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

function ensureDir(dirPath) {
  fs.mkdirSync(dirPath, { recursive: true });
}

function readJson(filePath, fallback = null) {
  if (!fs.existsSync(filePath)) {
    return fallback;
  }
  return JSON.parse(fs.readFileSync(filePath, "utf8"));
}

function writeJson(filePath, data) {
  ensureDir(path.dirname(filePath));
  fs.writeFileSync(filePath, JSON.stringify(data, null, 2) + "\n", "utf8");
}

function readText(filePath, fallback = "") {
  if (!fs.existsSync(filePath)) {
    return fallback;
  }
  return fs.readFileSync(filePath, "utf8");
}

function writeText(filePath, content) {
  ensureDir(path.dirname(filePath));
  fs.writeFileSync(filePath, content, "utf8");
}

function formatDateKey(date = new Date()) {
  const y = date.getFullYear();
  const m = String(date.getMonth() + 1).padStart(2, "0");
  const d = String(date.getDate()).padStart(2, "0");
  return `${y}_${m}_${d}`;
}

function getWeekKey(date = new Date()) {
  const d = new Date(Date.UTC(date.getFullYear(), date.getMonth(), date.getDate()));
  const dayNum = d.getUTCDay() || 7;
  d.setUTCDate(d.getUTCDate() + 4 - dayNum);
  const yearStart = new Date(Date.UTC(d.getUTCFullYear(), 0, 1));
  const weekNo = Math.ceil((((d - yearStart) / 86400000) + 1) / 7);
  return `${d.getUTCFullYear()}-W${String(weekNo).padStart(2, "0")}`;
}

module.exports = {
  ensureDir,
  readJson,
  writeJson,
  readText,
  writeText,
  formatDateKey,
  getWeekKey
};