"use strict";

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

function hashToken(token) {
  return crypto.createHash("sha256").update(String(token)).digest("hex");
}

class SessionStore {
  /**
   * @param {Object} options
   * @param {string} options.file - Путь к sessions.json
   * @param {number} options.ttlMs - Время жизни сессии в мс
   * @param {boolean} [options.persist=true] - Сохранять ли на диск
   * @param {import('../../logger').Logger} [options.logger]
   */
  constructor({ file, ttlMs = 7 * 24 * 60 * 60 * 1000, persist = true, logger = null }) {
    this.file = file;
    this.ttlMs = ttlMs;
    this.persist = persist;
    this.logger = logger;
    /** @type {Map<string, { user: string, expiresAt: number, createdAt: number }>} */
    this.sessions = new Map(); // key: hash(token)
    this._persistTimer = null;
    this._sweepInterval = null;

    if (this.persist && this.file) {
      this._load();
    }

    this._sweepInterval = setInterval(() => this.sweep(), 60 * 60 * 1000);
    if (this._sweepInterval.unref) {
      this._sweepInterval.unref();
    }
  }

  _load() {
    try {
      if (!fs.existsSync(this.file)) return;
      const raw = fs.readFileSync(this.file, "utf8");
      if (!raw.trim()) return;
      const data = JSON.parse(raw);
      const now = Date.now();
      let loaded = 0;
      for (const [tokenHash, session] of Object.entries(data)) {
        if (session && session.expiresAt && session.expiresAt > now && session.user) {
          this.sessions.set(tokenHash, {
            user: session.user,
            expiresAt: session.expiresAt,
            createdAt: session.createdAt || now,
          });
          loaded++;
        }
      }
      if (this.logger) {
        this.logger.debug("Сессии загружены с диска", { count: loaded });
      }
    } catch (err) {
      if (this.logger) {
        this.logger.warn("Ошибка при загрузке sessions.json, инициализация пустого хранилища", {
          error: err.message,
        });
      }
    }
  }

  create(user) {
    const rawToken = crypto.randomBytes(32).toString("hex");
    const tokenHash = hashToken(rawToken);
    const now = Date.now();
    const session = {
      user: String(user || "admin"),
      expiresAt: now + this.ttlMs,
      createdAt: now,
    };
    this.sessions.set(tokenHash, session);
    this._schedulePersist();
    return rawToken;
  }

  get(token) {
    if (!token) return null;
    const tokenHash = hashToken(token);
    const session = this.sessions.get(tokenHash);
    if (!session) return null;

    const now = Date.now();
    if (session.expiresAt <= now) {
      this.sessions.delete(tokenHash);
      this._schedulePersist();
      return null;
    }

    // Sliding TTL
    session.expiresAt = now + this.ttlMs;
    this._schedulePersist();
    return {
      user: session.user,
      expiresAt: session.expiresAt,
      createdAt: session.createdAt,
    };
  }

  delete(token) {
    if (!token) return;
    const tokenHash = hashToken(token);
    if (this.sessions.delete(tokenHash)) {
      this._schedulePersist();
    }
  }

  sweep() {
    const now = Date.now();
    let removed = 0;
    for (const [tokenHash, session] of this.sessions) {
      if (session.expiresAt <= now) {
        this.sessions.delete(tokenHash);
        removed++;
      }
    }
    if (removed > 0) {
      this._schedulePersist();
      if (this.logger) {
        this.logger.debug("Очищены устаревшие сессии", { count: removed });
      }
    }
  }

  _schedulePersist() {
    if (!this.persist || !this.file) return;
    if (this._persistTimer) return;

    this._persistTimer = setTimeout(() => {
      this._persistTimer = null;
      this._flushPersist();
    }, 500);

    if (this._persistTimer.unref) {
      this._persistTimer.unref();
    }
  }

  _flushPersist() {
    if (!this.persist || !this.file) return;
    try {
      const dir = path.dirname(this.file);
      if (!fs.existsSync(dir)) {
        fs.mkdirSync(dir, { recursive: true });
      }

      const obj = {};
      for (const [tokenHash, session] of this.sessions) {
        obj[tokenHash] = session;
      }

      const tmpFile = `${this.file}.${Date.now()}.${Math.random().toString(36).slice(2, 8)}.tmp`;
      const fd = fs.openSync(tmpFile, "w");
      try {
        fs.writeFileSync(fd, JSON.stringify(obj, null, 2), "utf8");
        fs.fsyncSync(fd);
      } finally {
        fs.closeSync(fd);
      }
      fs.renameSync(tmpFile, this.file);
    } catch (err) {
      if (this.logger) {
        this.logger.error("Ошибка при сохранении sessions.json", { error: err.message });
      }
    }
  }

  close() {
    if (this._sweepInterval) {
      clearInterval(this._sweepInterval);
      this._sweepInterval = null;
    }
    if (this._persistTimer) {
      clearTimeout(this._persistTimer);
      this._persistTimer = null;
    }
    this._flushPersist();
  }
}

module.exports = {
  SessionStore,
  hashToken,
};