import { Client } from '@modelcontextprotocol/sdk/client/index.js'
import { SSEClientTransport } from '@modelcontextprotocol/sdk/client/sse.js'
import { StdioClientTransport } from '@modelcontextprotocol/sdk/client/stdio.js'
import { tool } from 'ai'
import { z } from 'zod'

/**
 * Connects to an external MCP Server and maps its tools to Vercel AI SDK Tools.
 */
export async function createMcpTools(mcpConfig: { name: string, url?: string, command?: string, args?: string[] }) {
    let transport

    // Support both HTTP/SSE and STDIO transports
    if (mcpConfig.url) {
        transport = new SSEClientTransport(new URL(mcpConfig.url))
    } else if (mcpConfig.command) {
        transport = new StdioClientTransport({
            command: mcpConfig.command,
            args: mcpConfig.args || [],
        })
    } else {
        throw new Error('Invalid MCP config: Must provide either URL or Command.')
    }

    const client = new Client(
        { name: `payload-ai-client-${mcpConfig.name}`, version: '1.0.0' },
        { capabilities: {} }
    )

    await client.connect(transport)

    // Fetch available tools from the external MCP server
    const toolListResult = await client.listTools()
    const externalTools = toolListResult.tools || []

    const aiSdkTools: Record<string, any> = {}

    // Map each external tool to a Vercel AI SDK Tool
    for (const extTool of externalTools) {
        // Basic conversion of JSON Schema to Zod for the AI SDK
        // Note: For a production ready adapter, you might need a more robust jsonSchemaToZod converter
        // or use AI SDK's new experimental generateSchema feature if available.
        // Here we use a generic `z.any()` as a fallback since AI SDK requires a Zod schema.
        const toolSchema = extTool.inputSchema as Record<string, any>

        // We create a simplified parameter parser. 
        // An ideal approach uses `jsonSchemaToZod` library or native AI SDK JSON schema support
        // (introduced recently in `ai` package). 

        aiSdkTools[`${mcpConfig.name}_${extTool.name}`] = tool({
            description: `[From ${mcpConfig.name}] ${extTool.description || extTool.name}`,
            parameters: z.any().describe('JSON matching the original MCP input_schema'), // Simplify for prototype
            // @ts-ignore - AI strict mode overload bug with implicit zod inferences
            execute: async (args: any) => {
                const result = await client.callTool({
                    name: extTool.name,
                    arguments: args
                })
                return result
            }
        })
    }

    return { tools: aiSdkTools, client }
}