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Implement CHA-RL5a1 #147

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Nov 25, 2024
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Implement CHA-RL5a1 #147

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43 changes: 24 additions & 19 deletions Sources/AblyChat/Room.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -70,7 +70,7 @@ internal actor DefaultRoom<LifecycleManagerFactory: RoomLifecycleManagerFactory>
private nonisolated let realtime: RealtimeClient

private let lifecycleManager: any RoomLifecycleManager
private let channels: [RoomFeature: any RealtimeChannelProtocol]
private let channels: [any RealtimeChannelProtocol]

private let logger: InternalLogger

Expand All @@ -96,6 +96,7 @@ internal actor DefaultRoom<LifecycleManagerFactory: RoomLifecycleManagerFactory>
}
}

/// The features are returned in CHA-RC2e order.
static func fromRoomOptions(_ roomOptions: RoomOptions) -> [Self] {
var result: [Self] = [.messages]

Expand Down Expand Up @@ -133,8 +134,8 @@ internal actor DefaultRoom<LifecycleManagerFactory: RoomLifecycleManagerFactory>
let featuresWithOptions = RoomFeatureWithOptions.fromRoomOptions(options)

let featureChannelPartialDependencies = Self.createFeatureChannelPartialDependencies(roomID: roomID, featuresWithOptions: featuresWithOptions, realtime: realtime)
channels = featureChannelPartialDependencies.mapValues(\.channel)
let contributors = featureChannelPartialDependencies.values.map(\.contributor)
channels = featureChannelPartialDependencies.map(\.featureChannelPartialDependencies.channel)
let contributors = featureChannelPartialDependencies.map(\.featureChannelPartialDependencies.contributor)

lifecycleManager = await lifecycleManagerFactory.createManager(
contributors: contributors,
Expand Down Expand Up @@ -202,15 +203,19 @@ internal actor DefaultRoom<LifecycleManagerFactory: RoomLifecycleManagerFactory>
internal var contributor: DefaultRoomLifecycleContributor
}

/// The returned dictionary is guaranteed to have an entry for each element of `features`.
private static func createChannelsForFeaturesWithOptions(_ featuresWithOptions: [RoomFeatureWithOptions], roomID: String, realtime: RealtimeClient) -> [RoomFeature: RealtimeChannelProtocol] {
/// Each feature in `featuresWithOptions` is guaranteed to appear in the `features` member of precisely one of the returned array’s values.
///
/// The elements of `featuresWithOptions` must be in CHA-RC2e order.
private static func createFeatureChannelPartialDependencies(roomID: String, featuresWithOptions: [RoomFeatureWithOptions], realtime: RealtimeClient) -> [(features: [RoomFeature], featureChannelPartialDependencies: FeatureChannelPartialDependencies)] {
// CHA-RC3a

// Multiple features can share a realtime channel. We fetch each realtime channel exactly once, merging the channel options for the various features that use this channel.

// CHA-RL5a1: This spec point requires us to implement a special behaviour to handle the fact that multiple contributors can share a channel. I have decided, instead, to make it so that each channel has precisely one lifecycle contributor. I think this is a simpler, functionally equivalent approach and have suggested it in https://github.com/ably/specification/issues/240.

let featuresGroupedByChannelName = Dictionary(grouping: featuresWithOptions) { $0.toRoomFeature.channelNameForRoomID(roomID) }

let pairsOfFeatureAndChannel = featuresGroupedByChannelName.flatMap { channelName, features in
return featuresGroupedByChannelName.map { channelName, features in
var channelOptions = RealtimeChannelOptions()

