feat(congodb): implement CongoDB MongoDB wire-protocol compatible in-memory server and APIs

ts/congodb/server/handlers/AdminHandler.ts

@@ -0,0 +1,614 @@
+import * as plugins from '../../congodb.plugins.js';
+import type { ICommandHandler, IHandlerContext } from '../CommandRouter.js';
+
+/**
+ * AdminHandler - Handles administrative commands
+ */
+export class AdminHandler implements ICommandHandler {
+  async handle(context: IHandlerContext): Promise<plugins.bson.Document> {
+    const { command } = context;
+
+    // Determine which command to handle
+    if (command.ping !== undefined) {
+      return this.handlePing(context);
+    } else if (command.listDatabases !== undefined) {
+      return this.handleListDatabases(context);
+    } else if (command.listCollections !== undefined) {
+      return this.handleListCollections(context);
+    } else if (command.drop !== undefined) {
+      return this.handleDrop(context);
+    } else if (command.dropDatabase !== undefined) {
+      return this.handleDropDatabase(context);
+    } else if (command.create !== undefined) {
+      return this.handleCreate(context);
+    } else if (command.serverStatus !== undefined) {
+      return this.handleServerStatus(context);
+    } else if (command.buildInfo !== undefined) {
+      return this.handleBuildInfo(context);
+    } else if (command.whatsmyuri !== undefined) {
+      return this.handleWhatsMyUri(context);
+    } else if (command.getLog !== undefined) {
+      return this.handleGetLog(context);
+    } else if (command.hostInfo !== undefined) {
+      return this.handleHostInfo(context);
+    } else if (command.replSetGetStatus !== undefined) {
+      return this.handleReplSetGetStatus(context);
+    } else if (command.saslStart !== undefined) {
+      return this.handleSaslStart(context);
+    } else if (command.saslContinue !== undefined) {
+      return this.handleSaslContinue(context);
+    } else if (command.endSessions !== undefined) {
+      return this.handleEndSessions(context);
+    } else if (command.abortTransaction !== undefined) {
+      return this.handleAbortTransaction(context);
+    } else if (command.commitTransaction !== undefined) {
+      return this.handleCommitTransaction(context);
+    } else if (command.collStats !== undefined) {
+      return this.handleCollStats(context);
+    } else if (command.dbStats !== undefined) {
+      return this.handleDbStats(context);
+    } else if (command.connectionStatus !== undefined) {
+      return this.handleConnectionStatus(context);
+    } else if (command.currentOp !== undefined) {
+      return this.handleCurrentOp(context);
+    } else if (command.collMod !== undefined) {
+      return this.handleCollMod(context);
+    } else if (command.renameCollection !== undefined) {
+      return this.handleRenameCollection(context);
+    }
+
+    return {
+      ok: 0,
+      errmsg: 'Unknown admin command',
+      code: 59,
+      codeName: 'CommandNotFound',
+    };
+  }
+
+  /**
+   * Handle ping command
+   */
+  private async handlePing(context: IHandlerContext): Promise<plugins.bson.Document> {
+    return { ok: 1 };
+  }
+
+  /**
+   * Handle listDatabases command
+   */
+  private async handleListDatabases(context: IHandlerContext): Promise<plugins.bson.Document> {
+    const { storage, command } = context;
+
+    const dbNames = await storage.listDatabases();
+    const nameOnly = command.nameOnly || false;
+
+    if (nameOnly) {
+      return {
+        ok: 1,
+        databases: dbNames.map(name => ({ name })),
+      };
+    }
+
+    // Build database list with sizes
+    const databases: plugins.bson.Document[] = [];
+    let totalSize = 0;
+
+    for (const name of dbNames) {
+      const collections = await storage.listCollections(name);
+      let dbSize = 0;
+
+      for (const collName of collections) {
+        const docs = await storage.findAll(name, collName);
+        // Estimate size (rough approximation)
+        dbSize += docs.reduce((sum, doc) => sum + JSON.stringify(doc).length, 0);
+      }
+
+      totalSize += dbSize;
+
+      databases.push({
+        name,
+        sizeOnDisk: dbSize,
+        empty: dbSize === 0,
+      });
+    }
+
+    return {
+      ok: 1,
+      databases,
+      totalSize,
+      totalSizeMb: totalSize / (1024 * 1024),
+    };
+  }
+
+  /**
+   * Handle listCollections command
+   */
+  private async handleListCollections(context: IHandlerContext): Promise<plugins.bson.Document> {
+    const { storage, database, command } = context;
+
+    const filter = command.filter || {};
+    const nameOnly = command.nameOnly || false;
+    const cursor = command.cursor || {};
+    const batchSize = cursor.batchSize || 101;
+
+    const collNames = await storage.listCollections(database);
+
+    let collections: plugins.bson.Document[] = [];
+
+    for (const name of collNames) {
+      // Apply name filter
+      if (filter.name && filter.name !== name) {
+        // Check regex
+        if (filter.name.$regex) {
+          const regex = new RegExp(filter.name.$regex, filter.name.$options);
+          if (!regex.test(name)) continue;
+        } else {
+          continue;
+        }
+      }
+
+      if (nameOnly) {
+        collections.push({ name });
+      } else {
+        collections.push({
+          name,
+          type: 'collection',
+          options: {},
+          info: {
+            readOnly: false,
+            uuid: new plugins.bson.UUID(),
+          },
+          idIndex: {
+            v: 2,
+            key: { _id: 1 },
+            name: '_id_',
+          },
+        });
+      }
+    }
+
+    return {
+      ok: 1,
+      cursor: {
+        id: plugins.bson.Long.fromNumber(0),
+        ns: `${database}.$cmd.listCollections`,
+        firstBatch: collections,
+      },
+    };
+  }
+
+  /**
+   * Handle drop command (drop collection)
+   */
+  private async handleDrop(context: IHandlerContext): Promise<plugins.bson.Document> {
+    const { storage, database, command } = context;
+
+    const collection = command.drop;
+
+    const existed = await storage.dropCollection(database, collection);
+
+    if (!existed) {
+      return {
+        ok: 0,
+        errmsg: `ns not found ${database}.${collection}`,
+        code: 26,
+        codeName: 'NamespaceNotFound',
+      };
+    }
+
+    return { ok: 1, ns: `${database}.${collection}` };
+  }
+
+  /**
+   * Handle dropDatabase command
+   */
+  private async handleDropDatabase(context: IHandlerContext): Promise<plugins.bson.Document> {
+    const { storage, database } = context;
+
+    await storage.dropDatabase(database);
+
+    return { ok: 1, dropped: database };
+  }
+
+  /**
+   * Handle create command (create collection)
+   */
+  private async handleCreate(context: IHandlerContext): Promise<plugins.bson.Document> {
+    const { storage, database, command } = context;
+
+    const collection = command.create;
+
+    // Check if already exists
+    const exists = await storage.collectionExists(database, collection);
+    if (exists) {
+      return {
+        ok: 0,
+        errmsg: `Collection ${database}.${collection} already exists.`,
+        code: 48,
+        codeName: 'NamespaceExists',
+      };
+    }
+
+    await storage.createCollection(database, collection);
+
+    return { ok: 1 };
+  }
+
+  /**
+   * Handle serverStatus command
+   */
+  private async handleServerStatus(context: IHandlerContext): Promise<plugins.bson.Document> {
+    const { server } = context;
+
+    const uptime = server.getUptime();
+    const connections = server.getConnectionCount();
+
+    return {
+      ok: 1,
+      host: `${server.host}:${server.port}`,
+      version: '7.0.0',
+      process: 'congodb',
+      pid: process.pid,
+      uptime,
+      uptimeMillis: uptime * 1000,
+      uptimeEstimate: uptime,
+      localTime: new Date(),
+      mem: {
+        resident: Math.floor(process.memoryUsage().rss / (1024 * 1024)),
+        virtual: Math.floor(process.memoryUsage().heapTotal / (1024 * 1024)),
+        supported: true,
+      },
+      connections: {
+        current: connections,
+        available: 1000 - connections,
+        totalCreated: connections,
+        active: connections,
+      },
+      network: {
+        bytesIn: 0,
+        bytesOut: 0,
+        numRequests: 0,
+      },
+      storageEngine: {
+        name: 'congodb',
+        supportsCommittedReads: true,
+        persistent: false,
+      },
+    };
+  }
+
+  /**
+   * Handle buildInfo command
+   */
+  private async handleBuildInfo(context: IHandlerContext): Promise<plugins.bson.Document> {
+    return {
+      ok: 1,
+      version: '7.0.0',
