{ config, lib, pkgs, ... }:

with lib;

let
  cfg = config.programs.phosh;

  # Based on https://source.puri.sm/Librem5/librem5-base/-/blob/4596c1056dd75ac7f043aede07887990fd46f572/default/sm.puri.OSK0.desktop
  oskItem = pkgs.makeDesktopItem {
    name = "sm.puri.OSK0";
    type = "Application";
    desktopName = "On-screen keyboard";
    exec = "${pkgs.squeekboard}/bin/squeekboard";
    categories = "GNOME;Core;";
    extraEntries = ''
      OnlyShowIn=GNOME;
      NoDisplay=true
      X-GNOME-Autostart-Phase=Panel
      X-GNOME-Provides=inputmethod
      X-GNOME-Autostart-Notify=true
      X-GNOME-AutoRestart=true
    '';
  };

  phocConfigType = types.submodule {
    options = {
      xwayland = mkOption {
        description = ''
          Whether to enable XWayland support.

          To start XWayland immediately, use `immediate`.
        '';
        type = types.enum [ "true" "false" "immediate" ];
        default = "false";
      };
      cursorTheme = mkOption {
        description = ''
          Cursor theme to use in Phosh.
        '';
        type = types.str;
        default = "default";
      };
      outputs = mkOption {
        description = ''
          Output configurations.
        '';
        type = types.attrsOf phocOutputType;
        default = {
          DSI-1 = {
            scale = 2;
          };
        };
      };
    };
  };

  phocOutputType = types.submodule {
    options = {
      modeline = mkOption {
        description = ''
          One or more modelines.
        '';
        type = types.either types.str (types.listOf types.str);
        default = [];
        example = [
          "87.25 720 776 848  976 1440 1443 1453 1493 -hsync +vsync"
          "65.13 768 816 896 1024 1024 1025 1028 1060 -HSync +VSync"
        ];
      };
      mode = mkOption {
        description = ''
          Default video mode.
        '';
        type = types.nullOr types.str;
        default = null;
        example = "768x1024";
      };
      scale = mkOption {
        description = ''
          Display scaling factor.
        '';
        type = types.nullOr types.ints.unsigned;
        default = null;
        example = 2;
      };
      rotate = mkOption {
        description = ''
          Screen transformation.
        '';
        type = types.enum [
          "90" "180" "270" "flipped" "flipped-90" "flipped-180" "flipped-270" null
        ];
        default = null;
      };
    };
  };

  optionalKV = k: v: if v == null then "" else "${k} = ${builtins.toString v}";

  renderPhocOutput = name: output: let
    modelines = if builtins.isList output.modeline
      then output.modeline
      else [ output.modeline ];
    renderModeline = l: "modeline = ${l}";
  in ''
    [output:${name}]
    ${concatStringsSep "\n" (map renderModeline modelines)}
    ${optionalKV "mode" output.mode}
    ${optionalKV "scale" output.scale}
    ${optionalKV "rotate" output.rotate}
  '';

  renderPhocConfig = phoc: let
    outputs = mapAttrsToList renderPhocOutput phoc.outputs;
  in ''
    [core]
    xwayland = ${phoc.xwayland}
    ${concatStringsSep "\n" outputs}
    [cursor]
    theme = ${phoc.cursorTheme}
  '';
in {
  options = {
    programs.phosh = {
      enable = mkEnableOption ''
        Whether to enable, Phosh, related packages and default configurations.
      '';
      phocConfig = mkOption {
        description = ''
          Configurations for the Phoc compositor.
        '';
        type = types.oneOf [ types.lines types.path phocConfigType ];
        default = {};
      };
    };
  };

  config = mkIf cfg.enable {
    environment.systemPackages = [
      pkgs.phoc
      pkgs.phosh
      pkgs.squeekboard
      oskItem
    ];

    programs.feedbackd.enable = true;

    # https://source.puri.sm/Librem5/phosh/-/issues/303
    security.pam.services.phosh = {
      text = ''
        auth    requisite       pam_nologin.so
        auth    required        pam_succeed_if.so user != root quiet_success
        auth    required        pam_securetty.so
        auth    requisite       pam_nologin.so
      '';
    };

    services.gnome3.core-shell.enable = true;
    services.gnome3.core-os-services.enable = true;
    services.xserver.displayManager.sessionPackages = [ pkgs.phosh ];

    environment.etc."phosh/phoc.ini".source =
      if builtins.isPath cfg.phocConfig then cfg.phocConfig
      else if builtins.isString cfg.phocConfig then pkgs.writeText "phoc.ini" cfg.phocConfig
      else pkgs.writeText "phoc.ini" (renderPhocConfig cfg.phocConfig);
  };
}