// SessionManager.swift — Focus session state, screenshot engine, distraction detection

import AppKit
import SwiftUI
import UserNotifications
import ScreenCaptureKit

@Observable
@MainActor
final class SessionManager {
    static let shared = SessionManager()

    // MARK: - State

    var activeSession: FocusSession?
    var activeTask: AppTask?
    var activeSteps: [Step] = []
    var currentStepIndex: Int = 0
    var isSessionActive: Bool = false
    var sessionStartDate: Date?
    var distractionCount: Int = 0
    var lastNudge: String?
    var resumeCard: ResumeCard?
    var showingResumeCard: Bool = false
    var errorMessage: String?
    var isLoading: Bool = false

    // Proactive agent
    var proactiveCard: ProactiveCard?
    /// Set when the user approves a proposed action — shown as a confirmation toast
    var approvedActionLabel: String?

    // Screenshot engine
    var isCapturing: Bool = false
    /// Live pipeline status shown in FocusSessionView (updated at each stage)
    var argusStatus: String = ""

    private var captureTask: Task<Void, Never>?
    private let captureInterval: TimeInterval = 5.0

    // Rolling screenshot history buffer (max 4 entries, ~20-second window)
    // Provides temporal context to the VLM so it can detect patterns across captures.
    private struct ScreenshotHistoryEntry {
        let summary: String   // vlm_summary text from the previous analysis
        let timestamp: Date
    }
    @ObservationIgnored private var screenshotHistory: [ScreenshotHistoryEntry] = []

    // App switch tracking
    @ObservationIgnored private var appSwitches: [(name: String, bundleId: String, time: Date)] = []
    @ObservationIgnored private var appSwitchObserver: (any NSObjectProtocol)?
    @ObservationIgnored private var lastApp: (name: String, bundleId: String) = ("", "")
    @ObservationIgnored private var lastAppEnteredAt: Date = Date()

    // Argus subprocess (device-side VLM)
    @ObservationIgnored private var argusProcess: Process?
    @ObservationIgnored private var argusReadTask: Task<Void, Never>?
    private let argusPythonPath = "/Users/joyzhuo/miniconda3/envs/gmr/bin/python3"
    private let argusRepoPath = "/Users/joyzhuo/yhack/lockinbro-argus"

    private init() {}

    // MARK: - Computed

    var currentStep: Step? {
        guard currentStepIndex < activeSteps.count else { return nil }
        return activeSteps[currentStepIndex]
    }

    var completedCount: Int { activeSteps.filter(\.isDone).count }
    var totalSteps: Int { activeSteps.count }

    var sessionElapsed: TimeInterval {
        guard let start = sessionStartDate else { return 0 }
        return Date().timeIntervalSince(start)
    }

    // MARK: - Session Lifecycle

    // Persisted so we can end a stale session after an app restart
    private var persistedSessionId: String? {
        get { UserDefaults.standard.string(forKey: "lockInBro.lastSessionId") }
        set {
            if let v = newValue { UserDefaults.standard.set(v, forKey: "lockInBro.lastSessionId") }
            else { UserDefaults.standard.removeObject(forKey: "lockInBro.lastSessionId") }
        }
    }

    func startSession(task: AppTask?) async {
        isLoading = true
        errorMessage = nil
        do {
            let session: FocusSession
            do {
                session = try await APIClient.shared.startSession(taskId: task?.id)
            } catch NetworkError.httpError(409, _) {
                // End whichever session is active — prefer the locally known one,
                // fall back to the last persisted ID (survives app restarts)
                let staleId = activeSession?.id ?? persistedSessionId
                if let id = staleId {
                    _ = try? await APIClient.shared.endSession(sessionId: id, status: "completed")
                }
                session = try await APIClient.shared.startSession(taskId: task?.id)
            }
            activeSession = session
            persistedSessionId = session.id
            activeTask = task
            activeSteps = []
            currentStepIndex = 0
            isSessionActive = true
            sessionStartDate = Date()
            distractionCount = 0
            lastNudge = nil

