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index.js
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index.js
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/**
* slice() reference.
*/
var slice = Array.prototype.slice;
/**
* Expose `co`.
*/
module.exports = co['default'] = co.co = co;
/**
* Wrap the given generator `fn` into a
* function that returns a promise.
* This is a separate function so that
* every `co()` call doesn't create a new,
* unnecessary closure.
*
* @param {GeneratorFunction} fn
* @return {Function}
* @api public
*/
co.wrap = function (fn) {
createPromise.__generatorFunction__ = fn;
return createPromise;
function createPromise() {
return new CoRoutine().wrap(this, fn, arguments);
}
};
/**
* Execute the generator function or a generator
* and return a promise.
*
* @param {Function} gen
* @return {Promise}
* @api public
*/
function co(gen) {
return new CoRoutine().execute(this, gen, arguments);
}
/**
* Initialize a new `CoRoutine`.
*
* @api private
*/
function CoRoutine() {
}
/**
* CoRoutine prototype.
*/
CoRoutinePrototype = CoRoutine.prototype;
/**
* Execute the generator function or a generator
* and return a promise.
*
* @param {Object} generatorContext
* @param {Function} generator
* @param {Object} args
* @return {Promise}
* @api private
*/
CoRoutinePrototype.execute = function(generatorContext, generator, args) {
var ctx = this;
return new Promise(function(resolve, reject) {
var executedGenerator = ctx._executeGenerator(generatorContext, generator, args);
ctx._start(executedGenerator, resolve, reject);
});
};
/**
* Execute the generator function or a generator for `wrap`
* and return a promise.
*
* @param {Object} generatorContext
* @param {Function} generator
* @param {Object} args
* @return {Promise}
* @api private
*/
CoRoutinePrototype.wrap = function(generatorContext, generator, args) {
var ctx = this;
return new Promise(function(resolve, reject) {
var executedGenerator = ctx._executeGeneratorForWrap(generatorContext, generator, args);
ctx._start(executedGenerator, resolve, reject);
});
};
/**
* Execute the generator function,
* and return an invoked generator object.
*
* @param {Object} generatorContext
* @param {Function} generator
* @param {Object} args
* @return {Object}
* @api private
*/
CoRoutinePrototype._executeGenerator = function(generatorContext, generator, args) {
if (!this._isFunction(generator)) return generator;
var argc = args.length;
if (argc === 1) {
return generator.call(generatorContext);
} else if (argc === 2) {
return generator.call(generatorContext, args[1]);
} else {
return generator.apply(generatorContext, slice.call(args, 1));
}
};
/**
* Execute the generator function for `wrap`,
* and return an invoked generator object.
*
* @param {Object} generatorContext
* @param {Function} generator
* @param {Object} args
* @return {Object}
* @api private
*/
CoRoutinePrototype._executeGeneratorForWrap = function(generatorContext, generator, args) {
if (!this._isFunction(generator)) return generator;
var argc = args.length;
if (argc === 0) {
return generator.call(generatorContext);
} else if (argc === 1) {
return generator.call(generatorContext, args[0]);
} else {
return generator.apply(generatorContext, args);
}
};
/**
* Start to process the main logic.
*
* @param {Object} executedGenerator
* @param {Function} resolve
* @param {Function} reject
* @api private
*/
CoRoutinePrototype._start = function(executedGenerator, resolve, reject) {
if (!executedGenerator || !this._isFunction(executedGenerator.next)) resolve(executedGenerator);
this._generator = executedGenerator;
this._resolve = resolve;
this._reject = reject;
this._onFulfilled();
};
/**
* @param {Mixed} res
* @return {Promise}
* @api private
*/
CoRoutinePrototype._onFulfilled = function(res) {
var ret;
try {
ret = this._generator.next(res);
} catch (e) {
return this._reject(e);
}
this._next(ret);
};
/**
* @param {Error} err
* @return {Promise}
* @api private
*/
CoRoutinePrototype._onRejected = function(err) {
var ret;
try {
ret = this._generator.throw(err);
} catch (e) {
return this._reject(e);
}
this._next(ret);
};
/**
* Get the next value in the generator
*
* @param {Object} ret
* @api private
*/
CoRoutinePrototype._next = function(ret) {
if (ret.done) {
this._resolve(ret.value);
} else {
this._executePromise(ret.value);
}
};
/**
* Execute a converted promise from a `yield`ed value.