+      gitVersion: 'congodb',
+      modules: [],
+      allocator: 'system',
+      javascriptEngine: 'none',
+      sysInfo: 'deprecated',
+      versionArray: [7, 0, 0, 0],
+      openssl: {
+        running: 'disabled',
+        compiled: 'disabled',
+      },
+      buildEnvironment: {
+        distmod: 'congodb',
+        distarch: process.arch,
+        cc: '',
+        ccflags: '',
+        cxx: '',
+        cxxflags: '',
+        linkflags: '',
+        target_arch: process.arch,
+        target_os: process.platform,
+      },
+      bits: 64,
+      debug: false,
+      maxBsonObjectSize: 16777216,
+      storageEngines: ['congodb'],
+    };
+  }
+
+  /**
+   * Handle whatsmyuri command
+   */
+  private async handleWhatsMyUri(context: IHandlerContext): Promise<plugins.bson.Document> {
+    const { server } = context;
+    return {
+      ok: 1,
+      you: `127.0.0.1:${server.port}`,
+    };
+  }
+
+  /**
+   * Handle getLog command
+   */
+  private async handleGetLog(context: IHandlerContext): Promise<plugins.bson.Document> {
+    const { command } = context;
+
+    if (command.getLog === '*') {
+      return {
+        ok: 1,
+        names: ['global', 'startupWarnings'],
+      };
+    }
+
+    return {
+      ok: 1,
+      totalLinesWritten: 0,
+      log: [],
+    };
+  }
+
+  /**
+   * Handle hostInfo command
+   */
+  private async handleHostInfo(context: IHandlerContext): Promise<plugins.bson.Document> {
+    return {
+      ok: 1,
+      system: {
+        currentTime: new Date(),
+        hostname: 'localhost',
+        cpuAddrSize: 64,
+        memSizeMB: Math.floor(process.memoryUsage().heapTotal / (1024 * 1024)),
+        numCores: 1,
+        cpuArch: process.arch,
+        numaEnabled: false,
+      },
+      os: {
+        type: process.platform,
+        name: process.platform,
+        version: process.version,
+      },
+      extra: {},
+    };
+  }
+
+  /**
+   * Handle replSetGetStatus command
+   */
+  private async handleReplSetGetStatus(context: IHandlerContext): Promise<plugins.bson.Document> {
+    // We're standalone, not a replica set
+    return {
+      ok: 0,
+      errmsg: 'not running with --replSet',
+      code: 76,
+      codeName: 'NoReplicationEnabled',
+    };
+  }
+
+  /**
+   * Handle saslStart command (authentication)
+   */
+  private async handleSaslStart(context: IHandlerContext): Promise<plugins.bson.Document> {
+    // We don't require authentication, but we need to respond properly
+    // to let drivers know auth is "successful"
+    return {
+      ok: 1,
+      conversationId: 1,
+      done: true,
+      payload: Buffer.from([]),
+    };
+  }
+
+  /**
+   * Handle saslContinue command
+   */
+  private async handleSaslContinue(context: IHandlerContext): Promise<plugins.bson.Document> {
+    return {
+      ok: 1,
+      conversationId: 1,
+      done: true,
+      payload: Buffer.from([]),
+    };
+  }
+
+  /**
+   * Handle endSessions command
+   */
+  private async handleEndSessions(context: IHandlerContext): Promise<plugins.bson.Document> {
+    return { ok: 1 };
+  }
+
+  /**
+   * Handle abortTransaction command
+   */
+  private async handleAbortTransaction(context: IHandlerContext): Promise<plugins.bson.Document> {
+    // Transactions are not fully supported, but acknowledge the command
+    return { ok: 1 };
+  }
+
+  /**
+   * Handle commitTransaction command
+   */
+  private async handleCommitTransaction(context: IHandlerContext): Promise<plugins.bson.Document> {
+    // Transactions are not fully supported, but acknowledge the command
+    return { ok: 1 };
+  }
+
+  /**
+   * Handle collStats command
+   */
+  private async handleCollStats(context: IHandlerContext): Promise<plugins.bson.Document> {
+    const { storage, database, command } = context;
+
+    const collection = command.collStats;
+
+    const exists = await storage.collectionExists(database, collection);
+    if (!exists) {
+      return {
+        ok: 0,
+        errmsg: `ns not found ${database}.${collection}`,
+        code: 26,
+        codeName: 'NamespaceNotFound',
+      };
+    }
+
+    const docs = await storage.findAll(database, collection);
+    const size = docs.reduce((sum, doc) => sum + JSON.stringify(doc).length, 0);
+    const count = docs.length;
+    const avgObjSize = count > 0 ? size / count : 0;
+
+    const indexes = await storage.getIndexes(database, collection);
+
+    return {
+      ok: 1,
+      ns: `${database}.${collection}`,
+      count,
+      size,
+      avgObjSize,
+      storageSize: size,
+      totalIndexSize: 0,
+      indexSizes: indexes.reduce((acc: any, idx: any) => {
+        acc[idx.name] = 0;
+        return acc;
+      }, {}),
+      nindexes: indexes.length,
+    };
+  }
+
+  /**
+   * Handle dbStats command
+   */
+  private async handleDbStats(context: IHandlerContext): Promise<plugins.bson.Document> {
+    const { storage, database } = context;
+
+    const collections = await storage.listCollections(database);
+    let totalSize = 0;
+    let totalObjects = 0;
+
+    for (const collName of collections) {
+      const docs = await storage.findAll(database, collName);
+      totalObjects += docs.length;
+      totalSize += docs.reduce((sum, doc) => sum + JSON.stringify(doc).length, 0);
+    }
+
+    return {
+      ok: 1,
+      db: database,
+      collections: collections.length,
+      views: 0,
+      objects: totalObjects,
+      avgObjSize: totalObjects > 0 ? totalSize / totalObjects : 0,
+      dataSize: totalSize,
+      storageSize: totalSize,
+      indexes: collections.length, // At least _id index per collection
+      indexSize: 0,
+      totalSize,
+    };
+  }
+
+  /**
+   * Handle connectionStatus command
+   */
+  private async handleConnectionStatus(context: IHandlerContext): Promise<plugins.bson.Document> {
+    return {
+      ok: 1,
+      authInfo: {
+        authenticatedUsers: [],
+        authenticatedUserRoles: [],
+      },
+    };
+  }
+
+  /**
+   * Handle currentOp command
+   */
+  private async handleCurrentOp(context: IHandlerContext): Promise<plugins.bson.Document> {
+    return {
+      ok: 1,
+      inprog: [],
+    };
+  }
+
+  /**
+   * Handle collMod command
+   */
+  private async handleCollMod(context: IHandlerContext): Promise<plugins.bson.Document> {
+    // We don't support modifying collection options, but acknowledge the command
+    return { ok: 1 };
+  }
+
+  /**
+   * Handle renameCollection command
+   */
+  private async handleRenameCollection(context: IHandlerContext): Promise<plugins.bson.Document> {
+    const { storage, command } = context;
+
+    const from = command.renameCollection;
+    const to = command.to;
+    const dropTarget = command.dropTarget || false;
+
+    if (!from || !to) {
+      return {
+        ok: 0,
+        errmsg: 'renameCollection requires both source and target',
+        code: 2,
+        codeName: 'BadValue',
+      };
+    }
+
+    // Parse namespace (format: "db.collection")
+    const fromParts = from.split('.');
+    const toParts = to.split('.');
+
+    if (fromParts.length < 2 || toParts.length < 2) {
+      return {
+        ok: 0,
+        errmsg: 'Invalid namespace format',
+        code: 73,
+        codeName: 'InvalidNamespace',
+      };
+    }
+
+    const fromDb = fromParts[0];
+    const fromColl = fromParts.slice(1).join('.');
+    const toDb = toParts[0];
+    const toColl = toParts.slice(1).join('.');
+
+    // Check if source exists
+    const sourceExists = await storage.collectionExists(fromDb, fromColl);
+    if (!sourceExists) {
+      return {
+        ok: 0,
+        errmsg: `source namespace ${from} does not exist`,
+        code: 26,
+        codeName: 'NamespaceNotFound',
+      };
+    }
+
+    // Check if target exists
+    const targetExists = await storage.collectionExists(toDb, toColl);
+    if (targetExists) {
+      if (dropTarget) {
+        await storage.dropCollection(toDb, toColl);
+      } else {
+        return {
+          ok: 0,
+          errmsg: `target namespace ${to} already exists`,
+          code: 48,
+          codeName: 'NamespaceExists',
+        };
+      }
+    }
+
+    // Same database rename
+    if (fromDb === toDb) {
+      await storage.renameCollection(fromDb, fromColl, toColl);
+    } else {
+      // Cross-database rename: copy documents then drop source
+      await storage.createCollection(toDb, toColl);
+      const docs = await storage.findAll(fromDb, fromColl);
+
+      for (const doc of docs) {
+        await storage.insertOne(toDb, toColl, doc);
+      }
+
+      await storage.dropCollection(fromDb, fromColl);
+    }
+
+    return { ok: 1 };
+  }
+}

