cmux/Sources/Panels/BrowserPanel.swift

import Foundation
import Combine
import WebKit
import AppKit

enum BrowserSearchEngine: String, CaseIterable, Identifiable {
    case google
    case duckduckgo
    case bing

    var id: String { rawValue }

    var displayName: String {
        switch self {
        case .google: return "Google"
        case .duckduckgo: return "DuckDuckGo"
        case .bing: return "Bing"
        }
    }

    func searchURL(query: String) -> URL? {
        let trimmed = query.trimmingCharacters(in: .whitespacesAndNewlines)
        guard !trimmed.isEmpty else { return nil }

        var components: URLComponents?
        switch self {
        case .google:
            components = URLComponents(string: "https://www.google.com/search")
        case .duckduckgo:
            components = URLComponents(string: "https://duckduckgo.com/")
        case .bing:
            components = URLComponents(string: "https://www.bing.com/search")
        }

        components?.queryItems = [
            URLQueryItem(name: "q", value: trimmed),
        ]
        return components?.url
    }
}

enum BrowserSearchSettings {
    static let searchEngineKey = "browserSearchEngine"
    static let searchSuggestionsEnabledKey = "browserSearchSuggestionsEnabled"
    static let defaultSearchEngine: BrowserSearchEngine = .google
    static let defaultSearchSuggestionsEnabled: Bool = true

    static func currentSearchEngine(defaults: UserDefaults = .standard) -> BrowserSearchEngine {
        guard let raw = defaults.string(forKey: searchEngineKey),
              let engine = BrowserSearchEngine(rawValue: raw) else {
            return defaultSearchEngine
        }
        return engine
    }

    static func currentSearchSuggestionsEnabled(defaults: UserDefaults = .standard) -> Bool {
        // Mirror @AppStorage behavior: bool(forKey:) returns false if key doesn't exist.
        // Default to enabled unless user explicitly set a value.
        if defaults.object(forKey: searchSuggestionsEnabledKey) == nil {
            return defaultSearchSuggestionsEnabled
        }
        return defaults.bool(forKey: searchSuggestionsEnabledKey)
    }
}

enum BrowserUserAgentSettings {
    // Force a Safari UA. Some WebKit builds return a minimal UA without Version/Safari tokens,
    // and some installs may have legacy Chrome UA overrides. Both can cause Google to serve
    // fallback/old UIs or trigger bot checks.
    static let safariUserAgent = "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/26.2 Safari/605.1.15"
}

func normalizedBrowserHistoryNamespace(bundleIdentifier: String) -> String {
    if bundleIdentifier.hasPrefix("com.cmuxterm.app.debug.") {
        return "com.cmuxterm.app.debug"
    }
    if bundleIdentifier.hasPrefix("com.cmuxterm.app.staging.") {
        return "com.cmuxterm.app.staging"
    }
    return bundleIdentifier
}

@MainActor
final class BrowserHistoryStore: ObservableObject {
    static let shared = BrowserHistoryStore()

    struct Entry: Codable, Identifiable, Hashable {
        let id: UUID
        var url: String
        var title: String?
        var lastVisited: Date
        var visitCount: Int
        var typedCount: Int
        var lastTypedAt: Date?

        private enum CodingKeys: String, CodingKey {
            case id
            case url
            case title
            case lastVisited
            case visitCount
            case typedCount
            case lastTypedAt
        }

        init(
            id: UUID,
            url: String,
            title: String?,
            lastVisited: Date,
            visitCount: Int,
            typedCount: Int = 0,
            lastTypedAt: Date? = nil
        ) {
            self.id = id
            self.url = url
            self.title = title
            self.lastVisited = lastVisited
            self.visitCount = visitCount
            self.typedCount = typedCount
            self.lastTypedAt = lastTypedAt
        }

        init(from decoder: Decoder) throws {
            let container = try decoder.container(keyedBy: CodingKeys.self)
            id = try container.decode(UUID.self, forKey: .id)
            url = try container.decode(String.self, forKey: .url)
            title = try container.decodeIfPresent(String.self, forKey: .title)
            lastVisited = try container.decode(Date.self, forKey: .lastVisited)
            visitCount = try container.decode(Int.self, forKey: .visitCount)
            typedCount = try container.decodeIfPresent(Int.self, forKey: .typedCount) ?? 0
            lastTypedAt = try container.decodeIfPresent(Date.self, forKey: .lastTypedAt)
        }
    }

    @Published private(set) var entries: [Entry] = []

    private let fileURL: URL?
    private var didLoad: Bool = false
    private var saveTask: Task<Void, Never>?
    private let maxEntries: Int = 5000
    private let saveDebounceNanoseconds: UInt64 = 120_000_000

    private struct SuggestionCandidate {
        let entry: Entry
        let urlLower: String
        let urlSansSchemeLower: String
        let hostLower: String
        let pathAndQueryLower: String
        let titleLower: String
    }

    private struct ScoredSuggestion {
        let entry: Entry
        let score: Double
    }

    init(fileURL: URL? = nil) {
        // Avoid calling @MainActor-isolated static methods from default argument context.
        self.fileURL = fileURL ?? BrowserHistoryStore.defaultHistoryFileURL()
    }

    func loadIfNeeded() {
        guard !didLoad else { return }
        didLoad = true
        guard let fileURL else { return }
        migrateLegacyTaggedHistoryFileIfNeeded(to: fileURL)

        // Load synchronously on first access so the first omnibar query can use
        // persisted history immediately (important for deterministic UI behavior).
        let data: Data
        do {
            data = try Data(contentsOf: fileURL)
        } catch {
            return
        }

        let decoded: [Entry]
        do {
            decoded = try JSONDecoder().decode([Entry].self, from: data)
        } catch {
            return
        }

        // Most-recent first.
        entries = decoded.sorted(by: { $0.lastVisited > $1.lastVisited })

        // Remove entries with invalid hosts (no TLD), e.g. "https://news."
        let beforeCount = entries.count
        entries.removeAll { entry in
            guard let url = URL(string: entry.url),
                  let host = url.host?.lowercased() else { return false }
            let trimmed = host.hasSuffix(".") ? String(host.dropLast()) : host
            return !trimmed.contains(".")
        }
        if entries.count != beforeCount {
            scheduleSave()
        }
    }

    func recordVisit(url: URL?, title: String?) {
        loadIfNeeded()

        guard let url else { return }
        guard let scheme = url.scheme?.lowercased(),
              scheme == "http" || scheme == "https" else { return }
        // Skip URLs whose host lacks a TLD (e.g. "https://news.").
        if let host = url.host?.lowercased() {
            let trimmed = host.hasSuffix(".") ? String(host.dropLast()) : host
            if !trimmed.contains(".") { return }
        }

        let urlString = url.absoluteString
        guard urlString != "about:blank" else { return }
        let normalizedKey = normalizedHistoryKey(url: url)

        if let idx = entries.firstIndex(where: {
            if $0.url == urlString { return true }
            return normalizedHistoryKey(urlString: $0.url) == normalizedKey
        }) {
            entries[idx].lastVisited = Date()
            entries[idx].visitCount += 1
            // Prefer non-empty titles, but don't clobber an existing title with empty/whitespace.
            if let title, !title.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty {
                entries[idx].title = title
            }
        } else {
            entries.insert(Entry(
                id: UUID(),
                url: urlString,
                title: title?.trimmingCharacters(in: .whitespacesAndNewlines),
                lastVisited: Date(),
                visitCount: 1
            ), at: 0)
        }

