/*
 * Copyright (C) 2018, 2019 StApps
 * This program is free software: you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation, version 3.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program. If not, see <https://www.gnu.org/licenses/>.
 */
import chalk from 'chalk';
import {stringify} from 'flatted';
import {isNodeEnvironment, isProductiveNodeEnvironment} from './common';
import {Transport} from './Transport';

/**
 * Logger with colors, loglevel and transport
 *
 * Log level can be defined by setting the environment variable STAPPS_LOG_LEVEL to a valid log level. Log levels are
 * set in a binary way. For example STAPPS_LOG_LEVEL=12 does result in logs only for `Logger.warn` and `Logger.error`.
 *
 * Log levels in that order are:
 * ```
 * INFO: 1
 * LOG: 2
 * WARN: 4
 * ERROR: 8
 * OK: 16
 * ```
 */
export class Logger {
  /**
   * Log levels
   */
  private static logLevels = [
    'INFO',
    'LOG',
    'WARN',
    'ERROR',
    'OK',
  ];

  /**
   * Transport for errors
   */
  private static transport?: Transport;

  /**
   * Check if intended log level is allowed in environment log level
   *
   * @param logLevel
   */
  private static checkLogLevel(logLevel: string): boolean {
    const logLevelNumber = Math.pow(2, Logger.logLevels.indexOf(logLevel) + 1) - 1;

    /* tslint:disable-next-line:no-bitwise */
    return !!(Logger.getLogLevel() & logLevelNumber);
  }

  /**
   * Return log level from environment
   */
  private static getLogLevel(): number {
    if (isNodeEnvironment() && typeof process.env.STAPPS_LOG_LEVEL !== 'undefined') {
      // Node.js environment exists
      return parseInt(process.env.STAPPS_LOG_LEVEL, 10);
    } else if (typeof window !== 'undefined' && typeof (window as any).STAPPS_LOG_LEVEL === 'number') {
      // browser environment exists
      return (window as any).STAPPS_LOG_LEVEL;
    }

    // Log everything
    return 31;
  }

  /**
   * Log an error
   *
   * @param args Arguments to log
   */
  public static async error(...args: any[]): Promise<string | void> {
    if (!Logger.checkLogLevel('ERROR')) {
      return;
    }

    /* tslint:disable-next-line:no-console */
    console.error(chalk.bold.red(`[ERROR] ${Logger.stringifyArguments(...args)}`));

    if (isProductiveNodeEnvironment()) {
      if (typeof Logger.transport !== 'undefined') {
        return Logger.transport.send('Error', Logger.stringifyArguments(...args));
      } else if (!process.env.ALLOW_NO_TRANSPORT) {
        throw new Error(`Error couldn't be transported! Please set a transport or set ALLOW_NO_TRANSPORT='true'.`);
      }
    }
  }

  /**
   * Log an information
   *
   * @param args Arguments to log
   */
  public static info(...args: any[]): void {
    if (!Logger.checkLogLevel('INFO')) {
      return;
    }

    /* tslint:disable-next-line:no-console */
    console.info(chalk.cyan(`[INFO] ${Logger.stringifyArguments(args)}`));
  }

  /**
   * Check if the logger is initialized correctly
   */
  public static initialized(): void {
    if (isProductiveNodeEnvironment() && typeof Logger.transport === 'undefined') {
      if (!process.env.ALLOW_NO_TRANSPORT) {
        throw new Error(`Productive environment doesn't set a transport for error notifications.`);
      } else {
        /* tslint:disable-next-line:no-console */
        console.warn(chalk.yellow(`Productive environment doesn't set a transport for error notifications.`));
      }
    }
  }

  /**
   * Log something
   *
   * @param args Arguments to log
   */
  public static log(...args: any[]): void {
    if (!this.checkLogLevel('LOG')) {
      return;
    }

    /* tslint:disable-next-line:no-console */
    console.log(chalk.white(`[LOG] ${Logger.stringifyArguments(args)}`));
  }

  /**
   * Log something successful
   *
   * @param args Arguments to log
   */
  public static ok(...args: any[]): void {
    if (!this.checkLogLevel('OK')) {
      return;
    }

    /* tslint:disable-next-line:no-console */
    console.log(chalk.bold.green(`[OK] ${Logger.stringifyArguments(args)}`));
  }

  /**
   * Set a transport
   *
   * @param transport Transport to set
   */
  public static setTransport(transport?: Transport) {
    Logger.transport = transport;
  }

  /**
   * Stringify a list of arguments
   *
   * @param args Arguments to stringify
   */
  public static stringifyArguments(...args: any[]): string {
    const result: string[] = [];

    args.forEach((argument) => {
      const type = typeof argument;

      if (['string', 'number'].indexOf(type) !== -1) {
        result.push(argument);
      } else if (argument instanceof Error) {
        result.push(argument.message);
        if (typeof argument.stack !== 'undefined') {
          result.push(argument.stack);
        }
      } else {
        result.push(stringify(argument, null, 2));
      }
    });

    return result.join(', ');
  }

  /**
   * Log a warning
   *
   * @param args Arguments to log
   */
  public static warn(...args: any[]): void {
    if (!this.checkLogLevel('WARN')) {
      return;
    }

    /* tslint:disable-next-line:no-console */
    console.warn(chalk.yellow(`[WARN] ${Logger.stringifyArguments(args)}`));
  }
}