import * as plugins from '../tsmdb.plugins.js';
import type { IStorageAdapter } from '../storage/IStorageAdapter.js';
import type { IParsedCommand } from './WireProtocol.js';
import type { TsmdbServer } from './TsmdbServer.js';
import { IndexEngine } from '../engine/IndexEngine.js';
import { TransactionEngine } from '../engine/TransactionEngine.js';
import { SessionEngine } from '../engine/SessionEngine.js';

// Import handlers
import { HelloHandler } from './handlers/HelloHandler.js';
import { InsertHandler } from './handlers/InsertHandler.js';
import { FindHandler } from './handlers/FindHandler.js';
import { UpdateHandler } from './handlers/UpdateHandler.js';
import { DeleteHandler } from './handlers/DeleteHandler.js';
import { AggregateHandler } from './handlers/AggregateHandler.js';
import { IndexHandler } from './handlers/IndexHandler.js';
import { AdminHandler } from './handlers/AdminHandler.js';

/**
 * Handler context passed to command handlers
 */
export interface IHandlerContext {
  storage: IStorageAdapter;
  server: TsmdbServer;
  database: string;
  command: plugins.bson.Document;
  documentSequences?: Map<string, plugins.bson.Document[]>;
  /** Get or create an IndexEngine for a collection */
  getIndexEngine: (collName: string) => IndexEngine;
  /** Transaction engine instance */
  transactionEngine: TransactionEngine;
  /** Current transaction ID (if in a transaction) */
  txnId?: string;
  /** Session ID (from lsid) */
  sessionId?: string;
  /** Session engine instance */
  sessionEngine: SessionEngine;
}

/**
 * Command handler interface
 */
export interface ICommandHandler {
  handle(context: IHandlerContext): Promise<plugins.bson.Document>;
}

/**
 * CommandRouter - Routes incoming commands to appropriate handlers
 */
export class CommandRouter {
  private storage: IStorageAdapter;
  private server: TsmdbServer;
  private handlers: Map<string, ICommandHandler> = new Map();

  // Cursor state for getMore operations
  private cursors: Map<bigint, ICursorState> = new Map();
  private cursorIdCounter: bigint = BigInt(1);

  // Index engine cache: db.collection -> IndexEngine
  private indexEngines: Map<string, IndexEngine> = new Map();

  // Transaction engine (shared across all handlers)
  private transactionEngine: TransactionEngine;

  // Session engine (shared across all handlers)
  private sessionEngine: SessionEngine;

  constructor(storage: IStorageAdapter, server: TsmdbServer) {
    this.storage = storage;
    this.server = server;
    this.transactionEngine = new TransactionEngine(storage);
    this.sessionEngine = new SessionEngine();
    // Link session engine to transaction engine for auto-abort on session expiry
    this.sessionEngine.setTransactionEngine(this.transactionEngine);
    this.registerHandlers();
  }

  /**
   * Get or create an IndexEngine for a database.collection
   */
  getIndexEngine(dbName: string, collName: string): IndexEngine {
    const key = `${dbName}.${collName}`;
    let engine = this.indexEngines.get(key);
    if (!engine) {
      engine = new IndexEngine(dbName, collName, this.storage);
      this.indexEngines.set(key, engine);
    }
    return engine;
  }

  /**
   * Clear index engine cache for a collection (used when collection is dropped)
   */
  clearIndexEngineCache(dbName: string, collName?: string): void {
    if (collName) {
      this.indexEngines.delete(`${dbName}.${collName}`);
    } else {
      // Clear all engines for the database
      for (const key of this.indexEngines.keys()) {
        if (key.startsWith(`${dbName}.`)) {
          this.indexEngines.delete(key);
        }
      }
    }
  }

  /**
   * Register all command handlers
   */
  private registerHandlers(): void {
    // Create handler instances with shared state
    const helloHandler = new HelloHandler();
    const findHandler = new FindHandler(this.cursors, () => this.cursorIdCounter++);
    const insertHandler = new InsertHandler();
    const updateHandler = new UpdateHandler();
    const deleteHandler = new DeleteHandler();
    const aggregateHandler = new AggregateHandler(this.cursors, () => this.cursorIdCounter++);
    const indexHandler = new IndexHandler();
    const adminHandler = new AdminHandler();

    // Handshake commands
    this.handlers.set('hello', helloHandler);
    this.handlers.set('ismaster', helloHandler);
    this.handlers.set('isMaster', helloHandler);

    // CRUD commands
    this.handlers.set('find', findHandler);
    this.handlers.set('insert', insertHandler);
    this.handlers.set('update', updateHandler);
    this.handlers.set('delete', deleteHandler);
    this.handlers.set('findAndModify', updateHandler);
    this.handlers.set('getMore', findHandler);
    this.handlers.set('killCursors', findHandler);

