"use strict";
var levels = require("./levels");
var _ = require('underscore');
var DEFAULT_FORMAT = ':remote-addr - -' +
  ' ":method :url HTTP/:http-version"' +
  ' :status :content-length ":referrer"' +
  ' ":user-agent"';
/**
 * 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'
 *
 * 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`
 *
 * @param {String|Function|Object} format or options
 * @return {Function}
 * @api public
 */

function getLogger(logger4js, options) {
	if ('object' == typeof options) {
		options = options || {};
	} else if (options) {
		options = { format: options };
	} else {
		options = {};
	}

	var thislogger = logger4js
  , level = levels.toLevel(options.level, levels.INFO)
  , fmt = options.format || DEFAULT_FORMAT
  , nolog = options.nolog ? createNoLogCondition(options.nolog) : null;

  return function (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') {

			var start = new Date()
			, statusCode
			, writeHead = res.writeHead
			, url = req.originalUrl;

			// flag as logging
			req._logging = true;

			// proxy for statusCode.
			res.writeHead = function(code, headers){
				res.writeHead = writeHead;
				res.writeHead(code, headers);
				res.__statusCode = statusCode = code;
				res.__headers = headers || {};

				//status code response level handling
				if(options.level === 'auto'){
					level = levels.INFO;
					if(code >= 300) level = levels.WARN;
					if(code >= 400) level = levels.ERROR;
				} else {
					level = levels.toLevel(options.level, levels.INFO);
				}
			};

			//hook on end request to emit the log entry of the HTTP request.
			res.on('finish', function() {
				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;
				}
				if (thislogger.isLevelEnabled(level)) {
          var default_tokens = assemble_tokens(req, res);
					if (typeof fmt === 'function') {
						var line = fmt(req, res, function(str){ return format(str, default_tokens); });
						if (line) thislogger.log(level, line);
					} else {
						thislogger.log(level, format(fmt, default_tokens));
					}
				}
			});
		}

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

/**
 * Adds custom {token, replacement} objects to defaults, overwriting the defaults if any tokens clash
 *
 * @param  {IncomingMessage} req
 * @param  {ServerResponse} res
 * @param  {Array} custom_tokens [{ token: string-or-regexp, replacement: string-or-replace-function }]
 * @return {Array}
 */
function assemble_tokens(req, res) {
  var default_tokens = [];
  default_tokens.push({ token: ':url', replacement: req.originalUrl });
  default_tokens.push({ token: ':method', replacement: req.method });
  default_tokens.push({ token: ':status', replacement: res.__statusCode || res.statusCode });
  default_tokens.push({ token: ':response-time', replacement: res.responseTime });
  default_tokens.push({ token: ':date', replacement: new Date().toUTCString() });
  default_tokens.push({ token: ':referrer', replacement: req.headers.referer || req.headers.referrer || '' });
  default_tokens.push({ token: ':http-version', replacement: req.httpVersionMajor + '.' + req.httpVersionMinor });
  default_tokens.push({ token: ':remote-addr', replacement: req.ip || req._remoteAddress ||
    (req.socket && (req.socket.remoteAddress || (req.socket.socket && req.socket.socket.remoteAddress))) });
  default_tokens.push({ token: ':user-agent', replacement: req.headers['user-agent'] });
  default_tokens.push({ token: ':content-length', replacement: (res._headers && res._headers['content-length']) ||
      (res.__headers && res.__headers['Content-Length']) || '-' });
  default_tokens.push({ token: /:req\[([^\]]+)\]/g, replacement: function(_, field) {
    return req.headers[field.toLowerCase()];
  } });
  default_tokens.push({ token: /:res\[([^\]]+)\]/g, replacement: function(_, field) {
    return res._headers ?
      (res._headers[field.toLowerCase()] || res.__headers[field])
      : (res.__headers && res.__headers[field]);
  } });

  return default_tokens;
};

/**
 * Return formatted log line.
 *
 * @param  {String} str
 * @param  {IncomingMessage} req
 * @param  {ServerResponse} res
 * @return {String}
 * @api private
 */

function format(str, tokens) {
  return _.reduce(tokens, function(current_string, token) {
    return current_string.replace(token.token, token.replacement);
  }, str);
}

/**
 * Return RegExp Object about nolog
 *
 * @param  {String} 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) {
  var regexp = null;

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

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

    if (Array.isArray(nolog)) {
      var regexpsAsStrings = nolog.map(
        function convertToStrings(o) {
          return o.source ? o.source : o;
        }
      );
      regexp = new RegExp(regexpsAsStrings.join('|'));
    }
  }

  return regexp;
}

exports.connectLogger = getLogger;