1/**
  2 * Module dependencies.
  3 */
  4
  5var tty = require('tty');
  6
  7/**
  8 * Expose `debug()` as the module.
  9 */
 10
 11module.exports = debug;
 12
 13/**
 14 * Enabled debuggers.
 15 */
 16
 17var names = []
 18  , skips = [];
 19
 20(process.env.DEBUG || '')
 21  .split(/[\s,]+/)
 22  .forEach(function(name){
 23    name = name.replace('*', '.*?');
 24    if (name[0] === '-') {
 25      skips.push(new RegExp('^' + name.substr(1) + '$'));
 26    } else {
 27      names.push(new RegExp('^' + name + '$'));
 28    }
 29  });
 30
 31/**
 32 * Colors.
 33 */
 34
 35var colors = [6, 2, 3, 4, 5, 1];
 36
 37/**
 38 * Previous debug() call.
 39 */
 40
 41var prev = {};
 42
 43/**
 44 * Previously assigned color.
 45 */
 46
 47var prevColor = 0;
 48
 49/**
 50 * Is stdout a TTY? Colored output is disabled when `true`.
 51 */
 52
 53var isatty = tty.isatty(2);
 54
 55/**
 56 * Select a color.
 57 *
 58 * @return {Number}
 59 * @api private
 60 */
 61
 62function color() {
 63  return colors[prevColor++ % colors.length];
 64}
 65
 66/**
 67 * Humanize the given `ms`.
 68 *
 69 * @param {Number} m
 70 * @return {String}
 71 * @api private
 72 */
 73
 74function humanize(ms) {
 75  var sec = 1000
 76    , min = 60 * 1000
 77    , hour = 60 * min;
 78
 79  if (ms >= hour) return (ms / hour).toFixed(1) + 'h';
 80  if (ms >= min) return (ms / min).toFixed(1) + 'm';
 81  if (ms >= sec) return (ms / sec | 0) + 's';
 82  return ms + 'ms';
 83}
 84
 85/**
 86 * Create a debugger with the given `name`.
 87 *
 88 * @param {String} name
 89 * @return {Type}
 90 * @api public
 91 */
 92
 93function debug(name) {
 94  function disabled(){}
 95  disabled.enabled = false;
 96
 97  var match = skips.some(function(re){
 98    return re.test(name);
 99  });
100
101  if (match) return disabled;
102
103  match = names.some(function(re){
104    return re.test(name);
105  });
106
107  if (!match) return disabled;
108  var c = color();
109
110  function colored(fmt) {
111    fmt = coerce(fmt);
112
113    var curr = new Date;
114    var ms = curr - (prev[name] || curr);
115    prev[name] = curr;
116
117    fmt = '  \u001b[9' + c + 'm' + name + ' '
118      + '\u001b[3' + c + 'm\u001b[90m'
119      + fmt + '\u001b[3' + c + 'm'
120      + ' +' + humanize(ms) + '\u001b[0m';
121
122    console.error.apply(this, arguments);
123  }
124
125  function plain(fmt) {
126    fmt = coerce(fmt);
127
128    fmt = new Date().toUTCString()
129      + ' ' + name + ' ' + fmt;
130    console.error.apply(this, arguments);
131  }
132
133  colored.enabled = plain.enabled = true;
134
135  return isatty || process.env.DEBUG_COLORS
136    ? colored
137    : plain;
138}
139
140/**
141 * Coerce `val`.
142 */
143
144function coerce(val) {
145  if (val instanceof Error) return val.stack || val.message;
146  return val;
147}