64 lines
2.0 KiB
Swift
64 lines
2.0 KiB
Swift
//
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// Copyright 2022 New Vector Ltd
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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import Foundation
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/// A FIFO queue which will ensure only one user indicator is shown at a given time.
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///
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/// `UserIndicatorQueue` offers a `shared` queue that can be used by any clients app-wide, but clients are also allowed
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/// to create local `UserIndicatorQueue` if the context requres multiple simultaneous indicators.
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public class UserIndicatorQueue {
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private class Weak<T: AnyObject> {
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weak var element: T?
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init(_ element: T) {
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self.element = element
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}
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}
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private var queue: [Weak<UserIndicator>]
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public init() {
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queue = []
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}
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/// Add a new indicator to the queue by providing a request.
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///
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/// The queue will start the indicator right away, if there are no currently running indicators,
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/// otherwise the indicator will be put on hold.
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public func add(_ request: UserIndicatorRequest) -> UserIndicator {
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let indicator = UserIndicator(request: request) { [weak self] in
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self?.startNextIfIdle()
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}
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queue.append(Weak(indicator))
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startNextIfIdle()
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return indicator
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}
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private func startNextIfIdle() {
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cleanup()
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if let indicator = queue.first?.element, indicator.state == .pending {
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indicator.start()
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}
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}
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private func cleanup() {
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queue.removeAll {
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$0.element == nil || $0.element?.state == .completed
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}
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}
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}
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