ts/congodb/server/handlers/AggregateHandler.ts

@@ -0,0 +1,342 @@
+import * as plugins from '../../congodb.plugins.js';
+import type { ICommandHandler, IHandlerContext, ICursorState } from '../CommandRouter.js';
+import { AggregationEngine } from '../../engine/AggregationEngine.js';
+
+/**
+ * AggregateHandler - Handles aggregate command
+ */
+export class AggregateHandler implements ICommandHandler {
+  private cursors: Map<bigint, ICursorState>;
+  private nextCursorId: () => bigint;
+
+  constructor(
+    cursors: Map<bigint, ICursorState>,
+    nextCursorId: () => bigint
+  ) {
+    this.cursors = cursors;
+    this.nextCursorId = nextCursorId;
+  }
+
+  async handle(context: IHandlerContext): Promise<plugins.bson.Document> {
+    const { storage, database, command } = context;
+
+    const collection = command.aggregate;
+    const pipeline = command.pipeline || [];
+    const cursor = command.cursor || {};
+    const batchSize = cursor.batchSize || 101;
+
+    // Validate
+    if (typeof collection !== 'string' && collection !== 1) {
+      return {
+        ok: 0,
+        errmsg: 'aggregate command requires a collection name or 1',
+        code: 2,
+        codeName: 'BadValue',
+      };
+    }
+
+    if (!Array.isArray(pipeline)) {
+      return {
+        ok: 0,
+        errmsg: 'pipeline must be an array',
+        code: 2,
+        codeName: 'BadValue',
+      };
+    }
+
+    try {
+      // Get source documents
+      let documents: plugins.bson.Document[] = [];
+
+      if (collection === 1 || collection === '1') {
+        // Database-level aggregation (e.g., $listLocalSessions)
+        documents = [];
+      } else {
+        // Collection-level aggregation
+        const exists = await storage.collectionExists(database, collection);
+        if (exists) {
+          documents = await storage.findAll(database, collection);
+        }
+      }
+
+      // Handle $lookup and $graphLookup stages that reference other collections
+      const processedPipeline = await this.preprocessPipeline(
+        storage,
+        database,
+        pipeline,
+        documents
+      );
+
+      // Run aggregation
+      let results: plugins.bson.Document[];
+
+      // Check for special stages that we handle manually
+      if (this.hasSpecialStages(pipeline)) {
+        results = await this.executeWithSpecialStages(
+          storage,
+          database,
+          documents,
+          pipeline
+        );
+      } else {
+        results = AggregationEngine.aggregate(documents as any, processedPipeline);
+      }
+
+      // Handle $out and $merge stages
+      const lastStage = pipeline[pipeline.length - 1];
+      if (lastStage && lastStage.$out) {
+        await this.handleOut(storage, database, results, lastStage.$out);
+        return { ok: 1, cursor: { id: plugins.bson.Long.fromNumber(0), ns: `${database}.${collection}`, firstBatch: [] } };
+      }
+
+      if (lastStage && lastStage.$merge) {
+        await this.handleMerge(storage, database, results, lastStage.$merge);
+        return { ok: 1, cursor: { id: plugins.bson.Long.fromNumber(0), ns: `${database}.${collection}`, firstBatch: [] } };
+      }
+
+      // Build cursor response
+      const effectiveBatchSize = Math.min(batchSize, results.length);
+      const firstBatch = results.slice(0, effectiveBatchSize);
+      const remaining = results.slice(effectiveBatchSize);
+
+      let cursorId = BigInt(0);
+      if (remaining.length > 0) {
+        cursorId = this.nextCursorId();
+        this.cursors.set(cursorId, {
+          id: cursorId,
+          database,
+          collection: typeof collection === 'string' ? collection : '$cmd.aggregate',
+          documents: remaining,
+          position: 0,
+          batchSize,
+          createdAt: new Date(),
+        });
+      }
+
+      return {
+        ok: 1,
+        cursor: {
+          id: plugins.bson.Long.fromBigInt(cursorId),
+          ns: `${database}.${typeof collection === 'string' ? collection : '$cmd.aggregate'}`,
+          firstBatch,
+        },
+      };
+    } catch (error: any) {
+      return {
+        ok: 0,
+        errmsg: error.message || 'Aggregation failed',
+        code: 1,
+        codeName: 'InternalError',
+      };
+    }
+  }
+
+  /**
+   * Preprocess pipeline to handle cross-collection lookups
+   */
+  private async preprocessPipeline(
+    storage: any,
+    database: string,
+    pipeline: plugins.bson.Document[],
+    documents: plugins.bson.Document[]
+  ): Promise<plugins.bson.Document[]> {
+    // For now, return the pipeline as-is
+    // Cross-collection lookups are handled in executeWithSpecialStages
+    return pipeline;
+  }
+
+  /**
+   * Check if pipeline has stages that need special handling
+   */
+  private hasSpecialStages(pipeline: plugins.bson.Document[]): boolean {
+    return pipeline.some(stage =>
+      stage.$lookup ||
+      stage.$graphLookup ||
+      stage.$unionWith
+    );
+  }
+
+  /**
+   * Execute pipeline with special stage handling
+   */
+  private async executeWithSpecialStages(
+    storage: any,
+    database: string,
+    documents: plugins.bson.Document[],
+    pipeline: plugins.bson.Document[]
+  ): Promise<plugins.bson.Document[]> {
+    let results: plugins.bson.Document[] = [...documents];
+
+    for (const stage of pipeline) {
+      if (stage.$lookup) {
+        const lookupSpec = stage.$lookup;
+        const fromCollection = lookupSpec.from;
+
+        // Get foreign collection documents
+        const foreignExists = await storage.collectionExists(database, fromCollection);
+        const foreignDocs = foreignExists
+          ? await storage.findAll(database, fromCollection)
+          : [];
+
+        results = AggregationEngine.executeLookup(results as any, lookupSpec, foreignDocs);
+      } else if (stage.$graphLookup) {
+        const graphLookupSpec = stage.$graphLookup;
+        const fromCollection = graphLookupSpec.from;
+
+        const foreignExists = await storage.collectionExists(database, fromCollection);
+        const foreignDocs = foreignExists
+          ? await storage.findAll(database, fromCollection)
+          : [];
+
+        results = AggregationEngine.executeGraphLookup(results as any, graphLookupSpec, foreignDocs);
+      } else if (stage.$unionWith) {
+        let unionSpec = stage.$unionWith;
+        let unionColl: string;
+        let unionPipeline: plugins.bson.Document[] | undefined;
+
+        if (typeof unionSpec === 'string') {
+          unionColl = unionSpec;
+        } else {
+          unionColl = unionSpec.coll;
+          unionPipeline = unionSpec.pipeline;
+        }
+
+        const unionExists = await storage.collectionExists(database, unionColl);
+        const unionDocs = unionExists
+          ? await storage.findAll(database, unionColl)
+          : [];
+
+        results = AggregationEngine.executeUnionWith(results as any, unionDocs, unionPipeline);
+      } else if (stage.$facet) {
+        // Execute each facet pipeline separately
