{config, pkgs, ...}:
# TODO: this file need some make-up (Nicolas Pierron)

with pkgs.lib;

let
  kernelPackages = config.boot.kernelPackages;
  # List of font directories.
  fontDirectories = config.fonts.fonts;

  options = {
    services = {

      xserver = {

        enable = mkOption {
          default = false;
          description = "
            Whether to enable the X server.
          ";
        };

        autorun = mkOption {
          default = true;
          description = "
            Switch to false to create upstart-job and configuration, 
            but not run it automatically
          ";
        };

        exportConfiguration = mkOption {
          default = false;
          description = "
            Create /etc/X11/xorg.conf and a file with environment
            variables
          ";
        };

        tcpEnable = mkOption {
          default = false;
          description = "
            Whether to enable TCP socket for the X server.
          ";
        };

        resolutions = mkOption {
          default = [{x = 1024; y = 768;} {x = 800; y = 600;} {x = 640; y = 480;}];
          description = "
            The screen resolutions for the X server.  The first element is the default resolution.
          ";
        };

        videoDriver = mkOption {
          default = "vesa";
          example = "i810";
          description = "
            The name of the video driver for your graphics card.
          ";
        };

        driSupport = mkOption {
          default = false;
          description = "
            Whether to enable accelerated OpenGL rendering through the
            Direct Rendering Interface (DRI).
          ";
        };

/*
        sessionType = mkOption {
          default = "gnome";
          example = "xterm";
          description = "
            The kind of session to start after login.  Current possibilies
            are <literal>kde</literal> (which starts KDE),
            <literal>gnome</literal> (which starts
            <command>gnome-terminal</command>) and <literal>xterm</literal>
            (which starts <command>xterm</command>).
          ";
        };

        windowManager = mkOption {
          default = "";
          description = "
            This option selects the window manager.  Available values are
            <literal>twm</literal> (extremely primitive),
            <literal>metacity</literal>, <literal>xmonad</literal>
            and <literal>compiz</literal>.  If
            left empty, the <option>sessionType</option> determines the
            window manager, e.g., Metacity for Gnome, and
            <command>kwm</command> for KDE.
          ";
        };

        sessionStarter = mkOption {
          example = "${pkgs.xterm}/bin/xterm -ls";
          description = "
            The command executed after login and after the window manager
            has been started.  Used if
            <option>services.xserver.sessionType</option> is empty.
          ";
        };
*/

        startSSHAgent = mkOption {
          default = true;
          description = "
            Whether to start the SSH agent when you log in.  The SSH agent
            remembers private keys for you so that you don't have to type in
            passphrases every time you make an SSH connection.  Use
            <command>ssh-add</command> to add a key to the agent.
          ";
        };

        isClone = mkOption {
          default = true;
          example = false;
          description = "
            Whether to enable the X server clone mode for dual-head.
          ";
        };

        synaptics = {
          enable = mkOption {
            default = false;
            example = true;
            description = "
              Whether to replace mouse with touchpad.
            ";
          };
          dev = mkOption {
            default = "/dev/input/event0";
            description = "
              Event device for Synaptics touchpad.
            ";
          };
          minSpeed = mkOption {
            default = "0.06";
            description = "Cursor speed factor for precision finger motion";
          };
          maxSpeed = mkOption {
            default = "0.12";
            description = "Cursor speed factor for highest-speed finger motion";
          };
          twoFingerScroll = mkOption {
            default = false;
            description = "Whether to enable two-finger drag-scrolling";
          };
        };

        layout = mkOption {
          default = "us";
          description = "
            Keyboard layout.
          ";
        };

        xkbModel = mkOption {
          default = "pc104";
          example = "presario";
          description = "
            Keyboard model.
          ";
        };

        xkbOptions = mkOption {
          default = "";
          example = "grp:caps_toggle, grp_led:scroll";
          description = "
            X keyboard options; layout switching goes here.
          ";
        };

