# AdGuard Home Module
# Provides: Private DNS-over-HTTPS with ClientID-based access control
#
# Usage:
#   myModules.adguard = {
#     enable = true;
#     domain = "dns.example.com";
#     clients = [
#       { name = "phone"; idSecret = "adguard_client_phone"; }
#     ];
#   };

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

let
  cfg = config.myModules.adguard;
in
{
  options.myModules.adguard = {
    enable = lib.mkEnableOption "AdGuard Home DNS server";

    domain = lib.mkOption {
      type = lib.types.str;
      example = "dns.example.com";
      description = "Public domain name for DoH endpoint";
    };

    port = lib.mkOption {
      type = lib.types.port;
      default = 3000;
      description = "Internal port for AdGuard HTTP/DoH listener";
    };

    upstreamDoh = lib.mkOption {
      type = lib.types.str;
      default = "https://dns.mullvad.net/dns-query";
      description = "Upstream DoH server URL";
    };

    bootstrapDns = lib.mkOption {
      type = lib.types.listOf (lib.types.str);
      default = [ "194.242.2.2" "2a07:e340::2" ];
      description = "Bootstrap DNS servers for resolving DoH upstream";
    };

    filters = lib.mkOption {
      type = lib.types.listOf (lib.types.submodule {
        options = {
          name = lib.mkOption {
            type = lib.types.str;
            description = "Friendly name for the filter list";
          };
          url = lib.mkOption {
            type = lib.types.str;
            description = "URL of the filter list (txt format)";
          };
          enabled = lib.mkOption {
            type = lib.types.bool;
            default = true;
            description = "Whether the filter is enabled";
          };
        };
      });
      default = [
        { name = "AdGuard DNS filter"; url = "https://adguardteam.github.io/HostlistsRegistry/assets/filter_1.txt"; }
        { name = "AdAway Default Blocklist"; url = "https://adguardteam.github.io/HostlistsRegistry/assets/filter_2.txt"; }
        { name = "HaGeZi Multi Light"; url = "https://hagezi.github.io/dns-blocklists/wildcard/light.txt"; }
        { name = "OISD Basic"; url = "https://small.oisd.nl/"; }
        { name = "Peter Lowe's List"; url = "https://pgl.yoyo.org/adservers/serverlist.php?hostformat=adguard&showintro=0&mimetype=plaintext"; }
      ];
      description = "DNS blocklists to maintain in AdGuard Home";
    };
  };

  config = lib.mkIf cfg.enable {
    # Generate a temporary JSON file containing the filters for yq to inject
    systemd.tmpfiles.rules = [
      "f /run/adguardhome_filters.json 0644 root root - ${builtins.toJSON { filters = map (f: { inherit (f) name url enabled; }) cfg.filters; }}"
    ];

    services.adguardhome = {
      enable = true;
      host = "127.0.0.1";
      port = cfg.port;
      settings = {
        dns = {
          bind_hosts = [ "0.0.0.0" ];
          port = 5353;
          upstream_dns = [ cfg.upstreamDoh ];
          bootstrap_dns = cfg.bootstrapDns;
          querylog_enabled = true;
          querylog_file_enabled = true;
          statistics_enabled = true;
        };

        tls = {
          enabled = true;
          server_name = cfg.domain;
          certificate_path = "/var/lib/acme/${cfg.domain}/fullchain.pem";
          private_key_path = "/var/lib/acme/${cfg.domain}/key.pem";
          port_https = 3001; # Prevent conflict with Nginx on port 443
          port_dns_over_tls = 853;
          port_dns_over_quic = 0;
          allow_unencrypted_doh = false;
        };

        filtering = {
          protection_enabled = true;
          filtering_enabled = true;
        };

        safebrowsing = {
          enabled = false;
        };

        parental = {
          enabled = false;
        };

        safesearch = {
          enabled = false;
        };

        log = {
          file = "";
          max_backups = 0;
          max_size = 100;
          compress = false;
          local_time = false;
          verbose = false;
        };
      };
    };

    # Inject filters into AdGuardHome.yaml before starting
    systemd.services.adguardhome = {
      requires = [ "acme-${cfg.domain}.service" ];
      after = [ "acme-${cfg.domain}.service" ];
      serviceConfig.SupplementaryGroups = [ "acme" ];
      serviceConfig.SystemCallFilter = lib.mkForce []; # Allow yq-go to run its syscalls
      preStart = lib.mkAfter ''
        if [ -f /var/lib/private/AdGuardHome/AdGuardHome.yaml ]; then
          ${pkgs.yq-go}/bin/yq -i '.filters = load("/run/adguardhome_filters.json").filters' /var/lib/private/AdGuardHome/AdGuardHome.yaml
        fi
      '';
    };

    # Open firewall for DoT
    networking.firewall.allowedTCPPorts = [ 853 ];
    networking.firewall.allowedUDPPorts = [ 853 ];

    # Nginx configuration (kept to satisfy ACME challenges for DoT certificates)
    services.nginx.virtualHosts."${cfg.domain}" = {
      enableACME = true;
      forceSSL = true;

      # Block all paths (no DoH or UI exposed via Nginx)
      locations."/" = {
        return = "404";
      };
    };

    # Ensure nginx user can access ACME certs
    users.users.nginx.extraGroups = [ "acme" ];
  };
}