wishthis/node_modules/config-chain/index.js

var ProtoList = require('proto-list')
  , path = require('path')
  , fs = require('fs')
  , ini = require('ini')
  , EE = require('events').EventEmitter
  , url = require('url')
  , http = require('http')

var exports = module.exports = function () {
  var args = [].slice.call(arguments)
    , conf = new ConfigChain()

  while(args.length) {
    var a = args.shift()
    if(a) conf.push
          ( 'string' === typeof a
            ? json(a)
            : a )
  }

  return conf
}

//recursively find a file...

var find = exports.find = function () {
  var rel = path.join.apply(null, [].slice.call(arguments))

  function find(start, rel) {
    var file = path.join(start, rel)
    try {
      fs.statSync(file)
      return file
    } catch (err) {
      if(path.dirname(start) !== start) // root
        return find(path.dirname(start), rel)
    }
  }
  return find(__dirname, rel)
}

var parse = exports.parse = function (content, file, type) {
  content = '' + content
  // if we don't know what it is, try json and fall back to ini
  // if we know what it is, then it must be that.
  if (!type) {
    try { return JSON.parse(content) }
    catch (er) { return ini.parse(content) }
  } else if (type === 'json') {
    if (this.emit) {
      try { return JSON.parse(content) }
      catch (er) { this.emit('error', er) }
    } else {
      return JSON.parse(content)
    }
  } else {
    return ini.parse(content)
  }
}

var json = exports.json = function () {
  var args = [].slice.call(arguments).filter(function (arg) { return arg != null })
  var file = path.join.apply(null, args)
  var content
  try {
    content = fs.readFileSync(file,'utf-8')
  } catch (err) {
    return
  }
  return parse(content, file, 'json')
}

var env = exports.env = function (prefix, env) {
  env = env || process.env
  var obj = {}
  var l = prefix.length
  for(var k in env) {
    if(k.indexOf(prefix) === 0)
      obj[k.substring(l)] = env[k]
  }

  return obj
}

exports.ConfigChain = ConfigChain
function ConfigChain () {
  EE.apply(this)
  ProtoList.apply(this, arguments)
  this._awaiting = 0
  this._saving = 0
  this.sources = {}
}

// multi-inheritance-ish
var extras = {
  constructor: { value: ConfigChain }
}
Object.keys(EE.prototype).forEach(function (k) {
  extras[k] = Object.getOwnPropertyDescriptor(EE.prototype, k)
})
ConfigChain.prototype = Object.create(ProtoList.prototype, extras)

ConfigChain.prototype.del = function (key, where) {
  // if not specified where, then delete from the whole chain, scorched
  // earth style
  if (where) {
    var target = this.sources[where]
    target = target && target.data
    if (!target) {
      return this.emit('error', new Error('not found '+where))
    }
    delete target[key]
  } else {
    for (var i = 0, l = this.list.length; i < l; i ++) {
      delete this.list[i][key]
    }
  }
  return this
}

ConfigChain.prototype.set = function (key, value, where) {
  var target

  if (where) {
    target = this.sources[where]
    target = target && target.data
    if (!target) {
      return this.emit('error', new Error('not found '+where))
    }
  } else {
    target = this.list[0]
    if (!target) {
      return this.emit('error', new Error('cannot set, no confs!'))
    }
  }
  target[key] = value
  return this
}

ConfigChain.prototype.get = function (key, where) {
  if (where) {
    where = this.sources[where]
    if (where) where = where.data
    if (where && Object.hasOwnProperty.call(where, key)) return where[key]
    return undefined
  }
  return this.list[0][key]
}

ConfigChain.prototype.save = function (where, type, cb) {
  if (typeof type === 'function') cb = type, type = null
  var target = this.sources[where]
  if (!target || !(target.path || target.source) || !target.data) {
    // TODO: maybe save() to a url target could be a PUT or something?
    // would be easy to swap out with a reddis type thing, too
    return this.emit('error', new Error('bad save target: '+where))
  }

  if (target.source) {
    var pref = target.prefix || ''
    Object.keys(target.data).forEach(function (k) {
      target.source[pref + k] = target.data[k]
    })
    return this
  }

  var type = type || target.type
  var data = target.data
  if (target.type === 'json') {
    data = JSON.stringify(data)
  } else {
    data = ini.stringify(data)
  }

  this._saving ++
  fs.writeFile(target.path, data, 'utf8', function (er) {
    this._saving --
    if (er) {
      if (cb) return cb(er)
      else return this.emit('error', er)
    }
    if (this._saving === 0) {
      if (cb) cb()
      this.emit('save')
    }
  }.bind(this))
  return this
}

ConfigChain.prototype.addFile = function (file, type, name) {
  name = name || file
  var marker = {__source__:name}
  this.sources[name] = { path: file, type: type }
  this.push(marker)
  this._await()
  fs.readFile(file, 'utf8', function (er, data) {
    if (er) this.emit('error', er)
    this.addString(data, file, type, marker)
  }.bind(this))
  return this
}

ConfigChain.prototype.addEnv = function (prefix, env, name) {
  name = name || 'env'
  var data = exports.env(prefix, env)
  this.sources[name] = { data: data, source: env, prefix: prefix }
  return this.add(data, name)
}

ConfigChain.prototype.addUrl = function (req, type, name) {
  this._await()
  var href = url.format(req)
  name = name || href
  var marker = {__source__:name}
  this.sources[name] = { href: href, type: type }
  this.push(marker)
  http.request(req, function (res) {
    var c = []
    var ct = res.headers['content-type']
    if (!type) {
      type = ct.indexOf('json') !== -1 ? 'json'
           : ct.indexOf('ini') !== -1 ? 'ini'
           : href.match(/\.json$/) ? 'json'
           : href.match(/\.ini$/) ? 'ini'
           : null
      marker.type = type
    }

    res.on('data', c.push.bind(c))
    .on('end', function () {
      this.addString(Buffer.concat(c), href, type, marker)
    }.bind(this))
    .on('error', this.emit.bind(this, 'error'))

  }.bind(this))
  .on('error', this.emit.bind(this, 'error'))
  .end()

  return this
}

ConfigChain.prototype.addString = function (data, file, type, marker) {
  data = this.parse(data, file, type)
  this.add(data, marker)
  return this
}

ConfigChain.prototype.add = function (data, marker) {
  if (marker && typeof marker === 'object') {
    var i = this.list.indexOf(marker)
    if (i === -1) {
      return this.emit('error', new Error('bad marker'))
    }
    this.splice(i, 1, data)
    marker = marker.__source__
    this.sources[marker] = this.sources[marker] || {}
    this.sources[marker].data = data
    // we were waiting for this.  maybe emit 'load'
    this._resolve()
  } else {
    if (typeof marker === 'string') {
      this.sources[marker] = this.sources[marker] || {}
      this.sources[marker].data = data
    }
    // trigger the load event if nothing was already going to do so.
    this._await()
    this.push(data)
    process.nextTick(this._resolve.bind(this))
  }
  return this
}

ConfigChain.prototype.parse = exports.parse

ConfigChain.prototype._await = function () {
  this._awaiting++
}

ConfigChain.prototype._resolve = function () {
  this._awaiting--
  if (this._awaiting === 0) this.emit('load', this)
}