        useInternalAGPGART = mkOption {
          default = "";
          example = "no";
          description = "
            Just the wrapper for an xorg.conf option.
          ";
        };

        extraDeviceConfig = mkOption {
          default = "";
          example = "VideoRAM 131072";
          description = "
            Just anything to add into Device section.
          ";
        };

        extraMonitorSettings = mkOption {
          default = "";
          example = "HorizSync 28-49";
          description = "
            Just anything to add into Monitor section.
          ";
        };

        extraDisplaySettings = mkOption {
          default = "";
          example = "Virtual 2048 2048";
          description = "
            Just anything to add into Display subsection (located in Screen section).
          ";
        };
   
        extraModules = mkOption {
          default = "";
          example = "
            SubSection \"extmod\"
            EndSubsection
          ";
          description = "
            Just anything to add into Modules section.
          ";
        };

        serverLayoutOptions = mkOption {
          default = "";
          example = "
            Option \"AIGLX\" \"true\"
          ";
          description = "
            Just anything to add into Monitor section.
          ";
        };

        defaultDepth = mkOption {
          default = 24;
          example = 8;
          description = "
            Default colour depth.
          ";
        };
        
        useXFS = mkOption {
          default = false;
          example = "unix/:7100";
          description = "
            Way to access the X Font Server to use.
          ";
        };

        tty = mkOption {
          default = 7;
          example = 9;
          description = "
            Virtual console for the X server.
          ";
        };

        display = mkOption {
          default = 0;
          example = 1;
          description = "
            Display number for the X server.
          ";
        };

        package = mkOption {
          default = pkgs.xorg;
          description = "
            Alternative X.org package to use. For 
            example, you can replace individual drivers.
          ";
        };

        virtualScreen = mkOption {
          default = null;
          example = {
            x=2048;
            y=2048;
          };
          description = "
            Virtual screen size for Xrandr
          ";
        };
      };

    };
  };
in

let

  # Abbreviations.
  cfg = config.services.xserver;
  xorg = cfg.package;
  stdenv = pkgs.stdenv;

  knownVideoDrivers = {
    nvidia = { modulesFirst = [ kernelPackages.nvidia_x11 ]; };  #make sure it first loads the nvidia libs
    vesa =   { modules = [xorg.xf86videovesa]; };
    vga =    { modules = [xorg.xf86videovga]; };
    sis =    { modules = [xorg.xf86videosis]; };
    i810 =   { modules = [xorg.xf86videoi810]; };
    intel =  { modules = [xorg.xf86videointel]; };
    nv =     { modules = [xorg.xf86videonv]; };
    ati =    { modules = [xorg.xf86videoati]; };
    via =    { modules = [xorg.xf86videovia]; };
    cirrus = { modules = [xorg.xf86videocirrus]; };
  };

  # Get a bunch of user settings.
  videoDriver = cfg.videoDriver;
  resolutions = map (res: ''"${toString res.x}x${toString res.y}"'') (cfg.resolutions);

  videoDriverModules = attrByPath [videoDriver] (throw "unknown video driver: `${videoDriver}'") knownVideoDrivers;

  modules = 
    attrByPath ["modulesFirst"] [] videoDriverModules
    ++ [
      xorg.xorgserver
      xorg.xf86inputevdev
    ] 
    ++ attrByPath ["modules"] [] videoDriverModules
    ++ (optional cfg.synaptics.enable ["${xorg.xf86inputsynaptics}"]);


  fontsForXServer =
    fontDirectories ++
    # We don't want these fonts in fonts.conf, because then modern,
    # fontconfig-based applications will get horrible bitmapped
    # Helvetica fonts.  It's better to get a substitution (like Nimbus
    # Sans) than that horror.  But we do need the Adobe fonts for some
    # old non-fontconfig applications.  (Possibly this could be done
    # better using a fontconfig rule.)
    [ pkgs.xorg.fontadobe100dpi
      pkgs.xorg.fontadobe75dpi
    ];
    

