import Foundation
import Logging
#if !os(macOS)
    import CoreMedia
    import Siesta
    import UIKit
#endif

final class MPVClient: ObservableObject {
    private var logger = Logger(label: "mpv-client")

    var mpv: OpaquePointer!
    var mpvGL: OpaquePointer!
    var queue: DispatchQueue!
    var glView: MPVOGLView!
    var backend: MPVBackend!

    func create(frame: CGRect) -> MPVOGLView {
        glView = MPVOGLView(frame: frame)

        mpv = mpv_create()
        if mpv == nil {
            print("failed creating context\n")
            exit(1)
        }

        checkError(mpv_request_log_messages(mpv, "warn"))
        checkError(mpv_initialize(mpv))
        checkError(mpv_set_option_string(mpv, "vo", "libmpv"))
        checkError(mpv_set_option_string(mpv, "hwdec", "yes"))

        checkError(mpv_set_option_string(mpv, "override-display-fps", "\(UIScreen.main.maximumFramesPerSecond)"))
        checkError(mpv_set_option_string(mpv, "video-sync", "display-resample"))

        let api = UnsafeMutableRawPointer(mutating: (MPV_RENDER_API_TYPE_OPENGL as NSString).utf8String)
        var initParams = mpv_opengl_init_params(
            get_proc_address: getProcAddress(_:_:),
            get_proc_address_ctx: nil,
            extra_exts: nil
        )

        withUnsafeMutablePointer(to: &initParams) { initParams in
            var params = [
                mpv_render_param(type: MPV_RENDER_PARAM_API_TYPE, data: api),
                mpv_render_param(type: MPV_RENDER_PARAM_OPENGL_INIT_PARAMS, data: initParams),
                mpv_render_param()
            ]

            var mpvGL: OpaquePointer?

            if mpv_render_context_create(&mpvGL, mpv, &params) < 0 {
                puts("failed to initialize mpv GL context")
                exit(1)
            }

            glView.mpvGL = UnsafeMutableRawPointer(mpvGL)

            mpv_render_context_set_update_callback(
                mpvGL,
                glUpdate(_:),
                UnsafeMutableRawPointer(Unmanaged.passUnretained(glView).toOpaque())
            )
        }

        queue = DispatchQueue(label: "mpv", qos: .background)
        queue!.async {
            mpv_set_wakeup_callback(self.mpv, wakeUp, UnsafeMutableRawPointer(Unmanaged.passUnretained(self).toOpaque()))
        }

        return glView
    }

    func readEvents() {
        queue?.async { [self] in
            while self.mpv != nil {
                let event = mpv_wait_event(self.mpv, 0)
                if event!.pointee.event_id == MPV_EVENT_NONE {
                    break
                }
                backend.handle(event)
            }
        }
    }

    func loadFile(_ url: URL, time: CMTime? = nil, completionHandler: ((Int32) -> Void)? = nil) {
        var args = [url.absoluteString]
        if let time = time {
            args.append("replace")
            args.append("start=\(Int(time.seconds))")
        }

        command("loadfile", args: args, returnValueCallback: completionHandler)
    }

    func addAudio(_ url: URL, completionHandler: ((Int32) -> Void)? = nil) {
        command("audio-add", args: [url.absoluteString], returnValueCallback: completionHandler)
    }

    func play() {
        setFlagAsync("pause", false)
    }

    func pause() {
        setFlagAsync("pause", true)
    }

    func togglePlay() {
        command("cycle", args: ["pause"])
    }

    func stop() {
        command("stop")
    }

    var currentTime: CMTime {
        CMTime.secondsInDefaultTimescale(getDouble("time-pos"))
    }

    var duration: CMTime {
        CMTime.secondsInDefaultTimescale(getDouble("duration"))
    }

    func seek(relative time: CMTime, completionHandler: ((Bool) -> Void)? = nil) {
        command("seek", args: [String(time.seconds)]) { _ in
            completionHandler?(true)
        }
    }

    func seek(to time: CMTime, completionHandler: ((Bool) -> Void)? = nil) {
        command("seek", args: [String(time.seconds), "absolute"]) { _ in
            completionHandler?(true)
        }
    }

    func setSize(_ width: Double, _ height: Double) {
        logger.info("setting player size to \(width),\(height)")
        #if !os(macOS)
            guard width <= UIScreen.main.bounds.width, height <= UIScreen.main.bounds.height else {
                logger.info("requested size is greater than screen size, ignoring")
                return
            }
        #endif

        glView?.frame = CGRect(x: 0, y: 0, width: width, height: height)
    }

    func setNeedsDrawing(_ needsDrawing: Bool) {
        logger.info("needs drawing: \(needsDrawing)")
        glView.needsDrawing = needsDrawing
    }

    func command(
        _ command: String,
        args: [String?] = [],
        checkForErrors: Bool = true,
        returnValueCallback: ((Int32) -> Void)? = nil
    ) {
        guard mpv != nil else {
            return
        }
        var cargs = makeCArgs(command, args).map { $0.flatMap { UnsafePointer<CChar>(strdup($0)) } }
        defer {
            for ptr in cargs where ptr != nil {
                free(UnsafeMutablePointer(mutating: ptr!))
            }
        }
        logger.info("\(command) -- \(args)")
        let returnValue = mpv_command(mpv, &cargs)
        if checkForErrors {
            checkError(returnValue)
        }
        if let cb = returnValueCallback {
            cb(returnValue)
        }
    }

    private func setFlagAsync(_ name: String, _ flag: Bool) {
        var data: Int = flag ? 1 : 0
        mpv_set_property_async(mpv, 0, name, MPV_FORMAT_FLAG, &data)
    }

    private func getDouble(_ name: String) -> Double {
        var data = Double()
        mpv_get_property(mpv, name, MPV_FORMAT_DOUBLE, &data)
        return data
    }

    private func makeCArgs(_ command: String, _ args: [String?]) -> [String?] {
        if !args.isEmpty, args.last == nil {
            fatalError("Command do not need a nil suffix")
        }

        var strArgs = args
        strArgs.insert(command, at: 0)
        strArgs.append(nil)

        return strArgs
    }

    func checkError(_ status: CInt) {
        if status < 0 {
            logger.error(.init(stringLiteral: "MPV API error: \(String(cString: mpv_error_string(status)))\n"))
        }
    }
}

private func getProcAddress(_: UnsafeMutableRawPointer?, _ name: UnsafePointer<Int8>?) -> UnsafeMutableRawPointer? {
    let symbolName = CFStringCreateWithCString(kCFAllocatorDefault, name, CFStringBuiltInEncodings.ASCII.rawValue)
    let addr = CFBundleGetFunctionPointerForName(CFBundleGetBundleWithIdentifier("com.apple.opengles" as CFString), symbolName)

    return addr
}

private func glUpdate(_ ctx: UnsafeMutableRawPointer?) {
    let glView = unsafeBitCast(ctx, to: MPVOGLView.self)

    guard glView.needsDrawing else {
        return
    }

    DispatchQueue.main.async {
        glView.setNeedsDisplay()
    }
}

private func wakeUp(_ context: UnsafeMutableRawPointer?) {
    let client = unsafeBitCast(context, to: MPVClient.self)
    client.readEvents()
}