        // Keep most-recent first and bound size.
        entries.sort(by: { $0.lastVisited > $1.lastVisited })
        if entries.count > maxEntries {
            entries.removeLast(entries.count - maxEntries)
        }

        scheduleSave()
    }

    func recordTypedNavigation(url: URL?) {
        loadIfNeeded()

        guard let url else { return }
        guard let scheme = url.scheme?.lowercased(),
              scheme == "http" || scheme == "https" else { return }
        // Skip URLs whose host lacks a TLD (e.g. "https://news.").
        if let host = url.host?.lowercased() {
            let trimmed = host.hasSuffix(".") ? String(host.dropLast()) : host
            if !trimmed.contains(".") { return }
        }

        let urlString = url.absoluteString
        guard urlString != "about:blank" else { return }

        let now = Date()
        let normalizedKey = normalizedHistoryKey(url: url)
        if let idx = entries.firstIndex(where: {
            if $0.url == urlString { return true }
            return normalizedHistoryKey(urlString: $0.url) == normalizedKey
        }) {
            entries[idx].typedCount += 1
            entries[idx].lastTypedAt = now
            entries[idx].lastVisited = now
        } else {
            entries.insert(Entry(
                id: UUID(),
                url: urlString,
                title: nil,
                lastVisited: now,
                visitCount: 1,
                typedCount: 1,
                lastTypedAt: now
            ), at: 0)
        }

        entries.sort(by: { $0.lastVisited > $1.lastVisited })
        if entries.count > maxEntries {
            entries.removeLast(entries.count - maxEntries)
        }

        scheduleSave()
    }

    func suggestions(for input: String, limit: Int = 10) -> [Entry] {
        loadIfNeeded()
        guard limit > 0 else { return [] }

        let q = input.trimmingCharacters(in: .whitespacesAndNewlines).lowercased()
        guard !q.isEmpty else { return [] }
        let queryTokens = tokenizeSuggestionQuery(q)
        let now = Date()

        let matched = entries.compactMap { entry -> ScoredSuggestion? in
            let candidate = makeSuggestionCandidate(entry: entry)
            guard let score = suggestionScore(candidate: candidate, query: q, queryTokens: queryTokens, now: now) else {
                return nil
            }
            return ScoredSuggestion(entry: entry, score: score)
        }
        .sorted { lhs, rhs in
            if lhs.score != rhs.score { return lhs.score > rhs.score }
            if lhs.entry.lastVisited != rhs.entry.lastVisited { return lhs.entry.lastVisited > rhs.entry.lastVisited }
            if lhs.entry.visitCount != rhs.entry.visitCount { return lhs.entry.visitCount > rhs.entry.visitCount }
            return lhs.entry.url < rhs.entry.url
        }

        if matched.count <= limit { return matched.map(\.entry) }
        return Array(matched.prefix(limit).map(\.entry))
    }

    func recentSuggestions(limit: Int = 10) -> [Entry] {
        loadIfNeeded()
        guard limit > 0 else { return [] }

        let ranked = entries.sorted { lhs, rhs in
            if lhs.typedCount != rhs.typedCount { return lhs.typedCount > rhs.typedCount }
            let lhsTypedDate = lhs.lastTypedAt ?? .distantPast
            let rhsTypedDate = rhs.lastTypedAt ?? .distantPast
            if lhsTypedDate != rhsTypedDate { return lhsTypedDate > rhsTypedDate }
            if lhs.lastVisited != rhs.lastVisited { return lhs.lastVisited > rhs.lastVisited }
            if lhs.visitCount != rhs.visitCount { return lhs.visitCount > rhs.visitCount }
            return lhs.url < rhs.url
        }

        if ranked.count <= limit { return ranked }
        return Array(ranked.prefix(limit))
    }

    func clearHistory() {
        loadIfNeeded()
        saveTask?.cancel()
        saveTask = nil
        entries = []
        guard let fileURL else { return }
        try? FileManager.default.removeItem(at: fileURL)
    }

    @discardableResult
    func removeHistoryEntry(urlString: String) -> Bool {
        loadIfNeeded()
        let normalized = normalizedHistoryKey(urlString: urlString)
        let originalCount = entries.count
        entries.removeAll { entry in
            if entry.url == urlString { return true }
            guard let normalized else { return false }
            return normalizedHistoryKey(urlString: entry.url) == normalized
        }
        let didRemove = entries.count != originalCount
        if didRemove {
            scheduleSave()
        }
        return didRemove
    }

    func flushPendingSaves() {
        loadIfNeeded()
        saveTask?.cancel()
        saveTask = nil
        guard let fileURL else { return }
        try? Self.persistSnapshot(entries, to: fileURL)
    }

    private func scheduleSave() {
        guard let fileURL else { return }

        saveTask?.cancel()
        let snapshot = entries
        let debounceNanoseconds = saveDebounceNanoseconds

        saveTask = Task.detached(priority: .utility) {
            do {
                try await Task.sleep(nanoseconds: debounceNanoseconds) // debounce
            } catch {
                return
            }
            if Task.isCancelled { return }

            do {
                try Self.persistSnapshot(snapshot, to: fileURL)
            } catch {
                return
            }
        }
    }

    private func migrateLegacyTaggedHistoryFileIfNeeded(to targetURL: URL) {
        let fm = FileManager.default
        guard !fm.fileExists(atPath: targetURL.path) else { return }
        guard let legacyURL = Self.legacyTaggedHistoryFileURL(),
              legacyURL != targetURL,
              fm.fileExists(atPath: legacyURL.path) else {
            return
        }

        do {
            let dir = targetURL.deletingLastPathComponent()
            try fm.createDirectory(at: dir, withIntermediateDirectories: true, attributes: nil)
            try fm.copyItem(at: legacyURL, to: targetURL)
        } catch {
            return
        }
    }

