feat(mcp-server): implement MCP server core with adapter framework

- Add JSON-RPC 2.0 protocol handler
- Implement stdio transport for process communication
- Create extensible adapter framework (ToolAdapter, ResourceAdapter)
- Build adapter registry with lifecycle management
- Implement MCPServer core class with MCP protocol support
- Add mock adapter for testing
- Support tools/list, tools/call, and initialize methods

Package structure:
- src/server/protocol: JSON-RPC and MCP types
- src/server/transport: Stdio transport implementation
- src/adapters: Base adapter classes and registry
- src/utils: Logger utilities
- tests/adapters: Mock adapter for testing

Relates to #27

Author: prosdev

packages/mcp-server/package.json

@@ -0,0 +1,35 @@
+{
+  "name": "@lytics/dev-agent-mcp",
+  "version": "0.1.0",
+  "description": "MCP server for dev-agent with extensible adapter framework",
+  "private": true,
+  "main": "./dist/index.js",
+  "types": "./dist/index.d.ts",
+  "bin": {
+    "dev-agent-mcp": "./dist/index.js"
+  },
+  "scripts": {
+    "build": "tsc",
+    "dev": "tsc --watch",
+    "typecheck": "tsc --noEmit",
+    "lint": "biome lint ./src",
+    "test": "vitest run",
+    "test:watch": "vitest"
+  },
+  "dependencies": {
+    "@lytics/dev-agent-core": "workspace:*",
+    "@lytics/dev-agent-subagents": "workspace:*"
+  },
+  "devDependencies": {
+    "@types/node": "^22.0.0",
+    "typescript": "^5.7.2",
+    "vitest": "^2.1.8"
+  },
+  "files": [
+    "dist"
+  ],
+  "publishConfig": {
+    "access": "public"
+  }
+}
+

packages/mcp-server/src/adapters/Adapter.ts

@@ -0,0 +1,30 @@
+/**
+ * Base Adapter Class
+ * All adapters (Tool, Resource, Prompt) extend from this
+ */
+
+import type { AdapterContext, AdapterMetadata } from './types';
+
+export abstract class Adapter {
+  /**
+   * Adapter metadata (name, version, description)
+   */
+  abstract readonly metadata: AdapterMetadata;
+
+  /**
+   * Initialize the adapter with context
+   * Called once when adapter is registered
+   */
+  abstract initialize(context: AdapterContext): Promise<void>;
+
+  /**
+   * Optional: Cleanup when adapter is unregistered or server stops
+   */
+  shutdown?(): Promise<void>;
+
+  /**
+   * Optional: Health check for adapter
+   * @returns true if healthy, false otherwise
+   */
+  healthCheck?(): Promise<boolean>;
+}

