import CryptoKit
import Foundation
import WebKit

#if DEBUG
import Bonsplit
#endif

// MARK: - Settings

enum ReactGrabSettings {
    static let versionKey = "reactGrabVersion"
    static let defaultVersion = "0.1.29"

    /// Known versions and their SHA-256 integrity hashes.
    /// Add new entries when bumping the default or to allow user-selected versions.
    static let knownHashes: [String: String] = [
        "0.1.29": "4a1e71090e8ad8bb6049de80ccccdc0f5bb147b9f8fb88886d871612ac7ca04b",
    ]

    static func scriptURL(for version: String) -> URL {
        URL(string: "https://unpkg.com/react-grab@\(version)/dist/index.global.js")!
    }

    static var configuredVersion: String {
        let stored = UserDefaults.standard.string(forKey: versionKey)?.trimmingCharacters(in: .whitespacesAndNewlines) ?? ""
        return stored.isEmpty ? defaultVersion : stored
    }
}

// MARK: - Script Loader

/// Fetches, integrity-checks, and caches the react-grab script.
/// Shared across all BrowserPanel instances.
enum ReactGrabScriptLoader {
    private static var cachedScript: String?
    private static var cachedVersion: String?
    private static var prefetchTask: Task<String?, Never>?

    static func prefetch() {
        let version = ReactGrabSettings.configuredVersion
        // Invalidate cache if version changed.
        if cachedVersion != version {
            cachedScript = nil
            cachedVersion = nil
        }
        guard cachedScript == nil else { return }
        guard prefetchTask == nil else { return }
        prefetchTask = Task.detached(priority: .low) {
            let result = await doFetch(version: version)
            await MainActor.run { prefetchTask = nil }
            return result
        }
    }

    static func fetch() async -> String? {
        let version = ReactGrabSettings.configuredVersion
        if cachedVersion == version, let cached = cachedScript { return cached }
        prefetch()
        return await prefetchTask?.value
    }

    private static func doFetch(version: String) async -> String? {
        let url = ReactGrabSettings.scriptURL(for: version)
        do {
            let (data, _) = try await URLSession.shared.data(from: url)
            if let expectedHash = ReactGrabSettings.knownHashes[version] {
                let hash = SHA256.hash(data: data)
                let hex = hash.compactMap { String(format: "%02x", $0) }.joined()
                guard hex == expectedHash else {
                    NSLog("ReactGrab: integrity mismatch for v%@ (got %@)", version, hex)
                    return nil
                }
            }
            guard let script = String(data: data, encoding: .utf8) else { return nil }
            await MainActor.run {
                cachedScript = script
                cachedVersion = version
            }
            return script
        } catch {
            NSLog("ReactGrab: fetch failed for v%@: %@", version, error.localizedDescription)
            return nil
        }
    }
}

// MARK: - WKScriptMessageHandler

private let reactGrabMessageHandlerName = "cmuxReactGrab"

class ReactGrabMessageHandler: NSObject, WKScriptMessageHandler {
    private let onStateChange: @MainActor (Bool) -> Void

    init(onStateChange: @escaping @MainActor (Bool) -> Void) {
        self.onStateChange = onStateChange
    }

    func userContentController(
        _ userContentController: WKUserContentController,
        didReceive message: WKScriptMessage
    ) {
        guard let body = message.body as? [String: Any],
              let isActive = body["isActive"] as? Bool else { return }
        #if DEBUG
        dlog("reactGrab.messageHandler isActive=\(isActive)")
        #endif
        Task { @MainActor in
            #if DEBUG
            dlog("reactGrab.messageHandler.mainActor isActive=\(isActive)")
            #endif
            onStateChange(isActive)
        }
    }
}

// MARK: - BrowserPanel extension

extension BrowserPanel {
    func setupReactGrabMessageHandler(for webView: WKWebView) {
        let handler = ReactGrabMessageHandler { [weak self] isActive in
            self?.isReactGrabActive = isActive
        }
        reactGrabMessageHandler = handler
        webView.configuration.userContentController.add(handler, name: reactGrabMessageHandlerName)
    }

    func injectReactGrab() async {
        #if DEBUG
        dlog("reactGrab.inject.start")
        #endif
        guard let scriptSource = await ReactGrabScriptLoader.fetch() else {
            #if DEBUG
            dlog("reactGrab.inject.fetchFailed")
            #endif
            return
        }
        #if DEBUG
        dlog("reactGrab.inject.fetched len=\(scriptSource.count)")
        #endif

        let handlerName = reactGrabMessageHandlerName
        let combined = """
        (function() {
            if (window.__REACT_GRAB__) { window.__REACT_GRAB__.activate(); return; }
            window.addEventListener('react-grab:init', function(e) {
                var api = e.detail;
                if (!api) return;
                api.activate();
                var lastActive;
                api.registerPlugin({
                    name: 'cmux-bridge',
                    hooks: {
                        onStateChange: function(state) {
                            if (state.isActive === lastActive) return;
                            lastActive = state.isActive;
                            var h = window.webkit && window.webkit.messageHandlers && window.webkit.messageHandlers.\(handlerName);
                            if (h) h.postMessage({ isActive: state.isActive });
                        }
                    }
                });
            }, { once: true });
        })();
        \(scriptSource)
        """
        #if DEBUG
        dlog("reactGrab.inject.evalJS len=\(combined.count)")
        #endif
        webView.evaluateJavaScript(combined) { [weak self] _, error in
            #if DEBUG
            dlog("reactGrab.inject.evalJS.done error=\(error?.localizedDescription ?? "none")")
            #endif
            if let error {
                NSLog("ReactGrab: injection failed: %@", error.localizedDescription)
                Task { @MainActor in self?.isReactGrabActive = false }
            }
        }
        #if DEBUG
        dlog("reactGrab.inject.end")
        #endif
    }

    func toggleReactGrab() {
        #if DEBUG
        dlog("reactGrab.toggle.start")
        #endif
        let script = "window.__REACT_GRAB__?.toggle()"
        webView.evaluateJavaScript(script, completionHandler: nil)
        #if DEBUG
        dlog("reactGrab.toggle.end")
        #endif
    }

    func toggleOrInjectReactGrab() async {
        if isReactGrabActive {
            toggleReactGrab()
        } else {
            await injectReactGrab()
        }
    }

    func resetReactGrabState() {
        isReactGrabActive = false
    }
}