+        const facetResults: plugins.bson.Document = {};
+
+        for (const [facetName, facetPipeline] of Object.entries(stage.$facet)) {
+          const facetDocs = await this.executeWithSpecialStages(
+            storage,
+            database,
+            results,
+            facetPipeline as plugins.bson.Document[]
+          );
+          facetResults[facetName] = facetDocs;
+        }
+
+        results = [facetResults];
+      } else {
+        // Regular stage - pass to mingo
+        results = AggregationEngine.aggregate(results as any, [stage]);
+      }
+    }
+
+    return results;
+  }
+
+  /**
+   * Handle $out stage - write results to a collection
+   */
+  private async handleOut(
+    storage: any,
+    database: string,
+    results: plugins.bson.Document[],
+    outSpec: string | { db?: string; coll: string }
+  ): Promise<void> {
+    let targetDb = database;
+    let targetColl: string;
+
+    if (typeof outSpec === 'string') {
+      targetColl = outSpec;
+    } else {
+      targetDb = outSpec.db || database;
+      targetColl = outSpec.coll;
+    }
+
+    // Drop existing collection
+    await storage.dropCollection(targetDb, targetColl);
+
+    // Create new collection and insert results
+    await storage.createCollection(targetDb, targetColl);
+
+    for (const doc of results) {
+      if (!doc._id) {
+        doc._id = new plugins.bson.ObjectId();
+      }
+      await storage.insertOne(targetDb, targetColl, doc);
+    }
+  }
+
+  /**
+   * Handle $merge stage - merge results into a collection
+   */
+  private async handleMerge(
+    storage: any,
+    database: string,
+    results: plugins.bson.Document[],
+    mergeSpec: any
+  ): Promise<void> {
+    let targetDb = database;
+    let targetColl: string;
+
+    if (typeof mergeSpec === 'string') {
+      targetColl = mergeSpec;
+    } else if (typeof mergeSpec.into === 'string') {
+      targetColl = mergeSpec.into;
+    } else {
+      targetDb = mergeSpec.into.db || database;
+      targetColl = mergeSpec.into.coll;
+    }
+
+    const on = mergeSpec.on || '_id';
+    const whenMatched = mergeSpec.whenMatched || 'merge';
+    const whenNotMatched = mergeSpec.whenNotMatched || 'insert';
+
+    // Ensure target collection exists
+    await storage.createCollection(targetDb, targetColl);
+
+    for (const doc of results) {
+      // Find matching document
+      const existingDocs = await storage.findAll(targetDb, targetColl);
+      const onFields = Array.isArray(on) ? on : [on];
+
+      let matchingDoc = null;
+      for (const existing of existingDocs) {
+        let matches = true;
+        for (const field of onFields) {
+          if (JSON.stringify(existing[field]) !== JSON.stringify(doc[field])) {
+            matches = false;
+            break;
+          }
+        }
+        if (matches) {
+          matchingDoc = existing;
+          break;
+        }
+      }
+
+      if (matchingDoc) {
+        // Handle whenMatched
+        if (whenMatched === 'replace') {
+          await storage.updateById(targetDb, targetColl, matchingDoc._id, doc);
+        } else if (whenMatched === 'keepExisting') {
+          // Do nothing
+        } else if (whenMatched === 'merge') {
+          const merged = { ...matchingDoc, ...doc };
+          await storage.updateById(targetDb, targetColl, matchingDoc._id, merged);
+        } else if (whenMatched === 'fail') {
+          throw new Error('Document matched but whenMatched is fail');
+        }
+      } else {
+        // Handle whenNotMatched
+        if (whenNotMatched === 'insert') {
+          if (!doc._id) {
+            doc._id = new plugins.bson.ObjectId();
+          }
+          await storage.insertOne(targetDb, targetColl, doc);
+        } else if (whenNotMatched === 'discard') {
+          // Do nothing
+        } else if (whenNotMatched === 'fail') {
+          throw new Error('Document not matched but whenNotMatched is fail');
+        }
+      }
+    }
+  }
+}

ts/congodb/server/handlers/DeleteHandler.ts

@@ -0,0 +1,100 @@
+import * as plugins from '../../congodb.plugins.js';
+import type { ICommandHandler, IHandlerContext } from '../CommandRouter.js';
+import { QueryEngine } from '../../engine/QueryEngine.js';
+
+/**
+ * DeleteHandler - Handles delete commands
+ */
+export class DeleteHandler implements ICommandHandler {
+  async handle(context: IHandlerContext): Promise<plugins.bson.Document> {
+    const { storage, database, command, documentSequences } = context;
+
+    const collection = command.delete;
+    if (typeof collection !== 'string') {
+      return {
+        ok: 0,
+        errmsg: 'delete command requires a collection name',
+        code: 2,
+        codeName: 'BadValue',
+      };
+    }
+
+    // Get deletes from command or document sequences
+    let deletes: plugins.bson.Document[] = command.deletes || [];
+
+    // Check for OP_MSG document sequences
+    if (documentSequences && documentSequences.has('deletes')) {
+      deletes = documentSequences.get('deletes')!;
+    }
+
+    if (!Array.isArray(deletes) || deletes.length === 0) {
+      return {
+        ok: 0,
+        errmsg: 'delete command requires deletes array',
+        code: 2,
+        codeName: 'BadValue',
+      };
+    }
+
+    const ordered = command.ordered !== false;
+    const writeErrors: plugins.bson.Document[] = [];
+    let totalDeleted = 0;
+
+    // Check if collection exists
+    const exists = await storage.collectionExists(database, collection);
+    if (!exists) {
+      // Collection doesn't exist, return success with 0 deleted
+      return { ok: 1, n: 0 };
+    }
+
+    for (let i = 0; i < deletes.length; i++) {
+      const deleteSpec = deletes[i];
+      const filter = deleteSpec.q || deleteSpec.filter || {};
+      const limit = deleteSpec.limit;
+
+      // limit: 0 means delete all matching, limit: 1 means delete one
+      const deleteAll = limit === 0;
+
+      try {
+        // Get all documents
+        const documents = await storage.findAll(database, collection);
+
+        // Apply filter
+        const matchingDocs = QueryEngine.filter(documents, filter);
+
+        if (matchingDocs.length === 0) {
+          continue;
+        }
+
+        // Determine which documents to delete
+        const docsToDelete = deleteAll ? matchingDocs : matchingDocs.slice(0, 1);
+
+        // Delete the documents
+        const idsToDelete = docsToDelete.map(doc => doc._id);
+        const deleted = await storage.deleteByIds(database, collection, idsToDelete);
+        totalDeleted += deleted;
+      } catch (error: any) {
+        writeErrors.push({
+          index: i,
+          code: error.code || 1,
+          errmsg: error.message || 'Delete failed',
+        });
+
+        if (ordered) {
+          break;
+        }
+      }
+    }
+
+    const response: plugins.bson.Document = {
+      ok: 1,
+      n: totalDeleted,
+    };
+
+    if (writeErrors.length > 0) {
+      response.writeErrors = writeErrors;
+    }
+
+    return response;
+  }
+}