// channel setup for presence and occupancy
Expand All @@ -234,23 +239,23 @@ internal actor DefaultRoom<LifecycleManagerFactory: RoomLifecycleManagerFactory>
}

let channel = realtime.getChannel(channelName, opts: channelOptions)
return features.map { ($0.toRoomFeature, channel) }
}

return Dictionary(uniqueKeysWithValues: pairsOfFeatureAndChannel)
}
// Give the contributor the first of the enabled features that correspond to this channel, using CHA-RC2e ordering. This will determine which feature is used for atttachment and detachment errors.
let contributorFeature = features[0].toRoomFeature
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private static func createFeatureChannelPartialDependencies(roomID: String, featuresWithOptions: [RoomFeatureWithOptions], realtime: RealtimeClient) -> [RoomFeature: FeatureChannelPartialDependencies] {
let channelsByFeature = createChannelsForFeaturesWithOptions(featuresWithOptions, roomID: roomID, realtime: realtime)
let contributor = DefaultRoomLifecycleContributor(channel: .init(underlyingChannel: channel), feature: contributorFeature)
let featureChannelPartialDependencies = FeatureChannelPartialDependencies(channel: channel, contributor: contributor)

return .init(uniqueKeysWithValues: channelsByFeature.map { feature, channel in
let contributor = DefaultRoomLifecycleContributor(channel: .init(underlyingChannel: channel), feature: feature)
return (feature, .init(channel: channel, contributor: contributor))
})
return (features.map(\.toRoomFeature), featureChannelPartialDependencies)
}
}

private static func createFeatureChannels(partialDependencies: [RoomFeature: FeatureChannelPartialDependencies], lifecycleManager: RoomLifecycleManager) -> [RoomFeature: DefaultFeatureChannel] {
partialDependencies.mapValues { partialDependencies in
private static func createFeatureChannels(partialDependencies: [(features: [RoomFeature], featureChannelPartialDependencies: FeatureChannelPartialDependencies)], lifecycleManager: RoomLifecycleManager) -> [RoomFeature: DefaultFeatureChannel] {
let pairsOfFeatureAndPartialDependencies = partialDependencies.flatMap { features, partialDependencies in
features.map { (feature: $0, partialDependencies: partialDependencies) }
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}

return Dictionary(uniqueKeysWithValues: pairsOfFeatureAndPartialDependencies).mapValues { partialDependencies in
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.init(
channel: partialDependencies.channel,
contributor: partialDependencies.contributor,
Expand Down Expand Up @@ -299,7 +304,7 @@ internal actor DefaultRoom<LifecycleManagerFactory: RoomLifecycleManagerFactory>
await lifecycleManager.performReleaseOperation()

// CHA-RL3h
for channel in channels.values {
for channel in channels {
realtime.channels.release(channel.name)
}
}
Expand Down
4 changes: 3 additions & 1 deletion Tests/AblyChatTests/DefaultRoomTests.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -64,6 +64,7 @@ struct DefaultRoomTests {
// @spec CHA-RC2c
// @spec CHA-RC2d
// @spec CHA-RC2f
// @spec CHA-RL5a1 - We implement this spec point by _not allowing multiple contributors to share a channel_; this is an approach that I’ve suggested in https://github.com/ably/specification/issues/240.
@Test
func fetchesChannelAndCreatesLifecycleContributorForEnabledFeatures() async throws {
// Given: a DefaultRoom instance, initialized with options that request that the room use a strict subset of the possible features
Expand All @@ -83,9 +84,10 @@ struct DefaultRoomTests {

// Then: It:
// - fetches the channel that corresponds to each feature requested by the room options, plus the messages feature
// - initializes the RoomLifecycleManager with a contributor for each fetched channel, and the feature assigned to each contributor is the feature, of the enabled features that correspond to that channel, which appears first in the CHA-RC2e list
// - initializes the RoomLifecycleManager with a contributor for each feature requested by the room options, plus the messages feature
let lifecycleManagerCreationArguments = try #require(await lifecycleManagerFactory.createManagerArguments.first)
let expectedFeatures: [RoomFeature] = [.messages, .presence, .reactions]
let expectedFeatures: [RoomFeature] = [.messages, .reactions] // i.e. since messages and presence share a channel, we create a single contributor for this channel and its assigned feature is messages
#expect(lifecycleManagerCreationArguments.contributors.count == expectedFeatures.count)
#expect(Set(lifecycleManagerCreationArguments.contributors.map(\.feature)) == Set(expectedFeatures))

Expand Down