nconf-lite/lib/nconf/provider.js

254 lines
No EOL
7.6 KiB
JavaScript

/*
* provider.js: Abstraction providing an interface into pluggable configuration storage.
*
* (C) 2011, Charlie Robbins
*
*/
var async = require('async'),
common = require('./common'),
stores = require('./stores');
//
// ### function Provider (options)
// #### @options {Object} Options for this instance.
// Constructor function for the Provider object responsible
// for exposing the pluggable storage features of `nconf`.
//
var Provider = exports.Provider = function (options) {
options = options || {};
this.overrides = options.overrides || null
this.useArgv = options.useArgv || false;
this.store = stores.create(options.type || 'memory', options);
};
//
// ### function use (type, options)
// #### @type {string} Type of the nconf store to use.
// #### @options {Object} Options for the store instance.
// Sets the active `this.store` to a new instance of the
// specified `type`.
//
Provider.prototype.use = function (type, options) {
var self = this;
options = options || {};
function sameOptions () {
return Object.keys(options).every(function (key) {
return options[key] === self.store[key];
});
}
if (!this.store || type.toLowerCase() !== this.store.type
|| !sameOptions()) {
this.store = stores.create(type, options);
}
return this;
};
//
// ### function get (key, callback)
// #### @key {string} Key to retrieve for this instance.
// #### @callback {function} **Optional** Continuation to respond to when complete.
// Retrieves the value for the specified key (if any).
//
Provider.prototype.get = function (key, callback) {
if (this.overrides && Object.prototype.hasOwnProperty.call(this.overrides, key)) {
if (callback) {
callback(null, this.overrides[key]);
}
return this.overrides[key];
}
return this._execute('get', 1, key, callback);
};
//
// ### function set (key, value, callback)
// #### @key {string} Key to set in this instance
// #### @value {literal|Object} Value for the specified key
// #### @callback {function} **Optional** Continuation to respond to when complete.
// Sets the `value` for the specified `key` in this instance.
//
Provider.prototype.set = function (key, value, callback) {
return this._execute('set', 2, key, value, callback);
};
//
// ### function merge ([key,] value [, callback])
// #### @key {string} Key to merge the value into
// #### @value {literal|Object} Value to merge into the key
// #### @callback {function} **Optional** Continuation to respond to when complete.
// Merges the properties in `value` into the existing object value at `key`.
//
// 1. If the existing value `key` is not an Object, it will be completely overwritten.
// 2. If `key` is not supplied, then the `value` will be merged into the root.
//
Provider.prototype.merge = function () {
var self = this,
args = Array.prototype.slice.call(arguments),
callback = typeof args[args.length - 1] === 'function' && args.pop(),
value = args.pop(),
key = args.pop();
function mergeProperty (prop, next) {
return self._execute('merge', 2, prop, value[prop], next);
}
if (!key) {
if (Array.isArray(value) || typeof value !== 'object') {
return onError(new Error('Cannot merge non-Object into top-level.'), callback);
}
return async.forEach(Object.keys(value), mergeProperty, callback || function () { })
}
return this._execute('merge', 2, key, value, callback);
};
//
// ### function mergeFiles (files, callback)
// #### @files {Object|Array} List of files (or settings object) to load.
// #### @callback {function} Continuation to respond to when complete.
// Merges all `key:value` pairs in the `files` supplied into the
// store that is managed by this provider instance.
//
Provider.prototype.mergeFiles = function (files, callback) {
var self = this;
common.loadFiles(files, function (err, merged) {
return !err
? self.merge(merged, callback)
: onError(err);
});
};
//
// ### function clear (key, callback)
// #### @key {string} Key to remove from this instance
// #### @callback {function} **Optional** Continuation to respond to when complete.
// Removes the value for the specified `key` from this instance.
//
Provider.prototype.clear = function (key, callback) {
return this._execute('clear', 1, key, callback);
};
//
// ### function load (callback)
// #### @callback {function} Continuation to respond to when complete.
// Responds with an Object representing all keys associated in this instance.
//
Provider.prototype.load = function (callback) {
//
// If we don't have a callback and the current
// store is capable of loading synchronously
// then do so.
//
if (!callback && this.store.loadSync) {
return this.store.loadSync();
}
return !this.store.load
? onError(new Error('nconf store ' + this.store.type + ' has no load() method'), callback)
: this.store.load(callback);
};
//
// ### function save (value, callback)
// #### @value {Object} **Optional** Config object to set for this instance
// #### @callback {function} Continuation to respond to when complete.
// Removes any existing configuration settings that may exist in this
// instance and then adds all key-value pairs in `value`.
//
Provider.prototype.save = function (value, callback) {
if (!callback) {
callback = value;
value = null;
//
// If we still don't have a callback and the
// current store is capable of saving synchronously
// then do so.
//
if (!callback && this.store.saveSync) {
return this.store.saveSync();
}
}
return !this.store.save
? onError(new Error('nconf store ' + this.store.type + ' has no save() method'), callback)
: this.store.save(value, callback);
};
//
// ### function reset (callback)
// #### @callback {function} **Optional** Continuation to respond to when complete.
// Clears all keys associated with this instance.
//
Provider.prototype.reset = function (callback) {
return this._execute('reset', 0, callback);
};
//
// ### @private function _execute (action, syncLength, [arguments])
// #### @action {string} Action to execute on `this.store`.
// #### @syncLength {number} Function length of the sync version.
// #### @arguments {Array} Arguments array to apply to the action
// Executes the specified `action` on `this.store`, ensuring a callback supplied
// to a synchronous store function is still invoked.
//
Provider.prototype._execute = function (action, syncLength /* [arguments] */) {
var args = Array.prototype.slice.call(arguments, 2),
callback,
response;
if (this.store[action].length > syncLength) {
return this.store[action].apply(this.store, args);
}
callback = typeof args[args.length - 1] === 'function' && args.pop();
response = this.store[action].apply(this.store, args);
if (callback) {
callback(null, response);
}
return response;
}
//
// ### getter @useArgv {boolean}
// Gets a property indicating if we should wrap calls to `.get`
// by checking `optimist.argv`.
//
Provider.prototype.__defineGetter__('useArgv', function () {
return this._useArgv;
});
//
// ### setter @useArgv {boolean}
// Sets a property indicating if we should wrap calls to `.get`
// by checking `optimist.argv`.
//
Provider.prototype.__defineSetter__('useArgv', function (val) {
this._useArgv = val || false;
if (this._useArgv) {
this._argv = this._argv || require('optimist').argv;
this.overrides = this.overrides || this._argv;
}
});
//
// Throw the `err` if a callback is not supplied
//
function onError(err, callback) {
if (callback) {
return callback(err);
}
throw err;
}