# SPDX-FileCopyrightText: 2024 Lubin Bailly <lubin.bailly@dgnum.eu>
#
# SPDX-License-Identifier: EUPL-1.2

{
  lib,
  config,
  pkgs,
  ...
}:
let
  inherit (lib)
    attrNames
    concatMapStringsSep
    concatStringsSep
    escapeXML
    filter
    getExe
    hasPrefix
    hasSuffix
    head
    importJSON
    mapAttrs'
    mapAttrsToList
    mkDefault
    mkEnableOption
    mkIf
    mkOption
    optionalString
    pathIsDirectory
    removePrefix
    ;
  inherit (lib.strings)
    sanitizeDerivationName
    ;
  inherit (lib.types)
    attrs
    attrsOf
    deferredModule
    listOf
    path
    submodule
    str
    ;
  yaml = pkgs.formats.yaml { };
  json = pkgs.formats.json { };
  cfg = config.services.extranix;

  module-eval =
    module-name: module:
    let
      ignored-eval = lib.evalModules {
        modules = module.ignored-modules;
        inherit (module) specialArgs;
      };
      ignored-opts-doc = pkgs.nixosOptionsDoc { inherit (ignored-eval) options; };
      ignored-opts = importJSON "${ignored-opts-doc.optionsJSON}/share/doc/nixos/options.json";
      eval = lib.evalModules {
        modules = module.paths ++ module.ignored-modules;
        inherit (module) specialArgs;
      };
      opts-doc = pkgs.nixosOptionsDoc { inherit (eval) options; };
      opts = importJSON "${opts-doc.optionsJSON}/share/doc/nixos/options.json";
      filtered-opts = removeAttrs opts (attrNames ignored-opts);
      path-translation =
        let
          translations = map (
            { base, url }:
            {
              url = "${url}${optionalString (!hasSuffix "/" url) "/"}";
              base =
                let
                  base1 = toString base;
                in
                base1 + (optionalString (!hasSuffix "/" base1) "/");
            }
          ) module.path-translations;
        in
        path:
        let
          fullPath = path + (optionalString (pathIsDirectory path) "/default.nix");
          fitting = filter ({ base, ... }: hasPrefix base fullPath) translations;
          translate-info = head (
            fitting
            ++ [
              (throw (
                "${fullPath} is not in any base path of ${module-name}. Base paths are "
                + concatMapStringsSep "\n" ({ base, ... }: base) translations
              ))
            ]
          );
          innerPath = removePrefix translate-info.base fullPath;
        in
        {
          name = "<${innerPath}>";
          url = "${translate-info.url}${innerPath}";
        };
      result' = json.generate "options-extranix-fileDesc.json" {
        last_update = "-/-";
        options = mapAttrsToList (title: val: {
          inherit title;
          inherit (val)
            type
            readOnly
            loc
            ;
          descriptionHTML = pkgs.runCommand "option-${title}.html" { } ''
            ${getExe pkgs.pandoc} -f markdown-raw_html ${pkgs.writeText "option-${title}.md" val.description} > $out
          '';
          description = escapeXML val.description;
          example = escapeXML (val.example.text or "");
          default = escapeXML (val.default.text or "");
          declarations = map path-translation val.declarations;
        }) filtered-opts;
      };
      result =
        pkgs.runCommand "options-extranix.json"
          {
            nativeBuildInputs = [ pkgs.jq ];
          }
          ''
            jq -r '.options[].descriptionHTML | "--rawfile\n" + . + "\n" + .' ${result'} | xargs \
              jq -c '.options |= map(.descriptionHTML as $desc | .descriptionHTML |= $ARGS.named.[$desc])' ${result'} \
              > $out
          '';
    in
    result;

  options-files = mapAttrs' (name: value: {
    name = sanitizeDerivationName name;
    value = module-eval name value;
  }) cfg.modules;

  webroot = pkgs.callPackage ./webroot.nix {
    inherit options-files;
    inherit (cfg) static-data;
    settings = yaml.generate "config.yaml" cfg.settings;
    hugo-theme-extranix-options-search = pkgs.callPackage ./hugo-theme-extranix-options-search.nix { };
  };
in
{
  options.services.extranix = {
    enable = mkEnableOption "extranix documentation";
    modules = mkOption {
      type =

        attrsOf (submodule {
          options = {
            specialArgs = mkOption {
              type = attrs;
              default = { };
              description = ''
                Special arguments to give to evalModules.
              '';
            };
            paths = mkOption {
              type = listOf deferredModule;
              description = ''
                Modules to from which to document options.
              '';
            };
            ignored-modules = mkOption {
              type = listOf deferredModule;
              default = [ ];
              description = ''
                Modules required to make modules of `paths` valid.
              '';
              example = ''
                import "''${infra-modulesPath}/module-list.nix"
              '';
            };
            path-translations = mkOption {
              type = listOf (submodule {
                options = {
                  base = mkOption {
                    type = path;
                    description = ''
                      Base path of some module files to be documented.
                    '';
                  };
                  url = mkOption {
                    type = str;
                    description = ''
                      Url root to use for files on this path.
                    '';
                  };
                };
              });
              description = ''
                Rules to convert file paths to urls in the documentation to indicate where
                the option is declared.
              '';
            };
          };
        });
      description = ''
        Sets of modules to be documented separately. The identifier to give for
        `settings.params.release_current_stable` (which is the default module shown) is the key after
        passing through `sanitizeDerivationName`.
      '';
    };
    settings = mkOption {
      inherit (yaml) type;
      description = ''
        Settings for the `config.yaml` for the hugo instantiation.
      '';
      example = {
        baseUrl = "https://example.org/";
        title = "Module documentation";
        languageCode = "en-us";
        params = {
          release_current_stable = "Some-Module";
          logo = "logo.png";
          footer_credits_line = ''
            Based on <a href="https://github.com/mipmip/home-manager-option-search">Home Manager Option Search</a>
          '';
          footer_copyright_line = ''
            Made by catvayor for the <a href="https://dgnum.eu">DGNum</a>.
          '';
          main_menu = [
            {
              name = ''Sources'';
              url = "https://git.example.org/";
            }
          ];
        };
      };
    };
    static-data = mkOption {
      type = path;
      description = ''
        Static files for the website. Should have `images/favicon.png` for favicon.
      '';
    };
    host = mkOption {
      type = str;
      description = ''
        Hostname of the service.
      '';
    };
  };
  config = mkIf cfg.enable {
    services = {
      extranix.settings = {
        theme = "extranix-options-search";
        params = {
          releases = mapAttrsToList (name: _: {
            inherit name;
            value = sanitizeDerivationName name;
          }) cfg.modules;
          release_current_stable = mkDefault (head (attrNames options-files));
        };
      };
      nginx = {
        enable = true;
        virtualHosts.${cfg.host}.locations."/".alias = "${webroot}/";
      };
    };
    assertions = [
      {
        assertion = cfg.modules != { };
        message = ''
          `services.extranix` can't be enabled without any modules to document.
        '';
      }
      {
        assertion = options-files ? ${cfg.settings.params.release_current_stable};
        message = ''
          `services.extranix.settings.params.release_current_stable` should be the
          `sanitizeDerivationName` of a key of `services.extranix.modules`, here one of:
            + ${concatStringsSep "\n  + " (attrNames options-files)}
        '';
      }
    ];
  };
}