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

with lib;

let
  cfg = config.hardware.deviceTree;

  overlayType = types.submodule {
    options = {
      name = mkOption {
        type = types.str;
        description = lib.mdDoc ''
          Name of this overlay
        '';
      };

      filter = mkOption {
        type = types.nullOr types.str;
        default = null;
        example = "*rpi*.dtb";
        description = lib.mdDoc ''
          Only apply to .dtb files matching glob expression.
        '';
      };

      dtsFile = mkOption {
        type = types.nullOr types.path;
        description = lib.mdDoc ''
          Path to .dts overlay file, overlay is applied to
          each .dtb file matching "compatible" of the overlay.
        '';
        default = null;
        example = literalExpression "./dts/overlays.dts";
      };

      dtsText = mkOption {
        type = types.nullOr types.str;
        default = null;
        description = lib.mdDoc ''
          Literal DTS contents, overlay is applied to
          each .dtb file matching "compatible" of the overlay.
        '';
        example = ''
          /dts-v1/;
          /plugin/;
          / {
                  compatible = "raspberrypi";
          };
          &{/soc} {
                  pps {
                          compatible = "pps-gpio";
                          status = "okay";
                  };
          };
        '';
      };

      dtboFile = mkOption {
        type = types.nullOr types.path;
        default = null;
        description = lib.mdDoc ''
          Path to .dtbo compiled overlay file.
        '';
      };
    };
  };

  filterDTBs = src: if cfg.filter == null
    then src
    else
      pkgs.runCommand "dtbs-filtered" {} ''
        mkdir -p $out
        cd ${src}
        find . -type f -name '${cfg.filter}' -print0 \
          | xargs -0 cp -v --no-preserve=mode --target-directory $out --parents
      '';

  filteredDTBs = filterDTBs cfg.dtbSource;

  # Fill in `dtboFile` for each overlay if not set already.
  # Existence of one of these is guarded by assertion below
  withDTBOs = xs: flip map xs (o: o // { dtboFile =
    let
      includePaths = ["${getDev cfg.kernelPackage}/lib/modules/${cfg.kernelPackage.modDirVersion}/source/scripts/dtc/include-prefixes"] ++ cfg.dtboBuildExtraIncludePaths;
      extraPreprocessorFlags = cfg.dtboBuildExtraPreprocessorFlags;
    in
    if o.dtboFile == null then
      let
        dtsFile = if o.dtsFile == null then (pkgs.writeText "dts" o.dtsText) else o.dtsFile;
      in
      pkgs.deviceTree.compileDTS {
        name = "${o.name}-dtbo";
        inherit includePaths extraPreprocessorFlags dtsFile;
      }
    else o.dtboFile; } );

in
{
  imports = [
    (mkRemovedOptionModule [ "hardware" "deviceTree" "base" ] "Use hardware.deviceTree.kernelPackage instead")
  ];

  options = {
      hardware.deviceTree = {
        enable = mkOption {
          default = pkgs.stdenv.hostPlatform.linux-kernel.DTB or false;
          type = types.bool;
          description = lib.mdDoc ''
            Build device tree files. These are used to describe the
            non-discoverable hardware of a system.
          '';
        };

        kernelPackage = mkOption {
          default = config.boot.kernelPackages.kernel;
          defaultText = literalExpression "config.boot.kernelPackages.kernel";
          example = literalExpression "pkgs.linux_latest";
          type = types.path;
          description = lib.mdDoc ''
            Kernel package where device tree include directory is from. Also used as default source of dtb package to apply overlays to
          '';
        };

        dtboBuildExtraPreprocessorFlags = mkOption {
          default = [];
          example = literalExpression "[ \"-DMY_DTB_DEFINE\" ]";
          type = types.listOf types.str;
          description = lib.mdDoc ''
            Additional flags to pass to the preprocessor during dtbo compilations
          '';
        };

        dtboBuildExtraIncludePaths = mkOption {
          default = [];
          example = literalExpression ''
            [
              ./my_custom_include_dir_1
              ./custom_include_dir_2
            ]
          '';
          type = types.listOf types.path;
          description = lib.mdDoc ''
            Additional include paths that will be passed to the preprocessor when creating the final .dts to compile into .dtbo
          '';
        };

        dtbSource = mkOption {
          default = "${cfg.kernelPackage}/dtbs";
          defaultText = literalExpression "\${cfg.kernelPackage}/dtbs";
          type = types.path;
          description = lib.mdDoc ''
            Path to dtb directory that overlays and other processing will be applied to. Uses
            device trees bundled with the Linux kernel by default.
          '';
        };

        name = mkOption {
          default = null;
          example = "some-dtb.dtb";
          type = types.nullOr types.str;
          description = lib.mdDoc ''
            The name of an explicit dtb to be loaded, relative to the dtb base.
            Useful in extlinux scenarios if the bootloader doesn't pick the
            right .dtb file from FDTDIR.
          '';
        };

        filter = mkOption {
          type = types.nullOr types.str;
          default = null;
          example = "*rpi*.dtb";
          description = lib.mdDoc ''
            Only include .dtb files matching glob expression.
          '';
        };

        overlays = mkOption {
          default = [];
          example = literalExpression ''
            [
              { name = "pps"; dtsFile = ./dts/pps.dts; }
              { name = "spi";
                dtsText = "...";
              }
              { name = "precompiled"; dtboFile = ./dtbos/example.dtbo; }
            ]
          '';
          type = types.listOf (types.coercedTo types.path (path: {
            name = baseNameOf path;
            filter = null;
            dtboFile = path;
          }) overlayType);
          description = lib.mdDoc ''
            List of overlays to apply to base device-tree (.dtb) files.
          '';
        };

        package = mkOption {
          default = null;
          type = types.nullOr types.path;
          internal = true;
          description = lib.mdDoc ''
            A path containing the result of applying `overlays` to `kernelPackage`.
          '';
        };
      };
  };

  config = mkIf (cfg.enable) {

    assertions = let
      invalidOverlay = o: (o.dtsFile == null) && (o.dtsText == null) && (o.dtboFile == null);
    in lib.singleton {
      assertion = lib.all (o: !invalidOverlay o) cfg.overlays;
      message = ''
        deviceTree overlay needs one of dtsFile, dtsText or dtboFile set.
        Offending overlay(s):
        ${toString (map (o: o.name) (builtins.filter invalidOverlay cfg.overlays))}
      '';
    };

    hardware.deviceTree.package = if (cfg.overlays != [])
      then pkgs.deviceTree.applyOverlays filteredDTBs (withDTBOs cfg.overlays)
      else filteredDTBs;
  };
}