// app/utils/refreshSession.util.js

const crypto = require("crypto");

const {
  generateRefreshToken,
  verifyRefreshToken,
} = require("./jwt.util");

const refreshSessions = new Map();


// Default = 7 days
const REFRESH_SESSION_TTL =
  7 * 24 * 60 * 60 * 1000;


const hashRefreshToken = (token) => {
  return crypto
    .createHash("sha256")
    .update(token)
    .digest("hex");
};

const createRefreshSession = (userId) => {

  // Unique session ID
  const sessionId =
    crypto.randomUUID();


  // Create raw Refresh JWT
  const refreshToken =
    generateRefreshToken({
      sub: userId,
      sid: sessionId,
    });


  // Hash raw refresh token
  const tokenHash =
    hashRefreshToken(
      refreshToken
    );


  // Expiration time
  const expiresAt =
    Date.now() +
    REFRESH_SESSION_TTL;


  // Save only HASH in RAM
  refreshSessions.set(
    sessionId,
    {
      userId,
      tokenHash,
      expiresAt,
    }
  );


  return {
    refreshToken,
    sessionId,
  };
};

const validateRefreshSession = (
  refreshToken
) => {

  if (!refreshToken) {
    return null;
  }


  let decoded;

  try {

    decoded =
      verifyRefreshToken(
        refreshToken
      );

  } catch (error) {

    return null;

  }


  const sessionId =
    decoded.sid;

  const userId =
    decoded.sub;


  if (!sessionId || !userId) {
    return null;
  }


  // Get session from RAM
  const session =
    refreshSessions.get(
      sessionId
    );


  if (!session) {
    return null;
  }


  // Check session expiration
  if (
    Date.now() >
    session.expiresAt
  ) {

    refreshSessions.delete(
      sessionId
    );

    return null;
  }


  // Hash received refresh token
  const receivedHash =
    hashRefreshToken(
      refreshToken
    );


  // Compare stored hash
  if (
    receivedHash !==
    session.tokenHash
  ) {
    return null;
  }


  // Extra user check
  if (
    session.userId !==
    userId
  ) {
    return null;
  }


  return {
    userId,
    sessionId,
  };
};

const deleteRefreshSession = (
  sessionId
) => {

  refreshSessions.delete(
    sessionId
  );
};

const deleteAllUserSessions = (
  userId
) => {

  for (
    const [sessionId, session]
    of refreshSessions.entries()
  ) {

    if (
      session.userId === userId
    ) {

      refreshSessions.delete(
        sessionId
      );

    }

  }
};


module.exports = {
  createRefreshSession,
  validateRefreshSession,
  deleteRefreshSession,
  deleteAllUserSessions,
};