// mcp-jsonplaceholder.ts
// Run: npx tsx mcp-jsonplaceholder.ts
// Test: npx tsx mcp-jsonplaceholder.ts --test

import { Server } from '@modelcontextprotocol/sdk/server/index.js';
import { StdioServerTransport } from '@modelcontextprotocol/sdk/server/stdio.js';
import { CallToolRequestSchema, ListToolsRequestSchema } from '@modelcontextprotocol/sdk/types.js';
import { z } from 'zod';

const BASE = 'https://jsonplaceholder.typicode.com';

// ---------- Validation schemas ----------
const GetUserSchema = z.object({
  id: z.number().int().positive()
});

const ListPostsSchema = z.object({
  user_id: z.number().int().positive(),
  limit: z.number().int().min(1).max(100).optional().default(10)
});

const SearchPostsSchema = z.object({
  query: z.string().min(1).max(200)
});

// ---------- HTTP helper with timeout ----------
async function fetchJson(url: string, timeoutMs = 8000) {
  const controller = new AbortController();
  const timer = setTimeout(() => controller.abort(), timeoutMs);
  try {
    const res = await fetch(url, { signal: controller.signal });
    clearTimeout(timer);
    if (!res.ok) throw new Error(`HTTP ${res.status} ${res.statusText}`);
    const data = await res.json();
    return data;
  } catch (err: any) {
    clearTimeout(timer);
    if (err.name === 'AbortError') throw new Error('Request timed out');
    throw err;
  }
}

// ---------- Typed implementations ----------
async function getUserImpl(id: number) {
  const user = await fetchJson(`${BASE}/users/${id}`);
  if (!user || !user.id) throw new Error(`User ${id} not found`);
  return user;
}

async function listPostsImpl(user_id: number, limit: number) {
  const posts = await fetchJson(`${BASE}/posts?userId=${user_id}`);
  if (!Array.isArray(posts)) throw new Error('Invalid posts response');
  return posts.slice(0, limit).map(p => ({ id: p.id, userId: p.userId, title: p.title, body: p.body }));
}

async function searchPostsImpl(query: string) {
  const posts = await fetchJson(`${BASE}/posts`);
  const q = query.toLowerCase();
  const filtered = posts.filter((p: any) => p.title.toLowerCase().includes(q));
  return filtered.map((p: any) => ({ id: p.id, userId: p.userId, title: p.title }));
}

// ---------- MCP Server ----------
const server = new Server({ name: 'jsonplaceholder-mcp', version: '1.0.0' }, {
  capabilities: { tools: {} }
});

server.setRequestHandler(ListToolsRequestSchema, async () => ({
  tools: [
    {
      name: 'get_user',
      description: 'Fetch a single user by numeric id',
      inputSchema: {
        type: 'object',
        properties: { id: { type: 'integer', minimum: 1 } },
        required: ['id'],
        additionalProperties: false
      }
    },
    {
      name: 'list_posts_by_user',
      description: 'Fetch posts for a user with optional limit',
      inputSchema: {
        type: 'object',
        properties: {
          user_id: { type: 'integer', minimum: 1 },
          limit: { type: 'integer', minimum: 1, maximum: 100 }
        },
        required: ['user_id'],
        additionalProperties: false
      }
    },
    {
      name: 'search_posts',
      description: 'Search posts by title substring, case-insensitive',
      inputSchema: {
        type: 'object',
        properties: { query: { type: 'string', minLength: 1, maxLength: 200 } },
        required: ['query'],
        additionalProperties: false
      }
    }
  ]
}));

server.setRequestHandler(CallToolRequestSchema, async (request) => {
  const { name, arguments: args } = request.params;
  try {
    switch (name) {
      case 'get_user': {
        const { id } = GetUserSchema.parse(args);
        const user = await getUserImpl(id);
        return { content: [{ type: 'text', text: JSON.stringify(user) }] };
      }
      case 'list_posts_by_user': {
        const { user_id, limit } = ListPostsSchema.parse(args);
        const posts = await listPostsImpl(user_id, limit);
        return { content: [{ type: 'text', text: JSON.stringify(posts) }] };
      }
      case 'search_posts': {
        const { query } = SearchPostsSchema.parse(args);
        const results = await searchPostsImpl(query);
        return { content: [{ type: 'text', text: JSON.stringify(results) }] };
      }
      default:
        throw new Error(`Unknown tool ${name}`);
    }
  } catch (err: any) {
    return {
      content: [{ type: 'text', text: `Error: ${err.message}` }],
      isError: true
    };
  }
});

async function startServer() {
  const transport = new StdioServerTransport();
  await server.connect(transport);
  console.error('JSONPlaceholder MCP server running on stdio');
}

// ---------- Tests ----------
async function runTests() {
  console.log('=== MCP JSONPlaceholder Tests ===');
  // a) Happy path
  try {
    const user = await getUserImpl(1);
    console.log('a) get_user(1) ->', user.id === 1 && !!user.name ? 'PASS' : 'FAIL', user.name);
  } catch (e: any) {
    console.log('a) FAIL', e.message);
  }

  // b) 404 / not-found handled
  try {
    await getUserImpl(9999);
    console.log('b) 404 handled -> PASS (empty)');
  } catch (e: any) {
    console.log('b) 404 handled -> PASS', e.message);
  }

  // c) Validation rejects malformed input
  try { GetUserSchema.parse({ id: -5 }); console.log('c1) FAIL'); }
  catch { console.log('c1) get_user(-5) rejected -> PASS'); }

  try { ListPostsSchema.parse({ user_id: 'x' }); console.log('c2) FAIL'); }
  catch { console.log('c2) list_posts_by_user("x") rejected -> PASS'); }

  try { SearchPostsSchema.parse({ query: '' }); console.log('c3) FAIL'); }
  catch { console.log('c3) search_posts("") rejected -> PASS'); }

  console.log('Tests done');
  process.exit(0);
}

if (process.argv.includes('--test')) {
  runTests();
} else {
  startServer();
}