const http = require("http");
const fs = require("fs");
const path = require("path");

const PORT = process.env.PORT || 3000;
const DATA = path.join(__dirname, "data.json");

function readData() {
  try { return JSON.parse(fs.readFileSync(DATA, "utf8")); } catch (_) { return { subscribers: [], payments: [] }; }
}
function writeData(data) {
  fs.writeFileSync(DATA, JSON.stringify(data, null, 2));
}
function body(req) {
  return new Promise((resolve) => {
    let s = "";
    req.on("data", (c) => (s += c));
    req.on("end", () => { try { resolve(JSON.parse(s || "{}")); } catch (_) { resolve({}); } });
  });
}

http.createServer(async (req, res) => {
  res.setHeader("Access-Control-Allow-Origin", "*");
  res.setHeader("Access-Control-Allow-Methods", "GET, POST, DELETE, OPTIONS");
  res.setHeader("Access-Control-Allow-Headers", "Content-Type");
  
  if (req.method === "OPTIONS") {
    res.writeHead(200);
    return res.end();
  }

  // API: список абонентов
  if (req.method === "GET" && req.url === "/api/subscribers") {
    const data = readData();
    res.writeHead(200, { "Content-Type": "application/json" });
    return res.end(JSON.stringify(data.subscribers));
  }
  
  // API: добавить абонента
  if (req.method === "POST" && req.url === "/api/subscribers") {
    const sub = await body(req);
    const data = readData();
    const newSub = {
      id: Date.now(),
      accountNumber: "LS" + Date.now(),
      name: sub.name || "",
      address: sub.address || "",
      phone: sub.phone || "",
      balance: 0,
      status: "active",
      createdAt: new Date().toISOString().slice(0, 10)
    };
    data.subscribers.push(newSub);
    writeData(data);
    res.writeHead(200, { "Content-Type": "application/json" });
    return res.end(JSON.stringify({ ok: true, subscriber: newSub }));
  }
  
  // API: обновить абонента
  if (req.method === "PUT" && /^\/api\/subscribers\/\d+$/.test(req.url)) {
    const id = parseInt(req.url.split("/")[3]);
    const update = await body(req);
    const data = readData();
    const idx = data.subscribers.findIndex(s => s.id === id);
    if (idx !== -1) {
      data.subscribers[idx] = { ...data.subscribers[idx], ...update };
      writeData(data);
      res.writeHead(200, { "Content-Type": "application/json" });
      return res.end(JSON.stringify({ ok: true }));
    }
    res.writeHead(404);
    return res.end(JSON.stringify({ error: "Not found" }));
  }
  
  // API: удалить абонента
  if (req.method === "DELETE" && /^\/api\/subscribers\/\d+$/.test(req.url)) {
    const id = parseInt(req.url.split("/")[3]);
    const data = readData();
    const idx = data.subscribers.findIndex(s => s.id === id);
    if (idx !== -1) {
      data.subscribers.splice(idx, 1);
      writeData(data);
      res.writeHead(200, { "Content-Type": "application/json" });
      return res.end(JSON.stringify({ ok: true }));
    }
    res.writeHead(404);
    return res.end(JSON.stringify({ error: "Not found" }));
  }
  
  // API: платежи
  if (req.method === "GET" && req.url.startsWith("/api/payments")) {
    const data = readData();
    const subscriberId = req.url.split("=")[1];
    const payments = subscriberId 
      ? data.payments.filter(p => p.subscriberId == subscriberId)
      : data.payments;
    res.writeHead(200, { "Content-Type": "application/json" });
    return res.end(JSON.stringify(payments));
  }
  
  // API: добавить платёж
  if (req.method === "POST" && req.url === "/api/payments") {
    const payment = await body(req);
    const data = readData();
    const newPayment = {
      id: Date.now(),
      subscriberId: payment.subscriberId,
      amount: parseFloat(payment.amount) || 0,
      date: payment.date || new Date().toISOString().slice(0, 10),
      comment: payment.comment || ""
    };
    data.payments.push(newPayment);
    
    // Обновить баланс абонента
    const subIdx = data.subscribers.findIndex(s => s.id == payment.subscriberId);
    if (subIdx !== -1) {
      data.subscribers[subIdx].balance = (data.subscribers[subIdx].balance || 0) + newPayment.amount;
    }
    
    writeData(data);
    res.writeHead(200, { "Content-Type": "application/json" });
    return res.end(JSON.stringify({ ok: true, payment: newPayment }));
  }
  
  // Статика
  let file = req.url === "/" ? "/index.html" : req.url.split("?")[0];
  const full = path.join(__dirname, file);
  if (full.startsWith(__dirname) && fs.existsSync(full) && fs.statSync(full).isFile()) {
    const ext = path.extname(full);
    const type = ext === ".css" ? "text/css" : ext === ".js" ? "application/javascript" : "text/html";
    res.writeHead(200, { "Content-Type": type + "; charset=utf-8" });
    return res.end(fs.readFileSync(full));
  }
  
  res.writeHead(404);
  res.end("Not found");
}).listen(PORT, () => console.log("Сервер запущен на порту " + PORT));