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

let

  inherit (lib)
    any attrNames concatMapStringsSep concatStringsSep filterAttrs
    genAttrs hasPrefix isString mapAttrsToList mkDefault
    mkEnableOption mkIf mkOption mkOptionType mkOverride optionalString
    recursiveUpdate ;
  inherit (lib.types)
    attrsOf bool either enum int lines listOf nullOr package path
    str submodule unspecified ;

  localIcinga = config.nixsap.apps.icinga2.enable;

  cfg = config.nixsap.apps.icingaweb2;

  attrs = opts: submodule { options = opts; };
  mandatory = t: mkOption { type = t; };
  optional = t: mkOption { type = nullOr t; default = null; };
  default = d: t: mkOption { type = t; default = d; };
  explicit = filterAttrs (n: v: n != "_module" && v != null);
  show = v: optionalString (v != null) (toString v);

  permission =
    let
      allowed =
        [
          "config/authentication/groups"
          "config/authentication/roles/show"
          "config/authentication/users"
          "module"
          "monitoring/command"
        ];
    in mkOptionType {
      name = "string starting with one of ${concatMapStringsSep ", " (s: ''"${s}"'') allowed}";
      check = x: isString x && any (p: hasPrefix p x) allowed;
    };

  role = attrs {
    users = default [] (listOf str);
    groups = default [] (listOf str);
    permissions = mandatory (listOf permission);
    objects = optional str;
  };

  database = attrs {
    db       = mandatory str;
    host     = mandatory str;
    passfile = optional path;
    port     = optional int;
    type     = mandatory (enum [ "mysql" "pgsql" ]);
    user     = mandatory str;
  };

  configIni = pkgs.writeText "config.ini" ''
    [global]
    show_stacktraces = "${if cfg.stacktrace then "1" else "0"}"
    config_backend = "db"
    config_resource = "icingaweb2db"

    [logging]
    level = "${cfg.logLevel}"
    ${if cfg.log == "syslog" then ''
      log = "syslog"
      application = "icingaweb2"
     '' else ''
      log = "file"
      file = "${cfg.log}"
     ''
    }
  '';

  # XXX Livestatus is not supported by IcingaWeb2 (2.1.0)
  # https://dev.icinga.org/issues/8254
  # "We'll postpone this issue because Icinga 2.4 will introduce
  #  an API for querying monitoring data. Maybe we drop support
  #  for Livestatus completely"
  modules.monitoring.backendsIni = pkgs.writeText "backends.ini" ''
    [icinga2]
    type = "ido"
    resource = "icinga2db"
  '';

  modules.monitoring.configIni = pkgs.writeText "config.ini" ''
    [security]
    protected_customvars = "${concatStringsSep "," cfg.protectedCustomVars}"
  '';

  modules.monitoring.commandtransportsIni = pkgs.writeText "commandtransports.ini" ''
    ${optionalString localIcinga ''
      [local]
      transport = "local"
      path = "${config.nixsap.apps.icinga2.commandPipe}"
      ''
    }
  '';

  groupsIni = pkgs.writeText "groups.ini" (
    optionalString (cfg.authentication == "database") ''
      [database]
      backend = "db"
      resource = "icingaweb2db"
    ''
  );

  authenticationIni = pkgs.writeText "authentication.ini" (
    if cfg.authentication == "sproxy" then ''
      [sproxy]
      backend = "sproxy"
    '' else ''
      [database]
      backend = "db"
      resource = "icingaweb2db"
    ''
  );

  rolesIni = pkgs.writeText "roles.ini" ''
    [root]
    users = "root"
    permissions = "config/authentication/roles/show, config/authentication/users/*, config/authentication/groups/*, module/*, monitoring/command/*"

    ${
      concatStringsSep "\n\n" (
        mapAttrsToList (n: s: ''
          [${n}]
          users = "${concatStringsSep ", " s.users}"
          groups = "${concatStringsSep ", " s.groups}"
          permissions = "${concatStringsSep ", " s.permissions}"
          ${optionalString (s.objects != null) ''
            monitoring/filter/objects = "${s.objects}"
            ''}
        '') (explicit cfg.roles)
      )
    }
  '';

  mkResource = name: opts:
    ''
      cat <<'__EOF__'

