/**
 * @license
 * Copyright 2017 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

export type LogLevelString =
  | 'debug'
  | 'verbose'
  | 'info'
  | 'warn'
  | 'error'
  | 'silent';

export interface LogOptions {
  level: LogLevelString;
}

export type LogCallback = (callbackParams: LogCallbackParams) => void;

export interface LogCallbackParams {
  level: LogLevelString;
  message: string;
  args: unknown[];
  type: string;
}

/**
 * A container for all of the Logger instances
 */
export const instances: Logger[] = [];

/**
 * The JS SDK supports 5 log levels and also allows a user the ability to
 * silence the logs altogether.
 *
 * The order is a follows:
 * DEBUG < VERBOSE < INFO < WARN < ERROR
 *
 * All of the log types above the current log level will be captured (i.e. if
 * you set the log level to `INFO`, errors will still be logged, but `DEBUG` and
 * `VERBOSE` logs will not)
 */
export enum LogLevel {
  DEBUG,
  VERBOSE,
  INFO,
  WARN,
  ERROR,
  SILENT
}

const levelStringToEnum: { [key in LogLevelString]: LogLevel } = {
  'debug': LogLevel.DEBUG,
  'verbose': LogLevel.VERBOSE,
  'info': LogLevel.INFO,
  'warn': LogLevel.WARN,
  'error': LogLevel.ERROR,
  'silent': LogLevel.SILENT
};

/**
 * The default log level
 */
const defaultLogLevel: LogLevel = LogLevel.INFO;

/**
 * We allow users the ability to pass their own log handler. We will pass the
 * type of log, the current log level, and any other arguments passed (i.e. the
 * messages that the user wants to log) to this function.
 */
export type LogHandler = (
  loggerInstance: Logger,
  logType: LogLevel,
  ...args: unknown[]
) => void;

/**
 * By default, `console.debug` is not displayed in the developer console (in
 * chrome). To avoid forcing users to have to opt-in to these logs twice
 * (i.e. once for firebase, and once in the console), we are sending `DEBUG`
 * logs to the `console.log` function.
 */
const ConsoleMethod = {
  [LogLevel.DEBUG]: 'log',
  [LogLevel.VERBOSE]: 'log',
  [LogLevel.INFO]: 'info',
  [LogLevel.WARN]: 'warn',
  [LogLevel.ERROR]: 'error'
};

/**
 * The default log handler will forward DEBUG, VERBOSE, INFO, WARN, and ERROR
 * messages on to their corresponding console counterparts (if the log method
 * is supported by the current log level)
 */
const defaultLogHandler: LogHandler = (instance, logType, ...args): void => {
  if (logType < instance.logLevel) {
    return;
  }
  const now = new Date().toISOString();
  const method = ConsoleMethod[logType as keyof typeof ConsoleMethod];
  if (method) {
    console[method as 'log' | 'info' | 'warn' | 'error'](
      `[${now}]  ${instance.name}:`,
      ...args
    );
  } else {
    throw new Error(
      `Attempted to log a message with an invalid logType (value: ${logType})`
    );
  }
};

export class Logger {
  /**
   * Gives you an instance of a Logger to capture messages according to
   * Firebase's logging scheme.
   *
   * @param name The name that the logs will be associated with
   */
  constructor(public name: string) {
    /**
     * Capture the current instance for later use
     */
    instances.push(this);
  }

  /**
   * The log level of the given Logger instance.
   */
  private _logLevel = defaultLogLevel;

  get logLevel(): LogLevel {
    return this._logLevel;
  }

  set logLevel(val: LogLevel) {
    if (!(val in LogLevel)) {
      throw new TypeError(`Invalid value "${val}" assigned to \`logLevel\``);
    }
    this._logLevel = val;
  }

  // Workaround for setter/getter having to be the same type.
  setLogLevel(val: LogLevel | LogLevelString): void {
    this._logLevel = typeof val === 'string' ? levelStringToEnum[val] : val;
  }

  /**
   * The main (internal) log handler for the Logger instance.
   * Can be set to a new function in internal package code but not by user.
   */
  private _logHandler: LogHandler = defaultLogHandler;
  get logHandler(): LogHandler {
    return this._logHandler;
  }
  set logHandler(val: LogHandler) {
    if (typeof val !== 'function') {
      throw new TypeError('Value assigned to `logHandler` must be a function');
    }
    this._logHandler = val;
  }

  /**
   * The optional, additional, user-defined log handler for the Logger instance.
   */
  private _userLogHandler: LogHandler | null = null;
  get userLogHandler(): LogHandler | null {
    return this._userLogHandler;
  }
  set userLogHandler(val: LogHandler | null) {
    this._userLogHandler = val;
  }

  /**
   * The functions below are all based on the `console` interface
   */

  debug(...args: unknown[]): void {
    this._userLogHandler && this._userLogHandler(this, LogLevel.DEBUG, ...args);
    this._logHandler(this, LogLevel.DEBUG, ...args);
  }
  log(...args: unknown[]): void {
    this._userLogHandler &&
      this._userLogHandler(this, LogLevel.VERBOSE, ...args);
    this._logHandler(this, LogLevel.VERBOSE, ...args);
  }
  info(...args: unknown[]): void {
    this._userLogHandler && this._userLogHandler(this, LogLevel.INFO, ...args);
    this._logHandler(this, LogLevel.INFO, ...args);
  }
  warn(...args: unknown[]): void {
    this._userLogHandler && this._userLogHandler(this, LogLevel.WARN, ...args);
    this._logHandler(this, LogLevel.WARN, ...args);
  }
  error(...args: unknown[]): void {
    this._userLogHandler && this._userLogHandler(this, LogLevel.ERROR, ...args);
    this._logHandler(this, LogLevel.ERROR, ...args);
  }
}

export function setLogLevel(level: LogLevelString | LogLevel): void {
  instances.forEach(inst => {
    inst.setLogLevel(level);
  });
}

export function setUserLogHandler(
  logCallback: LogCallback | null,
  options?: LogOptions
): void {
  for (const instance of instances) {
    let customLogLevel: LogLevel | null = null;
    if (options && options.level) {
      customLogLevel = levelStringToEnum[options.level];
    }
    if (logCallback === null) {
      instance.userLogHandler = null;
    } else {
      instance.userLogHandler = (
        instance: Logger,
        level: LogLevel,
        ...args: unknown[]
      ) => {
        const message = args
          .map(arg => {
            if (arg == null) {
              return null;
            } else if (typeof arg === 'string') {
              return arg;
            } else if (typeof arg === 'number' || typeof arg === 'boolean') {
              return arg.toString();
            } else if (arg instanceof Error) {
              return arg.message;
            } else {
              try {
                return JSON.stringify(arg);
              } catch (ignored) {
                return null;
              }
            }
          })
          .filter(arg => arg)
          .join(' ');
        if (level >= (customLogLevel ?? instance.logLevel)) {
          logCallback({
            level: LogLevel[level].toLowerCase() as LogLevelString,
            message,
            args,
            type: instance.name
          });
        }
      };
    }
  }
}