    // Aggregation
    this.handlers.set('aggregate', aggregateHandler);
    this.handlers.set('count', findHandler);
    this.handlers.set('distinct', findHandler);

    // Index operations
    this.handlers.set('createIndexes', indexHandler);
    this.handlers.set('dropIndexes', indexHandler);
    this.handlers.set('listIndexes', indexHandler);

    // Admin/Database operations
    this.handlers.set('ping', adminHandler);
    this.handlers.set('listDatabases', adminHandler);
    this.handlers.set('listCollections', adminHandler);
    this.handlers.set('drop', adminHandler);
    this.handlers.set('dropDatabase', adminHandler);
    this.handlers.set('create', adminHandler);
    this.handlers.set('serverStatus', adminHandler);
    this.handlers.set('buildInfo', adminHandler);
    this.handlers.set('whatsmyuri', adminHandler);
    this.handlers.set('getLog', adminHandler);
    this.handlers.set('hostInfo', adminHandler);
    this.handlers.set('replSetGetStatus', adminHandler);
    this.handlers.set('isMaster', helloHandler);
    this.handlers.set('saslStart', adminHandler);
    this.handlers.set('saslContinue', adminHandler);
    this.handlers.set('endSessions', adminHandler);
    this.handlers.set('abortTransaction', adminHandler);
    this.handlers.set('commitTransaction', adminHandler);
    this.handlers.set('collStats', adminHandler);
    this.handlers.set('dbStats', adminHandler);
    this.handlers.set('connectionStatus', adminHandler);
    this.handlers.set('currentOp', adminHandler);
    this.handlers.set('collMod', adminHandler);
    this.handlers.set('renameCollection', adminHandler);
  }

  /**
   * Route a command to its handler
   */
  async route(parsedCommand: IParsedCommand): Promise<plugins.bson.Document> {
    const { commandName, command, database, documentSequences } = parsedCommand;

    // Extract session ID from lsid using SessionEngine helper
    let sessionId = SessionEngine.extractSessionId(command.lsid);
    let txnId: string | undefined;

    // If we have a session ID, register/touch the session
    if (sessionId) {
      this.sessionEngine.getOrCreateSession(sessionId);
    }

    // Check if this starts a new transaction
    if (command.startTransaction && sessionId) {
      txnId = this.transactionEngine.startTransaction(sessionId);
      this.sessionEngine.startTransaction(sessionId, txnId, command.txnNumber);
    } else if (sessionId && this.sessionEngine.isInTransaction(sessionId)) {
      // Continue existing transaction
      txnId = this.sessionEngine.getTransactionId(sessionId);
      // Verify transaction is still active
      if (txnId && !this.transactionEngine.isActive(txnId)) {
        this.sessionEngine.endTransaction(sessionId);
        txnId = undefined;
      }
    }

    // Create handler context
    const context: IHandlerContext = {
      storage: this.storage,
      server: this.server,
      database,
      command,
      documentSequences,
      getIndexEngine: (collName: string) => this.getIndexEngine(database, collName),
      transactionEngine: this.transactionEngine,
      sessionEngine: this.sessionEngine,
      txnId,
      sessionId,
    };

    // Find handler
    const handler = this.handlers.get(commandName);

    if (!handler) {
      // Unknown command
      return {
        ok: 0,
        errmsg: `no such command: '${commandName}'`,
        code: 59,
        codeName: 'CommandNotFound',
      };
    }

    try {
      return await handler.handle(context);
    } catch (error: any) {
      // Handle known error types
      if (error.code) {
        return {
          ok: 0,
          errmsg: error.message,
          code: error.code,
          codeName: error.codeName || 'UnknownError',
        };
      }

      // Generic error
      return {
        ok: 0,
        errmsg: error.message || 'Internal error',
        code: 1,
        codeName: 'InternalError',
      };
    }
  }

  /**
   * Close the command router and cleanup resources
   */
  close(): void {
    // Close session engine (stops cleanup interval, clears sessions)
    this.sessionEngine.close();
    // Clear cursors
    this.cursors.clear();
    // Clear index engine cache
    this.indexEngines.clear();
  }

  /**
   * Get session engine (for administrative purposes)
   */
  getSessionEngine(): SessionEngine {
    return this.sessionEngine;
  }

  /**
   * Get transaction engine (for administrative purposes)
   */
  getTransactionEngine(): TransactionEngine {
    return this.transactionEngine;
  }
}

/**
 * Cursor state for multi-batch queries
 */
export interface ICursorState {
  id: bigint;
  database: string;
  collection: string;
  documents: plugins.bson.Document[];
  position: number;
  batchSize: number;
  createdAt: Date;
}