    private func makeSuggestionCandidate(entry: Entry) -> SuggestionCandidate {
        let urlLower = entry.url.lowercased()
        let urlSansSchemeLower = stripHTTPSSchemePrefix(urlLower)
        let components = URLComponents(string: entry.url)
        let hostLower = components?.host?.lowercased() ?? ""
        let path = (components?.percentEncodedPath ?? components?.path ?? "").lowercased()
        let query = (components?.percentEncodedQuery ?? components?.query ?? "").lowercased()
        let pathAndQueryLower: String
        if query.isEmpty {
            pathAndQueryLower = path
        } else {
            pathAndQueryLower = "\(path)?\(query)"
        }
        let titleLower = (entry.title ?? "").trimmingCharacters(in: .whitespacesAndNewlines).lowercased()
        return SuggestionCandidate(
            entry: entry,
            urlLower: urlLower,
            urlSansSchemeLower: urlSansSchemeLower,
            hostLower: hostLower,
            pathAndQueryLower: pathAndQueryLower,
            titleLower: titleLower
        )
    }

    private func suggestionScore(
        candidate: SuggestionCandidate,
        query: String,
        queryTokens: [String],
        now: Date
    ) -> Double? {
        let queryIncludesScheme = query.hasPrefix("http://") || query.hasPrefix("https://")
        let urlMatchValue = queryIncludesScheme ? candidate.urlLower : candidate.urlSansSchemeLower
        let isSingleCharacterQuery = query.count == 1
        if isSingleCharacterQuery {
            let hasSingleCharStrongMatch =
                candidate.hostLower.hasPrefix(query) ||
                candidate.titleLower.hasPrefix(query) ||
                urlMatchValue.hasPrefix(query)
            guard hasSingleCharStrongMatch else { return nil }
        }

        let queryMatches =
            urlMatchValue.contains(query) ||
            candidate.hostLower.contains(query) ||
            candidate.pathAndQueryLower.contains(query) ||
            candidate.titleLower.contains(query)

        let tokenMatches = !queryTokens.isEmpty && queryTokens.allSatisfy { token in
            candidate.urlSansSchemeLower.contains(token) ||
            candidate.hostLower.contains(token) ||
            candidate.pathAndQueryLower.contains(token) ||
            candidate.titleLower.contains(token)
        }

        guard queryMatches || tokenMatches else { return nil }

        var score = 0.0

        if urlMatchValue == query { score += 1200 }
        if candidate.hostLower == query { score += 980 }
        if candidate.hostLower.hasPrefix(query) { score += 680 }
        if urlMatchValue.hasPrefix(query) { score += 560 }
        if candidate.titleLower.hasPrefix(query) { score += 420 }
        if candidate.pathAndQueryLower.hasPrefix(query) { score += 300 }

        if candidate.hostLower.contains(query) { score += 210 }
        if candidate.pathAndQueryLower.contains(query) { score += 165 }
        if candidate.titleLower.contains(query) { score += 145 }

        for token in queryTokens {
            if candidate.hostLower == token { score += 260 }
            else if candidate.hostLower.hasPrefix(token) { score += 170 }
            else if candidate.hostLower.contains(token) { score += 110 }

            if candidate.pathAndQueryLower.hasPrefix(token) { score += 80 }
            else if candidate.pathAndQueryLower.contains(token) { score += 52 }

            if candidate.titleLower.hasPrefix(token) { score += 74 }
            else if candidate.titleLower.contains(token) { score += 48 }
        }

        // Blend recency and repeat visits so history feels closer to browser frecency.
        let ageHours = max(0, now.timeIntervalSince(candidate.entry.lastVisited) / 3600)
        let recencyScore = max(0, 110 - (ageHours / 3))
        let frequencyScore = min(120, log1p(Double(max(1, candidate.entry.visitCount))) * 38)
        let typedFrequencyScore = min(190, log1p(Double(max(0, candidate.entry.typedCount))) * 80)
        let typedRecencyScore: Double
        if let lastTypedAt = candidate.entry.lastTypedAt {
            let typedAgeHours = max(0, now.timeIntervalSince(lastTypedAt) / 3600)
            typedRecencyScore = max(0, 85 - (typedAgeHours / 4))
        } else {
            typedRecencyScore = 0
        }
        score += recencyScore + frequencyScore + typedFrequencyScore + typedRecencyScore

        return score
    }

    private func stripHTTPSSchemePrefix(_ value: String) -> String {
        if value.hasPrefix("https://") {
            return String(value.dropFirst("https://".count))
        }
        if value.hasPrefix("http://") {
            return String(value.dropFirst("http://".count))
        }
        return value
    }

    private func normalizedHistoryKey(url: URL) -> String? {
        guard var components = URLComponents(url: url, resolvingAgainstBaseURL: true) else { return nil }
        return normalizedHistoryKey(components: &components)
    }

    private func normalizedHistoryKey(urlString: String) -> String? {
        guard var components = URLComponents(string: urlString) else { return nil }
        return normalizedHistoryKey(components: &components)
    }

    private func normalizedHistoryKey(components: inout URLComponents) -> String? {
        guard let scheme = components.scheme?.lowercased(),
              scheme == "http" || scheme == "https",
              var host = components.host?.lowercased() else {
            return nil
        }

        if host.hasPrefix("www.") {
            host.removeFirst(4)
        }

        if (scheme == "http" && components.port == 80) ||
            (scheme == "https" && components.port == 443) {
            components.port = nil
        }

        let portPart: String
        if let port = components.port {
            portPart = ":\(port)"
        } else {
            portPart = ""
        }

        var path = components.percentEncodedPath
        if path.isEmpty { path = "/" }
        while path.count > 1, path.hasSuffix("/") {
            path.removeLast()
        }

        let queryPart: String
        if let query = components.percentEncodedQuery, !query.isEmpty {
            queryPart = "?\(query.lowercased())"
        } else {
            queryPart = ""
        }

        return "\(scheme)://\(host)\(portPart)\(path)\(queryPart)"
    }

    private func tokenizeSuggestionQuery(_ query: String) -> [String] {
        var tokens: [String] = []
        var seen = Set<String>()
        let separators = CharacterSet.whitespacesAndNewlines.union(.punctuationCharacters).union(.symbols)
        for raw in query.components(separatedBy: separators) {
            let token = raw.trimmingCharacters(in: .whitespacesAndNewlines)
            guard !token.isEmpty else { continue }
            guard !seen.contains(token) else { continue }
            seen.insert(token)
            tokens.append(token)
        }
        return tokens
    }

    nonisolated private static func defaultHistoryFileURL() -> URL? {
        let fm = FileManager.default
        guard let appSupport = fm.urls(for: .applicationSupportDirectory, in: .userDomainMask).first else {
            return nil
        }
        let bundleId = Bundle.main.bundleIdentifier ?? "cmux"
        let namespace = normalizedBrowserHistoryNamespace(bundleIdentifier: bundleId)
        let dir = appSupport.appendingPathComponent(namespace, isDirectory: true)
        return dir.appendingPathComponent("browser_history.json", isDirectory: false)
    }

