/**
 * This is the common logic for both the Node.js and web browser
 * implementations of `debug()`.
 *
 * Expose `debug()` as the module.
 */

exports = module.exports = debug;
exports.coerce = coerce;
exports.disable = disable;
exports.enable = enable;
exports.enabled = enabled;
exports.humanize = require('ms');

/**
 * The currently active debug mode names, and names to skip.
 */

exports.names = [];
exports.skips = [];

/**
 * Map of special "%n" handling functions, for the debug "format" argument.
 *
 * Valid key names are a single, lowercased letter, i.e. "n".
 */

exports.formatters = {};

/**
 * Previously assigned color.
 */

var prevColor = 0;

/**
 * Previous log timestamp.
 */

var prevTime;

/**
 * Select a color.
 *
 * @return {Number}
 * @api private
 */

function selectColor() {
 return exports.colors[prevColor++ % exports.colors.length];
}

/**
 * Create a debugger with the given `namespace`.
 *
 * @param {String} namespace
 * @return {Function}
 * @api public
 */

function debug(namespace) {

 // define the `disabled` version
 function disabled() {
 }
 disabled.enabled = false;

 // define the `enabled` version
 function enabled() {

 var self = enabled;

 // set `diff` timestamp
 var curr = +new Date();
 var ms = curr - (prevTime || curr);
 self.diff = ms;
 self.prev = prevTime;
 self.curr = curr;
 prevTime = curr;

 // add the `color` if not set
 if (null == self.useColors) self.useColors = exports.useColors();
 if (null == self.color && self.useColors) self.color = selectColor();

 var args = Array.prototype.slice.call(arguments);

 args[0] = exports.coerce(args[0]);

 if ('string' !== typeof args[0]) {
 // anything else let's inspect with %o
 args = ['%o'].concat(args);
 }

 // apply any `formatters` transformations
 var index = 0;
 args[0] = args[0].replace(/%([a-z%])/g, function(match, format) {
 // if we encounter an escaped % then don't increase the array index
 if (match === '%%') return match;
 index++;
 var formatter = exports.formatters[format];
 if ('function' === typeof formatter) {
 var val = args[index];
 match = formatter.call(self, val);

 // now we need to remove `args[index]` since it's inlined in the `format`
 args.splice(index, 1);
 index--;
 }
 return match;
 });

 if ('function' === typeof exports.formatArgs) {
 args = exports.formatArgs.apply(self, args);
 }
 var logFn = enabled.log || exports.log || console.log.bind(console);
 logFn.apply(self, args);
 }
 enabled.enabled = true;

 var fn = exports.enabled(namespace) ? enabled : disabled;

 fn.namespace = namespace;

 return fn;
}

/**
 * Enables a debug mode by namespaces. This can include modes
 * separated by a colon and wildcards.
 *
 * @param {String} namespaces
 * @api public
 */

function enable(namespaces) {
 exports.save(namespaces);

 var split = (namespaces || '').split(/[\s,]+/);
 var len = split.length;

 for (var i = 0; i < len; i++) {
 if (!split[i]) continue; // ignore empty strings
 namespaces = split[i].replace(/\*/g, '.*?');
 if (namespaces[0] === '-') {
 exports.skips.push(new RegExp('^' + namespaces.substr(1) + '$'));
 } else {
 exports.names.push(new RegExp('^' + namespaces + '$'));
 }
 }
}

/**
 * Disable debug output.
 *
 * @api public
 */

function disable() {
 exports.enable('');
}

/**
 * Returns true if the given mode name is enabled, false otherwise.
 *
 * @param {String} name
 * @return {Boolean}
 * @api public
 */

function enabled(name) {
 var i, len;
 for (i = 0, len = exports.skips.length; i < len; i++) {
 if (exports.skips[i].test(name)) {
 return false;
 }
 }
 for (i = 0, len = exports.names.length; i < len; i++) {
 if (exports.names[i].test(name)) {
 return true;
 }
 }
 return false;
}

/**
 * Coerce `val`.
 *
 * @param {Mixed} val
 * @return {Mixed}
 * @api private
 */

function coerce(val) {
 if (val instanceof Error) return val.stack || val.message;
 return val;
}