69 lines
2.0 KiB
Swift
69 lines
2.0 KiB
Swift
// Copyright 2022 Tokamak contributors
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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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// Created by Carson Katri on 5/30/22.
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//
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/// A type that can visit a `Scene`.
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public protocol SceneVisitor: ViewVisitor {
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func visit<S: Scene>(_ scene: S)
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}
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public extension Scene {
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func _visitChildren<V: SceneVisitor>(_ visitor: V) {
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visitor.visit(body)
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}
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}
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/// A type that creates a `Result` by visiting multiple `Scene`s.
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protocol SceneReducer: ViewReducer {
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associatedtype Result
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static func reduce<S: Scene>(into partialResult: inout Result, nextScene: S)
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static func reduce<S: Scene>(partialResult: Result, nextScene: S) -> Result
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}
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extension SceneReducer {
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static func reduce<S: Scene>(into partialResult: inout Result, nextScene: S) {
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partialResult = Self.reduce(partialResult: partialResult, nextScene: nextScene)
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}
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static func reduce<S: Scene>(partialResult: Result, nextScene: S) -> Result {
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var result = partialResult
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Self.reduce(into: &result, nextScene: nextScene)
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return result
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}
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}
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/// A `SceneVisitor` that uses a `SceneReducer`
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/// to collapse the `Scene` values into a single `Result`.
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final class SceneReducerVisitor<R: SceneReducer>: SceneVisitor {
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var result: R.Result
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init(initialResult: R.Result) {
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result = initialResult
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}
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func visit<S>(_ scene: S) where S: Scene {
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R.reduce(into: &result, nextScene: scene)
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}
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func visit<V>(_ view: V) where V: View {
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R.reduce(into: &result, nextView: view)
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}
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}
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extension SceneReducer {
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typealias SceneVisitor = SceneReducerVisitor<Self>
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}
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