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

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

const EMPTY_DATA = {
  fuelCards: [],
  log: []
};

function load() {
  try {
    const content = fs.readFileSync(DATA_FILE, "utf8");
    return JSON.parse(content);
  } catch {
    return EMPTY_DATA;
  }
}

function save(data) {
  fs.writeFileSync(DATA_FILE, JSON.stringify(data, null, 2));
}

function logAction(action, details) {
  const data = load();
  data.log.push({
    when: new Date().toISOString(),
    what: `${action}: ${details}`,
    who: "user"
  });
  save(data);
}

const server = http.createServer((req, res) => {
  const parsedUrl = url.parse(req.url, true);
  const pathname = parsedUrl.pathname.split("?")[0];
  const method = req.method;

  res.setHeader("Access-Control-Allow-Origin", "*");
  res.setHeader("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS");
  res.setHeader("Access-Control-Allow-Headers", "Content-Type");

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

  if (pathname === "/api/fuel-cards" && method === "GET") {
    const data = load();
    res.writeHead(200, { "Content-Type": "application/json" });
    res.end(JSON.stringify(data.fuelCards));
    return;
  }

  if (pathname === "/api/fuel-cards" && method === "POST") {
    let body = "";
    req.on("data", chunk => { body += chunk; });
    req.on("end", () => {
      try {
        const card = JSON.parse(body);
        const data = load();
        card.id = Date.now();
        card.createdAt = new Date().toISOString();
        data.fuelCards.push(card);
        save(data);
        logAction("Добавлен талон", `водитель: ${card.driver}, авто: ${card.vehicle}, литраж: ${card.liters}л`);
        res.writeHead(201, { "Content-Type": "application/json" });
        res.end(JSON.stringify(card));
      } catch (err) {
        res.writeHead(400, { "Content-Type": "application/json" });
        res.end(JSON.stringify({ error: err.message }));
      }
    });
    return;
  }

  if (pathname === "/api/fuel-cards" && method === "PUT") {
    let body = "";
    req.on("data", chunk => { body += chunk; });
    req.on("end", () => {
      try {
        const updated = JSON.parse(body);
        const data = load();
        const index = data.fuelCards.findIndex(c => c.id === updated.id);
        if (index === -1) {
          res.writeHead(404, { "Content-Type": "application/json" });
          res.end(JSON.stringify({ error: "Не найдено" }));
          return;
        }
        const old = data.fuelCards[index];
        data.fuelCards[index] = { ...old, ...updated };
        save(data);
        logAction("Изменён талон", `ID: ${updated.id}, водитель: ${updated.driver}`);
        res.writeHead(200, { "Content-Type": "application/json" });
        res.end(JSON.stringify(data.fuelCards[index]));
      } catch (err) {
        res.writeHead(400, { "Content-Type": "application/json" });
        res.end(JSON.stringify({ error: err.message }));
      }
    });
    return;
  }

  if (pathname.startsWith("/api/fuel-cards/") && method === "DELETE") {
    const id = parseInt(parsedUrl.pathname.split("/").pop());
    const data = load();
    const card = data.fuelCards.find(c => c.id === id);
    if (!card) {
      res.writeHead(404, { "Content-Type": "application/json" });
      res.end(JSON.stringify({ error: "Не найдено" }));
      return;
    }
    data.fuelCards = data.fuelCards.filter(c => c.id !== id);
    save(data);
    logAction("Удалён талон", `водитель: ${card.driver}, авто: ${card.vehicle}, литраж: ${card.liters}л`);
    res.writeHead(200, { "Content-Type": "application/json" });
    res.end(JSON.stringify({ success: true }));
    return;
  }

  if (pathname === "/api/log" && method === "GET") {
    const data = load();
    res.writeHead(200, { "Content-Type": "application/json" });
    res.end(JSON.stringify(data.log.slice(-50).reverse()));
    return;
  }

  if (pathname === "/api/stats" && method === "GET") {
    const data = load();
    const cards = data.fuelCards;
    
    const totalLiters = cards.reduce((sum, c) => sum + (parseFloat(c.liters) || 0), 0);
    const totalAmount = cards.reduce((sum, c) => sum + (parseFloat(c.amount) || 0), 0);
    const totalCards = cards.length;
    
    const byDriver = {};
    cards.forEach(c => {
      if (!byDriver[c.driver]) {
        byDriver[c.driver] = { liters: 0, amount: 0, count: 0 };
      }
      byDriver[c.driver].liters += parseFloat(c.liters) || 0;
      byDriver[c.driver].amount += parseFloat(c.amount) || 0;
      byDriver[c.driver].count += 1;
    });

    const byVehicle = {};
    cards.forEach(c => {
      if (!byVehicle[c.vehicle]) {
        byVehicle[c.vehicle] = { liters: 0, amount: 0, count: 0 };
      }
      byVehicle[c.vehicle].liters += parseFloat(c.liters) || 0;
      byVehicle[c.vehicle].amount += parseFloat(c.amount) || 0;
      byVehicle[c.vehicle].count += 1;
    });

    const byGasStation = {};
    cards.forEach(c => {
      if (!byGasStation[c.gasStation]) {
        byGasStation[c.gasStation] = { liters: 0, amount: 0, count: 0 };
      }
      byGasStation[c.gasStation].liters += parseFloat(c.liters) || 0;
      byGasStation[c.gasStation].amount += parseFloat(c.amount) || 0;
      byGasStation[c.gasStation].count += 1;
    });

    const stats = {
      totalLiters,
      totalAmount,
      totalCards,
      byDriver,
      byVehicle,
      byGasStation,
      avgPricePerLiter: totalLiters > 0 ? (totalAmount / totalLiters).toFixed(2) : 0
    };

    res.writeHead(200, { "Content-Type": "application/json" });
    res.end(JSON.stringify(stats));
    return;
  }

  const filePath = path.join(__dirname, parsedUrl.pathname === "/" ? "index.html" : parsedUrl.pathname);
  const ext = path.extname(filePath).toLowerCase();
  const mimeTypes = {
    ".html": "text/html",
    ".css": "text/css",
    ".js": "application/javascript",
    ".json": "application/json",
    ".png": "image/png",
    ".jpg": "image/jpeg",
    ".svg": "image/svg+xml"
  };

  fs.readFile(filePath, (err, content) => {
    if (err) {
      if (err.code === "ENOENT") {
        res.writeHead(404);
        res.end("Not found");
      } else {
        res.writeHead(500);
        res.end("Server error");
      }
      return;
    }
    res.writeHead(200, { "Content-Type": mimeTypes[ext] || "text/plain" });
    res.end(content);
  });
});

server.listen(PORT, () => {
  console.log(`Сервер запущен на порту ${PORT}`);
});