    nonisolated private static func legacyTaggedHistoryFileURL() -> URL? {
        guard let bundleId = Bundle.main.bundleIdentifier else { return nil }
        let namespace = normalizedBrowserHistoryNamespace(bundleIdentifier: bundleId)
        guard namespace != bundleId else { return nil }
        let fm = FileManager.default
        guard let appSupport = fm.urls(for: .applicationSupportDirectory, in: .userDomainMask).first else {
            return nil
        }
        let dir = appSupport.appendingPathComponent(bundleId, isDirectory: true)
        return dir.appendingPathComponent("browser_history.json", isDirectory: false)
    }

    nonisolated private static func persistSnapshot(_ snapshot: [Entry], to fileURL: URL) throws {
        let dir = fileURL.deletingLastPathComponent()
        try FileManager.default.createDirectory(at: dir, withIntermediateDirectories: true, attributes: nil)

        let encoder = JSONEncoder()
        encoder.outputFormatting = [.withoutEscapingSlashes]
        let data = try encoder.encode(snapshot)
        try data.write(to: fileURL, options: [.atomic])
    }
}

actor BrowserSearchSuggestionService {
    static let shared = BrowserSearchSuggestionService()

    func suggestions(engine: BrowserSearchEngine, query: String) async -> [String] {
        let trimmed = query.trimmingCharacters(in: .whitespacesAndNewlines)
        guard !trimmed.isEmpty else { return [] }

        // Deterministic UI-test hook for validating remote suggestion rendering
        // without relying on external network behavior.
        let forced = ProcessInfo.processInfo.environment["CMUX_UI_TEST_REMOTE_SUGGESTIONS_JSON"]
            ?? UserDefaults.standard.string(forKey: "CMUX_UI_TEST_REMOTE_SUGGESTIONS_JSON")
        if let forced,
           let data = forced.data(using: .utf8),
           let parsed = try? JSONSerialization.jsonObject(with: data) as? [Any] {
            return parsed.compactMap { item in
                guard let s = item as? String else { return nil }
                let value = s.trimmingCharacters(in: .whitespacesAndNewlines)
                return value.isEmpty ? nil : value
            }
        }

        // Google's endpoint can intermittently throttle/block app-style traffic.
        // Query fallbacks in parallel so we can show predictions quickly.
        if engine == .google {
            return await fetchRemoteSuggestionsWithGoogleFallbacks(query: trimmed)
        }

        return await fetchRemoteSuggestions(engine: engine, query: trimmed)
    }

    private func fetchRemoteSuggestionsWithGoogleFallbacks(query: String) async -> [String] {
        await withTaskGroup(of: [String].self, returning: [String].self) { group in
            group.addTask {
                await self.fetchRemoteSuggestions(engine: .google, query: query)
            }
            group.addTask {
                await self.fetchRemoteSuggestions(engine: .duckduckgo, query: query)
            }
            group.addTask {
                await self.fetchRemoteSuggestions(engine: .bing, query: query)
            }

            while let result = await group.next() {
                if !result.isEmpty {
                    group.cancelAll()
                    return result
                }
            }

            return []
        }
    }

    private func fetchRemoteSuggestions(engine: BrowserSearchEngine, query: String) async -> [String] {
        let url: URL?
        switch engine {
        case .google:
            var c = URLComponents(string: "https://suggestqueries.google.com/complete/search")
            c?.queryItems = [
                URLQueryItem(name: "client", value: "firefox"),
                URLQueryItem(name: "q", value: query),
            ]
            url = c?.url
        case .duckduckgo:
            var c = URLComponents(string: "https://duckduckgo.com/ac/")
            c?.queryItems = [
                URLQueryItem(name: "q", value: query),
                URLQueryItem(name: "type", value: "list"),
            ]
            url = c?.url
        case .bing:
            var c = URLComponents(string: "https://www.bing.com/osjson.aspx")
            c?.queryItems = [
                URLQueryItem(name: "query", value: query),
            ]
            url = c?.url
        }

        guard let url else { return [] }

        var req = URLRequest(url: url)
        req.timeoutInterval = 0.65
        req.cachePolicy = .returnCacheDataElseLoad
        req.setValue(BrowserUserAgentSettings.safariUserAgent, forHTTPHeaderField: "User-Agent")
        req.setValue("en-US,en;q=0.9", forHTTPHeaderField: "Accept-Language")

        let data: Data
        let response: URLResponse
        do {
            (data, response) = try await URLSession.shared.data(for: req)
        } catch {
            return []
        }

        guard let http = response as? HTTPURLResponse,
              (200..<300).contains(http.statusCode) else {
            return []
        }

        switch engine {
        case .google, .bing:
            return parseOSJSON(data: data)
        case .duckduckgo:
            return parseDuckDuckGo(data: data)
        }
    }

    private func parseOSJSON(data: Data) -> [String] {
        // Format: [query, [suggestions...], ...]
        guard let root = try? JSONSerialization.jsonObject(with: data) as? [Any],
              root.count >= 2,
              let list = root[1] as? [Any] else {
            return []
        }
        var out: [String] = []
        out.reserveCapacity(list.count)
        for item in list {
            guard let s = item as? String else { continue }
            let trimmed = s.trimmingCharacters(in: .whitespacesAndNewlines)
            guard !trimmed.isEmpty else { continue }
            out.append(trimmed)
        }
        return out
    }

    private func parseDuckDuckGo(data: Data) -> [String] {
        // Format: [{phrase:"..."}, ...]
        guard let root = try? JSONSerialization.jsonObject(with: data) as? [Any] else {
            return []
        }
        var out: [String] = []
        out.reserveCapacity(root.count)
        for item in root {
            guard let dict = item as? [String: Any],
                  let phrase = dict["phrase"] as? String else { continue }
            let trimmed = phrase.trimmingCharacters(in: .whitespacesAndNewlines)
            guard !trimmed.isEmpty else { continue }
            out.append(trimmed)
        }
        return out
    }
}

/// BrowserPanel provides a WKWebView-based browser panel.
/// All browser panels share a WKProcessPool for cookie sharing.
@MainActor
final class BrowserPanel: Panel, ObservableObject {
    /// Shared process pool for cookie sharing across all browser panels
    private static let sharedProcessPool = WKProcessPool()

    let id: UUID
    let panelType: PanelType = .browser

    /// The workspace ID this panel belongs to
    private(set) var workspaceId: UUID

    /// The underlying web view
    let webView: WKWebView

    /// Prevent the omnibar from auto-focusing for a short window after explicit programmatic focus.
    /// This avoids races where SwiftUI focus state steals first responder back from WebKit.
    private var suppressOmnibarAutofocusUntil: Date?

