# mautrix-slack Matrix-Slack bridge
# Bridges Slack to Matrix via appservice
# Implementation follows mautrix-gmessages pattern for config management
{ config, pkgs, pkgs-unstable, lib, ... }:

with lib;

let
  cfg = config.services.mautrix-slack;
  yamlFormat = pkgs.formats.yaml { };

  exampleConfigPath = "${cfg.package}/example-config.yaml";

  configOverrides = {
    homeserver = {
      address = cfg.matrix.homeserverUrl;
      domain = cfg.matrix.serverName;
    };
    appservice = {
      address = "http://${cfg.appservice.hostname}:${toString cfg.appservice.port}";
      hostname = cfg.appservice.hostname;
      port = cfg.appservice.port;
      id = cfg.appservice.id;
      bot = {
        username = cfg.appservice.senderLocalpart;
        displayname = cfg.appservice.botDisplayName;
        avatar = cfg.appservice.botAvatar;
      };
      username_template = "${cfg.appservice.userPrefix}{{.}}";
    };
    database = {
      type = cfg.database.type;
      uri = cfg.database.uri;
      max_open_conns = cfg.database.maxOpenConnections;
      max_idle_conns = cfg.database.maxIdleConnections;
    };
    bridge = {
      command_prefix = cfg.bridge.commandPrefix;
      permissions = cfg.bridge.permissions;
    };
    encryption = {
      allow = cfg.encryption.enable;
      default = cfg.encryption.default;
      require = cfg.encryption.require;
    };
    logging = {
      min_level = cfg.logging.level;
    };
  };

in
{
  options.services.mautrix-slack = {
    enable = mkEnableOption "mautrix-slack Matrix-Slack bridge";

    package = mkOption {
      type = types.package;
      default = pkgs-unstable.mautrix-slack;
      description = "Package providing the bridge executable.";
    };

    user = mkOption {
      type = types.str;
      default = "mautrix_slack";
      description = "System user for the bridge.";
    };

    group = mkOption {
      type = types.str;
      default = "mautrix_slack";
      description = "Primary group for the bridge.";
    };

    dataDir = mkOption {
      type = types.path;
      default = "/var/lib/mautrix_slack";
      description = "State directory.";
    };

    extraPackages = mkOption {
      type = types.listOf types.package;
      default = [];
      description = "Additional packages exposed to the service PATH.";
    };

    extraConfig = mkOption {
      type = yamlFormat.type;
      default = {};
      description = "Optional YAML fragment merged into the config.";
    };

    # Matrix homeserver configuration
    matrix = {
      homeserverUrl = mkOption {
        type = types.str;
        default = "http://127.0.0.1:8008";
        description = "Matrix homeserver URL for bridge connections";
      };

      serverName = mkOption {
        type = types.str;
        description = "Matrix server name for bridge users";
      };
    };

    # Database configuration
    database = {
      type = mkOption {
        type = types.str;
        default = "postgres";
        description = "Database type (sqlite3 or postgres)";
      };

      uri = mkOption {
        type = types.str;
        default = "postgresql:///mautrix_slack?host=/run/postgresql";
        description = "Database connection string";
      };

      maxOpenConnections = mkOption {
        type = types.int;
        default = 32;
        description = "Maximum number of open database connections";
      };

      maxIdleConnections = mkOption {
        type = types.int;
        default = 4;
        description = "Maximum number of idle database connections";
      };
    };

    # Logging configuration
    logging = {
      level = mkOption {
        type = types.str;
        default = "info";
        description = "Log level (debug, info, warn, error)";
      };
    };

    # Bridge behavior configuration
    bridge = {
      commandPrefix = mkOption {
        type = types.str;
        default = "!slack";
        description = "Command prefix for bridge commands";
      };

      permissions = mkOption {
        type = types.attrsOf types.str;
        default = {
          "example.com" = "user";
        };
        description = "Bridge permissions mapping";
      };
    };

