//

// DataStoreWarmup.swift

// DuckDuckGo

//

// Copyright © 2024 DuckDuckGo. All rights reserved.

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

// http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

//

import Combine

import WebKit

/// WKWebsiteDataStore is basically non-functional until a web view has been instanciated and a page is successfully loaded.

public class DataStoreWarmup {

public enum ApplicationState: String {

case active

case inactive

case background

case handlingShortcut

case unknown

}

public init() { }

@MainActor

public func ensureReady(applicationState: ApplicationState) async {

Pixel.fire(pixel: .webkitWarmupStart(appState: applicationState.rawValue))

await BlockingNavigationDelegate().loadInBackgroundWebView(url: URL(string: "about:blank")!)

Pixel.fire(pixel: .webkitWarmupFinished(appState: applicationState.rawValue))

}

}

public class BlockingNavigationDelegate: NSObject, WKNavigationDelegate {

var finished: PassthroughSubject? = PassthroughSubject<Void, Never>()

public func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction) async -> WKNavigationActionPolicy {

return .allow

}

public func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {

if let finished {

finished.send()

self.finished = nil

} else {

Pixel.fire(pixel: .webKitWarmupUnexpectedDidFinish, includedParameters: [.appVersion])

}

}

public func webViewWebContentProcessDidTerminate(_ webView: WKWebView) {

Pixel.fire(pixel: .webKitDidTerminateDuringWarmup)

if let finished {

finished.send()

self.finished = nil

} else {

Pixel.fire(pixel: .webKitWarmupUnexpectedDidTerminate, includedParameters: [.appVersion])

}

}

var cancellable: AnyCancellable?

public func waitForLoad() async {

await withCheckedContinuation { continuation in

cancellable = finished?.sink { _ in

continuation.resume()

}

}

}

@MainActor

public func prepareWebView() -> WKWebView {

let config = WKWebViewConfiguration.persistent()

let webView = WKWebView(frame: .zero, configuration: config)

webView.navigationDelegate = self

return webView

}

@MainActor

public func loadInBackgroundWebView(url: URL) async {

let webView = prepareWebView()

let request = URLRequest(url: url)

webView.load(request)

await waitForLoad()

}

}