      [${name}]
      type = "db"
      db = "${opts.type}"
      dbname = "${opts.db}"
      host = "${opts.host}"
      port = "${show opts.port}"
      username = "${opts.user}"
      __EOF__
      ${optionalString (opts.passfile != null) ''
        pwd=$(cat '${opts.passfile}')
        printf 'password="%s"\n' "$pwd"
      ''}
    '';

  genResourcesIni = pkgs.writeBashScript "resources" (concatStringsSep "\n" (
    mapAttrsToList mkResource (explicit cfg.resources)
  ));

  defaultPool = {
    pm.max_children = 10;
    pm.max_requests = 1000;
    pm.max_spare_servers = 5;
    pm.min_spare_servers = 3;
    pm.strategy = "dynamic";
  };

  configureFiles = ''
    set -euo pipefail
    umask 0277
    mkdir -p '${cfg.configDir}'
    ${pkgs.findutils}/bin/find \
      ${cfg.configDir} \
      -mindepth 1 -maxdepth 1 \
      -not -name dashboards \
      -not -name preferences \
      -exec rm -rf '{}' \; || true

    mkdir -p '${cfg.configDir}/dashboards'
    mkdir -p '${cfg.configDir}/preferences'
    mkdir -p '${cfg.configDir}/enabledModules'
    mkdir -p '${cfg.configDir}/modules/monitoring'

    ln -sf '${pkgs.icingaweb2}/modules/monitoring' '${cfg.configDir}/enabledModules/monitoring'
    ${genResourcesIni} > '${cfg.configDir}/resources.ini'
    ln -sf '${authenticationIni}' '${cfg.configDir}/authentication.ini'
    ln -sf '${configIni}' '${cfg.configDir}/config.ini'
    ln -sf '${groupsIni}' '${cfg.configDir}/groups.ini'
    ln -sf '${rolesIni}' '${cfg.configDir}/roles.ini'

    ln -sf '${modules.monitoring.backendsIni}' \
           '${cfg.configDir}/modules/monitoring/backends.ini'

    ln -sf '${modules.monitoring.configIni}' \
           '${cfg.configDir}/modules/monitoring/config.ini'

    ln -sf '${modules.monitoring.commandtransportsIni}' \
           '${cfg.configDir}/modules/monitoring/commandtransports.ini'

    chmod u=rX,g=,o= '${cfg.configDir}'
    chmod -R u=rwX,g=,o= '${cfg.configDir}/dashboards'
    chmod -R u=rwX,g=,o= '${cfg.configDir}/preferences'
    chown -R icingaweb2:icingaweb2 '${cfg.configDir}'
  '';

  configureDB = with cfg.resources.icingaweb2db; {
    mysql =
      let
        mkMyCnf = pkgs.writeBashScript "my.cnf.sh" ''
          cat <<'__EOF__'
          [client]
          host = ${host}
          ${optionalString (port != null) "port = ${toString port}"}
          user = ${user}
          __EOF__
          ${optionalString (passfile != null) ''
            pwd=$(cat '${passfile}')
            printf 'password = %s\n' "$pwd"
          ''}
        '';
        mysql = "${pkgs.mysql.client}/bin/mysql";
      in pkgs.writeBashScript "configureMySQL" ''
        set -euo pipefail
        cnf=$(mktemp)
        trap 'rm -f "$cnf"' EXIT
        chmod 0600 "$cnf"
        ${mkMyCnf} > "$cnf"
        #shellcheck disable=SC2016
        while ! ${mysql} --defaults-file="$cnf" -e 'CREATE DATABASE IF NOT EXISTS `${db}`'; do
          sleep 5s
        done
        tt=$(${mysql} --defaults-file="$cnf" -N -e 'SELECT COUNT(*) FROM information_schema.tables WHERE table_schema = "${db}"')
        if [ "$tt" -eq 0 ]; then
          ${mysql} --defaults-file="$cnf" -v '${db}' < '${pkgs.icingaweb2}/etc/schema/mysql.schema.sql'
          ${optionalString (cfg.initialRootPasswordHash != "") ''
            #shellcheck disable=SC2016
            ${mysql} --defaults-file="$cnf" -e \
              'INSERT INTO icingaweb_user (name, active, password_hash) VALUES ("root", 1, "${cfg.initialRootPasswordHash}")' '${db}'
            ''
          }
        fi
      '';

      pgsql =
        let
          psql = pkgs.writeBashScript "icingaweb2pgsql" ''
            exec ${pkgs.postgresql}/bin/psql \
              -v ON_ERROR_STOP=1 \
              --no-password \
              --host='${host}' \
              --port=${toString port} \
              --dbname='${db}' \
              --username='${user}' \
              "$@"
          '';
        in pkgs.writeBashScript "configurePgSQL" ''
          set -euo pipefail
          ${optionalString (passfile != null) ''
            pgpass=$(mktemp)
            trap 'rm -f "$pgpass"' EXIT
            chmod 0600 "$cnf"
            printf '*:*:*:*:' > "$pgpass"
            cat '${passfile}' >> "$pgpass"
            export PGPASSFILE="$pgpass"
          ''}