            if let task {
                let steps = try await APIClient.shared.getSteps(taskId: task.id)
                activeSteps = steps.sorted { $0.sortOrder < $1.sortOrder }
                // Pick first in-progress or first pending step
                currentStepIndex = activeSteps.firstIndex(where: { $0.isActive })
                    ?? activeSteps.firstIndex(where: { $0.status == "pending" })
                    ?? 0
            }

            screenshotHistory = []
            await requestNotificationPermission()
            startArgus(session: session, task: task)
            startAppObserver()
        } catch {
            errorMessage = error.localizedDescription
        }
        isLoading = false
    }

    func endSession(status: String = "completed") async {
        stopArgus()
        stopCapture()
        stopAppObserver()
        if let session = activeSession {
            _ = try? await APIClient.shared.endSession(sessionId: session.id, status: status)
        }
        activeSession = nil
        activeTask = nil
        activeSteps = []
        isSessionActive = false
        sessionStartDate = nil
        lastNudge = nil
        resumeCard = nil
        showingResumeCard = false
        proactiveCard = nil
        approvedActionLabel = nil
        screenshotHistory = []
        persistedSessionId = nil
    }

    func fetchResumeCard() async {
        guard let session = activeSession else { return }
        do {
            let response = try await APIClient.shared.resumeSession(sessionId: session.id)
            resumeCard = response.resumeCard
            showingResumeCard = true
        } catch {
            errorMessage = error.localizedDescription
        }
    }

    func completeCurrentStep() async {
        guard let step = currentStep else { return }
        do {
            let updated = try await APIClient.shared.completeStep(stepId: step.id)
            if let idx = activeSteps.firstIndex(where: { $0.id == updated.id }) {
                activeSteps[idx] = updated
            }
            // Advance to next pending
            if let next = activeSteps.firstIndex(where: { $0.status == "pending" }) {
                currentStepIndex = next
            }
        } catch {
            errorMessage = error.localizedDescription
        }
    }

    // MARK: - App Switch Observer

    private func startAppObserver() {
        let current = NSWorkspace.shared.frontmostApplication
        lastApp = (current?.localizedName ?? "", current?.bundleIdentifier ?? "")
        lastAppEnteredAt = Date()
        appSwitches = []

        appSwitchObserver = NSWorkspace.shared.notificationCenter.addObserver(
            forName: NSWorkspace.didActivateApplicationNotification,
            object: nil,
            queue: .main
        ) { [weak self] notification in
            guard let app = notification.userInfo?[NSWorkspace.applicationUserInfoKey] as? NSRunningApplication
            else { return }
            Task { @MainActor [weak self] in self?.handleAppSwitch(app: app) }
        }
    }

    private func stopAppObserver() {
        if let observer = appSwitchObserver {
            NSWorkspace.shared.notificationCenter.removeObserver(observer)
            appSwitchObserver = nil
        }
        appSwitches = []
    }

    private func handleAppSwitch(app: NSRunningApplication) {
        let name = app.localizedName ?? "Unknown"
        let bundleId = app.bundleIdentifier ?? ""
        let now = Date()

        guard name != lastApp.name else { return }

        // Log previous app's dwell time to backend (fire-and-forget)
        let duration = max(1, Int(now.timeIntervalSince(lastAppEnteredAt)))
        let prev = lastApp
        if let session = activeSession, !prev.name.isEmpty {
            Task {
                _ = try? await APIClient.shared.appActivity(
                    sessionId: session.id,
                    appBundleId: prev.bundleId,
                    appName: prev.name,
                    durationSeconds: duration
                )
            }
        }

        lastApp = (name, bundleId)
        lastAppEnteredAt = now

        appSwitches.append((name: name, bundleId: bundleId, time: now))
        if appSwitches.count > 30 { appSwitches.removeFirst() }