    # Appservice configuration
    appservice = {
      id = mkOption {
        type = types.str;
        default = "slack";
        description = "Appservice ID";
      };

      hostname = mkOption {
        type = types.str;
        default = "127.0.0.1";
        description = "Hostname for the appservice";
      };

      port = mkOption {
        type = types.port;
        default = 29319;
        description = "Port for the appservice API";
      };

      senderLocalpart = mkOption {
        type = types.str;
        default = "slackbot";
        description = "Localpart of the bridge bot user";
      };

      botDisplayName = mkOption {
        type = types.str;
        default = "Slack Bridge Bot";
        description = "Display name for the bridge bot";
      };

      botAvatar = mkOption {
        type = types.str;
        default = "";
        description = "Avatar MXC URI for the bridge bot";
      };

      userPrefix = mkOption {
        type = types.str;
        default = "slack_";
        description = "Prefix for Matrix users bridged from Slack";
      };
    };

    # Encryption configuration
    encryption = {
      enable = mkOption {
        type = types.bool;
        default = true;
        description = "Enable Matrix end-to-end encryption";
      };

      default = mkOption {
        type = types.bool;
        default = false;
        description = "Enable encryption by default in new portals";
      };

      require = mkOption {
        type = types.bool;
        default = false;
        description = "Require encryption in all portals";
      };
    };
  };

  config = mkIf cfg.enable {
    # User and group
    users.users.${cfg.user} = {
      isSystemUser = true;
      group = cfg.group;
      extraGroups = [ "matrix-appservices" ];
      home = cfg.dataDir;
      createHome = true;
    };
    users.groups.${cfg.group} = {};
    users.groups.matrix-appservices = {};

    # Systemd service with gmessages-style configuration
    systemd.services.mautrix-slack = {
      description = "mautrix-slack Matrix-Slack bridge";
      after = [ "network.target" ]
        ++ optional (cfg.database.type == "postgres") "postgresql.service";
      wants = [ "network-online.target" ];
      wantedBy = [ "multi-user.target" ];

      serviceConfig = {
        Type = "simple";
        User = cfg.user;
        Group = cfg.group;
        SupplementaryGroups = [ "matrix-appservices" ];
        WorkingDirectory = cfg.dataDir;

        # Use StateDirectory for persistent config and data management
        StateDirectory = cfg.user;
        StateDirectoryMode = "0750";

        # Two-stage pre-start: directory setup as root, then config generation as service user
        ExecStartPre = [
          # Stage 1: Create config directory as root (+ prefix)
          "+${pkgs.coreutils}/bin/mkdir -p /var/lib/${cfg.user}/config"
          "+${pkgs.coreutils}/bin/chown -R ${cfg.user}:${cfg.group} /var/lib/${cfg.user}"
          "+${pkgs.coreutils}/bin/chmod 750 /var/lib/${cfg.user}"
          "+${pkgs.coreutils}/bin/chmod 750 /var/lib/${cfg.user}/config"

          # Stage 2: Generate configuration using example template
          "${pkgs.writeShellScript "mautrix-slack-prepare-config" ''
            set -euo pipefail

            CONFIG_DIR=/var/lib/${cfg.user}/config
            CONFIG_PATH="$CONFIG_DIR/config.yaml"
            REG_PATH="/var/lib/matrix-appservices/mautrix_slack_registration.yaml"

            # Always regenerate config from example
            cd "$CONFIG_DIR"
            rm -f config.yaml
            ${cfg.package}/bin/mautrix-slack -c config.yaml -e

            ${pkgs.python3.withPackages (ps: [ ps.pyyaml ])}/bin/python3 <<'PY'
import json
import os
import pathlib
import pwd
import grp
import yaml