  configFile = stdenv.mkDerivation {
    name = "xserver.conf";
    src = ./xserver.conf;
    inherit fontsForXServer videoDriver resolutions;
    isClone = if cfg.isClone then "on" else "off";

    synapticsInputDevice = if cfg.synaptics.enable then ''
      Section "InputDevice"
        Identifier "Touchpad[0]"
        Driver "synaptics"
        Option "Device" "${cfg.synaptics.dev}"
        Option "Protocol" "PS/2"
        Option "LeftEdge" "1700"
        Option "RightEdge" "5300"
        Option "TopEdge" "1700"
        Option "BottomEdge" "4200"
        Option "FingerLow" "25"
        Option "FingerHigh" "30"
        Option "MaxTapTime" "180"
        Option "MaxTapMove" "220"
        Option "VertScrollDelta" "100"
        Option "MinSpeed" "${cfg.synaptics.minSpeed}"
        Option "MaxSpeed" "${cfg.synaptics.maxSpeed}"
        Option "AccelFactor" "0.0010"
        Option "SHMConfig" "on"
        Option "Repeater" "/dev/input/mice"
        Option "TapButton1" "1"
        Option "TapButton2" "2"
        Option "TapButton3" "3"
        Option "VertTwoFingerScroll" "${if cfg.synaptics.twoFingerScroll then "1" else "0"}"
        Option "HorizTwoFingerScroll" "${if cfg.synaptics.twoFingerScroll then "1" else "0"}"
      EndSection
    '' else "";

    xkbOptions = if cfg.xkbOptions == "" then "" else  ''
      Option "XkbOptions" "${cfg.xkbOptions}"
    '';

    setCorePointer = 
      if cfg.synaptics.enable then ''
        InputDevice "Touchpad[0]" "CorePointer"
      '' else "";

    internalAGPGART =
      if cfg.useInternalAGPGART == "yes" then
        ''  Option "UseInternalAGPGART" "yes"''
      else if cfg.useInternalAGPGART == "no" then
        ''  Option "UseInternalAGPGART" "no"''
      else "";

    extraDeviceConfig = cfg.extraDeviceConfig; 
    extraMonitorSettings = cfg.extraMonitorSettings; 
    extraDisplaySettings = cfg.extraDisplaySettings;
    extraModules = cfg.extraModules; 
    serverLayoutOptions = cfg.serverLayoutOptions; 
    defaultDepth = cfg.defaultDepth; 
    virtualScreen = if cfg.virtualScreen != null then 
        "Virtual ${toString cfg.virtualScreen.x} ${toString cfg.virtualScreen.y}" 
      else "";

    xfs = if cfg.useXFS == false then "" else 
      ''FontPath "${toString cfg.useXFS}"'';

    buildCommand = ''
      buildCommand= # urgh, don't substitute this

      export fontPaths=
      for i in $fontsForXServer; do
        if test "''${i:0:''${#NIX_STORE}}" == "$NIX_STORE"; then
          for j in $(find $i -name fonts.dir); do
            fontPaths="''${fontPaths}FontPath \"$(dirname $j)\"''\n"
          done
        fi
      done

      export modulePaths=
      for i in $(find ${toString modules} -type d); do
        if ls $i/*.so* > /dev/null 2>&1; then
          modulePaths="''${modulePaths}ModulePath \"$i\"''\n"
        fi
      done

      export moduleSection=""
      export screen=""
      export device=""
      export extensions=""