          #shellcheck disable=SC2016
          while ! ${psql} -c ';'; do
            sleep 5s
          done
          tt=$(${psql} --tuples-only -c "SELECT count(*) FROM pg_class WHERE relname='icingaweb_user'")
          if [ "$tt" -eq 0 ]; then
            ${psql} --single-transaction -f '${pkgs.icingaweb2}/etc/schema/pgsql.schema.sql'
            ${optionalString (cfg.initialRootPasswordHash != "") ''
              ${psql} -c \
                "INSERT INTO icingaweb_user (name, active, password_hash) VALUES ('root', 1, '${cfg.initialRootPasswordHash}')"
              ''
            }
          fi
        '';
  };

  keys = [ cfg.resources.icingaweb2db.passfile
           cfg.resources.icinga2db.passfile ];

in {

  options.nixsap.apps.icingaweb2 = {
    enable = mkEnableOption "Icinga Web 2";
    user = mkOption {
      description = ''
        The user the PHP-FPM pool runs as. And the owner of files.
      '';
      default = "icingaweb2";
      type = str;
    };
    nginxServer = mkOption {
      type = lines;
      default = "";
      example = ''
        listen 8080;
        server_name icinga.example.net;
      '';
    };
    configDir = mkOption {
      description = "Where to put config files. This directory will be created if does not exist.";
      type = path;
      default = "/icingaweb2";
    };
    php-fpm = {
      package = mkOption {
        description = "PHP package to use";
        type = package;
        default = pkgs.php;
      };
      pool = mkOption {
        description = "Options for the PHP FPM pool";
        type = attrsOf unspecified;
        default = {};
      };
    };

    resources = mkOption {
      description = "Composes resources.ini";
      type = attrs {
        icingaweb2db = mkOption {
          description = "Database for Icinga Web 2 settings";
          type = database;
        };
        icinga2db = mkOption {
          description = "Icinga2 database (read-only)";
          type = database;
        };
      };
    };

    authentication = mkOption {
      description = ''
        Authentication backend: either IcingaWeb2 database or Sproxy.
      '';
      type = enum [ "sproxy" "database" ];
      default = "database";
    };

    protectedCustomVars = mkOption {
      description = ''
        Icinga2 custom variables to be masked in WebUI.
        This can used for example to hide passwords. Wildcard are allowed.
      '';
      type = listOf str;
      default = [ "*pass*" "*pw*" "community" "http*auth_pair" ];
    };

    roles = mkOption {
      description = "Composes roles.ini";
      type = attrsOf role;
      default = {};
      example = {
        devops = {
          groups = [ "devops" ];
          permissions = [ "module/*" "monitoring/command/*" ];
        };
        all = {
          groups = [ "all" ];
          permissions = [ "module/*" ];
          objects = "hostgroup_name=Shops";
        };
      };
    };

    initialRootPasswordHash = mkOption {
      description = ''
        Initial root password for icingaweb2db.
        Use <literal>openssl passwd -1 mysecret</literal>
        to generate this hash. It is used only when database
        does not exist. So you may choose not to keep/commit
        this hash at all. You better change the root password
        after the first login.
      '';
      type = str;
      default = "";
    };

    stacktrace = mkOption {
      description = "whether to show PHP stacktraces";
      type = bool;
      default = false;
    };
    log = mkOption {
      type = either path (enum [ "syslog" ]);
      default = "syslog";
    };
    logLevel = mkOption {
      type = enum [ "INFO" "WARNING" "ERROR" "CRITICAL" "DEBUG" ];
      default = "WARNING";
    };
  };

  config = mkIf cfg.enable {
    nixsap.deployment.keyrings.root = keys;
    users.users.${config.nixsap.apps.nginx.user}.extraGroups = [ cfg.user ];
    users.users.icingaweb2.extraGroups = mkIf localIcinga [ config.nixsap.apps.icinga2.commandGroup ];

    nixsap.apps.php-fpm.icingaweb2 = mkOverride 0 {
      inherit (cfg) user;
      inherit (cfg.php-fpm) package;
      pool = recursiveUpdate defaultPool cfg.php-fpm.pool;
    };

    nixsap.apps.nginx.conf.http.servers.icingaweb2 = ''
      ${cfg.nginxServer}

      root ${pkgs.icingaweb2}/public;
      index index.php;
      try_files $1 $uri $uri/ /index.php$is_args$args;

      location ~ ^/index\.php(.*)$ {
        fastcgi_pass unix:${config.nixsap.apps.php-fpm.icingaweb2.pool.listen.socket};
        fastcgi_index index.php;
        include ${config.nixsap.apps.nginx.package}/conf/fastcgi_params;
        fastcgi_param SCRIPT_FILENAME ${pkgs.icingaweb2}/public/index.php;
        fastcgi_param ICINGAWEB_CONFIGDIR ${cfg.configDir};
        fastcgi_param REMOTE_USER $remote_user;
      }
    '';

    systemd.services.icingaweb2cfg = {
      description = "configure Icinga Web 2";
      after = [ "network.target" "local-fs.target" "keys.target" ];
      wants = [ "keys.target" ];
      wantedBy = [ "multi-user.target" ];
      preStart = configureFiles;
      serviceConfig = {
        ExecStart = configureDB.${cfg.resources.icingaweb2db.type};
        PermissionsStartOnly = true;
        RemainAfterExit = true;
        User = "icingaweb2";
      };
    };
  };
}