import Flutter
import UIKit

#if canImport(Valhalla)
import Valhalla
import ValhallaConfigModels
#endif

/// ============================================================================
/// [ValhallaBridge] - جسر التوجيه المحلي لمحرك Valhalla على iOS
/// ============================================================================
/// English:
/// Swift bridge connecting Flutter's MethodChannel (intaleq_tactical/valhalla)
/// to the native Valhalla offline routing engine on iOS.
/// The Jordan tile extract (valhalla_tiles.tar) downloaded by
/// OfflineRoutingPackageService into <Documents>/routing/jordan is opened by
/// the C++ engine through ValhallaConfig(tileExtractTar:), and every route
/// request runs 100% on-device with zero network usage.
///
/// العربية:
/// جسر سويفت يربط قناة فلاتر بمحرك Valhalla الأصلي على iOS. يفتح المحرك ملف
/// غراف طرق الأردن المنزّل من مجلد الحزمة ويحسب المسارات محلياً بالكامل مع
/// ارتفاعات SRTM وأسماء الشوارع الحقيقية وتعليمات انعطاف عربية.
/// ============================================================================
class ValhallaBridge: NSObject {
    static let channelName = "intaleq_tactical/valhalla"

    /// Serial queue guarding engine lifecycle + routing calls (C++ actor is not thread-safe).
    private let engineQueue = DispatchQueue(label: "com.intaleq.tactical.valhalla")

#if canImport(Valhalla)
    private var engine: Valhalla?
    private var engineDir: String?
#endif

    func register(with messenger: FlutterBinaryMessenger) {
        let channel = FlutterMethodChannel(name: ValhallaBridge.channelName, binaryMessenger: messenger)
        channel.setMethodCallHandler { [weak self] (call: FlutterMethodCall, result: @escaping FlutterResult) in
            guard let self = self else { return }
            switch call.method {
            case "ensureReady":
                let args = call.arguments as? [String: Any]
                let regionDir = args?["regionDir"] as? String
                self.handleEnsureReady(regionDirPath: regionDir, result: result)

            case "route":
                let args = call.arguments as? [String: Any]
                guard let requestJson = args?["request"] as? String else {
                    result(FlutterError(code: "BAD_ARGS", message: "Missing request JSON", details: nil))
                    return
                }
                self.handleRoute(requestJson: requestJson, result: result)

            case "release":
                self.releaseEngine()
                result(true)

            default:
                result(FlutterMethodNotImplemented)
            }
        }
    }

    // MARK: - ensureReady

    private func handleEnsureReady(regionDirPath: String?, result: @escaping FlutterResult) {
        let dir = Self.resolveRegionDir(regionDirPath)
        let tarPath = Self.findTar(named: "valhalla_tiles.tar", in: dir)?.path

        guard let tarPath = tarPath else {
            result(FlutterError(
                code: "DIR_NOT_FOUND",
                message: "Routing package not installed at \(dir.path) — download it from the server while online",
                details: nil))
            return
        }

#if canImport(Valhalla)
        engineQueue.async { [weak self] in
            guard let self = self else { return }
            // إعادة الاستخدام إن كان المحرك مبنياً على نفس الحزمة
            if let engine = self.engine, self.engineDir == dir.path {
                result(true)
                return
            }
            self.releaseEngineLocked()

            do {
                let config = try ValhallaConfig(tileExtractTar: URL(fileURLWithPath: tarPath))
                self.engine = try Valhalla(config)
                self.engineDir = dir.path
                NSLog("[ValhallaBridge] engine ready against \(tarPath)")
                DispatchQueue.main.async { result(true) }
            } catch {
                NSLog("[ValhallaBridge] engine init failed: \(error)")
                DispatchQueue.main.async {
                    result(FlutterError(code: "ENGINE_INIT_FAILED",
                                        message: "\(error)",
                                        details: nil))
                }
            }
        }
#else
        result(FlutterError(
            code: "FALLBACK_SYNTHETIC",
            message: "Valhalla SPM package is not linked into this build target",
            details: nil))
#endif
    }

    // MARK: - route

    private func handleRoute(requestJson: String, result: @escaping FlutterResult) {
#if canImport(Valhalla)
        engineQueue.async { [weak self] in
            guard let self = self, let engine = self.engine else {
                DispatchQueue.main.async {
                    result(FlutterError(code: "NOT_READY",
                                        message: "Call ensureReady before route",
                                        details: nil))
                }
                return
            }

            // route(rawRequest:) يعيد JSON خاماً؛ أخطاء المحرك تعود داخل الجسم
            // بصيغة {"code": int, "message": str} ويفكّها طرف Dart مباشرة.
            let rawResponse = engine.route(rawRequest: requestJson)
            DispatchQueue.main.async { result(rawResponse) }
        }
#else
        result(FlutterError(
            code: "FALLBACK_SYNTHETIC",
            message: "Valhalla SPM package is not linked into this build target",
            details: nil))
#endif
    }

    // MARK: - release

    func releaseEngine() {
#if canImport(Valhalla)
        engineQueue.async { [weak self] in
            self?.releaseEngineLocked()
        }
#else
        // no-op
#endif
    }

#if canImport(Valhalla)
    /// Must be called on engineQueue.
    private func releaseEngineLocked() {
        engine = nil
        engineDir = nil
    }
#endif

    // MARK: - Helpers

    private static func resolveRegionDir(_ regionDirPath: String?) -> URL {
        if let path = regionDirPath {
            return URL(fileURLWithPath: path, isDirectory: true)
        }
        let docs = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
        return docs.appendingPathComponent("routing/jordan", isDirectory: true)
    }

    /// بحث تكراري عن ملف الغراف داخل مجلد الحزمة (البنية قد تختلف بين الإصدارات)
    private static func findTar(named name: String, in dir: URL) -> URL? {
        let fm = FileManager.default
        var isDir: ObjCBool = false
        guard fm.fileExists(atPath: dir.path, isDirectory: &isDir), isDir.boolValue else {
            return nil
        }
        if fm.fileExists(atPath: dir.appendingPathComponent(name).path) {
            return dir.appendingPathComponent(name)
        }
        guard let children = try? fm.contentsOfDirectory(at: dir, includingPropertiesForKeys: [.isDirectoryKey]) else {
            return nil
        }
        for child in children {
            let isChildDir = (try? child.resourceValues(forKeys: [.isDirectoryKey]))?.isDirectory ?? false
            if isChildDir, let found = findTar(named: name, in: child) {
                return found
            }
        }
        return nil
    }
}