argument for `#{name}'")
  elsif keywords.empty?
    return args 
  end
  args = args + signature.args[args.size..-1].map do |argname|
    if keywords.has_key?(argname)
      keywords.delete(argname)
    else
      raise Sass::SyntaxError.new("Function #{name} requires an argument named $#{argname}")
    end
  end
  if keywords.size > 0
    if signature.var_kwargs
      args << keywords
    else
      argname = keywords.keys.sort.first
      if signature.args.include?(argname)
        raise Sass::SyntaxError.new("Function #{name} was passed argument $#{argname} both by position and by name")
      else
        raise Sass::SyntaxError.new("Function #{name} doesn't have an argument named $#{argname}")
      end
    end
  end
  args
end

def deep_copy
  node = dup
  node.instance_variable_set('@args', args.map {|a| a.deep_copy})
  node.instance_variable_set('@keywords', Hash[keywords.map {|k, v| [k, v.deep_copy]}])
  node
end

def initialize(name, args, keywords, splat)
  @name = name
  @args = args
  @keywords = keywords
  @splat = splat
  super()
end

def inspect
  args = @args.map {|a| a.inspect}.join(', ')
  keywords = Sass::Util.hash_to_a(@keywords).
      map {|k, v| "$#{k}: #{v.inspect}"}.join(', ')
  if self.splat
    splat = (args.empty? && keywords.empty?) ? "" : ", "
    splat = "#{splat}#{self.splat.inspect}..."
  end
  "#{name}(#{args}#{', ' unless args.empty? || keywords.empty?}#{keywords}#{splat})"
end

def perform_sass_fn(function, args, keywords, splat)
  Sass::Tree::Visitors::Perform.perform_arguments(function, args, keywords, splat) do |env|
    val = catch :_sass_return do
      function.tree.each {|c| Sass::Tree::Visitors::Perform.visit(c, env)}
      raise Sass::SyntaxError.new("Function #{@name} finished without @return")
    end
    val
  end
end

def to_literal(args)
  Script::String.new("#{name}(#{args.join(', ')})")
end

def to_sass(opts = {})
  arg_to_sass = lambda do |arg|
    sass = arg.to_sass(opts)
    sass = "(#{sass})" if arg.is_a?(Sass::Script::List) && arg.separator == :comma
    sass
  end
  args = @args.map(&arg_to_sass).join(', ')
  keywords = Sass::Util.hash_to_a(@keywords).
    map {|k, v| "$#{dasherize(k, opts)}: #{arg_to_sass[v]}"}.join(', ')
  if self.splat
    splat = (args.empty? && keywords.empty?) ? "" : ", "
    splat = "#{splat}#{arg_to_sass[self.splat]}..."
  end
  "#{dasherize(name, opts)}(#{args}#{', ' unless args.empty? || keywords.empty?}#{keywords}#{splat})"
end