# Maubot Matrix bot framework module
# Plugin-based Matrix bot system following established infrastructure patterns
{ config, pkgs, lib, ... }:

with lib;

let
  cfg = config.services.maubot;

  # Python environment with maubot and Instagram bot dependencies
  maubotEnv = pkgs.python3.withPackages (ps: with ps; [
    maubot
    yt-dlp
    # instaloader # Not available in nixpkgs, fallback to yt-dlp only
    aiohttp
    pillow
  ]);
in
{
  options.services.maubot = {
    enable = mkEnableOption "Maubot Matrix bot framework";
    
    homeserverUrl = mkOption {
      type = types.str;
      default = "http://127.0.0.1:8008";
      description = "Matrix homeserver URL for bot connections";
    };
    
    serverName = mkOption {
      type = types.str;
      default = "matrix.talu.uno";
      description = "Matrix server name for bot users";
    };
    
    port = mkOption {
      type = types.port;
      default = 29316;
      description = "Port for Maubot management interface";
    };
    
    adminUser = mkOption {
      type = types.str;
      default = "admin";
      description = "Admin username for Maubot management interface";
    };
    
    adminPasswordFile = mkOption {
      type = types.nullOr types.path;
      default = null;
      description = "Path to file containing admin password (more secure than adminPassword option)";
    };
    
    secretKeyFile = mkOption {
      type = types.nullOr types.path;
      default = null;
      description = "Path to file containing Maubot secret key for sessions";
    };
    
    registrationSecretFile = mkOption {
      type = types.nullOr types.path;
      default = null;
      description = "Path to file containing Matrix homeserver registration secret";
    };
    
    database = mkOption {
      type = types.str;
      default = "sqlite:/var/lib/maubot/bot.db";
      description = "Database connection string (sqlite:// or postgresql://)";
    };
    
    logLevel = mkOption {
      type = types.str;
      default = "INFO";
      description = "Log level (DEBUG, INFO, WARNING, ERROR)";
    };
    
    enableEncryption = mkOption {
      type = types.bool;
      default = true;
      description = "Enable end-to-end encryption support for bots";
    };
    
    publicUrl = mkOption {
      type = types.str;
      default = "http://localhost:29316";
      description = "Public URL where Maubot management interface is accessible";
    };

    plugins = mkOption {
      type = types.listOf types.path;
      default = [];
      description = "List of maubot plugin .mbp files to deploy";
    };
  };

  config = mkIf cfg.enable {
    # User and group
    users.users.maubot = {
      isSystemUser = true;
      group = "maubot";
      home = "/var/lib/maubot";
      createHome = true;
    };
    users.groups.maubot = {};

    # Configuration file generation
    environment.etc."maubot/config.yaml" = {
      text = ''
        # Maubot configuration - generated by NixOS
        # Database configuration
        database: "${cfg.database}"
        
        # Server configuration
        server:
          hostname: 127.0.0.1
          port: ${toString cfg.port}
          public_url: ${cfg.publicUrl}
          
        # Admin users for management interface
        admins:
          ${cfg.adminUser}: ${if cfg.adminPasswordFile != null then "REPLACE_ADMIN_PASSWORD" else "changeme-set-password"}

        # Bot configuration
        api_features:
          login: true
          plugin: true
          plugin_upload: true
          instance: true
          instance_database: true
          log: true
          
        # Logging configuration
        logging:
          version: 1
          formatters:
            precise:
              format: '[%(levelname)s@%(name)s] %(message)s'
          handlers:
            console:
              class: logging.StreamHandler
              formatter: precise
            file:
              class: logging.handlers.RotatingFileHandler
              formatter: precise
              filename: /var/log/maubot/maubot.log
              maxBytes: 52428800
              backupCount: 10
          loggers:
            maubot:
              level: ${cfg.logLevel}
            mau:
              level: ${cfg.logLevel}
            aiohttp:
              level: WARNING
          root:
            level: WARNING
            handlers: [console, file]
            
