import jwt from 'jsonwebtoken'

/**
 * Represents the response of a JWT validation.
 * @typedef {Object} JWTValidationResponse
 * @property {boolean} isValid - Indicates whether the JWT is valid or not.
 * @property {jwt.JwtPayload} [decodedToken] - The decoded JWT payload if the JWT is valid.
 * @property {boolean} [isExpired] - Indicates whether the JWT is expired or not, only present if isValid is false.
 */
type JWTValidationResponse =
  | { isValid: true; decodedToken: jwt.JwtPayload }
  | {
      isValid: false
      isExpired?: boolean
    }

/**
 * Represents a JSON Web Token (JWT) utility class.
 */
export default class JWT {
  /**
   * The secret key used for generating and verifying tokens.
   * @type {string}
   */
  private readonly tokenSecret: string
  /**
   * The default expiration time for a cache entry.
   * @type {string}
   */
  private readonly defaultExpiration?: string

  /**
   * Constructs a new instance of the class.
   * @param {string} tokenSecret - The secret used to sign the tokens.
   * @param {string} [defaultExpiration] - The default expiration time for the tokens.
   * @returns None
   */
  constructor(tokenSecret: string, defaultExpiration?: string) {
    this.tokenSecret = tokenSecret
    this.defaultExpiration = defaultExpiration
  }

  /**
   * Creates a JSON Web Token (JWT) using the provided data and options.
   * @param {object} data - The data to be included in the token payload.
   * @param {string} [expiration] - The expiration time for the token. If not provided, the default expiration time will be used.
   * @param {string} [overrideToken] - An optional token secret to override the default token secret.
   * @param {any} [opts] - Additional options to be passed to the jwt.sign() function.
   * @returns {string} - The generated JWT.
   */
  public createToken(
    data: object,
    expiration?: string,
    overrideToken?: string,
    opts?: any
  ): string {
    const exp = expiration || this.defaultExpiration
    return jwt.sign(
      data,
      overrideToken || this.tokenSecret,
      exp ? { expiresIn: exp, ...(opts || {}) } : opts || {}
    )
  }

  /**
   * Validates a JSON Web Token (JWT) and returns the validation response.
   * @param {string} token - The JWT to validate.
   * @returns {JWTValidationResponse} - The validation response object.
   */
  public validateToken(token: string): JWTValidationResponse {
    try {
      // Check if is valid
      const isValid = jwt.verify(token, this.tokenSecret)
      if (isValid) {
        const payload = jwt.decode(token, { json: true })
        if (payload) return { isValid: true, decodedToken: payload }
      }
    } catch (err) {
      console.error(err)
      if (err instanceof jwt.TokenExpiredError) return { isValid: false, isExpired: true }
    }
    return { isValid: false }
  }
}