packages/mcp-server/src/adapters/AdapterRegistry.ts

@@ -0,0 +1,186 @@
+/**
+ * Adapter Registry
+ * Manages adapter lifecycle and tool execution routing
+ */
+
+import { ErrorCode } from '../server/protocol/types';
+import type { ToolAdapter } from './ToolAdapter';
+import type { AdapterContext, ToolDefinition, ToolExecutionContext, ToolResult } from './types';
+
+export interface RegistryConfig {
+  autoDiscover?: boolean;
+  customAdaptersPath?: string;
+}
+
+export class AdapterRegistry {
+  private adapters = new Map<string, ToolAdapter>();
+  private context?: AdapterContext;
+  private config: RegistryConfig;
+
+  constructor(config: RegistryConfig = {}) {
+    this.config = config;
+  }
+
+  /**
+   * Register a single adapter
+   */
+  register(adapter: ToolAdapter): void {
+    const toolName = adapter.getToolDefinition().name;
+
+    if (this.adapters.has(toolName)) {
+      throw new Error(`Adapter already registered: ${toolName}`);
+    }
+
+    this.adapters.set(toolName, adapter);
+  }
+
+  /**
+   * Unregister an adapter
+   */
+  async unregister(toolName: string): Promise<void> {
+    const adapter = this.adapters.get(toolName);
+    if (!adapter) {
+      return;
+    }
+
+    // Call shutdown if available
+    if (adapter.shutdown) {
+      await adapter.shutdown();
+    }
+
+    this.adapters.delete(toolName);
+  }
+
+  /**
+   * Initialize all registered adapters
+   */
+  async initializeAll(context: AdapterContext): Promise<void> {
+    this.context = context;
+
+    const initPromises = Array.from(this.adapters.values()).map((adapter) =>
+      adapter.initialize(context)
+    );
+
+    await Promise.all(initPromises);
+  }
+
+  /**
+   * Get all tool definitions (for MCP tools/list)
+   */
+  getToolDefinitions(): ToolDefinition[] {
+    return Array.from(this.adapters.values()).map((adapter) => adapter.getToolDefinition());
+  }
+
+  /**
+   * Execute a tool by name
+   */
+  async executeTool(
+    toolName: string,
+    args: Record<string, unknown>,
+    context: ToolExecutionContext
+  ): Promise<ToolResult> {
+    const adapter = this.adapters.get(toolName);
+
+    if (!adapter) {
+      return {
+        success: false,
+        error: {
+          code: String(ErrorCode.ToolNotFound),
+          message: `Tool not found: ${toolName}`,
+          recoverable: false,
+        },
+      };
+    }
+
+    // Optional validation
+    if (adapter.validate) {
+      const validation = adapter.validate(args);
+      if (!validation.valid) {
+        return {
+          success: false,
+          error: {
+            code: String(ErrorCode.InvalidParams),
+            message: validation.error || 'Invalid arguments',
+            details: validation.details,
+            recoverable: true,
+            suggestion: 'Check the tool input schema and try again',
+          },
+        };
+      }
+    }
+
+    // Execute tool
+    try {
+      const startTime = Date.now();
+      const result = await adapter.execute(args, context);
+
+      // Add execution time if not present
+      if (result.success && result.metadata) {
+        result.metadata.executionTime = Date.now() - startTime;
+      }
+
+      return result;
+    } catch (error) {
+      context.logger.error('Tool execution failed', {
+        toolName,
+        error: error instanceof Error ? error.message : String(error),
+      });
+
+      return {
+        success: false,
+        error: {
+          code: String(ErrorCode.ToolExecutionError),
+          message: error instanceof Error ? error.message : 'Tool execution failed',
+          recoverable: true,
+          suggestion: 'Check the tool arguments and try again',
+        },
+      };
+    }
+  }
+
+  /**
+   * Get adapter by tool name
+   */
+  getAdapter(toolName: string): ToolAdapter | undefined {
+    return this.adapters.get(toolName);
+  }
+
+  /**
+   * Get all registered tool names
+   */
+  getToolNames(): string[] {
+    return Array.from(this.adapters.keys());
+  }
+
+  /**
+   * Check if a tool is registered
+   */
+  hasTool(toolName: string): boolean {
+    return this.adapters.has(toolName);
+  }
+
+  /**
+   * Get registry statistics
+   */
+  getStats(): {
+    totalAdapters: number;
+    toolNames: string[];
+  } {
+    return {
+      totalAdapters: this.adapters.size,
+      toolNames: this.getToolNames(),
+    };
+  }
+
+  /**
+   * Shutdown all adapters
+   */
+  async shutdownAll(): Promise<void> {
+    const shutdownPromises = Array.from(this.adapters.values())
+      .filter((adapter) => adapter.shutdown)
+      .map((adapter) => adapter.shutdown!());
+
+    await Promise.all(shutdownPromises);
+    this.adapters.clear();
+  }
+}