        # Plugin directories - using flat keys as expected by maubot
        plugin_directories.upload: /var/lib/maubot/plugins
        plugin_directories.load: 
          - /var/lib/maubot/plugins
        plugin_directories.trash: /var/lib/maubot/trash
          
        # Plugin databases configuration
        plugin_databases:
          sqlite: /var/lib/maubot/plugins
          postgres: null
          postgres_max_conns_per_plugin: 3
          postgres_opts: {}
          
        # Crypto configuration
        crypto:
          allow: ${if cfg.enableEncryption then "true" else "false"}
          allow_level: warn
          
        # Secret key for sessions
        secret_key: ${if cfg.secretKeyFile != null then "REPLACE_SECRET_KEY" else "insecure-default-change-me"}
      '';
      user = "maubot";
      group = "maubot";
      mode = "0440";
    };

    # Systemd service with hardening
    systemd.services.maubot = {
      description = "Maubot Matrix bot framework";
      after = [ "network.target" ];
      wantedBy = [ "multi-user.target" ];
      
      serviceConfig = {
        Type = "simple";
        User = "maubot";
        Group = "maubot";
        WorkingDirectory = "/var/lib/maubot";
        
        # Use StateDirectory for runtime data
        # RuntimeDirectory removed to avoid race condition with manual creation
        StateDirectory = "maubot";
        LogsDirectory = "maubot";
        
        # LoadCredential directives for secure secret injection
        LoadCredential =
          (optional (cfg.adminPasswordFile != null) "admin-password:${cfg.adminPasswordFile}") ++
          (optional (cfg.secretKeyFile != null) "secret-key:${cfg.secretKeyFile}");
        
        # Pre-start script to generate runtime config with secrets
        ExecStartPre =
          if (cfg.adminPasswordFile != null || cfg.secretKeyFile != null) then
            [
              (pkgs.writeShellScript "maubot-prepare-config" ''
                set -e

                # Ensure config directory exists
                ${pkgs.coreutils}/bin/mkdir -p /var/lib/maubot/config

                # Use text substitution to preserve YAML structure while injecting secrets
                ${pkgs.python3.withPackages (ps: [ ps.pyyaml ])}/bin/python3 << 'EOF'
import os
import re

# Read base configuration as text
with open('/etc/maubot/config.yaml', 'r') as f:
    config_text = f.read()

# Read secrets from CREDENTIALS_DIRECTORY if available
creds_dir = os.environ.get('CREDENTIALS_DIRECTORY')
if creds_dir:
    # Replace admin password placeholder
    admin_password_file = os.path.join(creds_dir, 'admin-password')
    if os.path.exists(admin_password_file):
        with open(admin_password_file, 'r') as f:
            admin_password = f.read().strip()
        config_text = config_text.replace('REPLACE_ADMIN_PASSWORD', admin_password)
    
    # Replace secret key placeholder
    secret_key_file = os.path.join(creds_dir, 'secret-key')
    if os.path.exists(secret_key_file):
        with open(secret_key_file, 'r') as f:
            secret_key = f.read().strip()
        config_text = config_text.replace('REPLACE_SECRET_KEY', secret_key)

# Write runtime config with restrictive permissions
os.umask(0o077)  # Ensure only owner can read
with open('/var/lib/maubot/config/config.yaml', 'w') as f:
    f.write(config_text)
EOF
              '')
            ]
          else
            [
              (pkgs.writeShellScript "maubot-prepare-config-simple" ''
                ${pkgs.coreutils}/bin/mkdir -p /var/lib/maubot/config
                ${pkgs.coreutils}/bin/cp /etc/maubot/config.yaml /var/lib/maubot/config/config.yaml
              '')
            ];

        # Start Maubot with runtime config
        ExecStart = "${maubotEnv}/bin/maubot -c /var/lib/maubot/config/config.yaml";

        # Restart policy
        Restart = "always";
        RestartSec = 10;
        
        # Security hardening following established patterns
        NoNewPrivileges = true;
        ProtectSystem = "strict";
        ProtectHome = true;
        # PrivateTmp disabled to allow access to /run/maubot
        PrivateTmp = false;
        PrivateDevices = true;
        ProtectKernelTunables = true;
        ProtectKernelModules = true;
        ProtectControlGroups = true;
        
