# nixos module to fully configure mhs35 support both in kernel and userland.
{
  config,
  lib,
  ...
}:

let
  inherit (lib)
    mkEnableOption
    mkIf
    mkOption
    optional
    types
    ;

  cfg = config.hardware.mhs35;

  mhs35-module = config.boot.kernelPackages.callPackage ./package.nix { };

  # just replace the text to avoid messing with merging device trees,
  # it's just simpler this way... :)
  panelDts = builtins.replaceStrings
    [ "rotation = <180>" "spi-max-frequency = <8000000>" ]
    [
      "rotation = <${toString cfg.rotation}>"
      "spi-max-frequency = <${toString cfg.spiFrequencyHz}>"
    ]
    (builtins.readFile ./dts/mhs35-overlay.dts);

  # touch matrices for panel. (libinput)
  # TODO(mel): 90 & 270 are missing, but are of course supported.
  # let's write the matrix out for them, too!
  defaultMatrices = {
    "0" = "0 1 0 -1 0 1";
    "180" = "0 -1 1 1 0 0";
  };
in
{
  options.hardware.mhs35 = {
    enable = mkEnableOption "goodtft MHS-3.5 SPI display support";

    rotation = mkOption {
      type = types.enum [ 0 90 180 270 ];
      default = 180;
      description = ''
        The panel rotation.
      '';
      # orientations (for pi4, when looking at screen upright):
      # * 0 - landscape, usb/rj-45 ports on the left
      # * 90 - portrait, ports on top
      # * 180 - landscape, ports on the right
      # * 270 - portrait, ports on bottom
    };

    spiFrequencyHz = mkOption {
      type = types.ints.positive;
      default = 8000000;
      description = ''
        Panel SPI frequency.
        8 MHz is the very very conservative default, the panel
        claims to support upto 125MHz.
      '';
    };

    touch = {
      enable = mkEnableOption "MHS-3.5 ADS7846 touch support" // {
        default = true;
      };

      calibrationMatrix = mkOption {
        type = types.nullOr types.str;
        default = defaultMatrices.${toString cfg.rotation} or null;
        description = ''
          Touch calibration matrix for touchscreen (libinput).
          Set as LIBINPUT_CALIBRATION_MATRIX in udev.
        '';
      };
    };
  };

  config = mkIf cfg.enable {
    assertions = [
      {
        assertion = !cfg.touch.enable || cfg.touch.calibrationMatrix != null;
        message = ''
          hardware.mhs35: no known touch calibration matrix for
          rotation ${toString cfg.rotation}!
          set `hardware.mhs35.touch.calibrationMatrix` explicitly.
          (and consider contributing the matrix! :3)
        '';
      }
    ];

    boot.extraModulePackages = [ mhs35-module ];

    # do not let the default in-tree ili9486 win control over our device!
    # (it also lists compatibility with "waveshare,rpi-lcd-35")
    boot.blacklistedKernelModules = [ "ili9486" ];

    hardware.deviceTree.overlays = [
      {
        name = "mhs35-overlay";
        dtsText = panelDts;
      }
    ] ++ optional cfg.touch.enable {
      name = "mhs35-touch-overlay";
      dtsFile = ./dts/mhs35-touch-overlay.dts;
    };

    services.libinput.enable = mkIf cfg.touch.enable true;

    services.udev.extraRules = mkIf cfg.touch.enable ''
      ATTRS{name}=="ADS7846 Touchscreen", ENV{LIBINPUT_CALIBRATION_MATRIX}="${cfg.touch.calibrationMatrix}"
    '';
  };
}