ts/congodb/server/handlers/FindHandler.ts

@@ -0,0 +1,301 @@
+import * as plugins from '../../congodb.plugins.js';
+import type { ICommandHandler, IHandlerContext, ICursorState } from '../CommandRouter.js';
+import { QueryEngine } from '../../engine/QueryEngine.js';
+
+/**
+ * FindHandler - Handles find, getMore, killCursors, count, distinct commands
+ */
+export class FindHandler implements ICommandHandler {
+  private cursors: Map<bigint, ICursorState>;
+  private nextCursorId: () => bigint;
+
+  constructor(
+    cursors: Map<bigint, ICursorState>,
+    nextCursorId: () => bigint
+  ) {
+    this.cursors = cursors;
+    this.nextCursorId = nextCursorId;
+  }
+
+  async handle(context: IHandlerContext): Promise<plugins.bson.Document> {
+    const { command } = context;
+
+    // Determine which operation to perform
+    if (command.find) {
+      return this.handleFind(context);
+    } else if (command.getMore !== undefined) {
+      return this.handleGetMore(context);
+    } else if (command.killCursors) {
+      return this.handleKillCursors(context);
+    } else if (command.count) {
+      return this.handleCount(context);
+    } else if (command.distinct) {
+      return this.handleDistinct(context);
+    }
+
+    return {
+      ok: 0,
+      errmsg: 'Unknown find-related command',
+      code: 59,
+      codeName: 'CommandNotFound',
+    };
+  }
+
+  /**
+   * Handle find command
+   */
+  private async handleFind(context: IHandlerContext): Promise<plugins.bson.Document> {
+    const { storage, database, command } = context;
+
+    const collection = command.find;
+    const filter = command.filter || {};
+    const projection = command.projection;
+    const sort = command.sort;
+    const skip = command.skip || 0;
+    const limit = command.limit || 0;
+    const batchSize = command.batchSize || 101;
+    const singleBatch = command.singleBatch || false;
+
+    // Ensure collection exists
+    const exists = await storage.collectionExists(database, collection);
+    if (!exists) {
+      // Return empty cursor for non-existent collection
+      return {
+        ok: 1,
+        cursor: {
+          id: plugins.bson.Long.fromNumber(0),
+          ns: `${database}.${collection}`,
+          firstBatch: [],
+        },
+      };
+    }
+
+    // Get all documents
+    let documents = await storage.findAll(database, collection);
+
+    // Apply filter
+    documents = QueryEngine.filter(documents, filter);
+
+    // Apply sort
+    if (sort) {
+      documents = QueryEngine.sort(documents, sort);
+    }
+
+    // Apply skip
+    if (skip > 0) {
+      documents = documents.slice(skip);
+    }
+
+    // Apply limit
+    if (limit > 0) {
+      documents = documents.slice(0, limit);
+    }
+
+    // Apply projection
+    if (projection) {
+      documents = QueryEngine.project(documents, projection) as any[];
+    }
+
+    // Determine how many documents to return in first batch
+    const effectiveBatchSize = Math.min(batchSize, documents.length);
+    const firstBatch = documents.slice(0, effectiveBatchSize);
+    const remaining = documents.slice(effectiveBatchSize);
+
+    // Create cursor if there are more documents
+    let cursorId = BigInt(0);
+    if (remaining.length > 0 && !singleBatch) {
+      cursorId = this.nextCursorId();
+      this.cursors.set(cursorId, {
+        id: cursorId,
+        database,
+        collection,
+        documents: remaining,
+        position: 0,
+        batchSize,
+        createdAt: new Date(),
+      });
+    }
+
+    return {
+      ok: 1,
+      cursor: {
+        id: plugins.bson.Long.fromBigInt(cursorId),
+        ns: `${database}.${collection}`,
+        firstBatch,
+      },
+    };
+  }
+
+  /**
+   * Handle getMore command
+   */
+  private async handleGetMore(context: IHandlerContext): Promise<plugins.bson.Document> {
+    const { database, command } = context;
+
+    const cursorIdInput = command.getMore;
+    const collection = command.collection;
+    const batchSize = command.batchSize || 101;
+
+    // Convert cursorId to bigint
+    let cursorId: bigint;
+    if (typeof cursorIdInput === 'bigint') {
+      cursorId = cursorIdInput;
+    } else if (cursorIdInput instanceof plugins.bson.Long) {
+      cursorId = cursorIdInput.toBigInt();
+    } else {
+      cursorId = BigInt(cursorIdInput);
+    }
+
+    const cursor = this.cursors.get(cursorId);
+    if (!cursor) {
+      return {
+        ok: 0,
+        errmsg: `cursor id ${cursorId} not found`,
+        code: 43,
+        codeName: 'CursorNotFound',
+      };
+    }
+
+    // Verify namespace
+    if (cursor.database !== database || cursor.collection !== collection) {
+      return {
+        ok: 0,
+        errmsg: 'cursor namespace mismatch',
+        code: 43,
+        codeName: 'CursorNotFound',
+      };
+    }
+
+    // Get next batch
+    const start = cursor.position;
+    const end = Math.min(start + batchSize, cursor.documents.length);
+    const nextBatch = cursor.documents.slice(start, end);
+    cursor.position = end;
+
+    // Check if cursor is exhausted
+    let returnCursorId = cursorId;
+    if (cursor.position >= cursor.documents.length) {
+      this.cursors.delete(cursorId);
+      returnCursorId = BigInt(0);
+    }
+
+    return {
+      ok: 1,
+      cursor: {
+        id: plugins.bson.Long.fromBigInt(returnCursorId),
+        ns: `${database}.${collection}`,
+        nextBatch,
+      },
+    };
+  }
+
+  /**
+   * Handle killCursors command
+   */
+  private async handleKillCursors(context: IHandlerContext): Promise<plugins.bson.Document> {
+    const { command } = context;
+
+    const collection = command.killCursors;
+    const cursorIds = command.cursors || [];
+
+    const cursorsKilled: plugins.bson.Long[] = [];
+    const cursorsNotFound: plugins.bson.Long[] = [];
+    const cursorsUnknown: plugins.bson.Long[] = [];
+
+    for (const idInput of cursorIds) {
+      let cursorId: bigint;
+      if (typeof idInput === 'bigint') {
+        cursorId = idInput;
+      } else if (idInput instanceof plugins.bson.Long) {
+        cursorId = idInput.toBigInt();
+      } else {
+        cursorId = BigInt(idInput);
+      }
+
+      if (this.cursors.has(cursorId)) {
+        this.cursors.delete(cursorId);
+        cursorsKilled.push(plugins.bson.Long.fromBigInt(cursorId));
+      } else {
+        cursorsNotFound.push(plugins.bson.Long.fromBigInt(cursorId));
+      }
+    }
+
+    return {
+      ok: 1,
+      cursorsKilled,
+      cursorsNotFound,
+      cursorsUnknown,
+      cursorsAlive: [],
+    };
+  }
+
+  /**
+   * Handle count command
+   */
+  private async handleCount(context: IHandlerContext): Promise<plugins.bson.Document> {
+    const { storage, database, command } = context;
+
+    const collection = command.count;
+    const query = command.query || {};
+    const skip = command.skip || 0;
+    const limit = command.limit || 0;
+
+    // Check if collection exists
+    const exists = await storage.collectionExists(database, collection);
+    if (!exists) {
+      return { ok: 1, n: 0 };
+    }
+
+    // Get all documents
+    let documents = await storage.findAll(database, collection);
+
+    // Apply filter
+    documents = QueryEngine.filter(documents, query);
+
+    // Apply skip
+    if (skip > 0) {
+      documents = documents.slice(skip);
+    }
+
+    // Apply limit
+    if (limit > 0) {
+      documents = documents.slice(0, limit);
+    }
+
+    return { ok: 1, n: documents.length };
+  }
+
+  /**
+   * Handle distinct command
+   */
+  private async handleDistinct(context: IHandlerContext): Promise<plugins.bson.Document> {
+    const { storage, database, command } = context;
+
+    const collection = command.distinct;
+    const key = command.key;
+    const query = command.query || {};
+
+    if (!key) {
+      return {
+        ok: 0,
+        errmsg: 'distinct requires a key',
+        code: 2,
+        codeName: 'BadValue',
+      };
+    }
+
+    // Check if collection exists
+    const exists = await storage.collectionExists(database, collection);
+    if (!exists) {
+      return { ok: 1, values: [] };
+    }
+
+    // Get all documents
+    const documents = await storage.findAll(database, collection);
+
+    // Get distinct values
+    const values = QueryEngine.distinct(documents, key, query);
+
+    return { ok: 1, values };
+  }
+}

