import Foundation
import MusubiCore
import Observation
import Remote

/// Ties outputs, audio, scenes and remote control together according to the role.
@MainActor @Observable
final class Coordinator {
    let settings: AppSettings
    let outputs: OutputController
    let audio: AudioController
    let store = SceneStore()

    private(set) var live = LiveState()
    private(set) var nodeServer: NodeServer?
    private(set) var browser: NodeBrowser?

    private var statusTimer: Timer?
    private var cpu = ProcessCPU()
    private var restoring = false

    init(settings: AppSettings, outputs: OutputController, audio: AudioController) {
        self.settings = settings
        self.outputs = outputs
        self.audio = audio
    }

    /// Restores the last live state, starts remote control, then applies launch arguments.
    func start() async {
        live = store.loadLiveState()
        restoring = true
        outputs.apply(live.local.video)
        audio.apply(live.local.audio)
        restoring = false
        Log.ndi.info("Restored \(self.live.sceneName ?? "live state", privacy: .public): \(self.live.local.video.count) video, \(self.live.local.audio.count) audio")

        outputs.onChange = { [weak self] in self?.localChanged() }
        audio.onChange = { [weak self] in self?.localChanged() }
        await startRemote()

        outputs.applyLaunchRoutes()
        audio.applyLaunchRoutes()
        applyLoginItemArgument()
        if let index = ProcessInfo.processInfo.arguments.firstIndex(of: "--load-scene"),
           index + 1 < ProcessInfo.processInfo.arguments.count {
            let name = ProcessInfo.processInfo.arguments[index + 1]
            if let scene = store.scenes.first(where: { $0.name == name }) { loadScene(scene) }
            else { Log.remote.error("--load-scene: no scene named \(name, privacy: .public)") }
        }

        statusTimer = Timer.scheduledTimer(withTimeInterval: 1, repeats: true) { [weak self] _ in
            MainActor.assumeIsolated { self?.sendStatus() }
        }
    }

    /// `--login-item on|off`: set up a headless node over SSH, where the settings window is hidden behind outputs.
    private func applyLoginItemArgument(_ arguments: [String] = ProcessInfo.processInfo.arguments) {
        guard let index = arguments.firstIndex(of: "--login-item"), index + 1 < arguments.count else { return }
        settings.launchAtLogin = arguments[index + 1] == "on"
        Log.ndi.info("Launch at login: \(self.settings.launchAtLogin ? "on" : "off", privacy: .public)")
    }

    /// (Re)starts the Bonjour side that fits the role; call after role or interface changes.
    func startRemote() async {
        nodeServer?.stop()
        nodeServer = nil
        browser?.stop()
        browser = nil

        switch settings.role {
        case .node:
            let server = NodeServer(name: settings.machineName)
            server.onCommand = { [weak self] in self?.handle($0) }
            nodeServer = server
            await server.start(interfaceName: settings.interfaceName)
        case .control:
            let browser = NodeBrowser(name: settings.machineName)
            browser.onNodeConnected = { [weak self] in self?.nodeConnected($0) }
            self.browser = browser
            await browser.start(interfaceName: settings.interfaceName)
        }
    }

    var remoteError: String? { nodeServer?.error ?? browser?.error }

    // MARK: - Control: nodes

    /// Shows a source on a node's screen.
    func show(_ assignment: VideoAssignment, onNode name: String) {
        Log.remote.info("UI: show \(assignment.source.ndiName, privacy: .public) on \(name, privacy: .public)/\(assignment.screen.name, privacy: .public)")
        var config = desiredConfig(forNode: name)
        config.video.removeAll { $0.screen == assignment.screen }
        config.video.append(assignment)
        live.nodes[name] = config
        browser?.node(named: name)?.send(.show(assignment))
        markModified()
    }

    func stop(_ screen: ScreenRef, onNode name: String) {
        Log.remote.info("UI: stop \(name, privacy: .public)/\(screen.name, privacy: .public)")
        var config = desiredConfig(forNode: name)
        config.video.removeAll { $0.screen == screen }
        live.nodes[name] = config
        browser?.node(named: name)?.send(.stop(screen))
        markModified()
    }

    private func desiredConfig(forNode name: String) -> MachineConfig {
        live.nodes[name] ?? browser?.node(named: name)?.status?.config ?? .empty
    }