    /// Prevent forcing web-view focus when another UI path requested omnibar focus.
    /// Used to keep omnibar text-field focus from being immediately stolen by panel focus.
    private var suppressWebViewFocusUntil: Date?
    private var suppressWebViewFocusForAddressBar: Bool = false
    private let blankURLString = "about:blank"

    /// Published URL being displayed
    @Published private(set) var currentURL: URL?

    /// Published page title
    @Published private(set) var pageTitle: String = ""

    /// Published favicon (PNG data). When present, the tab bar can render it instead of a SF symbol.
    @Published private(set) var faviconPNGData: Data?

    /// Published loading state
    @Published private(set) var isLoading: Bool = false

    /// Published can go back state
    @Published private(set) var canGoBack: Bool = false

    /// Published can go forward state
    @Published private(set) var canGoForward: Bool = false

    /// Published estimated progress (0.0 - 1.0)
    @Published private(set) var estimatedProgress: Double = 0.0

    /// Increment to request a UI-only flash highlight (e.g. from a keyboard shortcut).
    @Published private(set) var focusFlashToken: Int = 0

    private var cancellables = Set<AnyCancellable>()
    private var navigationDelegate: BrowserNavigationDelegate?
    private var uiDelegate: BrowserUIDelegate?
    private var webViewObservers: [NSKeyValueObservation] = []

    // Avoid flickering the loading indicator for very fast navigations.
    private let minLoadingIndicatorDuration: TimeInterval = 0.35
    private var loadingStartedAt: Date?
    private var loadingEndWorkItem: DispatchWorkItem?
    private var loadingGeneration: Int = 0

    private var faviconTask: Task<Void, Never>?
    private var lastFaviconURLString: String?
    private let minPageZoom: CGFloat = 0.25
    private let maxPageZoom: CGFloat = 5.0
    private let pageZoomStep: CGFloat = 0.1

    var displayTitle: String {
        if !pageTitle.isEmpty {
            return pageTitle
        }
        if let url = currentURL {
            return url.host ?? url.absoluteString
        }
        return "Browser"
    }

    var displayIcon: String? {
        "globe"
    }

    var isDirty: Bool {
        false
    }

    init(workspaceId: UUID, initialURL: URL? = nil) {
        self.id = UUID()
        self.workspaceId = workspaceId

        // Configure web view
        let config = WKWebViewConfiguration()
        config.processPool = BrowserPanel.sharedProcessPool
        // Ensure browser cookies/storage persist across navigations and launches.
        // This reduces repeated consent/bot-challenge flows on sites like Google.
        config.websiteDataStore = .default()

        // Enable developer extras (DevTools)
        config.preferences.setValue(true, forKey: "developerExtrasEnabled")

        // Enable JavaScript
        config.defaultWebpagePreferences.allowsContentJavaScript = true

        // Set up web view
        let webView = CmuxWebView(frame: .zero, configuration: config)
        webView.allowsBackForwardNavigationGestures = true

        // Match the empty-page background to the window so newly-created browsers
        // don't flash white before content loads.
        webView.underPageBackgroundColor = .windowBackgroundColor

        // Always present as Safari.
        webView.customUserAgent = BrowserUserAgentSettings.safariUserAgent

        self.webView = webView

        // Set up navigation delegate
        let navDelegate = BrowserNavigationDelegate()
        navDelegate.didFinish = { webView in
            BrowserHistoryStore.shared.recordVisit(url: webView.url, title: webView.title)
            Task { @MainActor [weak self] in
                self?.refreshFavicon(from: webView)
            }
        }
        navDelegate.didFailNavigation = { [weak self] _, failedURL in
            Task { @MainActor in
                guard let self else { return }
                // Clear stale title/favicon from the previous page so the tab
                // shows the failed URL instead of the old page's branding.
                self.pageTitle = failedURL.isEmpty ? "" : failedURL
                self.faviconPNGData = nil
                self.lastFaviconURLString = nil
            }
        }
        navDelegate.openInNewTab = { [weak self] url in
            self?.openLinkInNewTab(url: url)
        }
        webView.navigationDelegate = navDelegate
        self.navigationDelegate = navDelegate

        // Set up UI delegate (handles cmd+click, target=_blank, and context menu)
        let browserUIDelegate = BrowserUIDelegate()
        browserUIDelegate.openInNewTab = { [weak self] url in
            guard let self else { return }
            self.openLinkInNewTab(url: url)
        }
        webView.uiDelegate = browserUIDelegate
        self.uiDelegate = browserUIDelegate

        // Observe web view properties
        setupObservers()

        // Navigate to initial URL if provided
        if let url = initialURL {
            navigate(to: url)
        }
    }

    func updateWorkspaceId(_ newWorkspaceId: UUID) {
        workspaceId = newWorkspaceId
    }

    func triggerFlash() {
        focusFlashToken &+= 1
    }

    private func setupObservers() {
        // URL changes
        let urlObserver = webView.observe(\.url, options: [.new]) { [weak self] webView, _ in
            Task { @MainActor in
                self?.currentURL = webView.url
            }
        }
        webViewObservers.append(urlObserver)

        // Title changes
        let titleObserver = webView.observe(\.title, options: [.new]) { [weak self] webView, _ in
            Task { @MainActor in
                // Keep showing the last non-empty title while the new navigation is loading.
                // WebKit often clears title to nil/"" during reload/navigation, which causes
                // a distracting tab-title flash (e.g. to host/URL). Only accept non-empty titles.
                let trimmed = (webView.title ?? "").trimmingCharacters(in: .whitespacesAndNewlines)
                guard !trimmed.isEmpty else { return }
                self?.pageTitle = trimmed
            }
        }
        webViewObservers.append(titleObserver)

        // Loading state
        let loadingObserver = webView.observe(\.isLoading, options: [.new]) { [weak self] webView, _ in
            Task { @MainActor in
                self?.handleWebViewLoadingChanged(webView.isLoading)
            }
        }
        webViewObservers.append(loadingObserver)

        // Can go back
        let backObserver = webView.observe(\.canGoBack, options: [.new]) { [weak self] webView, _ in
            Task { @MainActor in
                self?.canGoBack = webView.canGoBack
            }
        }
        webViewObservers.append(backObserver)

        // Can go forward
        let forwardObserver = webView.observe(\.canGoForward, options: [.new]) { [weak self] webView, _ in
            Task { @MainActor in
                self?.canGoForward = webView.canGoForward
            }
        }
        webViewObservers.append(forwardObserver)

