{ config, lib, pkgs, domain, vhosts ? { }, ... }:

with lib;

let
  cfg = config.infra.gitea;
  vhost = vhosts.${cfg.hostname} or { };
  httpPort = vhost.ports.http or 3000;
  sshPort = vhost.ports.ssh or 2222;

  giteaBin = "${config.services.gitea.package}/bin/gitea";
  discoveryUrl = "${cfg.oidc.issuerUrl}/.well-known/openid-configuration";
in {
  options.infra.gitea = {
    enable = mkEnableOption "Gitea with Keycloak OIDC";

    hostname = mkOption {
      type = types.str;
      default = "git.${domain}";
      description = "Public hostname for Gitea";
    };

    oidc = {
      enable = mkOption {
        type = types.bool;
        default = true;
        description = "Register Keycloak as an OIDC authentication source";
      };

      name = mkOption {
        type = types.str;
        default = "Keycloak";
        description = "Display name for the OIDC auth source";
      };

      clientId = mkOption {
        type = types.str;
        description = "Keycloak OIDC client id";
      };

      clientSecretFile = mkOption {
        type = types.path;
        description = ''
          Path to a file (readable by the gitea user) containing the
          Keycloak OIDC client secret.
        '';
      };

      issuerUrl = mkOption {
        type = types.str;
        default = "https://auth.${domain}/realms/master";
        description = "Keycloak realm issuer URL";
      };
    };
  };

  config = mkIf cfg.enable {
    services.gitea = {
      enable = true;
      settings = {
        server = {
          DOMAIN = cfg.hostname;
          ROOT_URL = "https://${cfg.hostname}/";
          PROTOCOL = "http";
          HTTP_ADDR = "127.0.0.1";
          HTTP_PORT = httpPort;
          SSH_DOMAIN = cfg.hostname;
          SSH_PORT = sshPort;
          START_SSH_SERVER = true;
          SSH_LISTEN_PORT = sshPort;
          LANDING_PAGE = "explore";
        };
        service = {
          DISABLE_REGISTRATION = false;
          SHOW_REGISTRATION_BUTTON = false;
        };
        openid = {
          ENABLE_OPENID_SIGNIN = true;
          ENABLE_OPENID_SIGNUP = true;
        };
        oauth2_client = {
          ENABLE_AUTO_REGISTRATION = true;
          ACCOUNT_LINKING = "login";
          UPDATE_AVATAR = true;
        };
      };
    };

    networking.firewall.allowedTCPPorts = [ sshPort ];

    systemd.services.gitea-oidc = mkIf cfg.oidc.enable {
      description = "Register Keycloak OIDC authentication source in Gitea";
      after = [ "gitea.service" ];
      bindsTo = [ "gitea.service" ];
      wantedBy = [ "multi-user.target" ];
      serviceConfig = {
        Type = "oneshot";
        User = "gitea";
        Group = "gitea";
        RemainAfterExit = true;
      };
      environment = {
        GITEA_CUSTOM = "/var/lib/gitea/custom";
        GITEA_WORK_DIR = "/var/lib/gitea";
      };
      script = ''
        secret="$(cat ${cfg.oidc.clientSecretFile})"

        # Wait until Gitea has finished initialising its database
        for i in $(seq 1 60); do
          if ${giteaBin} admin auth list > /tmp/gitea-auth-list 2>/dev/null; then
            break
          fi
          sleep 2
        done

        ${giteaBin} admin auth list > /tmp/gitea-auth-list || true
        existing=$(grep -w '${cfg.oidc.name}' /tmp/gitea-auth-list | awk '{print $1}' | head -n1)

        if [ -n "$existing" ]; then
          ${giteaBin} admin auth update-oauth --id "$existing" \
            --name '${cfg.oidc.name}' \
            --provider openidConnect \
            --key '${cfg.oidc.clientId}' \
            --secret "$secret" \
            --auto-discover-url '${discoveryUrl}'
        else
          ${giteaBin} admin auth add-oauth \
            --name '${cfg.oidc.name}' \
            --provider openidConnect \
            --key '${cfg.oidc.clientId}' \
            --secret "$secret" \
            --auto-discover-url '${discoveryUrl}'
        fi
      '';
    };
  };
}