import AppKit
import Darwin
import Foundation
import WebKit

@MainActor
final class WkWebViewHarness: NSObject, WKNavigationDelegate
{
    private let app: NSApplication
    private let window: NSWindow
    private let webView: WKWebView
    private var finished = false

    init(app: NSApplication, pagePath: String, readRoot: String)
    {
        self.app = app

        let configuration = WKWebViewConfiguration()
        configuration.websiteDataStore = .nonPersistent()
        webView = WKWebView(
            frame: NSRect(x: 0, y: 0, width: 1224, height: 768),
            configuration: configuration
        )
        window = NSWindow(
            contentRect: webView.frame,
            styleMask: [ .titled, .closable, .resizable ],
            backing: .buffered,
            defer: false
        )

        super.init()

        webView.navigationDelegate = self
        window.title = "Juzhen WKWebView E2E"
        window.contentView = webView
        window.center()
        window.makeKeyAndOrderFront(nil)

        let pageUrl = URL(fileURLWithPath: pagePath)
        let readUrl = URL(fileURLWithPath: readRoot, isDirectory: true)
        webView.loadFileURL(pageUrl, allowingReadAccessTo: readUrl)

        DispatchQueue.main.asyncAfter(deadline: .now() + 20)
        { [weak self] in
            self?.finish(code: 2, reason: "timeout")
        }
    }

    func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!)
    {
        evaluate("navigator.userAgent")
        { value in
            print("WKWEBVIEW_USER_AGENT=\(value)")
        }
        click(buttonId: "run-core")
        pollTitle(expectedPrefix: "CORE PASS", timeoutAt: Date().addingTimeInterval(8))
        { [weak self] coreTitle in
            guard let self else { return }
            guard coreTitle.hasPrefix("CORE PASS") else
            {
                self.collectAndFinish(code: 3, reason: "core title: \(coreTitle)")
                return
            }
            self.click(buttonId: "run-observer")
            self.pollTitle(expectedPrefix: "PASS", timeoutAt: Date().addingTimeInterval(8))
            { [weak self] finalTitle in
                guard let self else { return }
                let success = finalTitle.hasPrefix("PASS")
                self.collectAndFinish(
                    code: success ? 0 : 4,
                    reason: "final title: \(finalTitle)"
                )
            }
        }
    }

    func webView(
        _ webView: WKWebView,
        didFail navigation: WKNavigation!,
        withError error: Error
    )
    {
        finish(code: 5, reason: "navigation failed: \(error)")
    }

    func webView(
        _ webView: WKWebView,
        didFailProvisionalNavigation navigation: WKNavigation!,
        withError error: Error
    )
    {
        finish(code: 6, reason: "provisional navigation failed: \(error)")
    }

    private func click(buttonId: String)
    {
        let script = "document.getElementById('\(buttonId)')?.click(); document.title;"
        evaluate(script)
        { value in
            print("WKWEBVIEW_CLICK_\(buttonId)=\(value)")
        }
    }

    private func pollTitle(
        expectedPrefix: String,
        timeoutAt: Date,
        completion: @escaping (String) -> Void
    )
    {
        evaluate("document.title")
        { [weak self] value in
            guard let self else { return }
            if value.hasPrefix(expectedPrefix) || value.hasPrefix("FAIL") || Date() >= timeoutAt
            {
                completion(value)
                return
            }
            DispatchQueue.main.asyncAfter(deadline: .now() + 0.1)
            { [weak self] in
                self?.pollTitle(
                    expectedPrefix: expectedPrefix,
                    timeoutAt: timeoutAt,
                    completion: completion
                )
            }
        }
    }

    private func collectAndFinish(code: Int32, reason: String)
    {
        let script = """
        JSON.stringify({
            title: document.title,
            summary: document.getElementById('summary-text')?.textContent || '',
            failures: Array.from(document.querySelectorAll('#results li[data-state="fail"]'))
                .map((item) => item.textContent),
            results: Array.from(document.querySelectorAll('#results li'))
                .map((item) => item.textContent)
        })
        """
        evaluate(script)
        { [weak self] value in
            print("WKWEBVIEW_RESULT=\(value)")
            self?.finish(code: code, reason: reason)
        }
    }

    private func evaluate(_ script: String, completion: @escaping (String) -> Void)
    {
        webView.evaluateJavaScript(script)
        { value, error in
            if let error
            {
                completion("EVALUATION_ERROR: \(error)")
                return
            }
            completion(String(describing: value ?? "nil"))
        }
    }

    private func finish(code: Int32, reason: String)
    {
        guard !finished else { return }
        finished = true
        print("WKWEBVIEW_EXIT_REASON=\(reason)")
        fflush(stdout)
        window.close()
        app.stop(nil)
        exit(code)
    }
}

@main
struct Main
{
    @MainActor
    private static var harness: WkWebViewHarness?

    @MainActor
    static func main()
    {
        guard CommandLine.arguments.count == 3 else
        {
            fputs("usage: harness <e2e.html> <read-root>\n", stderr)
            exit(64)
        }
        let app = NSApplication.shared
        app.setActivationPolicy(.accessory)
        harness = WkWebViewHarness(
            app: app,
            pagePath: CommandLine.arguments[1],
            readRoot: CommandLine.arguments[2]
        )
        app.run()
    }
}