        // Progress
        let progressObserver = webView.observe(\.estimatedProgress, options: [.new]) { [weak self] webView, _ in
            Task { @MainActor in
                self?.estimatedProgress = webView.estimatedProgress
            }
        }
        webViewObservers.append(progressObserver)
    }

    // MARK: - Panel Protocol

    func focus() {
        if shouldSuppressWebViewFocus() {
            return
        }

        guard let window = webView.window, !webView.isHiddenOrHasHiddenAncestor else { return }

        // If nothing meaningful is loaded yet, prefer letting the omnibar take focus.
        if !webView.isLoading {
            let urlString = webView.url?.absoluteString ?? currentURL?.absoluteString
            if urlString == nil || urlString == "about:blank" {
                return
            }
        }

        if Self.responderChainContains(window.firstResponder, target: webView) {
            return
        }
        window.makeFirstResponder(webView)
    }

    func unfocus() {
        guard let window = webView.window else { return }
        if Self.responderChainContains(window.firstResponder, target: webView) {
            window.makeFirstResponder(nil)
        }
    }

    func close() {
        // Ensure we don't keep a hidden WKWebView (or its content view) as first responder while
        // bonsplit/SwiftUI reshuffles views during close.
        unfocus()
        webView.stopLoading()
        webView.navigationDelegate = nil
        webView.uiDelegate = nil
        navigationDelegate = nil
        uiDelegate = nil
        webViewObservers.removeAll()
        faviconTask?.cancel()
        faviconTask = nil
    }

    private func refreshFavicon(from webView: WKWebView) {
        faviconTask?.cancel()
        faviconTask = nil

        guard let pageURL = webView.url else { return }
        guard let scheme = pageURL.scheme?.lowercased(), scheme == "http" || scheme == "https" else { return }

        faviconTask = Task { @MainActor [weak self, weak webView] in
            guard let self, let webView else { return }

            // Try to discover the best icon URL from the document.
            let js = """
            (() => {
              const links = Array.from(document.querySelectorAll(
                'link[rel~=\"icon\"], link[rel=\"shortcut icon\"], link[rel=\"apple-touch-icon\"], link[rel=\"apple-touch-icon-precomposed\"]'
              ));
              function score(link) {
                const v = (link.sizes && link.sizes.value) ? link.sizes.value : '';
                if (v === 'any') return 1000;
                let max = 0;
                for (const part of v.split(/\\s+/)) {
                  const m = part.match(/(\\d+)x(\\d+)/);
                  if (!m) continue;
                  const a = parseInt(m[1], 10);
                  const b = parseInt(m[2], 10);
                  if (Number.isFinite(a)) max = Math.max(max, a);
                  if (Number.isFinite(b)) max = Math.max(max, b);
                }
                return max;
              }
              links.sort((a, b) => score(b) - score(a));
              return links[0]?.href || '';
            })();
            """

            var discoveredURL: URL?
            if let href = try? await webView.evaluateJavaScript(js) as? String {
                let trimmed = href.trimmingCharacters(in: .whitespacesAndNewlines)
                if !trimmed.isEmpty, let u = URL(string: trimmed) {
                    discoveredURL = u
                }
            }

            let fallbackURL = URL(string: "/favicon.ico", relativeTo: pageURL)
            let iconURL = discoveredURL ?? fallbackURL
            guard let iconURL else { return }

            // Avoid repeated fetches.
            let iconURLString = iconURL.absoluteString
            if iconURLString == lastFaviconURLString, faviconPNGData != nil {
                return
            }
            lastFaviconURLString = iconURLString

            var req = URLRequest(url: iconURL)
            req.timeoutInterval = 2.0
            req.cachePolicy = .returnCacheDataElseLoad
            req.setValue(BrowserUserAgentSettings.safariUserAgent, forHTTPHeaderField: "User-Agent")

            let data: Data
            let response: URLResponse
            do {
                (data, response) = try await URLSession.shared.data(for: req)
            } catch {
                return
            }

            guard let http = response as? HTTPURLResponse,
                  (200..<300).contains(http.statusCode) else {
                return
            }

            // Use >= 2x the rendered point size so we don't upscale (blurry) on Retina.
            guard let png = Self.makeFaviconPNGData(from: data, targetPx: 32) else { return }
            // Only update if we got a real icon; keep the old one otherwise to avoid flashes.
            faviconPNGData = png
        }
    }

    @MainActor
    private static func makeFaviconPNGData(from raw: Data, targetPx: Int) -> Data? {
        guard let image = NSImage(data: raw) else { return nil }

        let px = max(16, min(128, targetPx))
        let size = NSSize(width: px, height: px)
        guard let rep = NSBitmapImageRep(
            bitmapDataPlanes: nil,
            pixelsWide: px,
            pixelsHigh: px,
            bitsPerSample: 8,
            samplesPerPixel: 4,
            hasAlpha: true,
            isPlanar: false,
            colorSpaceName: .deviceRGB,
            bytesPerRow: 0,
            bitsPerPixel: 0
        ) else {
            return nil
        }

        NSGraphicsContext.saveGraphicsState()
        defer { NSGraphicsContext.restoreGraphicsState() }
        let ctx = NSGraphicsContext(bitmapImageRep: rep)
        ctx?.imageInterpolation = .high
        ctx?.shouldAntialias = true
        NSGraphicsContext.current = ctx

        NSColor.clear.setFill()
        NSRect(origin: .zero, size: size).fill()

        // Aspect-fit into the target square.
        let srcSize = image.size
        let scale = min(size.width / max(1, srcSize.width), size.height / max(1, srcSize.height))
        let drawSize = NSSize(width: srcSize.width * scale, height: srcSize.height * scale)
        let drawOrigin = NSPoint(x: (size.width - drawSize.width) / 2.0, y: (size.height - drawSize.height) / 2.0)
        // Align to integral pixels to avoid soft edges at small sizes.
        let drawRect = NSRect(
            x: round(drawOrigin.x),
            y: round(drawOrigin.y),
            width: round(drawSize.width),
            height: round(drawSize.height)
        )

        image.draw(
            in: drawRect,
            from: NSRect(origin: .zero, size: srcSize),
            operation: .sourceOver,
            fraction: 1.0,
            respectFlipped: true,
            hints: [.interpolation: NSImageInterpolation.high]
        )

        return rep.representation(using: .png, properties: [:])
    }

    private func handleWebViewLoadingChanged(_ newValue: Bool) {
        if newValue {
            loadingGeneration &+= 1
            loadingEndWorkItem?.cancel()
            loadingEndWorkItem = nil
            loadingStartedAt = Date()
            isLoading = true
            return
        }

        let genAtEnd = loadingGeneration
        let startedAt = loadingStartedAt ?? Date()
        let elapsed = Date().timeIntervalSince(startedAt)
        let remaining = max(0, minLoadingIndicatorDuration - elapsed)

        loadingEndWorkItem?.cancel()
        loadingEndWorkItem = nil

        if remaining <= 0.0001 {
            isLoading = false
            return
        }

        let work = DispatchWorkItem { [weak self] in
            guard let self else { return }
            // If loading restarted, ignore this end.
            guard self.loadingGeneration == genAtEnd else { return }
            // If WebKit is still loading, ignore.
            guard !self.webView.isLoading else { return }
            self.isLoading = false
        }
        loadingEndWorkItem = work
        DispatchQueue.main.asyncAfter(deadline: .now() + remaining, execute: work)
    }

