import { createServer } from "node:http";
import { loadConfig } from "./config.js";
import { HttpClient } from "./http/client.js";
import { ProxyPool } from "./http/proxy.js";
import { SearchRunner } from "./run.js";
import { setUserAgents } from "./utils/ua.js";
import { loadApiKey } from "./api-key.js";
import { logger, childLogger } from "./utils/logger.js";
import { formatSearchResponse, formatErrorResponse } from "./output/agent.js";
import { createMCPHandler } from "./mcp.js";

const log = childLogger({ component: "api-server" });

function unauthorized(res, msg = "Unauthorized") {
  res.writeHead(401, { "Content-Type": "application/json" });
  res.end(JSON.stringify({ success: false, error: { code: "UNAUTHORIZED", message: msg } }));
}

function badRequest(res, msg) {
  res.writeHead(400, { "Content-Type": "application/json" });
  res.end(JSON.stringify({ success: false, error: { code: "BAD_REQUEST", message: msg } }));
}

function serverError(res, msg) {
  if (res.headersSent) return;
  res.writeHead(500, { "Content-Type": "application/json" });
  res.end(JSON.stringify({ success: false, error: { code: "INTERNAL_ERROR", message: msg } }));
}

function parseBody(req) {
  return new Promise((resolve, reject) => {
    let data = "";
    req.on("data", chunk => data += chunk);
    req.on("end", () => {
      try { resolve(JSON.parse(data)); }
      catch { reject(new Error("Invalid JSON")); }
    });
    req.on("error", reject);
  });
}

function authenticate(req) {
  const apiKey = loadApiKey();
  if (!apiKey) return true;

  const auth = req.headers["authorization"] || "";
  const token = auth.startsWith("Bearer ") ? auth.slice(7) : "";
  return token === apiKey;
}

export async function startServer(port = 9876) {
  const config = await loadConfig();
  if (config.http.user_agents) setUserAgents(config.http.user_agents);

  const httpClient = new HttpClient(config.http);
  const proxyPool = new ProxyPool(config.proxies, config.proxy);

  if (config.proxy.enabled) {
    httpClient.setProxyPool(proxyPool);
    log.info({ proxyCount: config.proxies.length }, "proxy pool attached to API server");
  }

  const runner = new SearchRunner({ httpClient, config });
  const handleMCP = createMCPHandler(runner);

  const server = createServer(async (req, res) => {
    res.setHeader("Access-Control-Allow-Origin", "*");
    res.setHeader("Access-Control-Allow-Methods", "GET, POST, OPTIONS");
    res.setHeader("Access-Control-Allow-Headers", "Content-Type, Authorization");

    if (req.method === "OPTIONS") {
      res.writeHead(204);
      res.end();
      return;
    }

    try {
      const url = new URL(req.url, `http://${req.headers.host || "localhost"}`);
      const path = url.pathname;

      // Health check — no auth required
      if (path === "/health" && req.method === "GET") {
        res.writeHead(200, { "Content-Type": "application/json" });
        const m = proxyPool.getMetrics();
        res.end(JSON.stringify({
          success: true,
          status: "ok",
          uptime: process.uptime(),
          proxyCount: config.proxies.length,
          proxyPool: {
            total: m.totalProxies,
            alive: m.alive,
            dead: m.dead,
            circuitOpen: m.circuitOpen,
            requestsTotal: m.requestsTotal,
            successRate: m.successRate,
            hourlyUsage: m.hourlyUsageCurrent
          }
        }));
        return;
      }

      // Metrics — requires auth
      if (path === "/metrics" && req.method === "GET") {
        if (!authenticate(req)) return unauthorized(res);
        res.writeHead(200, { "Content-Type": "application/json" });
        res.end(JSON.stringify({
          success: true,
          metrics: proxyPool.getMetrics(),
          proxies: proxyPool.getProxyDetail()
        }));
        return;
      }

