require 'gir_ffi/builders/argument_builder'
require 'gir_ffi/builders/return_value_builder'
require 'gir_ffi/builders/error_argument_builder'
require 'gir_ffi/builders/null_argument_builder'
require 'gir_ffi/variable_name_generator'

module GirFFI
  module Builders
    # Implements the creation of a Ruby function definition out of a GIR
    # IFunctionInfo.
    class FunctionBuilder
      def initialize info
        @info = info
      end

      def generate
        vargen = GirFFI::VariableNameGenerator.new
        @argument_builders = @info.args.map {|arg| ArgumentBuilder.new vargen, arg }
        @return_value_builder = ReturnValueBuilder.new(vargen,
                                                       @info.return_type,
                                                       @info.constructor?,
                                                       @info.skip_return?)

        link_array_length_arguments
        setup_error_argument vargen
        return filled_out_template
      end

      private

      def libmodule
        Object.const_get(@info.safe_namespace)::Lib
      end

      def link_array_length_arguments
        alldata = @argument_builders.dup << @return_value_builder

        alldata.each {|data|
          idx = data.type_info.array_length
          if idx > -1
            other_data = @argument_builders[idx]
            data.length_arg = other_data
            other_data.array_arg = data
          end
        }
      end

      def setup_error_argument vargen
        klass = @info.throws? ? ErrorArgumentBuilder : NullArgumentBuilder
        @errarg = klass.new vargen, nil, nil, :error
      end

      def filled_out_template
        meta = @info.method? ? '' : "self."

        code = "def #{meta}#{@info.safe_name} #{method_arguments.join(', ')}\n"
        code << method_body
        code << "\nend\n"
      end

      def method_body
        lines = preparation << function_call << post_processing << cleanup
        lines << "return #{return_values.join(', ')}" if has_return_values?
        lines.flatten.join("\n").indent
      end

      def function_call
        "#{capture}#{libmodule}.#{@info.symbol} #{function_call_arguments.join(', ')}"
      end

      def method_arguments
        @argument_builders.map(&:inarg).compact
      end

      def function_call_arguments
        ca = @argument_builders.map(&:callarg)
        ca << @errarg.callarg
        ca.unshift "self" if @info.method?
        ca.compact
      end

      def preparation
        pr = @argument_builders.map(&:pre)
        pr << @errarg.pre
        pr.flatten
      end

      def capture
        if has_capture?
          "#{@return_value_builder.callarg} = "
        else
          ""
        end
      end

      def post_processing
        # FIXME: Sorting knows too much about internals of ArgumentBuilder.
        args = @argument_builders.sort_by {|arg| arg.type_info.array_length}
        args << @return_value_builder
        args.unshift @errarg

        args.map {|arg| arg.post}
      end

      def cleanup
        @argument_builders.map {|item| item.cleanup}
      end

      def return_values
        @return_values ||= ([@return_value_builder.retval] +
                            @argument_builders.map(&:retval)).compact
      end

      def has_return_values?
        !return_values.empty?
      end

      def has_capture?
        @return_value_builder.is_relevant?
      end
    end
  end
end