    // MARK: - Navigation

    /// Navigate to a URL
    func navigate(to url: URL) {
        // Some installs can end up with a legacy Chrome UA override; keep this pinned.
        webView.customUserAgent = BrowserUserAgentSettings.safariUserAgent
        navigationDelegate?.lastAttemptedURL = url
        var request = URLRequest(url: url)
        // Behave like a normal browser (respect HTTP caching). Reload is handled separately.
        request.cachePolicy = .useProtocolCachePolicy
        webView.load(request)
    }

    /// Navigate with smart URL/search detection
    /// - If input looks like a URL, navigate to it
    /// - Otherwise, perform a web search
    func navigateSmart(_ input: String) {
        let trimmed = input.trimmingCharacters(in: .whitespacesAndNewlines)
        guard !trimmed.isEmpty else { return }

        if let url = resolveNavigableURL(from: trimmed) {
            BrowserHistoryStore.shared.recordTypedNavigation(url: url)
            navigate(to: url)
            return
        }

        let engine = BrowserSearchSettings.currentSearchEngine()
        guard let searchURL = engine.searchURL(query: trimmed) else { return }
        navigate(to: searchURL)
    }

    func resolveNavigableURL(from input: String) -> URL? {
        resolveBrowserNavigableURL(input)
    }

    deinit {
        webViewObservers.removeAll()
    }
}

func resolveBrowserNavigableURL(_ input: String) -> URL? {
    let trimmed = input.trimmingCharacters(in: .whitespacesAndNewlines)
    guard !trimmed.isEmpty else { return nil }
    guard !trimmed.contains(" ") else { return nil }

    // Check localhost/loopback before generic URL parsing because
    // URL(string: "localhost:3777") treats "localhost" as a scheme.
    let lower = trimmed.lowercased()
    if lower.hasPrefix("localhost") || lower.hasPrefix("127.0.0.1") || lower.hasPrefix("[::1]") {
        return URL(string: "http://\(trimmed)")
    }

    if let url = URL(string: trimmed), let scheme = url.scheme?.lowercased() {
        if scheme == "http" || scheme == "https" {
            return url
        }
        return nil
    }

    if trimmed.contains(":") || trimmed.contains("/") {
        return URL(string: "https://\(trimmed)")
    }

    if trimmed.contains(".") {
        return URL(string: "https://\(trimmed)")
    }

    return nil
}

extension BrowserPanel {

    /// Go back in history
    func goBack() {
        guard canGoBack else { return }
        webView.goBack()
    }

    /// Go forward in history
    func goForward() {
        guard canGoForward else { return }
        webView.goForward()
    }

    /// Open a link in a new browser surface in the same pane
    func openLinkInNewTab(url: URL) {
        guard let tabManager = AppDelegate.shared?.tabManager,
              let workspace = tabManager.tabs.first(where: { $0.id == workspaceId }),
              let paneId = workspace.paneId(forPanelId: id) else { return }
        workspace.newBrowserSurface(inPane: paneId, url: url, focus: true)
    }

    /// Reload the current page
    func reload() {
        webView.customUserAgent = BrowserUserAgentSettings.safariUserAgent
        webView.reload()
    }

    /// Stop loading
    func stopLoading() {
        webView.stopLoading()
    }

    @discardableResult
    func zoomIn() -> Bool {
        applyPageZoom(webView.pageZoom + pageZoomStep)
    }

    @discardableResult
    func zoomOut() -> Bool {
        applyPageZoom(webView.pageZoom - pageZoomStep)
    }

    @discardableResult
    func resetZoom() -> Bool {
        applyPageZoom(1.0)
    }

    /// Take a snapshot of the web view
    func takeSnapshot(completion: @escaping (NSImage?) -> Void) {
        let config = WKSnapshotConfiguration()
        webView.takeSnapshot(with: config) { image, error in
            if let error = error {
                NSLog("BrowserPanel snapshot error: %@", error.localizedDescription)
                completion(nil)
                return
            }
            completion(image)
        }
    }

    /// Execute JavaScript
    func evaluateJavaScript(_ script: String) async throws -> Any? {
        try await webView.evaluateJavaScript(script)
    }

    func suppressOmnibarAutofocus(for seconds: TimeInterval) {
        suppressOmnibarAutofocusUntil = Date().addingTimeInterval(seconds)
    }

    func suppressWebViewFocus(for seconds: TimeInterval) {
        suppressWebViewFocusUntil = Date().addingTimeInterval(seconds)
    }

    func clearWebViewFocusSuppression() {
        suppressWebViewFocusUntil = nil
    }

    func shouldSuppressOmnibarAutofocus() -> Bool {
        if let until = suppressOmnibarAutofocusUntil {
            return Date() < until
        }
        return false
    }

    func shouldSuppressWebViewFocus() -> Bool {
        if suppressWebViewFocusForAddressBar {
            return true
        }
        if let until = suppressWebViewFocusUntil {
            return Date() < until
        }
        return false
    }

    func beginSuppressWebViewFocusForAddressBar() {
        suppressWebViewFocusForAddressBar = true
    }

    func endSuppressWebViewFocusForAddressBar() {
        suppressWebViewFocusForAddressBar = false
    }

    /// Returns the most reliable URL string for omnibar-related matching and UI decisions.
    /// `currentURL` can lag behind navigation changes, so prefer the live WKWebView URL.
    func preferredURLStringForOmnibar() -> String? {
        if let webViewURL = webView.url?.absoluteString
            .trimmingCharacters(in: .whitespacesAndNewlines),
           !webViewURL.isEmpty,
           webViewURL != blankURLString {
            return webViewURL
        }

        if let current = currentURL?.absoluteString
            .trimmingCharacters(in: .whitespacesAndNewlines),
           !current.isEmpty,
           current != blankURLString {
            return current
        }

        return nil
    }

}

private extension BrowserPanel {
    @discardableResult
    func applyPageZoom(_ candidate: CGFloat) -> Bool {
        let clamped = max(minPageZoom, min(maxPageZoom, candidate))
        if abs(webView.pageZoom - clamped) < 0.0001 {
            return false
        }
        webView.pageZoom = clamped
        return true
    }

    static func responderChainContains(_ start: NSResponder?, target: NSResponder) -> Bool {
        var r = start
        var hops = 0
        while let cur = r, hops < 64 {
            if cur === target { return true }
            r = cur.nextResponder
            hops += 1
        }
        return false
    }
}

