source: trip-planner-front/node_modules/log4js/lib/connect-logger.js@ 6c1585f

/* eslint-disable no-plusplus */

const levels = require("./levels");

const DEFAULT_FORMAT =
  ":remote-addr - -" +
  ' ":method :url HTTP/:http-version"' +
  ' :status :content-length ":referrer"' +
  ' ":user-agent"';

/**
 * Return request url path,
 * adding this function prevents the Cyclomatic Complexity,
 * for the assemble_tokens function at low, to pass the tests.
 *
 * @param  {IncomingMessage} req
 * @return {string}
 * @api private
 */
function getUrl(req) {
  return req.originalUrl || req.url;
}

/**
 * Adds custom {token, replacement} objects to defaults,
 * overwriting the defaults if any tokens clash
 *
 * @param  {IncomingMessage} req
 * @param  {ServerResponse} res
 * @param  {Array} customTokens
 *    [{ token: string-or-regexp, replacement: string-or-replace-function }]
 * @return {Array}
 */
function assembleTokens(req, res, customTokens) {
  const arrayUniqueTokens = array => {
    const a = array.concat();
    for (let i = 0; i < a.length; ++i) {
      for (let j = i + 1; j < a.length; ++j) {
        // not === because token can be regexp object
        /* eslint eqeqeq:0 */
        if (a[i].token == a[j].token) {
          a.splice(j--, 1);
        }
      }
    }
    return a;
  };

  const defaultTokens = [];
  defaultTokens.push({ token: ":url", replacement: getUrl(req) });
  defaultTokens.push({ token: ":protocol", replacement: req.protocol });
  defaultTokens.push({ token: ":hostname", replacement: req.hostname });
  defaultTokens.push({ token: ":method", replacement: req.method });
  defaultTokens.push({
    token: ":status",
    replacement: res.__statusCode || res.statusCode
  });
  defaultTokens.push({
    token: ":response-time",
    replacement: res.responseTime
  });
  defaultTokens.push({ token: ":date", replacement: new Date().toUTCString() });
  defaultTokens.push({
    token: ":referrer",
    replacement: req.headers.referer || req.headers.referrer || ""
  });
  defaultTokens.push({
    token: ":http-version",
    replacement: `${req.httpVersionMajor}.${req.httpVersionMinor}`
  });
  defaultTokens.push({
    token: ":remote-addr",
    replacement:
      req.headers["x-forwarded-for"] ||
      req.ip ||
      req._remoteAddress ||
      (req.socket &&
        (req.socket.remoteAddress ||
          (req.socket.socket && req.socket.socket.remoteAddress)))
  });
  defaultTokens.push({
    token: ":user-agent",
    replacement: req.headers["user-agent"]
  });
  defaultTokens.push({
    token: ":content-length",
    replacement:
      res.getHeader("content-length") ||
      (res.__headers && res.__headers["Content-Length"]) ||
      "-"
  });
  defaultTokens.push({
    token: /:req\[([^\]]+)]/g,
    replacement(_, field) {
      return req.headers[field.toLowerCase()];
    }
  });
  defaultTokens.push({
    token: /:res\[([^\]]+)]/g,
    replacement(_, field) {
      return (
        res.getHeader(field.toLowerCase()) ||
        (res.__headers && res.__headers[field])
      );
    }
  });

  return arrayUniqueTokens(customTokens.concat(defaultTokens));
}

/**
 * Return formatted log line.
 *
 * @param  {string} str
 * @param {Array} tokens
 * @return {string}
 * @api private
 */
function format(str, tokens) {
  for (let i = 0; i < tokens.length; i++) {
    str = str.replace(tokens[i].token, tokens[i].replacement);
  }
  return str;
}

/**
 * Return RegExp Object about nolog
 *
 * @param  {(string|Array)} nolog
 * @return {RegExp}
 * @api private
 *
 * syntax
 *  1. String
 *   1.1 "\\.gif"
 *         NOT LOGGING http://example.com/hoge.gif and http://example.com/hoge.gif?fuga
 *         LOGGING http://example.com/hoge.agif
 *   1.2 in "\\.gif|\\.jpg$"
 *         NOT LOGGING http://example.com/hoge.gif and
 *           http://example.com/hoge.gif?fuga and http://example.com/hoge.jpg?fuga
 *         LOGGING http://example.com/hoge.agif,
 *           http://example.com/hoge.ajpg and http://example.com/hoge.jpg?hoge
 *   1.3 in "\\.(gif|jpe?g|png)$"
 *         NOT LOGGING http://example.com/hoge.gif and http://example.com/hoge.jpeg
 *         LOGGING http://example.com/hoge.gif?uid=2 and http://example.com/hoge.jpg?pid=3
 *  2. RegExp
 *   2.1 in /\.(gif|jpe?g|png)$/
 *         SAME AS 1.3
 *  3. Array
 *   3.1 ["\\.jpg$", "\\.png", "\\.gif"]
 *         SAME AS "\\.jpg|\\.png|\\.gif"
 */
function createNoLogCondition(nolog) {
  let regexp = null;

