/*
  Copyright 2019 the JSDoc Authors.

  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

      https://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.
*/
const _ = require('lodash');
const { default: ow } = require('ow');

/**
 * Logging levels for the JSDoc logger. The default logging level is
 * {@link module:@jsdoc/cli.LOG_LEVELS.WARN}.
 *
 * @alias module:@jsdoc/cli.LOG_LEVELS
 * @enum
 * @type {number}
 */
const LEVELS = {
  /**
   * Do not log any messages.
   *
   * @alias module:@jsdoc/cli.LOG_LEVELS.SILENT
   */
  SILENT: 0,
  /**
   * Log fatal errors that prevent JSDoc from running.
   *
   * @alias module:@jsdoc/cli.LOG_LEVELS.FATAL
   */
  FATAL: 10,
  /**
   * Log all errors, including errors from which JSDoc can recover.
   *
   * @alias module:@jsdoc/cli.LOG_LEVELS.ERROR
   */
  ERROR: 20,
  /**
   * Log the following messages:
   *
   * + Warnings
   * + Errors
   *
   * @alias module:@jsdoc/cli.LOG_LEVELS.WARN
   */
  WARN: 30,
  /**
   * Log the following messages:
   *
   * + Informational messages
   * + Warnings
   * + Errors
   *
   * @alias module:@jsdoc/cli.LOG_LEVELS.INFO
   */
  INFO: 40,
  /**
   * Log the following messages:
   *
   * + Debugging messages
   * + Informational messages
   * + Warnings
   * + Errors
   *
   * @alias module:@jsdoc/cli.LOG_LEVELS.DEBUG
   */
  DEBUG: 50,
  /**
   * Log all messages.
   *
   * @alias module:@jsdoc/cli.LOG_LEVELS.VERBOSE
   */
  VERBOSE: 1000,
};

const DEFAULT_LEVEL = LEVELS.WARN;
const FUNCS = {
  [LEVELS.DEBUG]: 'debug',
  [LEVELS.ERROR]: 'error',
  [LEVELS.INFO]: 'info',
  [LEVELS.FATAL]: 'error',
  [LEVELS.VERBOSE]: 'debug',
  [LEVELS.WARN]: 'warn',
};
const LEVELS_BY_NUMBER = _.invert(LEVELS);
const PREFIXES = {
  [LEVELS.DEBUG]: 'DEBUG: ',
  [LEVELS.ERROR]: 'ERROR: ',
  [LEVELS.FATAL]: 'FATAL: ',
  [LEVELS.WARN]: 'WARNING: ',
};

// Add a prefix to a log message if necessary.
function addPrefix(level, args) {
  const prefix = PREFIXES[level];

  if (prefix && _.isString(args[0])) {
    args[0] = prefix + args[0];
  }

  return args;
}

class Logger {
  constructor(opts) {
    ow(opts, ow.object);
    // We validate `opts.level` in the setter, so no need to validate it here.
    ow(
      opts.emitter,
      ow.object.partialShape({
        off: ow.function,
        on: ow.function,
        once: ow.function,
      })
    );

    this._console = opts._console || console;
    const emitter = (this._emitter = opts.emitter);

    this.level = opts.level || DEFAULT_LEVEL;

    for (const levelName of Object.keys(LEVELS)) {
      let levelNameLower;
      let levelNumber;

      // `logger:silent` events are not a thing.
      if (levelName === 'SILENT') {
        continue;
      }

      levelNameLower = levelName.toLowerCase();
      levelNumber = LEVELS[levelName];

      emitter.on(`logger:${levelNameLower}`, (...args) => this._maybeLog(levelNumber, args));
    }
  }

  _maybeLog(level, args) {
    if (this._level >= level) {
      args = addPrefix(level, args);
      this._console[FUNCS[level]](...args);
    }
  }

  get level() {
    return this._level;
  }

  set level(level) {
    let errorMsg;

    if (_.isUndefined(LEVELS_BY_NUMBER[level])) {
      errorMsg = `Unrecognized logging level ${level}. Known levels are: `;
      errorMsg += Object.keys(LEVELS)
        .map((k) => `${k}: ${LEVELS[k]}`)
        .join(', ');

      throw new TypeError(errorMsg);
    }

    this._level = level;
  }
}

module.exports = {
  LEVELS,
  Logger,
};