ts/congodb/server/handlers/HelloHandler.ts

@@ -0,0 +1,78 @@
+import * as plugins from '../../congodb.plugins.js';
+import type { ICommandHandler, IHandlerContext } from '../CommandRouter.js';
+
+/**
+ * HelloHandler - Handles hello/isMaster handshake commands
+ *
+ * This is the first command sent by MongoDB drivers to establish a connection.
+ * It returns server capabilities and configuration.
+ */
+export class HelloHandler implements ICommandHandler {
+  async handle(context: IHandlerContext): Promise<plugins.bson.Document> {
+    const { command, server } = context;
+
+    // Build response with server capabilities
+    const response: plugins.bson.Document = {
+      ismaster: true,
+      ok: 1,
+
+      // Maximum sizes
+      maxBsonObjectSize: 16777216,           // 16 MB
+      maxMessageSizeBytes: 48000000,         // 48 MB
+      maxWriteBatchSize: 100000,             // 100k documents per batch
+
+      // Timestamps
+      localTime: new Date(),
+
+      // Session support
+      logicalSessionTimeoutMinutes: 30,
+
+      // Connection info
+      connectionId: 1,
+
+      // Wire protocol versions (support MongoDB 3.6 through 7.0)
+      minWireVersion: 0,
+      maxWireVersion: 21,
+
+      // Server mode
+      readOnly: false,
+
+      // Topology info (standalone mode)
+      isWritablePrimary: true,
+
+      // Additional info
+      topologyVersion: {
+        processId: new plugins.bson.ObjectId(),
+        counter: plugins.bson.Long.fromNumber(0),
+      },
+    };
+
+    // Handle hello-specific fields
+    if (command.hello || command.hello === 1) {
+      response.helloOk = true;
+    }
+
+    // Handle client metadata
+    if (command.client) {
+      // Client is providing metadata about itself
+      // We just acknowledge it - no need to do anything special
+    }
+
+    // Handle SASL mechanisms query
+    if (command.saslSupportedMechs) {
+      response.saslSupportedMechs = [
+        // We don't actually support auth, but the driver needs to see this
+      ];
+    }
+
+    // Compression support (none for now)
+    if (command.compression) {
+      response.compression = [];
+    }
+
+    // Server version info
+    response.version = '7.0.0';
+
+    return response;
+  }
+}

ts/congodb/server/handlers/IndexHandler.ts

@@ -0,0 +1,207 @@
+import * as plugins from '../../congodb.plugins.js';
+import type { ICommandHandler, IHandlerContext } from '../CommandRouter.js';
+import { IndexEngine } from '../../engine/IndexEngine.js';
+
+// Cache of index engines per collection
+const indexEngines: Map<string, IndexEngine> = new Map();
+
+/**
+ * Get or create an IndexEngine for a collection
+ */
+function getIndexEngine(storage: any, database: string, collection: string): IndexEngine {
+  const key = `${database}.${collection}`;
+  let engine = indexEngines.get(key);
+
+  if (!engine) {
+    engine = new IndexEngine(database, collection, storage);
+    indexEngines.set(key, engine);
+  }
+
+  return engine;
+}
+
+/**
+ * IndexHandler - Handles createIndexes, dropIndexes, listIndexes commands
+ */
+export class IndexHandler implements ICommandHandler {
+  async handle(context: IHandlerContext): Promise<plugins.bson.Document> {
+    const { command } = context;
+
+    if (command.createIndexes) {
+      return this.handleCreateIndexes(context);
+    } else if (command.dropIndexes) {
+      return this.handleDropIndexes(context);
+    } else if (command.listIndexes) {
+      return this.handleListIndexes(context);
+    }
+
+    return {
+      ok: 0,
+      errmsg: 'Unknown index command',
+      code: 59,
+      codeName: 'CommandNotFound',
+    };
+  }
+
+  /**
+   * Handle createIndexes command
+   */
+  private async handleCreateIndexes(context: IHandlerContext): Promise<plugins.bson.Document> {
+    const { storage, database, command } = context;
+
+    const collection = command.createIndexes;
+    const indexes = command.indexes || [];
+
+    if (!Array.isArray(indexes)) {
+      return {
+        ok: 0,
+        errmsg: 'indexes must be an array',
+        code: 2,
+        codeName: 'BadValue',
+      };
+    }
+
+    // Ensure collection exists
+    await storage.createCollection(database, collection);
+
+    const indexEngine = getIndexEngine(storage, database, collection);
+    const createdNames: string[] = [];
+    let numIndexesBefore = 0;
+    let numIndexesAfter = 0;
+
+    try {
+      const existingIndexes = await indexEngine.listIndexes();
+      numIndexesBefore = existingIndexes.length;
+
+      for (const indexSpec of indexes) {
+        const key = indexSpec.key;
+        const options = {
+          name: indexSpec.name,
+          unique: indexSpec.unique,
+          sparse: indexSpec.sparse,
+          expireAfterSeconds: indexSpec.expireAfterSeconds,
+          background: indexSpec.background,
+          partialFilterExpression: indexSpec.partialFilterExpression,
+        };
+
+        const name = await indexEngine.createIndex(key, options);
+        createdNames.push(name);
+      }
+
+      const finalIndexes = await indexEngine.listIndexes();
+      numIndexesAfter = finalIndexes.length;
+    } catch (error: any) {
+      return {
+        ok: 0,
+        errmsg: error.message || 'Failed to create index',
+        code: error.code || 1,
+        codeName: error.codeName || 'InternalError',
+      };
+    }
+
+    return {
+      ok: 1,
+      numIndexesBefore,
+      numIndexesAfter,
+      createdCollectionAutomatically: false,
+      commitQuorum: 'votingMembers',
+    };
+  }
+
+  /**
+   * Handle dropIndexes command
+   */
+  private async handleDropIndexes(context: IHandlerContext): Promise<plugins.bson.Document> {
+    const { storage, database, command } = context;
+
+    const collection = command.dropIndexes;
+    const indexName = command.index;
+
+    // Check if collection exists
+    const exists = await storage.collectionExists(database, collection);
+    if (!exists) {
+      return {
+        ok: 0,
+        errmsg: `ns not found ${database}.${collection}`,
+        code: 26,
+        codeName: 'NamespaceNotFound',
+      };
+    }
+
+    const indexEngine = getIndexEngine(storage, database, collection);
+
+    try {
+      if (indexName === '*') {
+        // Drop all indexes except _id
+        await indexEngine.dropAllIndexes();
+      } else if (typeof indexName === 'string') {
+        // Drop specific index by name
+        await indexEngine.dropIndex(indexName);
+      } else if (typeof indexName === 'object') {
+        // Drop index by key specification
+        const indexes = await indexEngine.listIndexes();
+        const keyStr = JSON.stringify(indexName);
+
+        for (const idx of indexes) {
+          if (JSON.stringify(idx.key) === keyStr) {
+            await indexEngine.dropIndex(idx.name);
+            break;
+          }
+        }
+      }
+
+      return { ok: 1, nIndexesWas: 1 };
+    } catch (error: any) {
+      return {
+        ok: 0,
+        errmsg: error.message || 'Failed to drop index',
+        code: error.code || 27,
+        codeName: error.codeName || 'IndexNotFound',
+      };
+    }
+  }
+
+  /**
+   * Handle listIndexes command
+   */
+  private async handleListIndexes(context: IHandlerContext): Promise<plugins.bson.Document> {
+    const { storage, database, command } = context;
+
+    const collection = command.listIndexes;
+    const cursor = command.cursor || {};
+    const batchSize = cursor.batchSize || 101;
+
+    // Check if collection exists
+    const exists = await storage.collectionExists(database, collection);
+    if (!exists) {
+      return {
+        ok: 0,
+        errmsg: `ns not found ${database}.${collection}`,
+        code: 26,
+        codeName: 'NamespaceNotFound',
+      };
+    }
+
+    const indexEngine = getIndexEngine(storage, database, collection);
+    const indexes = await indexEngine.listIndexes();
+
+    // Format indexes for response
+    const indexDocs = indexes.map(idx => ({
+      v: idx.v || 2,
+      key: idx.key,
+      name: idx.name,
+      ...(idx.unique ? { unique: idx.unique } : {}),
+      ...(idx.sparse ? { sparse: idx.sparse } : {}),
+      ...(idx.expireAfterSeconds !== undefined ? { expireAfterSeconds: idx.expireAfterSeconds } : {}),
+    }));
+
+    return {
+      ok: 1,
+      cursor: {
+        id: plugins.bson.Long.fromNumber(0),
+        ns: `${database}.${collection}`,
+        firstBatch: indexDocs,
+      },
+    };
+  }
+}

