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76 lines
3.1 KiB
CoffeeScript
76 lines
3.1 KiB
CoffeeScript
_ = require 'underscore'
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Rx = require 'rx-lite'
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{ObservableListDataSource,
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DatabaseStore,
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Message,
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QueryResultSet,
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QuerySubscription} = require 'nylas-exports'
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_flatMapJoiningMessages = ($threadsResultSet) =>
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# DatabaseView leverages `QuerySubscription` for threads /and/ for the
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# messages on each thread, which are passed to out as `thread.metadata`.
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$messagesResultSets = {}
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# 2. when we receive a set of threads, we check to see if we have message
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# observables for each thread. If threads have been added to the result set,
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# we make a single database query and load /all/ the message metadata for
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# the new threads at once. (This is a performance optimization -it's about
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# ~80msec faster than making 100 queries for 100 new thread ids separately.)
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Rx.Observable.zip([
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$threadsResultSet,
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$threadsResultSet.flatMapLatest (threadsResultSet) =>
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missingIds = threadsResultSet.ids().filter (id) -> not $messagesResultSets[id]
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return Rx.Observable.from([[]]) if missingIds.length is 0
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Rx.Observable.fromPromise(DatabaseStore.findAll(Message, threadId: missingIds))
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])
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# 3. when that finishes, we group the loaded messsages by threadId and create
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# the missing observables. Creating a query subscription would normally load
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# an initial result set. To avoid that, we just hand new subscriptions the
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# results we loaded in #2.
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.flatMapLatest ([threadsResultSet, messagesForNewThreads]) =>
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messagesGrouped = {}
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for message in messagesForNewThreads
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messagesGrouped[message.threadId] ?= []
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messagesGrouped[message.threadId].push(message)
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oldSets = $messagesResultSets
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$messagesResultSets = {}
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sets = threadsResultSet.ids().map (id) =>
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$messagesResultSets[id] = oldSets[id] || _observableForThreadMessages(id, messagesGrouped[id])
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$messagesResultSets[id]
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sets.unshift(Rx.Observable.from([threadsResultSet]))
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# 4. We use `combineLatest` to merge the message observables into a single
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# stream (like Promise.all). When /any/ of them emit a new result set, we
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# trigger.
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Rx.Observable.combineLatest(sets)
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.flatMapLatest ([threadsResultSet, messagesResultSets...]) =>
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threadsWithMetadata = {}
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threadsResultSet.models().map (thread, idx) ->
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thread = new thread.constructor(thread)
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thread.metadata = messagesResultSets[idx]?.models()
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threadsWithMetadata[thread.id] = thread
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Rx.Observable.from([QueryResultSet.setByApplyingModels(threadsResultSet, threadsWithMetadata)])
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_observableForThreadMessages = (id, initialModels) ->
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subscription = new QuerySubscription(DatabaseStore.findAll(Message, threadId: id), {
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asResultSet: true,
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initialModels: initialModels
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})
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Rx.Observable.fromPrivateQuerySubscription('message-'+id, subscription)
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class ThreadListDataSource extends ObservableListDataSource
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constructor: (subscription) ->
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$resultSetObservable = Rx.Observable.fromPrivateQuerySubscription('thread-list', subscription)
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$resultSetObservable = _flatMapJoiningMessages($resultSetObservable)
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super($resultSetObservable, subscription.replaceRange)
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module.exports = ThreadListDataSource
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