*
* @param {Mixed} obj
* @api private
*/
CoRoutinePrototype._executePromise = function(obj) {
var promise = this._convertPromise(obj);
if (promise) {
var ctx = this;
promise.then(function(res) {
ctx._onFulfilled(res);
}, function(err) {
ctx._onRejected(err);
});
} else {
this._onRejected(new TypeError('You may only yield a function, promise, generator, array, or object, ' +
'but the following object was passed: "' + String(obj) + '"'));
}
};
/**
* Convert a `yield`ed value into a promise.
*
* @param {Mixed} obj
* @return {Promise}
* @api private
*/
CoRoutinePrototype._convertPromise = function(obj) {
var promise;
if (obj) {
if (this._isPromise(obj)) {
promise = obj;
} else if (this._isGenerator(obj) || this._isGeneratorFunction(obj)) {
promise = co(obj);
} else if (this._isFunction(obj)) {
promise = this._convertThunkToPromise(obj);
} else if (Array.isArray(obj)) {
promise = this._convertArrayToPromise(obj);
} else if (this._isObject(obj)) {
promise = this._convertObjectToPromise(obj);
}
}
return promise;
};
/**
* Convert a thunk to a promise.
*
* @param {Function}
* @return {Promise}
* @api private
*/
CoRoutinePrototype._convertThunkToPromise = function(fn) {
var ctx = this;
return new Promise(function (resolve, reject) {
fn.call(ctx, function (err, res) {
if (err) return reject(err);
if (arguments.length > 2) res = slice.call(arguments, 1);
resolve(res);
});
});
};
/**
* Convert an array of "yieldables" to a promise.
* Uses `Promise.all()` internally.
*
* @param {Array} obj
* @return {Promise}
* @api private
*/
CoRoutinePrototype._convertArrayToPromise = function(arr) {
var arrayLen = arr.length;
var promises = new Array(arrayLen);
for(var i = 0; i < arrayLen; i++) {
promises[i] = this._convertPromise(arr[i]);
}
return Promise.all(promises);
};
/**
* Convert an object of "yieldables" to a promise.
* Uses `Promise.all()` internally.
*
* @param {Object} obj
* @return {Promise}
* @api private
*/
CoRoutinePrototype._convertObjectToPromise = function(obj) {
var results = new obj.constructor();
var keys = Object.keys(obj);
var promises = [];
var keyLength = keys.length;
for (var i = 0; i < keyLength; i++) {
var key = keys[i];
var target = this._convertPromise(obj[key]) || obj[key];
if (target && this._isPromise(target)) {
defer(target, key);
} else {
results[key] = target;
}
}
function defer(promise, key) {
// predefine the key in the result
results[key] = undefined;
promises.push(promise.then(function (res) {
results[key] = res;
}));
}
return Promise.all(promises).then(function () {
return results;
});
};
/**
* Check if `obj` is a promise.
*
* @param {Object} obj
* @return {Boolean}
* @api private
*/
CoRoutinePrototype._isPromise = function(obj) {
return 'function' == typeof obj.then;
};
/**
* Check if `obj` is a function.
*
* @param {Object} obj
* @return {Boolean}
* @api private
*/
CoRoutinePrototype._isFunction = function(obj) {
return 'function' == typeof obj;
};
/**
* Check if `obj` is a generator.
*
* @param {Object} obj
* @return {Boolean}
* @api private
*/
CoRoutinePrototype._isGenerator = function(obj) {
return 'function' == typeof obj.next && 'function' == typeof obj.throw;
};
/**
* Check if `obj` is a generator function.
*
* @param {Object} obj
* @return {Boolean}
* @api private
*/
CoRoutinePrototype._isGeneratorFunction = function(obj) {
var constructor = obj.constructor;
if (!constructor) return false;
if ('GeneratorFunction' === constructor.name || 'GeneratorFunction' === constructor.displayName) return true;
return this._isGenerator(constructor.prototype);
};
/**
* Check if `obj` is a object.
*
* @param {Object} obj
* @return {Boolean}
* @api private
*/
CoRoutinePrototype._isObject = function(obj) {
return Object == obj.constructor;
};