import { Client } from '@modelcontextprotocol/sdk/client/index.js';
import { SSEClientTransport } from '@modelcontextprotocol/sdk/client/sse.js';
import { ToolDefinition, ToolResult } from './types';

/**
 * MCP Client for connecting to the GoHighLevel MCP Server.
 * Uses the official MCP SDK with SSE transport.
 */
export class MCPClient {
  private serverUrl: string;
  private client: Client | null = null;
  private transport: SSEClientTransport | null = null;
  private connected: boolean = false;
  private toolsCache: ToolDefinition[] | null = null;

  constructor(serverUrl: string) {
    this.serverUrl = serverUrl;
  }

  /**
   * Connect to the MCP server
   */
  async connect(): Promise<boolean> {
    if (this.connected && this.client) {
      return true;
    }

    try {
      // Create SSE transport
      this.transport = new SSEClientTransport(
        new URL(`${this.serverUrl}/sse`)
      );

      // Create MCP client
      this.client = new Client(
        { name: 'cresync-control-center', version: '1.0.0' },
        { capabilities: {} }
      );

      // Connect
      await this.client.connect(this.transport);
      this.connected = true;
      console.log('[MCP Client] Connected to server');
      return true;
    } catch (error) {
      console.error('[MCP Client] Connection failed:', error);
      this.connected = false;
      return false;
    }
  }

  /**
   * Disconnect from the MCP server
   */
  async disconnect(): Promise<void> {
    if (this.client) {
      await this.client.close();
      this.client = null;
      this.transport = null;
      this.connected = false;
    }
  }

  /**
   * Health check - try to connect and list tools
   */
  async healthCheck(): Promise<boolean> {
    try {
      // Simple HTTP check to /health endpoint
      const response = await fetch(`${this.serverUrl}/health`);
      return response.ok;
    } catch {
      return false;
    }
  }

  /**
   * Get available tools from MCP server
   * Uses REST endpoint for listing (faster than SSE for just getting list)
   */
  async getTools(): Promise<ToolDefinition[]> {
    if (this.toolsCache) {
      return this.toolsCache;
    }

    try {
      // Use REST endpoint for tool listing
      const response = await fetch(`${this.serverUrl}/tools`);
      if (!response.ok) {
        throw new Error(`Failed to fetch tools: ${response.status}`);
      }

      const data = await response.json();
      const tools = (data.tools || []).map((tool: any) => ({
        name: tool.name,
        description: tool.description || '',
        inputSchema: tool.inputSchema || { type: 'object', properties: {} }
      }));
      this.toolsCache = tools;

      console.log(`[MCP Client] Loaded ${tools.length} tools`);
      return tools;
    } catch (error) {
      console.error('[MCP Client] Failed to fetch tools:', error);
      return [];
    }
  }

  /**
   * Execute a tool via MCP protocol
   */
  async executeTool(toolName: string, input: Record<string, unknown>): Promise<ToolResult> {
    try {
      // Ensure connected
      if (!this.connected) {
        const connected = await this.connect();
        if (!connected) {
          return {
            toolCallId: '',
            success: false,
            error: 'Failed to connect to MCP server'
          };
        }
      }

      if (!this.client) {
        return {
          toolCallId: '',
          success: false,
          error: 'MCP client not initialized'
        };
      }

      // Call tool via MCP protocol
      const result = await this.client.callTool({
        name: toolName,
        arguments: input
      });

      // Parse result - MCP returns content array
      let resultData: unknown;
      if (result.content && Array.isArray(result.content)) {
        // Extract text content
        const textContent = result.content.find((c: any) => c.type === 'text');
        if (textContent && 'text' in textContent) {
          try {
            resultData = JSON.parse(textContent.text);
          } catch {
            resultData = textContent.text;
          }
        } else {
          resultData = result.content;
        }
      } else {
        resultData = result;
      }

      return {
        toolCallId: '',
        success: !result.isError,
        result: resultData,
        error: result.isError ? String(resultData) : undefined
      };
    } catch (error) {
      console.error(`[MCP Client] Tool execution failed for ${toolName}:`, error);
      return {
        toolCallId: '',
        success: false,
        error: error instanceof Error ? error.message : 'Tool execution failed'
      };
    }
  }

  /**
   * Clear tool cache
   */
  clearCache(): void {
    this.toolsCache = null;
  }
}

// Singleton instance
let mcpClientInstance: MCPClient | null = null;

/**
 * Get or create MCP client instance
 */
export async function createMCPClient(): Promise<MCPClient | null> {
  if (mcpClientInstance) {
    return mcpClientInstance;
  }

  // Import settings service
  const { settingsService } = await import('@/lib/settings/settings-service');
  const serverUrl = await settingsService.get('mcpServerUrl');

  if (!serverUrl) {
    console.warn('[MCP Client] Server URL not configured');
    return null;
  }

  mcpClientInstance = new MCPClient(serverUrl);
  return mcpClientInstance;
}

/**
 * Close and reset MCP client
 */
export async function closeMCPClient(): Promise<void> {
  if (mcpClientInstance) {
    await mcpClientInstance.disconnect();
    mcpClientInstance = null;
  }
}