  if (nolog instanceof RegExp) {
    regexp = nolog;
  }

  if (typeof nolog === "string") {
    regexp = new RegExp(nolog);
  }

  if (Array.isArray(nolog)) {
    // convert to strings
    const regexpsAsStrings = nolog.map(reg => (reg.source ? reg.source : reg));
    regexp = new RegExp(regexpsAsStrings.join("|"));
  }

  return regexp;
}

/**
 * Allows users to define rules around status codes to assign them to a specific
 * logging level.
 * There are two types of rules:
 *   - RANGE: matches a code within a certain range
 *     E.g. { 'from': 200, 'to': 299, 'level': 'info' }
 *   - CONTAINS: matches a code to a set of expected codes
 *     E.g. { 'codes': [200, 203], 'level': 'debug' }
 * Note*: Rules are respected only in order of prescendence.
 *
 * @param {Number} statusCode
 * @param {Level} currentLevel
 * @param {Object} ruleSet
 * @return {Level}
 * @api private
 */
function matchRules(statusCode, currentLevel, ruleSet) {
  let level = currentLevel;

  if (ruleSet) {
    const matchedRule = ruleSet.find(rule => {
      let ruleMatched = false;
      if (rule.from && rule.to) {
        ruleMatched = statusCode >= rule.from && statusCode <= rule.to;
      } else {
        ruleMatched = rule.codes.indexOf(statusCode) !== -1;
      }
      return ruleMatched;
    });
    if (matchedRule) {
      level = levels.getLevel(matchedRule.level, level);
    }
  }
  return level;
}

/**
 * Log requests with the given `options` or a `format` string.
 *
 * Options:
 *
 *   - `format`        Format string, see below for tokens
 *   - `level`         A log4js levels instance. Supports also 'auto'
 *   - `nolog`         A string or RegExp to exclude target logs
 *   - `statusRules`   A array of rules for setting specific logging levels base on status codes
 *   - `context`       Whether to add a response of express to the context
 *
 * Tokens:
 *
 *   - `:req[header]` ex: `:req[Accept]`
 *   - `:res[header]` ex: `:res[Content-Length]`
 *   - `:http-version`
 *   - `:response-time`
 *   - `:remote-addr`
 *   - `:date`
 *   - `:method`
 *   - `:url`
 *   - `:referrer`
 *   - `:user-agent`
 *   - `:status`
 *
 * @return {Function}
 * @param logger4js
 * @param options
 * @api public
 */
module.exports = function getLogger(logger4js, options) {
  /* eslint no-underscore-dangle:0 */
  if (typeof options === "string" || typeof options === "function") {
    options = { format: options };
  } else {
    options = options || {};
  }

  const thisLogger = logger4js;
  let level = levels.getLevel(options.level, levels.INFO);
  const fmt = options.format || DEFAULT_FORMAT;
  const nolog = createNoLogCondition(options.nolog);

  return (req, res, next) => {
    // mount safety
    if (req._logging) return next();

    // nologs
    if (nolog && nolog.test(req.originalUrl)) return next();

    if (thisLogger.isLevelEnabled(level) || options.level === "auto") {
      const start = new Date();
      const { writeHead } = res;

      // flag as logging
      req._logging = true;

      // proxy for statusCode.
      res.writeHead = (code, headers) => {
        res.writeHead = writeHead;
        res.writeHead(code, headers);

        res.__statusCode = code;
        res.__headers = headers || {};
      };

      // hook on end request to emit the log entry of the HTTP request.
      res.on("finish", () => {
        res.responseTime = new Date() - start;
        // status code response level handling
        if (res.statusCode && options.level === "auto") {
          level = levels.INFO;
          if (res.statusCode >= 300) level = levels.WARN;
          if (res.statusCode >= 400) level = levels.ERROR;
        }
        level = matchRules(res.statusCode, level, options.statusRules);

        const combinedTokens = assembleTokens(req, res, options.tokens || []);

        if (options.context) thisLogger.addContext("res", res);
        if (typeof fmt === "function") {
          const line = fmt(req, res, str => format(str, combinedTokens));
          if (line) thisLogger.log(level, line);
        } else {
          thisLogger.log(level, format(fmt, combinedTokens));
        }
        if (options.context) thisLogger.removeContext("res");
      });
    }

    // ensure next gets always called
    return next();
  };
};