ts/congodb/server/handlers/InsertHandler.ts

@@ -0,0 +1,91 @@
+import * as plugins from '../../congodb.plugins.js';
+import type { ICommandHandler, IHandlerContext } from '../CommandRouter.js';
+
+/**
+ * InsertHandler - Handles insert commands
+ */
+export class InsertHandler implements ICommandHandler {
+  async handle(context: IHandlerContext): Promise<plugins.bson.Document> {
+    const { storage, database, command, documentSequences } = context;
+
+    const collection = command.insert;
+    if (typeof collection !== 'string') {
+      return {
+        ok: 0,
+        errmsg: 'insert command requires a collection name',
+        code: 2,
+        codeName: 'BadValue',
+      };
+    }
+
+    // Get documents from command or document sequences
+    let documents: plugins.bson.Document[] = command.documents || [];
+
+    // Check for OP_MSG document sequences (for bulk inserts)
+    if (documentSequences && documentSequences.has('documents')) {
+      documents = documentSequences.get('documents')!;
+    }
+
+    if (!Array.isArray(documents) || documents.length === 0) {
+      return {
+        ok: 0,
+        errmsg: 'insert command requires documents array',
+        code: 2,
+        codeName: 'BadValue',
+      };
+    }
+
+    const ordered = command.ordered !== false;
+    const writeErrors: plugins.bson.Document[] = [];
+    let insertedCount = 0;
+
+    // Ensure collection exists
+    await storage.createCollection(database, collection);
+
+    // Insert documents
+    for (let i = 0; i < documents.length; i++) {
+      const doc = documents[i];
+
+      try {
+        // Ensure _id exists
+        if (!doc._id) {
+          doc._id = new plugins.bson.ObjectId();
+        }
+
+        await storage.insertOne(database, collection, doc);
+        insertedCount++;
+      } catch (error: any) {
+        const writeError: plugins.bson.Document = {
+          index: i,
+          code: error.code || 11000,
+          errmsg: error.message || 'Insert failed',
+        };
+
+        // Check for duplicate key error
+        if (error.message?.includes('Duplicate key')) {
+          writeError.code = 11000;
+          writeError.keyPattern = { _id: 1 };
+          writeError.keyValue = { _id: doc._id };
+        }
+
+        writeErrors.push(writeError);
+
+        if (ordered) {
+          // Stop on first error for ordered inserts
+          break;
+        }
+      }
+    }
+
+    const response: plugins.bson.Document = {
+      ok: 1,
+      n: insertedCount,
+    };
+
+    if (writeErrors.length > 0) {
+      response.writeErrors = writeErrors;
+    }
+
+    return response;
+  }
+}