// MARK: - Navigation Delegate

private class BrowserNavigationDelegate: NSObject, WKNavigationDelegate {
    var didFinish: ((WKWebView) -> Void)?
    var didFailNavigation: ((WKWebView, String) -> Void)?
    var openInNewTab: ((URL) -> Void)?
    /// The URL of the last navigation that was attempted. Used to preserve the omnibar URL
    /// when a provisional navigation fails (e.g. connection refused on localhost:3000).
    var lastAttemptedURL: URL?

    func webView(_ webView: WKWebView, didStartProvisionalNavigation navigation: WKNavigation!) {
        lastAttemptedURL = webView.url
    }

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

    func webView(_ webView: WKWebView, didFail navigation: WKNavigation!, withError error: Error) {
        NSLog("BrowserPanel navigation failed: %@", error.localizedDescription)
    }

    func webView(_ webView: WKWebView, didFailProvisionalNavigation navigation: WKNavigation!, withError error: Error) {
        let nsError = error as NSError
        NSLog("BrowserPanel provisional navigation failed: %@", error.localizedDescription)

        // Cancelled navigations (e.g. rapid typing) are not real errors.
        if nsError.domain == NSURLErrorDomain, nsError.code == NSURLErrorCancelled {
            return
        }

        let failedURL = nsError.userInfo[NSURLErrorFailingURLStringErrorKey] as? String
            ?? lastAttemptedURL?.absoluteString
            ?? ""
        didFailNavigation?(webView, failedURL)
        loadErrorPage(in: webView, failedURL: failedURL, error: nsError)
    }

    func webView(_ webView: WKWebView, webContentProcessDidTerminate: WKWebView) {
        NSLog("BrowserPanel web content process terminated, reloading")
        webView.reload()
    }

    private func loadErrorPage(in webView: WKWebView, failedURL: String, error: NSError) {
        let title: String
        let message: String

        switch (error.domain, error.code) {
        case (NSURLErrorDomain, NSURLErrorCannotConnectToHost),
             (NSURLErrorDomain, NSURLErrorCannotFindHost),
             (NSURLErrorDomain, NSURLErrorTimedOut):
            title = "Can\u{2019}t reach this page"
            message = "\(failedURL.isEmpty ? "The site" : failedURL) refused to connect. Check that a server is running on this address."
        case (NSURLErrorDomain, NSURLErrorNotConnectedToInternet),
             (NSURLErrorDomain, NSURLErrorNetworkConnectionLost):
            title = "No internet connection"
            message = "Check your network connection and try again."
        case (NSURLErrorDomain, NSURLErrorSecureConnectionFailed),
             (NSURLErrorDomain, NSURLErrorServerCertificateUntrusted),
             (NSURLErrorDomain, NSURLErrorServerCertificateHasUnknownRoot),
             (NSURLErrorDomain, NSURLErrorServerCertificateHasBadDate),
             (NSURLErrorDomain, NSURLErrorServerCertificateNotYetValid):
            title = "Connection isn\u{2019}t secure"
            message = "The certificate for this site is invalid."
        default:
            title = "Can\u{2019}t open this page"
            message = error.localizedDescription
        }

        let escapedURL = failedURL
            .replacingOccurrences(of: "&", with: "&amp;")
            .replacingOccurrences(of: "<", with: "&lt;")
            .replacingOccurrences(of: ">", with: "&gt;")
            .replacingOccurrences(of: "\"", with: "&quot;")

        let html = """
        <!DOCTYPE html>
        <html>
        <head>
        <meta charset="utf-8">
        <meta name="viewport" content="width=device-width">
        <style>
        body {
            font-family: -apple-system, BlinkMacSystemFont, sans-serif;
            display: flex; align-items: center; justify-content: center;
            min-height: 80vh; margin: 0; padding: 20px;
            background: #1a1a1a; color: #e0e0e0;
        }
        .container { text-align: center; max-width: 420px; }
        h1 { font-size: 18px; font-weight: 600; margin-bottom: 8px; }
        p { font-size: 13px; color: #999; line-height: 1.5; }
        .url { font-size: 12px; color: #666; word-break: break-all; margin-top: 16px; }
        button {
            margin-top: 20px; padding: 6px 20px;
            background: #333; color: #e0e0e0; border: 1px solid #555;
            border-radius: 6px; font-size: 13px; cursor: pointer;
        }
        button:hover { background: #444; }
        @media (prefers-color-scheme: light) {
            body { background: #fafafa; color: #222; }
            p { color: #666; }
            .url { color: #999; }
            button { background: #eee; color: #222; border-color: #ccc; }
            button:hover { background: #ddd; }
        }
        </style>
        </head>
        <body>
        <div class="container">
            <h1>\(title)</h1>
            <p>\(message)</p>
            <div class="url">\(escapedURL)</div>
            <button onclick="location.reload()">Reload</button>
        </div>
        </body>
        </html>
        """
        webView.loadHTMLString(html, baseURL: URL(string: failedURL))
    }

    func webView(
        _ webView: WKWebView,
        decidePolicyFor navigationAction: WKNavigationAction,
        decisionHandler: @escaping (WKNavigationActionPolicy) -> Void
    ) {
        // target=_blank or window.open() — open in a new tab instead of a new window
        if navigationAction.targetFrame == nil,
           let url = navigationAction.request.url {
            openInNewTab?(url)
            decisionHandler(.cancel)
            return
        }

        // Cmd+click on a regular link — open in a new tab
        if navigationAction.navigationType == .linkActivated,
           navigationAction.modifierFlags.contains(.command),
           let url = navigationAction.request.url {
            openInNewTab?(url)
            decisionHandler(.cancel)
            return
        }

        decisionHandler(.allow)
    }
}

// MARK: - UI Delegate

private class BrowserUIDelegate: NSObject, WKUIDelegate {
    var openInNewTab: ((URL) -> Void)?

    /// Handle cmd+click / target=_blank links. Returning nil tells WebKit not to open a new window;
    /// instead we open the URL as a new surface in the same pane.
    func webView(
        _ webView: WKWebView,
        createWebViewWith configuration: WKWebViewConfiguration,
        for navigationAction: WKNavigationAction,
        windowFeatures: WKWindowFeatures
    ) -> WKWebView? {
        if let url = navigationAction.request.url {
            openInNewTab?(url)
        }
        return nil
    }
}