import * as net from 'net';
import * as plugins from '../congodb.plugins.js';
import { WireProtocol, OP_QUERY } from './WireProtocol.js';
import { CommandRouter } from './CommandRouter.js';
import { MemoryStorageAdapter } from '../storage/MemoryStorageAdapter.js';
import { FileStorageAdapter } from '../storage/FileStorageAdapter.js';
import type { IStorageAdapter } from '../storage/IStorageAdapter.js';

/**
 * Server configuration options
 */
export interface ICongoServerOptions {
  /** Port to listen on (default: 27017) */
  port?: number;
  /** Host to bind to (default: 127.0.0.1) */
  host?: string;
  /** Storage type: 'memory' or 'file' (default: 'memory') */
  storage?: 'memory' | 'file';
  /** Path for file storage (required if storage is 'file') */
  storagePath?: string;
  /** Enable persistence for memory storage */
  persistPath?: string;
  /** Persistence interval in ms (default: 60000) */
  persistIntervalMs?: number;
}

/**
 * Connection state for each client
 */
interface IConnectionState {
  id: number;
  socket: net.Socket;
  buffer: Buffer;
  authenticated: boolean;
  database: string;
}

/**
 * CongoServer - MongoDB Wire Protocol compatible server
 *
 * This server implements the MongoDB wire protocol (OP_MSG) to allow
 * official MongoDB drivers to connect and perform operations.
 *
 * @example
 * ```typescript
 * import { CongoServer } from '@push.rocks/smartmongo/congodb';
 * import { MongoClient } from 'mongodb';
 *
 * const server = new CongoServer({ port: 27017 });
 * await server.start();
 *
 * const client = new MongoClient('mongodb://127.0.0.1:27017');
 * await client.connect();
 * ```
 */
export class CongoServer {
  private options: Required<ICongoServerOptions>;
  private server: net.Server | null = null;
  private storage: IStorageAdapter;
  private commandRouter: CommandRouter;
  private connections: Map<number, IConnectionState> = new Map();
  private connectionIdCounter = 0;
  private isRunning = false;
  private startTime: Date = new Date();

  constructor(options: ICongoServerOptions = {}) {
    this.options = {
      port: options.port ?? 27017,
      host: options.host ?? '127.0.0.1',
      storage: options.storage ?? 'memory',
      storagePath: options.storagePath ?? './data',
      persistPath: options.persistPath ?? '',
      persistIntervalMs: options.persistIntervalMs ?? 60000,
    };

    // Create storage adapter
    if (this.options.storage === 'file') {
      this.storage = new FileStorageAdapter(this.options.storagePath);
    } else {
      this.storage = new MemoryStorageAdapter({
        persistPath: this.options.persistPath || undefined,
        persistIntervalMs: this.options.persistPath ? this.options.persistIntervalMs : undefined,
      });
    }

    // Create command router
    this.commandRouter = new CommandRouter(this.storage, this);
  }

  /**
   * Get the storage adapter (for testing/debugging)
   */
  getStorage(): IStorageAdapter {
    return this.storage;
  }

  /**
   * Get server uptime in seconds
   */
  getUptime(): number {
    return Math.floor((Date.now() - this.startTime.getTime()) / 1000);
  }

  /**
   * Get current connection count
   */
  getConnectionCount(): number {
    return this.connections.size;
  }

  /**
   * Start the server
   */
  async start(): Promise<void> {
    if (this.isRunning) {
      throw new Error('Server is already running');
    }

    // Initialize storage
    await this.storage.initialize();

    return new Promise((resolve, reject) => {
      this.server = net.createServer((socket) => {
        this.handleConnection(socket);
      });

      this.server.on('error', (err) => {
        if (!this.isRunning) {
          reject(err);
        } else {
          console.error('Server error:', err);
        }
      });

      this.server.listen(this.options.port, this.options.host, () => {
        this.isRunning = true;
        this.startTime = new Date();
        resolve();
      });
    });
  }

  /**
   * Stop the server
   */
  async stop(): Promise<void> {
    if (!this.isRunning || !this.server) {
      return;
    }

    // Close all connections
    for (const conn of this.connections.values()) {
      conn.socket.destroy();
    }
    this.connections.clear();

    // Close storage
    await this.storage.close();

    return new Promise((resolve) => {
      this.server!.close(() => {
        this.isRunning = false;
        this.server = null;
        resolve();
      });
    });
  }

  /**
   * Handle a new client connection
   */
  private handleConnection(socket: net.Socket): void {
    const connectionId = ++this.connectionIdCounter;

    const state: IConnectionState = {
      id: connectionId,
      socket,
      buffer: Buffer.alloc(0),
      authenticated: true, // No auth required for now
      database: 'test',
    };

    this.connections.set(connectionId, state);

    socket.on('data', (data) => {
      this.handleData(state, Buffer.isBuffer(data) ? data : Buffer.from(data));
    });

    socket.on('close', () => {
      this.connections.delete(connectionId);
    });

    socket.on('error', (err) => {
      // Connection errors are expected when clients disconnect
      this.connections.delete(connectionId);
    });
  }

  /**
   * Handle incoming data from a client
   */
  private handleData(state: IConnectionState, data: Buffer): void {
    // Append new data to buffer
    state.buffer = Buffer.concat([state.buffer, data]);

    // Process messages from buffer
    this.processMessages(state);
  }

  /**
   * Process complete messages from the buffer
   */
  private async processMessages(state: IConnectionState): Promise<void> {
    while (state.buffer.length >= 16) {
      try {
        const result = WireProtocol.parseMessage(state.buffer);

        if (!result) {
          // Not enough data for a complete message
          break;
        }

        const { command, bytesConsumed } = result;

        // Remove processed bytes from buffer
        state.buffer = state.buffer.subarray(bytesConsumed);

        // Process the command
        const response = await this.commandRouter.route(command);

        // Encode and send response
        let responseBuffer: Buffer;
        if (command.opCode === OP_QUERY) {
          // Legacy OP_QUERY gets OP_REPLY response
          responseBuffer = WireProtocol.encodeOpReplyResponse(
            command.requestID,
            [response]
          );
        } else {
          // OP_MSG gets OP_MSG response
          responseBuffer = WireProtocol.encodeOpMsgResponse(
            command.requestID,
            response
          );
        }

        if (!state.socket.destroyed) {
          state.socket.write(responseBuffer);
        }
      } catch (error: any) {
        // Send error response
        const errorResponse = WireProtocol.encodeErrorResponse(
          0, // We don't have the requestID at this point
          1,
          error.message || 'Internal error'
        );

        if (!state.socket.destroyed) {
          state.socket.write(errorResponse);
        }

        // Clear buffer on parse errors to avoid infinite loops
        if (error.message?.includes('opCode') || error.message?.includes('section')) {
          state.buffer = Buffer.alloc(0);
        }
        break;
      }
    }
  }

  /**
   * Get the connection URI for this server
   */
  getConnectionUri(): string {
    return `mongodb://${this.options.host}:${this.options.port}`;
  }

  /**
   * Check if the server is running
   */
  get running(): boolean {
    return this.isRunning;
  }

  /**
   * Get the port the server is listening on
   */
  get port(): number {
    return this.options.port;
  }

  /**
   * Get the host the server is bound to
   */
  get host(): string {
    return this.options.host;
  }
}