ts/congodb/server/handlers/UpdateHandler.ts

@@ -0,0 +1,315 @@
+import * as plugins from '../../congodb.plugins.js';
+import type { ICommandHandler, IHandlerContext } from '../CommandRouter.js';
+import { QueryEngine } from '../../engine/QueryEngine.js';
+import { UpdateEngine } from '../../engine/UpdateEngine.js';
+
+/**
+ * UpdateHandler - Handles update, findAndModify commands
+ */
+export class UpdateHandler implements ICommandHandler {
+  async handle(context: IHandlerContext): Promise<plugins.bson.Document> {
+    const { command } = context;
+
+    // Check findAndModify first since it also has an 'update' field
+    if (command.findAndModify) {
+      return this.handleFindAndModify(context);
+    } else if (command.update && typeof command.update === 'string') {
+      // 'update' command has collection name as the value
+      return this.handleUpdate(context);
+    }
+
+    return {
+      ok: 0,
+      errmsg: 'Unknown update-related command',
+      code: 59,
+      codeName: 'CommandNotFound',
+    };
+  }
+
+  /**
+   * Handle update command
+   */
+  private async handleUpdate(context: IHandlerContext): Promise<plugins.bson.Document> {
+    const { storage, database, command, documentSequences } = context;
+
+    const collection = command.update;
+    if (typeof collection !== 'string') {
+      return {
+        ok: 0,
+        errmsg: 'update command requires a collection name',
+        code: 2,
+        codeName: 'BadValue',
+      };
+    }
+
+    // Get updates from command or document sequences
+    let updates: plugins.bson.Document[] = command.updates || [];
+
+    // Check for OP_MSG document sequences
+    if (documentSequences && documentSequences.has('updates')) {
+      updates = documentSequences.get('updates')!;
+    }
+
+    if (!Array.isArray(updates) || updates.length === 0) {
+      return {
+        ok: 0,
+        errmsg: 'update command requires updates array',
+        code: 2,
+        codeName: 'BadValue',
+      };
+    }
+
+    const ordered = command.ordered !== false;
+    const writeErrors: plugins.bson.Document[] = [];
+    let totalMatched = 0;
+    let totalModified = 0;
+    let totalUpserted = 0;
+    const upserted: plugins.bson.Document[] = [];
+
+    // Ensure collection exists
+    await storage.createCollection(database, collection);
+
+    for (let i = 0; i < updates.length; i++) {
+      const updateSpec = updates[i];
+      const filter = updateSpec.q || updateSpec.filter || {};
+      const update = updateSpec.u || updateSpec.update || {};
+      const multi = updateSpec.multi || false;
+      const upsert = updateSpec.upsert || false;
+      const arrayFilters = updateSpec.arrayFilters;
+
+      try {
+        // Get all documents
+        let documents = await storage.findAll(database, collection);
+
+        // Apply filter
+        let matchingDocs = QueryEngine.filter(documents, filter);
+
+        if (matchingDocs.length === 0 && upsert) {
+          // Upsert: create new document
+          const newDoc: plugins.bson.Document = { _id: new plugins.bson.ObjectId() };
+
+          // Apply filter fields to the new document
+          this.applyFilterToDoc(newDoc, filter);
+
+          // Apply update
+          const updatedDoc = UpdateEngine.applyUpdate(newDoc as any, update, arrayFilters);
+
+          // Handle $setOnInsert
+          if (update.$setOnInsert) {
+            Object.assign(updatedDoc, update.$setOnInsert);
+          }
+
+          await storage.insertOne(database, collection, updatedDoc);
+          totalUpserted++;
+          upserted.push({ index: i, _id: updatedDoc._id });
+        } else {
+          // Update existing documents
+          const docsToUpdate = multi ? matchingDocs : matchingDocs.slice(0, 1);
+          totalMatched += docsToUpdate.length;
+
+          for (const doc of docsToUpdate) {
+            const updatedDoc = UpdateEngine.applyUpdate(doc, update, arrayFilters);
+
+            // Check if document actually changed
+            const changed = JSON.stringify(doc) !== JSON.stringify(updatedDoc);
+            if (changed) {
+              await storage.updateById(database, collection, doc._id, updatedDoc);
+              totalModified++;
+            }
+          }
+        }
+      } catch (error: any) {
+        writeErrors.push({
+          index: i,
+          code: error.code || 1,
+          errmsg: error.message || 'Update failed',
+        });
+
+        if (ordered) {
+          break;
+        }
+      }
+    }
+
+    const response: plugins.bson.Document = {
+      ok: 1,
+      n: totalMatched + totalUpserted,
+      nModified: totalModified,
+    };
+
+    if (upserted.length > 0) {
+      response.upserted = upserted;
+    }
+
+    if (writeErrors.length > 0) {
+      response.writeErrors = writeErrors;
+    }
+
+    return response;
+  }
+
+  /**
+   * Handle findAndModify command
+   */
+  private async handleFindAndModify(context: IHandlerContext): Promise<plugins.bson.Document> {
+    const { storage, database, command } = context;
+
+    const collection = command.findAndModify;
+    const query = command.query || {};
+    const update = command.update;
+    const remove = command.remove || false;
+    const returnNew = command.new || false;
+    const upsert = command.upsert || false;
+    const sort = command.sort;
+    const fields = command.fields;
+    const arrayFilters = command.arrayFilters;
+
+    // Validate - either update or remove, not both
+    if (update && remove) {
+      return {
+        ok: 0,
+        errmsg: 'cannot specify both update and remove',
+        code: 2,
+        codeName: 'BadValue',
+      };
+    }
+
+    if (!update && !remove) {
+      return {
+        ok: 0,
+        errmsg: 'either update or remove is required',
+        code: 2,
+        codeName: 'BadValue',
+      };
+    }
+
+    // Ensure collection exists
+    await storage.createCollection(database, collection);
+
+    // Get matching documents
+    let documents = await storage.findAll(database, collection);
+    let matchingDocs = QueryEngine.filter(documents, query);
+
+    // Apply sort if specified
+    if (sort) {
+      matchingDocs = QueryEngine.sort(matchingDocs, sort);
+    }
+
+    const doc = matchingDocs[0];
+
+    if (remove) {
+      // Delete operation
+      if (!doc) {
+        return { ok: 1, value: null };
+      }
+
+      await storage.deleteById(database, collection, doc._id);
+
+      let result = doc;
+      if (fields) {
+        result = QueryEngine.project([doc], fields)[0] as any;
+      }
+
+      return {
+        ok: 1,
+        value: result,
+        lastErrorObject: {
+          n: 1,
+        },
+      };
+    } else {
+      // Update operation
+      if (!doc && !upsert) {
+        return { ok: 1, value: null };
+      }
+
+      let resultDoc: plugins.bson.Document;
+      let originalDoc: plugins.bson.Document | null = null;
+      let isUpsert = false;
+
+      if (doc) {
+        // Update existing
+        originalDoc = { ...doc };
+        resultDoc = UpdateEngine.applyUpdate(doc, update, arrayFilters);
+        await storage.updateById(database, collection, doc._id, resultDoc as any);
+      } else {
+        // Upsert
+        isUpsert = true;
+        const newDoc: plugins.bson.Document = { _id: new plugins.bson.ObjectId() };
+        this.applyFilterToDoc(newDoc, query);
+        resultDoc = UpdateEngine.applyUpdate(newDoc as any, update, arrayFilters);
+
+        if (update.$setOnInsert) {
+          Object.assign(resultDoc, update.$setOnInsert);
+        }
+
+        await storage.insertOne(database, collection, resultDoc);
+      }
+
+      // Apply projection
+      let returnValue = returnNew ? resultDoc : (originalDoc || null);
+      if (returnValue && fields) {
+        returnValue = QueryEngine.project([returnValue as any], fields)[0];
+      }
+
+      const response: plugins.bson.Document = {
+        ok: 1,
+        value: returnValue,
+        lastErrorObject: {
+          n: 1,
+          updatedExisting: !isUpsert && doc !== undefined,
+        },
+      };
+
+      if (isUpsert) {
+        response.lastErrorObject.upserted = resultDoc._id;
+      }
+
+      return response;
+    }
+  }
+
+  /**
+   * Apply filter equality conditions to a new document (for upsert)
+   */
+  private applyFilterToDoc(doc: plugins.bson.Document, filter: plugins.bson.Document): void {
+    for (const [key, value] of Object.entries(filter)) {
+      // Skip operators
+      if (key.startsWith('$')) continue;
+
+      // Handle nested paths
+      if (typeof value === 'object' && value !== null) {
+        // Check if it's an operator
+        const valueKeys = Object.keys(value);
+        if (valueKeys.some(k => k.startsWith('$'))) {
+          // Extract equality value from $eq if present
+          if ('$eq' in value) {
+            this.setNestedValue(doc, key, value.$eq);
+          }
+          continue;
+        }
+      }
+
+      // Direct value assignment
+      this.setNestedValue(doc, key, value);
+    }
+  }
+
+  /**
+   * Set a nested value using dot notation
+   */
+  private setNestedValue(obj: plugins.bson.Document, path: string, value: any): void {
+    const parts = path.split('.');
+    let current = obj;
+
+    for (let i = 0; i < parts.length - 1; i++) {
+      const part = parts[i];
+      if (!(part in current)) {
+        current[part] = {};
+      }
+      current = current[part];
+    }
+
+    current[parts[parts.length - 1]] = value;
+  }
+}

ts/congodb/server/handlers/index.ts

@@ -0,0 +1,10 @@
+// Export all command handlers
+
+export { HelloHandler } from './HelloHandler.js';
+export { InsertHandler } from './InsertHandler.js';
+export { FindHandler } from './FindHandler.js';
+export { UpdateHandler } from './UpdateHandler.js';
+export { DeleteHandler } from './DeleteHandler.js';
+export { AggregateHandler } from './AggregateHandler.js';
+export { IndexHandler } from './IndexHandler.js';
+export { AdminHandler } from './AdminHandler.js';