        // Only trigger card during active session and when none is already showing
        guard isSessionActive, proactiveCard == nil else { return }
        if let loop = detectRepetitiveLoop() {
            proactiveCard = ProactiveCard(source: .appSwitchLoop(apps: loop.apps, switchCount: loop.count))
        }
    }

    // Detects a back-and-forth pattern between exactly 2 apps within a 5-minute window.
    // Requires 3 full cycles (6 consecutive alternating switches) to avoid false positives.
    private func detectRepetitiveLoop() -> (apps: [String], count: Int)? {
        let cutoff = Date().addingTimeInterval(-300)
        let recent = appSwitches.filter { $0.time > cutoff }.map(\.name)
        guard recent.count >= 6 else { return nil }

        let last6 = Array(recent.suffix(6))
        guard Set(last6).count == 2 else { return nil }

        // Strictly alternating — no two consecutive identical app names
        for i in 1..<last6.count {
            if last6[i] == last6[i - 1] { return nil }
        }
        return (apps: Array(Set(last6)).sorted(), count: 3)
    }

    // MARK: - Argus Subprocess (device-side VLM)

    /// Launch the argus Python daemon as a subprocess.
    /// Argus captures screenshots itself, runs them through a local VLM (Ollama/Gemini),
    /// posts results to the backend, and emits RESULT:{json} lines to stdout for Swift to consume.
    /// Falls back to the internal `startCapture()` loop if the process cannot be launched.
    private func startArgus(session: FocusSession, task: AppTask?) {
        guard FileManager.default.fileExists(atPath: argusPythonPath),
              FileManager.default.fileExists(atPath: argusRepoPath) else {
            argusStatus = "⚠️ Argus not found — using fallback capture"
            startCapture()
            return
        }

        // Encode steps as JSON for --steps-json arg
        var stepsJSONString = "[]"
        if !activeSteps.isEmpty {
            let stepsArray: [[String: Any]] = activeSteps.map { step in
                var s: [String: Any] = [
                    "id": step.id,
                    "sort_order": step.sortOrder,
                    "title": step.title,
                    "status": step.status
                ]
                if let note = step.checkpointNote { s["checkpoint_note"] = note }
                return s
            }
            if let data = try? JSONSerialization.data(withJSONObject: stepsArray),
               let str = String(data: data, encoding: .utf8) {
                stepsJSONString = str
            }
        }

        let jwt = TokenStore.shared.token ?? ""
        let geminiKey = UserDefaults.standard.string(forKey: "geminiApiKey") ?? ""

        var arguments = [
            "-m", "argus",
            "--session-id", session.id,
            "--task-title", task?.title ?? "(no task)",
            "--task-goal", task?.description ?? "",
            "--steps-json", stepsJSONString,
            "--window-title", NSWorkspace.shared.frontmostApplication?.localizedName ?? "",
            "--vlm", "gemini",
            "--jwt", jwt,
            "--backend-url", "https://wahwa.com/api/v1",
            "--swift-ipc"
        ]
        if !geminiKey.isEmpty {
            arguments += ["--gemini-key", geminiKey]
        }

        let process = Process()
        process.executableURL = URL(fileURLWithPath: argusPythonPath)
        process.currentDirectoryURL = URL(fileURLWithPath: argusRepoPath)
        process.arguments = arguments

        // Pipe stdout for RESULT: lines; redirect stderr so argus logs don't clutter console
        let stdoutPipe = Pipe()
        let stderrPipe = Pipe()
        process.standardOutput = stdoutPipe
        process.standardError = stderrPipe

        do {
            try process.launch()
        } catch {
            argusStatus = "⚠️ Argus failed to launch — using fallback capture"
            startCapture()
            return
        }

        argusProcess = process
        isCapturing = true

        let taskLabel = task?.title ?? "session"
        argusStatus = "🚀 Argus started — waiting for first screenshot…"
        sendDebugNotification(title: "🚀 Argus VLM Started", body: "Screen monitoring active for \(taskLabel)")

