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

with lib;

let
  cfg = config.services.nginx;
  nginx = cfg.package;
  configFile = pkgs.writeText "nginx.conf" ''
    user ${cfg.user} ${cfg.group};
    daemon off;
    ${cfg.config}
    ${optionalString (cfg.httpConfig != "") ''
    http {
    ${cfg.httpConfig}
    ${cfg.httpServers}
    ${cfg.httpDefaultServer}
    }
    ''}
    ${cfg.appendConfig}
  '';
in

{
  options = {
    services.nginx = {
      enable = mkOption {
        default = false;
        type = types.bool;
        description = "
          Enable the nginx Web Server.
        ";
      };

      package = mkOption {
        default = pkgs.nginx;
        type = types.package;
        description = "
          Nginx package to use.
        ";
      };

      config = mkOption {
        default = "events {}";
        description = "
          Verbatim nginx.conf configuration.
        ";
      };

      appendConfig = mkOption {
        type = types.lines;
        default = "";
        description = ''
          Configuration lines appended to the generated Nginx
          configuration file. Commonly used by different modules
          providing http snippets. <option>appendConfig</option>
          can be specified more than once and it's value will be
          concatenated (contrary to <option>config</option> which
          can be set only once).
        '';
      };

      httpConfig = mkOption {
        type = types.lines;
        default = "";
        description = ''
          Configuration lines to be placed at the top inside of
          the http {} block. The option is intended to be used for
          the default configuration of the servers.
        '';
      };

      httpServers = mkOption {
        type = types.lines;
        default = "";
        description = ''
          Configuration lines to be placed inside of the http {}
          block. The option is intended to be used for defining
          individual servers.
        '';
      };

      httpDefaultServer = mkOption {
        type = types.lines;
        default = "";
        description = ''
          Configuration lines to be placed at the bottom inside of
          the http {} block. The option is intended to be used for
          setting up the default servers. The default server is used
          if no previously specified server matches a request.
        '';
      };

      stateDir = mkOption {
        default = "/var/spool/nginx";
        description = "
          Directory holding all state for nginx to run.
        ";
      };

      user = mkOption {
        type = types.str;
        default = "nginx";
        description = "User account under which nginx runs.";
      };

      group = mkOption {
        type = types.str;
        default = "nginx";
        description = "Group account under which nginx runs.";
      };

    };

  };

  config = mkIf cfg.enable {
    # TODO: test user supplied config file pases syntax test

    systemd.services.nginx = {
      description = "Nginx Web Server";
      after = [ "network.target" ];
      wantedBy = [ "multi-user.target" ];
      path = [ nginx ];
      preStart =
        ''
        mkdir -p ${cfg.stateDir}/logs
        chmod 700 ${cfg.stateDir}
        chown -R ${cfg.user}:${cfg.group} ${cfg.stateDir}
        '';
      serviceConfig = {
        ExecStart = "${nginx}/bin/nginx -c ${configFile} -p ${cfg.stateDir}";
        ExecReload = "${pkgs.coreutils}/bin/kill -HUP $MAINPID";
        Restart = "on-failure";
        RestartSec = "10s";
        StartLimitInterval = "1min";
      };
    };

    users.extraUsers = optionalAttrs (cfg.user == "nginx") (singleton
      { name = "nginx";
        group = cfg.group;
        uid = config.ids.uids.nginx;
      });

    users.extraGroups = optionalAttrs (cfg.group == "nginx") (singleton
      { name = "nginx";
        gid = config.ids.gids.nginx;
      });
  };
}