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

with lib;
let
  cfg = config.modules.headscale;
in
{
  options = {
    modules = {
      headscale = {
        enable = mkEnableOption "Deploy headscale";
        
        oidcClientSecretPath = mkOption {
          type = types.str;
          default = "/etc/headscale/oidc_client_secret.key";
          description = "Path to OIDC client secret file";
          example = "config.age.secrets.headscale-oidc-key.path";
        };
        
        litestream = {
          enable = mkEnableOption "Enable litestream for headscale database backups";
          
          replicas = mkOption {
            type = types.listOf (types.attrsOf types.anything);
            default = [];
            description = "List of litestream replica configurations";
            example = [
              {
                url = "s3://your-backup-bucket/headscale/db";
                access-key-id = "$LITESTREAM_ACCESS_KEY_ID";
                secret-access-key = "$LITESTREAM_SECRET_ACCESS_KEY";
                region = "us-east-1";
              }
            ];
          };
          
          backupPath = mkOption {
            type = types.nullOr types.str;
            default = null;
            description = "Local backup path (alternative to S3)";
            example = "/backup/headscale";
          };
          
          syncInterval = mkOption {
            type = types.str;
            default = "1s";
            description = "How often to sync to replicas";
          };
          
          retention = mkOption {
            type = types.str;
            default = "72h";
            description = "How long to retain snapshots";
          };
          
          environmentFile = mkOption {
            type = types.nullOr types.path;
            default = null;
            description = "Environment file containing S3 credentials (can be agenix secret)";
            example = "config.age.secrets.litestream-env.path";
          };
        };
      };
    };
  };

  config = mkIf cfg.enable {
    services.headscale = {
      enable = true;
      address = "0.0.0.0";
      port = 8080;
      
      settings = {
        server_url = "https://headscale.nekomimi.pet";
        
        # Metrics and gRPC
        metrics_listen_addr = "127.0.0.1:9090";
        grpc_listen_addr = "127.0.0.1:50443";
        grpc_allow_insecure = false;
        
        # Prefixes
        prefixes = {
          v4 = "100.64.0.0/10";
          v6 = "fd7a:115c:a1e0::/48";
          allocation = "sequential";
        };
        
        # Database
        database = {
          type = "sqlite";
          sqlite = {
            path = "/var/lib/headscale/db.sqlite";
            write_ahead_log = true;
          };
        };
        
        # Noise
        noise = {
          private_key_path = "/var/lib/headscale/noise_private.key";
        };
        
        # DERP
        derp = {
          urls = [
            "https://controlplane.tailscale.com/derpmap/default"
          ];
          paths = [];
          auto_update_enabled = true;
          update_frequency = "24h";
          server = {
            enabled = false;
            region_id = 999;
            region_code = "headscale";
            region_name = "Headscale Embedded DERP";
            stun_listen_addr = "0.0.0.0:3478";
            private_key_path = "/var/lib/headscale/derp_server_private.key";
            automatically_add_embedded_derp_region = true;
            ipv4 = "1.2.3.4";
            ipv6 = "2001:db8::1";
          };
        };
        
        # DNS
        dns = {
          magic_dns = true;
          base_domain = "dns.sharkgirl.pet";
          nameservers = {
            global = [
              "100.64.0.7"
              "1.1.1.1"
              "1.0.0.1"
              "2606:4700:4700::1111"
              "2606:4700:4700::1001"
            ];
          };
          search_domains = [];
        };
        
        # OIDC with configurable secret path
        oidc = {
          only_start_if_oidc_is_available = true;
          issuer = "https://pocketid.nekomimi.pet";
          client_id = "f345acad-3eac-45b7-9d91-57f388987a57";
          client_secret_path = cfg.oidcClientSecretPath;
          pkce = {
            enabled = true;
            method = "S256";
          };
        };
        
        # Policy
        policy = {
          mode = "database";
        };
        
        # TLS/ACME
        acme_url = "https://acme-v02.api.letsencrypt.org/directory";
        acme_email = "";
        tls_letsencrypt_hostname = "";
        tls_letsencrypt_cache_dir = "/var/lib/headscale/cache";
        tls_letsencrypt_challenge_type = "HTTP-01";
        tls_letsencrypt_listen = ":http";
        tls_cert_path = "";
        tls_key_path = "";
        
        # Logging
        log = {
          format = "text";
          level = "info";
        };
        
        # Misc settings
        disable_check_updates = false;
        ephemeral_node_inactivity_timeout = "30m";
        unix_socket = "/var/run/headscale/headscale.sock";
        unix_socket_permission = "0770";
        logtail = {
          enabled = false;
        };
        randomize_client_port = false;
      };
    };
    
    # Configurable Litestream for SQLite database backups
    services.litestream = mkIf cfg.litestream.enable {
      enable = true;
      settings = {
        dbs = [
          {
            path = "/var/lib/headscale/db.sqlite";
            sync-interval = cfg.litestream.syncInterval;
            retention = cfg.litestream.retention;
            replicas = 
              # Use custom replicas if provided
              if cfg.litestream.replicas != [] then
                cfg.litestream.replicas
              # Otherwise use local backup if path is provided
              else if cfg.litestream.backupPath != null then
                [{ path = cfg.litestream.backupPath; }]
              # Default empty (user must configure)
              else
                [];
          }
        ];
      };
    };
    
    # Configure systemd service to use agenix secrets
    systemd.services.headscale.serviceConfig = mkMerge [
      {
        SupplementaryGroups = [ "headscale-secrets" ];
      }
      # Add environment file for litestream if specified
      (mkIf (cfg.litestream.enable && cfg.litestream.environmentFile != null) {
        EnvironmentFile = cfg.litestream.environmentFile;
      })
    ];
    
    # Configure litestream service with environment file if specified
    systemd.services.litestream = mkIf (cfg.litestream.enable && cfg.litestream.environmentFile != null) {
      serviceConfig = {
        EnvironmentFile = cfg.litestream.environmentFile;
      };
    };
    
    # Create a group for accessing secrets
    users.groups.headscale-secrets = {};
  };
}