require 'tempfile'

module FFI
  class TypesGenerator

    ##
    # Maps different C types to the C type representations we use

    TYPE_MAP = {
               "char" => :char,
        "signed char" => :char,
      "__signed char" => :char,
      "unsigned char" => :uchar,

               "short"     => :short,
        "signed short"     => :short,
        "signed short int" => :short,
      "unsigned short"     => :ushort,
      "unsigned short int" => :ushort,

               "int" => :int,
        "signed int" => :int,
      "unsigned int" => :uint,

               "long" => :long,
               "long int" => :long,
        "signed long" => :long,
        "signed long int" => :long,
      "unsigned long" => :ulong,
      "unsigned long int" => :ulong,
      "long unsigned int" => :ulong,

               "long long"     => :long_long,
               "long long int" => :long_long,
        "signed long long"     => :long_long,
        "signed long long int" => :long_long,
      "unsigned long long"     => :ulong_long,
      "unsigned long long int" => :ulong_long,

      "char *" => :string,
      "void *" => :pointer,
    }

    def self.generate(options = {})
      typedefs = nil
      Tempfile.open 'ffi_types_generator' do |io|
        io.puts <<-C
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/resource.h>
        C

        io.close
        typedefs = `gcc -E -x c #{options[:cppflags]} -D_DARWIN_USE_64_BIT_INODE -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -c #{io.path}`
      end
      
      code = ""

      typedefs.each do |type|
        # We only care about single line typedef
        next unless type =~ /typedef/
        # Ignore unions or structs
        next if type =~ /union|struct/
        
        # strip off the starting typedef and ending ;
        type.gsub!(/^(.*typedef\s*)/, "")
        type.gsub!(/\s*;\s*$/, "")
    
        parts = type.split(/\s+/)
        def_type   = parts.join(" ")

        # GCC does mapping with __attribute__ stuf, also see
        # http://hal.cs.berkeley.edu/cil/cil016.html section 16.2.7.  Problem
        # with this is that the __attribute__ stuff can either occur before or
        # after the new type that is defined...
        if type =~ /__attribute__/
          if parts.last =~ /__QI__|__HI__|__SI__|__DI__|__word__/

            # In this case, the new type is BEFORE __attribute__ we need to
            # find the final_type as the type before the part that starts with
            # __attribute__
            final_type = ""
            parts.each do |p|
              break if p =~ /__attribute__/
              final_type = p
            end
          else
            final_type = parts.pop
          end
          
          def_type = case type
                     when /__QI__/   then "char"
                     when /__HI__/   then "short"
                     when /__SI__/   then "int"
                     when /__DI__/   then "long long"
                     when /__word__/ then "long"
                     else                 "int"
                     end

          def_type = "unsigned #{def_type}" if type =~ /unsigned/
        else
          final_type = parts.pop
          def_type   = parts.join(" ")
        end
        
        if type = TYPE_MAP[def_type]
          code << "rbx.platform.typedef.#{final_type} = #{type}\n"
          TYPE_MAP[final_type] = TYPE_MAP[def_type]
        else
          # Fallback to an ordinary pointer if we don't know the type
          if def_type =~ /\*/
            code << "rbx.platform.typedef.#{final_type} = pointer\n"
            TYPE_MAP[final_type] = :pointer
          end
        end
      end

      code
    end

  end
end

