require 'sass/script/functions'

module Sass
  module Script
    # A SassScript parse node representing a function call.
    #
    # A function call either calls one of the functions in {Script::Functions},
    # or if no function with the given name exists
    # it returns a string representation of the function call.
    class Funcall < Node
      # The name of the function.
      #
      # @return [String]
      attr_reader :name

      # The arguments to the function.
      #
      # @return [Array<Script::Node>]
      attr_reader :args

      # The keyword arguments to the function.
      #
      # @return [{String => Script::Node}]
      attr_reader :keywords

      # The splat argument for this function, if one exists.
      #
      # @return [Script::Node?]
      attr_accessor :splat

      # @param name [String] See \{#name}
      # @param args [Array<Script::Node>] See \{#args}
      # @param splat [Script::Node] See \{#splat}
      # @param keywords [{String => Script::Node}] See \{#keywords}
      def initialize(name, args, keywords, splat)
        @name = name
        @args = args
        @keywords = keywords
        @splat = splat
        super()
      end

      # @return [String] A string representation of the function call
      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

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

      # Returns the arguments to the function.
      #
      # @return [Array<Node>]
      # @see Node#children
      def children
        res = @args + @keywords.values
        res << @splat if @splat
        res
      end

      # @see Node#deep_copy
      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

      protected

      # Evaluates the function call.
      #
      # @param environment [Sass::Environment] The environment in which to evaluate the SassScript
      # @return [Literal] The SassScript object that is the value of the function call
      # @raise [Sass::SyntaxError] if the function call raises an ArgumentError
      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

      # This method is factored out from `_perform` so that compass can override
      # it with a cross-browser implementation for functions that require vendor prefixes
      # in the generated css.
      def to_literal(args)
        Script::String.new("#{name}(#{args.join(', ')})")
      end

      private

      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 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
    end
  end
end