import SwiftUI
import XuqmFileSDK

// JS bridge name used by DIALOG_OVERRIDE_JS to post messages to native.
private let kBridgeName = "ReactNativeWebView"

// Injected into every page to override browser dialogs and intercept downloads.
private let dialogOverrideJs = #"""
(function() {
  function post(obj) {
    window.webkit.messageHandlers.ReactNativeWebView.postMessage(JSON.stringify(obj));
  }

  window.alert = function(msg) { post({ __xwv: 'alert', msg: String(msg) }); };
  window.confirm = function(msg) { post({ __xwv: 'confirm', msg: String(msg) }); return true; };
  window.prompt = function(msg, def) { post({ __xwv: 'prompt', msg: String(msg), def: def || '' }); return def || ''; };

  window.open = function(url) {
    if (url) { window.location.href = url; }
    return null;
  };

  URL.revokeObjectURL = function() {};

  function readBlobAndPost(blobUrl, filename) {
    fetch(blobUrl)
      .then(function(r) { return r.blob(); })
      .then(function(blob) {
        var reader = new FileReader();
        reader.onloadend = function() {
          var b64 = reader.result.split(',')[1];
          post({ __xwv: 'blobdownload', url: blobUrl, filename: filename, data: b64 });
        };
        reader.readAsDataURL(blob);
      })
      .catch(function(err) {
        post({ __xwv: 'bloberror', msg: String(err) });
      });
  }

  var DL_RE = "\\.(exe|apk|ipa|zip|rar|tar|gz|dmg|pkg|deb|rpm|msi|pdf|doc|docx|xls|xlsx|ppt|pptx|mp4|mp3|mov|avi|mkv)(\\?|#|$)";
  var dlRe = new RegExp(DL_RE, 'i');

  function tryInterceptAnchor(el, e) {
    if (!el || el.tagName !== 'A') return false;
    var href = el.href || el.getAttribute('href') || '';
    if (!href || href.indexOf('javascript') === 0) return false;
    var hasDownloadAttr = el.hasAttribute('download');
    var dlName = el.getAttribute('download') || '';
    var isDL = hasDownloadAttr || dlRe.test(href);
    if (isDL) {
      if (e) { e.preventDefault(); e.stopPropagation(); }
      if (href.startsWith('blob:')) {
        readBlobAndPost(href, dlName);
      } else {
        post({ __xwv: 'download', url: href, filename: dlName });
      }
      return true;
    }
    return false;
  }

  document.addEventListener('click', function(e) {
    var el = e.target;
    while (el && el.tagName !== 'A') { el = el.parentElement; }
    tryInterceptAnchor(el, e);
  }, true);

  var _origClick = HTMLAnchorElement.prototype.click;
  HTMLAnchorElement.prototype.click = function() {
    if (!tryInterceptAnchor(this, null)) {
      _origClick.call(this);
    }
  };
})();
true;
"""#

private func buildInjectedJs(_ config: XWebViewConfig) -> String {
    dialogOverrideJs + "\n" + (config.injectedJavaScript ?? "")
}

#if canImport(UIKit)
import WebKit

// Weak wrapper prevents retain cycle: WKUserContentController → handler → webView.
private class WeakScriptHandler: NSObject, WKScriptMessageHandler {
    weak var target: (NSObject & WKScriptMessageHandler)?
    init(_ target: NSObject & WKScriptMessageHandler) { self.target = target }
    func userContentController(_ c: WKUserContentController, didReceive m: WKScriptMessage) {
        target?.userContentController(c, didReceive: m)
    }
}

@MainActor
public struct XWebViewView: UIViewRepresentable {
    private let config: XWebViewConfig

    public init(config: XWebViewConfig? = nil) {
        self.config = config ?? XWebViewBridge.shared.currentConfig()
    }

    public func makeCoordinator() -> Coordinator {
        Coordinator(config: config)
    }

    public func makeUIView(context: Context) -> WKWebView {
        let userController = WKUserContentController()

        // Inject DIALOG_OVERRIDE_JS + user script at document end.
        let script = WKUserScript(
            source: buildInjectedJs(config),
            injectionTime: .atDocumentEnd,
            forMainFrameOnly: true
        )
        userController.addUserScript(script)

        // Register JS → Native message channel via weak proxy to avoid retain cycle.
        userController.add(WeakScriptHandler(context.coordinator), name: kBridgeName)

        let configuration = WKWebViewConfiguration()
        configuration.userContentController = userController

        let webView = WKWebView(frame: .zero, configuration: configuration)
        webView.navigationDelegate = context.coordinator
        webView.uiDelegate = context.coordinator
        if let userAgent = config.userAgent {
            webView.customUserAgent = userAgent
        }
        context.coordinator.attach(webView)
        XWebViewBridge.shared.setController(context.coordinator)
        if !config.url.isEmpty, let url = URL(string: config.url) {
            webView.load(URLRequest(url: url))
        }
        return webView
    }

    public func updateUIView(_ webView: WKWebView, context: Context) {
        context.coordinator.attach(webView)
        if webView.url == nil, !config.url.isEmpty, let url = URL(string: config.url) {
            webView.load(URLRequest(url: url))
        }
    }

    public static func dismantleUIView(_ uiView: WKWebView, coordinator: Coordinator) {
        uiView.configuration.userContentController.removeScriptMessageHandler(forName: kBridgeName)
        coordinator.detach()
        if XWebViewBridge.shared.currentController() === coordinator {
            XWebViewBridge.shared.setController(nil)
        }
    }