        # Allow writing to data, log, and runtime directories
        ReadWritePaths = [ 
          "/var/lib/maubot" 
          "/var/log/maubot"
          "/run/maubot"
        ];
        
        # Network restrictions
        RestrictAddressFamilies = [ "AF_INET" "AF_INET6" "AF_UNIX" ];
        
        # System calls - Python application needs broader access
        SystemCallArchitectures = "native";
        SystemCallFilter = [
          "@system-service"
          "@network-io"
          "@file-system"
          "~@privileged"
        ];
        
        # Resource limits
        MemoryMax = "512M";
        CPUWeight = 50;  # Lower priority than Matrix server
        IOWeight = 50;
        
        # Process security
        UMask = "0027";
        LockPersonality = true;
        RestrictRealtime = true;
        RestrictSUIDSGID = true;
        RemoveIPC = true;
        
        # Logging
        StandardOutput = "journal";
        StandardError = "journal";
        SyslogIdentifier = "maubot";
      };
    };

    # Directory permissions
    systemd.tmpfiles.rules = [
      "d /var/lib/maubot 0755 maubot maubot -"
      "d /var/lib/maubot/plugins 0755 maubot maubot -"
      "d /var/lib/maubot/trash 0755 maubot maubot -"
      "d /var/log/maubot 0755 maubot maubot -"
      "d /run/maubot 0700 maubot maubot -"
    ] ++ (map (plugin:
      "L+ /var/lib/maubot/plugins/${baseNameOf plugin} - - - - ${plugin}"
    ) cfg.plugins);

    # Health check service
    systemd.services.maubot-health = {
      description = "Maubot health check";
      after = [ "maubot.service" ];
      
      serviceConfig = {
        Type = "oneshot";
        User = "nobody";
        Group = "nogroup";
        ExecStart = pkgs.writeShellScript "maubot-health" ''
          # Check if Maubot management interface is responding
          # Note: All maubot endpoints require auth, so 401 is expected and healthy
          HTTP_CODE=$(${pkgs.curl}/bin/curl -s -o /dev/null -w "%{http_code}" "http://localhost:${toString cfg.port}/_matrix/maubot/v1/login" 2>/dev/null)
          if [ "$HTTP_CODE" = "401" ] || [ "$HTTP_CODE" = "200" ]; then
            echo "Maubot health check: OK (HTTP $HTTP_CODE)"
            exit 0
          else
            echo "Maubot health check: FAILED (HTTP $HTTP_CODE)"
            exit 1
          fi
        '';
        StandardOutput = "journal";
        StandardError = "journal";
      };
    };

    systemd.timers.maubot-health = {
      description = "Maubot health check timer";
      wantedBy = [ "timers.target" ];
      timerConfig = {
        OnCalendar = "*:0/5"; # Every 5 minutes
        Persistent = true;
      };
    };
    
    # Health check failure handling - restart service if health check fails consistently
    systemd.services.maubot-health-restart = {
      description = "Restart Maubot on health check failure";
      serviceConfig = {
        Type = "oneshot";
        ExecStart = pkgs.writeShellScript "maubot-health-restart" ''
          # Check if maubot health service failed recently
          if systemctl is-failed maubot-health.service >/dev/null 2>&1; then
            echo "Maubot health check failed, restarting maubot service"
            systemctl restart maubot.service
            
            # Reset health check failure state
            systemctl reset-failed maubot-health.service
          fi
        '';
        User = "root";
        StandardOutput = "journal";
        StandardError = "journal";
      };
    };

    systemd.timers.maubot-health-restart = {
      description = "Monitor Maubot health check failures and restart if needed";
      wantedBy = [ "timers.target" ];
      timerConfig = {
        OnCalendar = "*:2/10"; # Every 10 minutes, offset from health check
        Persistent = true;
      };
    };

    # Maubot management interface only accessible via SSH tunnel (localhost:29316)
    # Do NOT expose to internet - admin UI has no rate limiting
  };
}