    /// A node (re)connected: it gets what the control wants, or the control adopts what the node shows.
    private func nodeConnected(_ node: NodeBrowser.Node) {
        if let desired = live.nodes[node.name] {
            node.send(.apply(desired))
            Log.remote.info("Sent configuration to \(node.name, privacy: .public): \(desired.video.count) video")
        } else {
            adoptWhenStatusArrives(node)
        }
    }

    private func adoptWhenStatusArrives(_ node: NodeBrowser.Node) {
        Task { [weak self] in
            for _ in 0..<10 {
                try? await Task.sleep(for: .seconds(1))
                guard let self, live.nodes[node.name] == nil else { return }
                if let config = node.status?.config {
                    Log.remote.info("Adopted configuration of \(node.name, privacy: .public): \(config.video.count) video")
                    live.nodes[node.name] = config
                    store.saveLiveState(live)
                    return
                }
            }
        }
    }

    // MARK: - Node: commands from the control

    private func handle(_ message: RemoteMessage) {
        Log.remote.info("Command: \(String(describing: message).prefix(200), privacy: .public)")
        switch message {
        case .apply(let config):
            outputs.apply(config.video)
            audio.apply(config.audio)
        case .show(let assignment):
            outputs.show(assignment)
        case .stop(let screen):
            outputs.stop(screen)
        case .hello, .status:
            break
        }
    }

    private func sendStatus() {
        let cpuPercent = cpu.sample()
        guard let nodeServer else { return }
        nodeServer.send(NodeStatus(
            screens: outputs.screenStatuses(),
            config: MachineConfig(video: outputs.desired, audio: audio.currentAudio()),
            cpuPercent: cpuPercent,
            sleepBlocked: outputs.isSleepBlocked
        ))
    }

    // MARK: - Scenes (control)

    var currentSceneName: String? { live.sceneName }
    var isModified: Bool { live.modified }

    func saveScene(as name: String? = nil) {
        var scene = Scene(
            id: name == nil ? (live.sceneID ?? UUID()) : UUID(),
            name: name ?? live.sceneName ?? "Szene",
            control: live.local,
            nodes: currentNodeConfigs()
        )
        if let name, let existing = store.scenes.first(where: { $0.name == name }) { scene.id = existing.id }
        store.save(scene)
        live.sceneID = scene.id
        live.sceneName = scene.name
        live.modified = false
        store.saveLiveState(live)
    }

    func loadScene(_ scene: Scene) {
        restoring = true
        outputs.apply(scene.control.video)
        audio.apply(scene.control.audio)
        restoring = false
        live = LiveState(local: scene.control, nodes: scene.nodes, sceneID: scene.id, sceneName: scene.name, modified: false)
        for (name, config) in scene.nodes {
            browser?.node(named: name)?.send(.apply(config))
        }
        store.saveLiveState(live)
        Log.ndi.info("Scene \(scene.name, privacy: .public) loaded")
    }

    func exportableScene() -> Scene {
        Scene(id: live.sceneID ?? UUID(), name: live.sceneName ?? "Szene", control: live.local, nodes: currentNodeConfigs())
    }

    private func currentNodeConfigs() -> [String: MachineConfig] {
        var nodes = live.nodes
        for node in browser?.nodes ?? [] where nodes[node.name] == nil {
            if let config = node.status?.config { nodes[node.name] = config }
        }
        return nodes
    }

    // MARK: - Live state

    private func localChanged() {
        live.local = MachineConfig(video: outputs.desired, audio: audio.currentAudio())
        guard !restoring else { return }
        markModified()
    }

    private func markModified() {
        Log.remote.debug("Live state saved: local \(self.live.local.video.count) video, nodes \(self.live.nodes.mapValues(\.video.count), privacy: .public)")
        if live.sceneID != nil { live.modified = true }
        store.saveLiveState(live)
    }
}

/// CPU usage of this process since the last sample, in percent of one core.
struct ProcessCPU {
    private var lastCPU = ProcessCPU.cpuSeconds()
    private var lastWall = ProcessInfo.processInfo.systemUptime

    mutating func sample() -> Double {
        let cpu = Self.cpuSeconds(), wall = ProcessInfo.processInfo.systemUptime
        defer { lastCPU = cpu; lastWall = wall }
        return wall > lastWall ? (cpu - lastCPU) / (wall - lastWall) * 100 : 0
    }

    static func cpuSeconds() -> Double {
        var usage = rusage()
        getrusage(RUSAGE_SELF, &usage)
        func seconds(_ t: timeval) -> Double { Double(t.tv_sec) + Double(t.tv_usec) / 1_000_000 }
        return seconds(usage.ru_utime) + seconds(usage.ru_stime)
    }
}