    @MainActor
    public final class Coordinator: NSObject, WKNavigationDelegate, WKUIDelegate, WKScriptMessageHandler, XWebViewController {
        private weak var webView: WKWebView?
        private let config: XWebViewConfig

        init(config: XWebViewConfig) {
            self.config = config
        }

        func attach(_ webView: WKWebView) { self.webView = webView }
        func detach() { webView = nil }

        public func canGoBack() -> Bool { webView?.canGoBack == true }
        public func canGoForward() -> Bool { webView?.canGoForward == true }
        public func currentUrl() -> String? { webView?.url?.absoluteString }
        public func goBack() { webView?.goBack() }
        public func goForward() { webView?.goForward() }
        public func reload() { webView?.reload() }
        public func load(url: String) {
            guard let url = URL(string: url) else { return }
            webView?.load(URLRequest(url: url))
        }
        public func postMessageToWeb(js: String) {
            webView?.evaluateJavaScript(js, completionHandler: nil)
        }

        // WKScriptMessageHandler — routes window.webkit.messageHandlers.ReactNativeWebView.postMessage()
        public func userContentController(
            _ userContentController: WKUserContentController,
            didReceive message: WKScriptMessage
        ) {
            guard let raw = message.body as? String else { return }
            guard let data = raw.data(using: .utf8),
                  let json = try? JSONSerialization.jsonObject(with: data) as? [String: Any] else {
                config.onMessage?(raw)
                return
            }
            guard let xwv = json["__xwv"] as? String else {
                config.onMessage?(raw)
                return
            }
            switch xwv {
            case "log", "alert", "confirm", "prompt", "bloberror":
                return
            case "download":
                let url = json["url"] as? String ?? ""
                let filename = (json["filename"] as? String)?.nilIfEmpty
                Task { await handleDownload(url: url, filename: filename) }
            case "blobdownload":
                let url = json["url"] as? String ?? ""
                let filename = (json["filename"] as? String)?.nilIfEmpty ?? "download.bin"
                let b64 = json["data"] as? String ?? ""
                Task { await handleBlobDownload(url: url, filename: filename, base64Data: b64) }
            default:
                break
            }
        }

        private func dispatchDownloadEvent(_ name: String, url: String, extra: String = "") {
            let escaped = url.jsEscaped
            let js = "window.dispatchEvent(new CustomEvent('\(name)',{detail:{url:'\(escaped)'\(extra)}}));"
            webView?.evaluateJavaScript(js, completionHandler: nil)
        }

        private func handleDownload(url: String, filename: String?) async {
            do {
                let localURL = try await FileSDK.shared.download(
                    url: url,
                    fileName: filename,
                    destination: config.downloadDestination
                ) { [weak self] progress in
                    Task { @MainActor [weak self] in
                        self?.dispatchDownloadEvent("__xwvDownloadProgress", url: url, extra: ",progress:\(progress)")
                    }
                }
                dispatchDownloadEvent("__xwvDownloadDone", url: url, extra: ",success:true")
                openOrSave(localURL: localURL, destination: config.downloadDestination)
            } catch {
                let msg = error.localizedDescription.jsEscaped
                dispatchDownloadEvent("__xwvDownloadDone", url: url, extra: ",success:false,error:'\(msg)'")
            }
        }

        private func handleBlobDownload(url: String, filename: String, base64Data: String) async {
            do {
                let localURL = try FileSDK.shared.saveBlobDownload(
                    base64Data: base64Data,
                    fileName: filename,
                    destination: config.downloadDestination
                )
                dispatchDownloadEvent("__xwvDownloadDone", url: url, extra: ",success:true")
                openOrSave(localURL: localURL, destination: config.downloadDestination)
            } catch {
                let msg = error.localizedDescription.jsEscaped
                dispatchDownloadEvent("__xwvDownloadDone", url: url, extra: ",success:false,error:'\(msg)'")
            }
        }

        private func openOrSave(localURL: URL, destination: FileDownloadDestination) {
            guard let wv = webView else { return }
            #if canImport(UIKit)
            switch destination {
            case .sandbox:
                let vc = UIActivityViewController(activityItems: [localURL], applicationActivities: nil)
                topViewController(from: wv)?.present(vc, animated: true)
            case .userPick:
                let picker = UIDocumentPickerViewController(forExporting: [localURL], asCopy: true)
                topViewController(from: wv)?.present(picker, animated: true)
            }
            #endif
        }

        #if canImport(UIKit)
        private func topViewController(from view: UIView) -> UIViewController? {
            var responder: UIResponder? = view
            while let r = responder {
                if let vc = r as? UIViewController { return vc }
                responder = r.next
            }
            return nil
        }
        #endif

        @available(iOS 15.0, *)
        public func webView(
            _ webView: WKWebView,
            requestMediaCapturePermissionFor origin: WKSecurityOrigin,
            initiatedByFrame frame: WKFrameInfo,
            type: WKMediaCaptureType,
            decisionHandler: @escaping (WKPermissionDecision) -> Void
        ) {
            decisionHandler(.grant)
        }
    }
}

private extension String {
    var jsEscaped: String {
        replacingOccurrences(of: "\\", with: "\\\\")
            .replacingOccurrences(of: "'", with: "\\'")
            .replacingOccurrences(of: "\n", with: "\\n")
            .replacingOccurrences(of: "\r", with: "\\r")
    }
    var nilIfEmpty: String? { isEmpty ? nil : self }
}

#else

public struct XWebViewView: View {
    private let config: XWebViewConfig

    public init(config: XWebViewConfig? = nil) {
        self.config = config ?? XWebViewBridge.shared.currentConfig()
    }

    public var body: some View {
        VStack(spacing: 12) {
            Text(config.title.isEmpty ? "WebView" : config.title)
                .font(.headline)
            Text("XWebView is available on iOS with UIKit-backed WebView.")
                .font(.subheadline)
                .foregroundStyle(.secondary)
        }
        .frame(maxWidth: .infinity, maxHeight: .infinity)
    }
}

#endif