CONFIG_PATH = pathlib.Path('config.yaml')
REG_PATH = pathlib.Path('/var/lib/matrix-appservices/mautrix_slack_registration.yaml')

with CONFIG_PATH.open('r', encoding='utf-8') as fh:
    config = yaml.safe_load(fh)

overrides = json.loads(${lib.escapeShellArg (builtins.toJSON configOverrides)})
extra_cfg = json.loads(${lib.escapeShellArg (builtins.toJSON cfg.extraConfig)})

def deep_update(target, data):
    for key, value in data.items():
        if isinstance(value, dict) and value is not None:
            if key not in target or not isinstance(target.get(key), dict):
                target[key] = {}
            deep_update(target[key], value)
        else:
            target[key] = value

deep_update(config, overrides)
if extra_cfg:
    deep_update(config, extra_cfg)

# Handle permissions explicitly to ensure example values are replaced
perms = overrides.get('bridge', {}).get('permissions')
if perms is not None:
    config.setdefault('bridge', {})['permissions'] = perms

# Read tokens from registration file if it exists
if REG_PATH.exists():
    with REG_PATH.open('r', encoding='utf-8') as fh:
        registration = yaml.safe_load(fh)

    if 'as_token' in registration:
        config.setdefault('appservice', {})['as_token'] = registration['as_token']
    if 'hs_token' in registration:
        config.setdefault('appservice', {})['hs_token'] = registration['hs_token']

with CONFIG_PATH.open('w', encoding='utf-8') as fh:
    yaml.safe_dump(config, fh, default_flow_style=False, sort_keys=False)

uid = pwd.getpwnam('${cfg.user}').pw_uid
gid_service = grp.getgrnam('${cfg.group}').gr_gid
gid_shared = grp.getgrnam('matrix-appservices').gr_gid

os.chown(CONFIG_PATH, uid, gid_service)
os.chmod(CONFIG_PATH, 0o640)
PY

            # Generate registration file if it doesn't exist
            if [ ! -f "$REG_PATH" ]; then
              mkdir -p $(dirname "$REG_PATH")
              ${cfg.package}/bin/mautrix-slack -c config.yaml -g -r "$REG_PATH"

              # Fix sender_localpart to match config (bridge generates random value)
              # See: https://github.com/mautrix/slack/issues - registration -g ignores config.yaml
              ${pkgs.gnused}/bin/sed -i "s/^sender_localpart: .*/sender_localpart: ${cfg.appservice.senderLocalpart}/" "$REG_PATH"

              chown ${cfg.user}:matrix-appservices "$REG_PATH"
              chmod 640 "$REG_PATH"
            fi
          ''}"
        ];

        # Start mautrix-slack with state directory config
        ExecStart = "${cfg.package}/bin/mautrix-slack -c /var/lib/${cfg.user}/config/config.yaml";

        # Restart policy
        Restart = "always";
        RestartSec = "10s";

        # Security hardening
        NoNewPrivileges = true;
        ProtectSystem = "strict";
        ProtectHome = true;
        PrivateTmp = true;
        PrivateDevices = true;
        ProtectKernelTunables = true;
        ProtectKernelModules = true;
        ProtectControlGroups = true;

        # Allow writing to data and shared appservices directory
        ReadWritePaths = [
          cfg.dataDir
          "/var/lib/matrix-appservices"
        ];

        # Resource limits
        MemoryMax = "256M";

        # Process security
        UMask = "0027";
        LockPersonality = true;
        RestrictRealtime = true;
        RestrictSUIDSGID = true;

        # Logging
        StandardOutput = "journal";
        StandardError = "journal";
        SyslogIdentifier = "mautrix-slack";
      };

      # Add extra packages to PATH if specified
      path = [ pkgs.coreutils ] ++ cfg.extraPackages;
    };

    # Directory permissions
    systemd.tmpfiles.rules = [
      "d ${cfg.dataDir} 0750 ${cfg.user} ${cfg.group} -"
      "d /var/lib/matrix-appservices 0770 root matrix-appservices -"
    ];
  };
}