packages/mcp-server/src/adapters/ToolAdapter.ts

@@ -0,0 +1,41 @@
+/**
+ * Tool Adapter Base Class
+ * Extends Adapter to provide tool-specific functionality
+ */
+
+import { Adapter } from './Adapter';
+import type { ToolDefinition, ToolExecutionContext, ToolResult, ValidationResult } from './types';
+
+export abstract class ToolAdapter extends Adapter {
+  /**
+   * Get the tool definition (name, description, schema)
+   * This is used by MCP to list available tools
+   */
+  abstract getToolDefinition(): ToolDefinition;
+
+  /**
+   * Execute the tool with given arguments
+   * @param args Tool arguments from MCP client
+   * @param context Execution context (logger, config, etc.)
+   * @returns Tool result (success/error with data)
+   */
+  abstract execute(
+    args: Record<string, unknown>,
+    context: ToolExecutionContext
+  ): Promise<ToolResult>;
+
+  /**
+   * Optional: Validate arguments before execution
+   * @param args Tool arguments to validate
+   * @returns Validation result
+   */
+  validate?(args: Record<string, unknown>): ValidationResult;
+
+  /**
+   * Optional: Estimate token usage for the response
+   * Used for token budget management
+   * @param args Tool arguments
+   * @returns Estimated token count
+   */
+  estimateTokens?(args: Record<string, unknown>): number;
+}

packages/mcp-server/src/adapters/types.ts

@@ -0,0 +1,69 @@
+/**
+ * Adapter Framework Types
+ */
+
+import type { JSONSchema, ToolDefinition } from '../server/protocol/types';
+
+// Adapter Metadata
+export interface AdapterMetadata {
+  name: string;
+  version: string;
+  description: string;
+  author?: string;
+}
+
+// Adapter Context (provided during initialization)
+export interface AdapterContext {
+  logger: Logger;
+  config: Config;
+}
+
+// Tool Execution Context (provided during tool execution)
+export interface ToolExecutionContext extends AdapterContext {
+  userId?: string; // For multi-user scenarios
+}
+
+// Logger Interface
+export interface Logger {
+  debug(message: string, meta?: Record<string, unknown>): void;
+  info(message: string, meta?: Record<string, unknown>): void;
+  warn(message: string, meta?: Record<string, unknown>): void;
+  error(message: string | Error, meta?: Record<string, unknown>): void;
+}
+
+// Config Interface
+export interface Config {
+  repositoryPath: string;
+  [key: string]: unknown;
+}
+
+// Tool Result
+export interface ToolResult {
+  success: boolean;
+  data?: unknown;
+  error?: AdapterError;
+  metadata?: {
+    tokenEstimate?: number;
+    executionTime?: number;
+    cached?: boolean;
+  };
+}
+
+// Adapter Error
+export interface AdapterError {
+  code: string;
+  message: string;
+  details?: unknown;
+  recoverable?: boolean;
+  suggestion?: string;
+}
+
+// Validation Result
+export interface ValidationResult {
+  valid: boolean;
+  error?: string;
+  details?: unknown;
+}
+
+// Re-export tool definition for convenience
+export type { JSONSchema, ToolDefinition } from '../server/protocol/types';

packages/mcp-server/src/index.ts

@@ -0,0 +1,25 @@
+/**
+ * MCP Server Entry Point
+ * Can be used as a standalone server or imported as a library
+ */
+
+// Adapter exports
+export { Adapter } from './adapters/Adapter';
+export { AdapterRegistry, type RegistryConfig } from './adapters/AdapterRegistry';
+export { ToolAdapter } from './adapters/ToolAdapter';
+export * from './adapters/types';
+// Core exports
+export { MCPServer, type MCPServerConfig } from './server/MCPServer';
+// Protocol exports
+export { JSONRPCHandler } from './server/protocol/jsonrpc';
+export * from './server/protocol/types';
+export { StdioTransport } from './server/transport/StdioTransport';
+// Transport exports
+export {
+  Transport,
+  type TransportConfig,
+  type TransportMessage,
+} from './server/transport/Transport';
+
+// Utility exports
+export { ConsoleLogger } from './utils/logger';