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Angular Promise Queuer
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| module = angular.module 'helpers.promise_queuer' | |
| # Lets us ensure that some promises don't execute if others are in progress | |
| # within a given context | |
| # | |
| # Notes: | |
| # This also helps us decouple the queuing logic from our promises. | |
| ### | |
| Architecture Notes: | |
| => Want to maintain the order in which the promises were queued | |
| => Need to ensure that promises dont even start unless previous ones finish | |
| 1) All operations are added to a queue | |
| 2) Whenever any operation finishes, a dequeue process is started | |
| 3) If a dequeue process is already started, don't start a new one | |
| ### | |
| module.service "PromiseQueuer", [ | |
| "$q" | |
| ($q) -> | |
| operationQueue = {} | |
| dequeueInProgress = false | |
| dequeue = (scopeName) -> | |
| callback = operationQueue[scopeName].shift() | |
| if callback | |
| callback().finally (data) => | |
| # If no more operations in the queue, stop dequeuing | |
| if operationQueue[scopeName].length == 0 | |
| dequeueInProgress = false | |
| data | |
| else | |
| dequeue(scopeName) | |
| # Begin dequeing all operations in queue | |
| startDequeue = (scopeName) -> | |
| return if dequeueInProgress | |
| dequeueInProgress = true | |
| dequeue(scopeName) | |
| perform = (scopeName, callback, deferred) -> | |
| result = callback() | |
| # If callback returns a promise | |
| if result.then | |
| result.then( | |
| (data) => | |
| deferred.resolve(data) | |
| , (response) => | |
| deferred.reject(response) | |
| ) | |
| # Otherwise, just return a resolved promise | |
| else | |
| deferred.resolve(result) | |
| deferred.promise | |
| api = {} | |
| api.enqueue = (scopeName, callback) -> | |
| deferred = $q.defer() | |
| operationQueue[scopeName] ||= [] | |
| operationQueue[scopeName].push => perform(scopeName, callback, deferred) | |
| startDequeue(scopeName) | |
| deferred.promise | |
| api | |
| ] |
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