      #if only my gf were this dirty
      if test "${toString videoDriver}" == "nvidia"; then
        export screen='
          Option "AddARGBGLXVisuals" "true"
          Option "DisableGLXRootClipping" "true"
          Option "RandRRotation" "on"
        '
        
        export device='
          Option "RenderAccel" "true"
          Option "AllowGLXWithComposite" "true"
          Option "AddARGBGLXVisuals" "true"
        '
        
        export extensions='
          Option "Composite" "Enable"
        '
      fi
        
      if [ "${toString videoDriver}" = i810 ]; then
        export extensions='
          Option "Composite" "Enable"
        ';
      fi;

      if [ "${toString videoDriver}" = ati ]; then
        export extensions='
          Option "Composite" "Enable"
        ';
      fi;

      if [ "${toString videoDriver}" = radeonhd ]; then
        export extensions='
          Option "Composite" "Enable"
        ';
      fi;

      substituteAll $src $out
    ''; # */
  };



in

mkIf cfg.enable {

  assertions = [ { assertion = config.services.hal.enable == true; message = "The X server needs HAL running. Set services.hal.enable to true"; } ];

  require = [
    options

    # services.xserver.*Manager
    ./display-managers/default.nix
    ./window-managers/default.nix
    ./desktop-managers/default.nix

    # services.extraJobs
    # ../../upstart-jobs/default.nix

    # environment.etc
    # ../../etc/default.nix

    # fonts.fonts
    # ../../system/fonts.nix

    # boot.extraModulePackages
    # security.extraSetuidPrograms
    # environment.extraPackages
  ];

  boot = {
    extraModulePackages = mkIf (cfg.videoDriver == "nvidia") [
      kernelPackages.nvidia_x11
    ];
  };

  environment = {
    etc = mkIf cfg.exportConfiguration [
      { source = "${configFile}";
        target = "X11/xorg.conf";
      }
      # -xkbdir command line option does not seems to be passed to xkbcomp.
      { source = "${pkgs.xkeyboard_config}/etc/X11/xkb";
        target = "X11/xkb";
      }
    ];

    extraPackages = [
      xorg.xrandr
      xorg.xrdb
      xorg.setxkbmap
      xorg.iceauth # required for KDE applications (it's called by dcopserver)
    ]
    ++ optional (videoDriver == "nvidia") [
      kernelPackages.nvidia_x11
    ];
  };

  services = {
    xserver = {
      displayManager = {
        xserverArgs = [
          "-ac"
          "-logverbose"
          "-verbose"
          "-terminate"
          "-logfile" "/var/log/X.${toString cfg.display}.log"
          "-config ${configFile}"
          ":${toString cfg.display}" "vt${toString cfg.tty}"
          "-xkbdir" "${pkgs.xkeyboard_config}/etc/X11/xkb"
        ] ++ optional (!cfg.tcpEnable) "-nolisten tcp";
      };
    };

    extraJobs = [{
      name = "xserver";
      job = ''
        start on ${if cfg.autorun then "hal" else "never"}

        start script
        
          rm -f /var/run/opengl-driver
          ${if videoDriver == "nvidia"
            then ''
              ln -sf ${kernelPackages.nvidia_x11} /var/run/opengl-driver
            ''
            else if cfg.driSupport
            then "ln -sf ${pkgs.mesa} /var/run/opengl-driver"
            else ""
           }

          ${cfg.displayManager.job.beforeScript}

          rm -f /tmp/.X0-lock

        end script

        ${cfg.displayManager.job.env}
        env FONTCONFIG_FILE=/etc/fonts/fonts.conf # !!! cleanup
        env XKB_BINDIR=${xorg.xkbcomp}/bin # Needed for the Xkb extension.

        ${if videoDriver == "nvidia" 
          then "env LD_LIBRARY_PATH=${xorg.libX11}/lib:${xorg.libXext}/lib:${kernelPackages.nvidia_x11}/lib"
          else ""
        }

        ${if videoDriver != "nvidia"
          then "env XORG_DRI_DRIVER_PATH=${pkgs.mesa}/lib/dri"
          else ""
        }

        exec ${cfg.displayManager.job.execCmd}
      '';
    }];
  };
}