import AppKit
import WebKit

@MainActor
enum RedditWebViewManager {
    private static let processPool = WKProcessPool()

    static func makeConfiguration(includeLoginBridge: Bool = true) -> WKWebViewConfiguration {
        let configuration = WKWebViewConfiguration()
        configuration.processPool = processPool
        configuration.websiteDataStore = .default()
        configuration.defaultWebpagePreferences.allowsContentJavaScript = true
        configuration.preferences.isElementFullscreenEnabled = true

        let isDarkMode = AppearanceManager.shared.isDarkMode
        let themeScript = WKUserScript(
            source: RedditThemeStyle.earlyInjectionScript(isDarkMode: isDarkMode),
            injectionTime: .atDocumentStart,
            forMainFrameOnly: true
        )
        configuration.userContentController.addUserScript(themeScript)

        let boundaryScript = WKUserScript(
            source: RedditPostBoundaryStyle.injectionScript,
            injectionTime: .atDocumentEnd,
            forMainFrameOnly: true
        )
        configuration.userContentController.addUserScript(boundaryScript)

        let chromeScript = WKUserScript(
            source: RedditHomeChromeStyle.injectionScript,
            injectionTime: .atDocumentStart,
            forMainFrameOnly: true
        )
        configuration.userContentController.addUserScript(chromeScript)

        let authChromeScript = WKUserScript(
            source: RedditAuthChromeStyle.injectionScript,
            injectionTime: .atDocumentStart,
            forMainFrameOnly: false
        )
        configuration.userContentController.addUserScript(authChromeScript)

        let shareBridgeScript = WKUserScript(
            source: RedditShareBridgeStyle.injectionScript,
            injectionTime: .atDocumentStart,
            forMainFrameOnly: true
        )
        configuration.userContentController.addUserScript(shareBridgeScript)
        configuration.userContentController.add(
            RedditShareScriptBridge.shared,
            name: RedditShareBridgeStyle.messageHandlerName
        )

        if includeLoginBridge {
            let loginBridgeScript = WKUserScript(
                source: RedditLoginBridgeStyle.injectionScript,
                injectionTime: .atDocumentStart,
                forMainFrameOnly: true
            )
            configuration.userContentController.addUserScript(loginBridgeScript)
            configuration.userContentController.add(
                RedditLoginScriptBridge.shared,
                name: RedditLoginBridgeStyle.messageHandlerName
            )
        }

        return configuration
    }

    static func makeWebView() -> WKWebView {
        let webView = WKWebView(frame: .zero, configuration: makeConfiguration())
        webView.allowsBackForwardNavigationGestures = true
        webView.allowsMagnification = true
        // Use the default WKWebView user agent instead of spoofing Safari.
        let isDarkMode = AppearanceManager.shared.isDarkMode
        applyTheme(to: webView, isDarkMode: isDarkMode)
        return webView
    }

    static func applyTheme(to webView: WKWebView, isDarkMode: Bool) {
        applyAppearance(to: webView, isDarkMode: isDarkMode)
        applyUnderPageBackground(to: webView, isDarkMode: isDarkMode)
        webView.evaluateJavaScript(
            RedditThemeStyle.syncScript(isDarkMode: isDarkMode),
            completionHandler: nil
        )
    }

    static func applyAppearance(to webView: WKWebView, isDarkMode: Bool) {
        let appearanceName: NSAppearance.Name = isDarkMode ? .darkAqua : .aqua
        webView.appearance = NSAppearance(named: appearanceName)
    }

    static func applyUnderPageBackground(to webView: WKWebView, isDarkMode: Bool) {
        webView.underPageBackgroundColor = AppearanceManager.webUnderPageBackgroundColor(isDarkMode: isDarkMode)
    }
}