require 'rbconfig'
require 'rubygems/version'

module Qt
  class NotInstalledError < StandardError; end

  class Qmake
    class << self
      QMAKES = %w{qmake-qt4 qmake}

      def installed?
        path != nil
      end

      def make_installed?
        make_path != nil
      end

      def command
        case platform
        when :linux
          "#{path} -spec linux-g++"
        when :freebsd
          "#{path} -spec freebsd-g++"
        when :mac_os_x
          "#{path} -spec macx-g++"
        end
      end

      def make!(name)
        @name = name

        check_make!
        check_qmake!

        system command
        system %{make}
      end

      #
      # We need integration tests for these!
      #
      def path
        @path ||= best_qmake
      end

      def make_path
         get_exe_path('gmake') || get_exe_path('make')
      end

      def platform
        case RbConfig::CONFIG['host_os']
        when /linux/
          :linux
	when /freebsd/i
	  :freebsd
        when /darwin/
          :mac_os_x
        end
      end

      def qt_version_of(qmake_path)
        Gem::Version.new(%x{#{qmake_path} -v}.lines.to_a[1][%r{Using Qt version ([^ ]+) },1])
      end

      def best_qmake
        if qmake_path = QMAKES.collect do |path|
          result = nil
          if qmake_path = get_exe_path(path)
            if (qt_version = qt_version_of(qmake_path)) >= Gem::Version.create('4.7')
              result = [ qmake_path, qt_version ]
            end
          end
          result
        end.compact.sort { |a, b| b.last <=> a.last }.first
          qmake_path.first
        else
          nil
        end
      end

      private
      def get_exe_path(command)
        path = %x{which #{command}}.strip
        path = nil if path == ''
        path
      end

      def check_make!
        if !make_installed?
          install_method = (
            case platform
            when :linux
              %{sudo apt-get install make or sudo yum install make}
            when :freebsd
              %{install /usr/ports/devel/gmake}
            when :darwin
              %{Install XCode, and/or sudo port install make}
            end
          )

          $stderr.puts <<-MSG
make is not installed. You'll need to install it to build #{@name}.
#{install_method} should do it for you.
MSG
          raise NotInstalledError
        end
      end

      def check_qmake!
        if !installed?
          install_method = (
            case platform
            when :linux
              <<-MSG
sudo apt-get install libqt4-dev qt4-qmake on Debian-based systems, or downloading
Nokia's prebuilt binary at http://qt.nokia.com/downloads/
MSG
            when :freebsd
              <<-MSG
Install /usr/ports/www/qt4-webkit and /usr/ports/devel/qmake4.
MSG
            when :darwin
              <<-MSG
sudo port install qt4-mac (for the patient) or downloading Nokia's pre-built binary
at http://qt.nokia.com/downloads/
MSG
            end
          ).strip

          $stderr.puts <<-MSG
qmake is not installed or is not the right version (#{@name} needs Qt 4.7 or above). 
You'll need to install it to build #{@name}.
#{install_method} should do it for you.
MSG
        end
      end
    end
  end
end