{
  config,
  lib,
  registry,
  ...
}:
let
  cfg = config.modules.services.homepage; # NOLINT(let_order)

  derivedAllowedHosts = lib.unique (
    lib.optional (selfRoute != null) selfRoute.domain
    ++ lib.optionals (selfAddress != null) [
      selfAddress
      "${selfAddress}:${toString cfg.listenPort}"
    ]
  );
  selfRoute = selfEntry.route or null;

  selfEntry = registry.join cfg.hostName cfg.entryName;
  selfAddress = selfEntry.address or null;
  homepageServices = map mkTab (lib.filter (tab: lib.hasAttr tab entriesByTab) orderedTabs);

  mkTab =
    tab:
    let
      sections = entriesByTab.${tab};
    in
    {
      ${tab} = map (section: { ${section} = sections.${section}; }) (orderedSections tab sections);
    };

  entriesByTab = lib.foldl' insertEntry { } sortedEntries;

  insertEntry =
    acc: item:
    acc
    // {
      ${item.homepage.tab} = (acc.${item.homepage.tab} or { }) // {
        ${item.homepage.section} = (acc.${item.homepage.tab}.${item.homepage.section} or [ ]) ++ [
          { ${item.homepage.name} = mkServiceAttrs item; }
        ];
      };
    };

  sortedEntries = lib.sort (left: right: left.homepage.name < right.homepage.name) homepageEntries;

  homepageEntries = lib.concatLists (
    lib.mapAttrsToList (
      host: entries:
      lib.mapAttrsToList (entry: homepage: {
        inherit host entry homepage;
        composite = registry.join host entry;
      }) entries
    ) registry.homepage
  );

  orderedTabs = tabOrder ++ lib.filter (tab: !lib.elem tab tabOrder) (lib.attrNames entriesByTab);

  tabOrder = [
    "Apps"
    "Download"
    "System"
  ];

  mkRegistryPath =
    registryName: host: entry:
    "registry.${registryName}.${host}.${entry}";

  mkHref =
    item:
    if item.homepage.href != null then
      item.homepage.href
    else if (item.composite.route or null) != null then
      if item.composite.route.port != null then
        "https://${item.composite.route.domain}"
      else if item.composite.route.http.port != null then
        "http://${item.composite.route.domain}"
      else
        throw "${mkRegistryPath "homepage" item.host item.entry} needs href or a matching TCP route entry"
    else
      throw "${mkRegistryPath "homepage" item.host item.entry} needs href or a matching route entry";

  mkServiceAttrs =
    item:
    lib.filterAttrs (_: value: value != null) {
      href = mkHref item;
      inherit (item.homepage) description icon;
    };

  sectionOrderByTab = {
    Apps = [
      "Media"
      "Files"
      "Other"
    ];
    Download = [
      "Library Managers"
      "Other Utilities"
      "Download Clients"
    ];
    System = [
      "Monitoring"
      "Network"
      "Machines"
      "Docker"
    ];
  };

  orderedSections =
    tab: sections:
    let
      sectionOrder = sectionOrderByTab.${tab} or [ ];
    in
    sectionOrder ++ lib.filter (section: !lib.elem section sectionOrder) (lib.attrNames sections);

in
{
  options.modules.services.homepage = {
    enable = lib.mkEnableOption "Homepage Dashboard";

    listenPort = lib.mkOption {
      type = lib.types.port;
      default = 8082;
      description = "Port for Homepage to bind to.";
    };

    hostName = lib.mkOption {
      type = lib.types.str;
      description = "Host registry key that owns the Homepage guest entry.";
    };

    entryName = lib.mkOption {
      type = lib.types.str;
      default = "homepage";
      description = "Registry entry name for this Homepage service.";
    };

    allowedHosts = lib.mkOption {
      type = lib.types.nullOr (lib.types.listOf lib.types.str);
      default = null;
      description = "Host headers accepted by Homepage. Defaults to matching address and route registry entries.";
    };

    environmentFile = lib.mkOption {
      type = lib.types.path;
      default = "/run/secrets/homepage.env";
      description = "Environment file passed to Homepage.";
    };
  };

  config = lib.mkIf cfg.enable {
    services.homepage-dashboard = {
      enable = true;
      openFirewall = true;
      inherit (cfg) listenPort;
      environmentFiles = [ cfg.environmentFile ];
      allowedHosts = lib.concatStringsSep "," (
        if cfg.allowedHosts == null then derivedAllowedHosts else cfg.allowedHosts
      );
      services = homepageServices;
      widgets = [
        {
          greeting = {
            text_size = "xl";
            text = "tracion";
          };
        }
        {
          openmeteo = {
            units = "metric";
            latitude = "{{HOMEPAGE_VAR_LATITUDE}}";
            longitude = "{{HOMEPAGE_VAR_LONGITUDE}}";
            cache = 5;
          };
        }
        {
          datetime = {
            text_size = "xl";
            locale = "en";
            format = {
              dateStyle = "full";
              timeStyle = "medium";
              hour12 = false;
            };
          };
        }
      ];
      settings = {
        title = "Tracion";
        theme = "dark";
        color = "slate";
        showStats = false;
        hideVersion = true;
        bookmarksStyle = "icons";
        useEqualHeights = true;
        layout = {
          Apps = {
            style = "row";
            columns = 1;
            tab = "Apps";
            Media = {
              style = "row";
              columns = 2;
            };
            Files = {
              style = "row";
              columns = 2;
            };
            Other = {
              style = "row";
              columns = 3;
              iconsOnly = true;
            };
          };
          Download = {
            style = "row";
            columns = 1;
            tab = "Download";
          };
          System = {
            tab = "System";
          };
        };
      };
    };
  };
}