      // Auth required for search endpoints
      if (!authenticate(req)) return unauthorized(res);

      if (path === "/search" && req.method === "POST") {
        const body = await parseBody(req);
        const { query, type = "image", limit = 10 } = body;
        if (!query) return badRequest(res, "Missing 'query' field");

        const start = Date.now();
        const data = await runner.run({ query, type, limit });
        const response = JSON.parse(formatSearchResponse(data));
        response.execution_time_ms = Date.now() - start;

        res.writeHead(data.image?.results?.length > 0 || data.web?.results?.length > 0 ? 200 : 404, {
          "Content-Type": "application/json"
        });
        res.end(JSON.stringify(response));
        return;
      }

      if (path === "/batch" && req.method === "POST") {
        const body = await parseBody(req);
        const { queries = [] } = body;

        if (!Array.isArray(queries) || queries.length === 0) {
          return badRequest(res, "Missing or empty 'queries' array");
        }
        if (queries.length > 50) {
          return badRequest(res, "Maximum 50 queries per batch");
        }

        const logBatch = childLogger({ component: "batch", batchSize: queries.length });

        const batchStart = Date.now();
        logBatch.info("batch started");

        const batchResults = await Promise.allSettled(
          queries.map(async (q, i) => {
            const qStart = Date.now();
            try {
              const data = await runner.run({
                query: q.query || "",
                type: q.type || "image",
                limit: q.limit || 10
              });
              return {
                index: i,
                query: q.query,
                type: q.type || "image",
                success: true,
                execution_time_ms: Date.now() - qStart,
                results: data,
                errors: data.errors || []
              };
            } catch (err) {
              return {
                index: i,
                query: q.query,
                type: q.type || "image",
                success: false,
                execution_time_ms: Date.now() - qStart,
                error: err.message
              };
            }
          })
        );

        const totalMs = Date.now() - batchStart;
        const ok = batchResults.filter(r => r.status === "fulfilled" && r.value.success).length;
        const fail = batchResults.filter(r => r.status === "fulfilled" && !r.value.success).length;

        logBatch.info({ total: queries.length, ok, fail, totalMs }, "batch completed");

        res.writeHead(200, { "Content-Type": "application/json" });
        res.end(JSON.stringify({
          success: true,
          batch_size: queries.length,
          execution_time_ms: totalMs,
          ok,
          fail,
          results: batchResults.map(r => r.status === "fulfilled" ? r.value : {
            index: -1,
            query: "unknown",
            success: false,
            error: r.reason?.message || "Promise rejected"
          }),
          metrics: {
            pool: proxyPool.getMetrics(),
            hourly_usage: proxyPool.getMetrics().hourlyUsageCurrent
          }
        }));
        return;
      }

      // MCP JSON-RPC endpoint
      if (path === "/mcp" && req.method === "POST") {
        const body = await parseBody(req);
        const mcpResp = await handleMCP(body);
        const status = mcpResp.error ? 400 : 200;
        res.writeHead(status, { "Content-Type": "application/json" });
        res.end(JSON.stringify(mcpResp));
        return;
      }

      // 404
      res.writeHead(404, { "Content-Type": "application/json" });
      res.end(JSON.stringify({ success: false, error: { code: "NOT_FOUND", message: `No endpoint: ${req.method} ${path}` } }));

    } catch (err) {
      log.error({ error: err.message }, "API error");
      serverError(res, err.message);
    }
  });

  server.listen(port, () => {
    log.info({ port }, "API server started");
    console.log(`\n  PolySearch API running on http://localhost:${port}`);
    console.log(`  Health:   http://localhost:${port}/health`);
    console.log(`  Search:   POST http://localhost:${port}/search`);
    console.log(`  Batch:    POST http://localhost:${port}/batch`);
    console.log(`  Metrics:  GET  http://localhost:${port}/metrics`);
    console.log(`  MCP:      POST http://localhost:${port}/mcp`);
    const key = loadApiKey();
    if (key) {
      console.log(`  Auth:     Authorization: Bearer <key>`);
      console.log(`  Key:      ${key.substring(0, 8)}...${key.slice(-4)}\n`);
    } else {
      console.log(`  Auth:     none (no API key configured)\n`);
    }
  });

  const shutdown = () => {
    log.info("shutting down API server");
    proxyPool.destroy();
    server.close(() => process.exit(0));
  };
  process.on("SIGINT", shutdown);
  process.on("SIGTERM", shutdown);

  return server;
}