        // Read RESULT: lines from argus stdout in a background task
        let fileHandle = stdoutPipe.fileHandleForReading
        sendDebugNotification(title: "🚀 Argus VLM Started", body: "Screen monitoring active for \(taskLabel)")

        argusReadTask = Task { [weak self] in
            do {
                for try await line in fileHandle.bytes.lines {
                    guard let self, !Task.isCancelled else { break }

                    if line.hasPrefix("STATUS:") {
                        let event = String(line.dropFirst("STATUS:".count))
                        await MainActor.run { self.handleArgusStatus(event) }
                    } else if line.hasPrefix("RESULT:") {
                        let jsonStr = String(line.dropFirst("RESULT:".count))
                        guard let data = jsonStr.data(using: .utf8) else { continue }
                        if let result = try? JSONDecoder().decode(DistractionAnalysisResponse.self, from: data) {
                            await MainActor.run {
                                let summary = result.vlmSummary ?? "no summary"
                                self.argusStatus = "✅ \(summary)"
                                self.sendDebugNotification(title: "✅ VLM Result", body: summary)
                                self.applyDistractionResult(result)
                            }
                        }
                    }
                }
            } catch {
                // Pipe closed — argus process ended
            }
        }
    }

    private func stopArgus() {
        argusReadTask?.cancel()
        argusReadTask = nil
        if let proc = argusProcess {
            proc.terminate()
            argusProcess = nil
            isCapturing = false
        }
    }

    // MARK: - Screenshot Capture Loop (fallback when argus is unavailable)

    private func startCapture() {
        isCapturing = true
        captureTask = Task { [weak self] in
            guard let self else { return }
            // Capture immediately on session start, then repeat on interval
            await self.captureAndAnalyze()
            while !Task.isCancelled && self.isSessionActive {
                try? await Task.sleep(for: .seconds(self.captureInterval))
                guard !Task.isCancelled && self.isSessionActive else { break }
                await self.captureAndAnalyze()
            }
        }
    }

    private func stopCapture() {
        captureTask?.cancel()
        captureTask = nil
        isCapturing = false
    }

    private func captureAndAnalyze() async {
        guard let session = activeSession else { return }
        guard let imageData = await captureScreen() else { return }

        let windowTitle = NSWorkspace.shared.frontmostApplication?.localizedName ?? "Unknown"
        var context = buildTaskContext()

        // Inject rolling history so the VLM has temporal context across captures.
        // Only summaries (text) are sent — not the raw images — to keep token cost low.
        if !screenshotHistory.isEmpty {
            let iso = ISO8601DateFormatter()
            context["screenshot_history"] = screenshotHistory.map { entry in
                ["summary": entry.summary, "timestamp": iso.string(from: entry.timestamp)]
            }
        }

        do {
            let result = try await APIClient.shared.analyzeScreenshot(
                imageData: imageData,
                windowTitle: windowTitle,
                sessionId: session.id,
                taskContext: context
            )

            // Append this result's summary to the rolling buffer (max 4 entries)
            if let summary = result.vlmSummary {
                screenshotHistory.append(ScreenshotHistoryEntry(summary: summary, timestamp: Date()))
                if screenshotHistory.count > 4 { screenshotHistory.removeFirst() }
            }

            applyDistractionResult(result)
        } catch {
            // Silent fail — don't interrupt the user
        }
    }

    private func captureScreen() async -> Data? {
        do {
            let content = try await SCShareableContent.current
            guard let display = content.displays.first else { return nil }

            let config = SCStreamConfiguration()
            config.width = 1280
            config.height = 720

            let filter = SCContentFilter(display: display, excludingWindows: [])
            let image = try await SCScreenshotManager.captureImage(
                contentFilter: filter,
                configuration: config
            )
            return cgImageToJPEG(image)
        } catch {
            return nil
        }
    }

    private func cgImageToJPEG(_ image: CGImage) -> Data? {
        let nsImage = NSImage(cgImage: image, size: .zero)
        guard let tiff = nsImage.tiffRepresentation,
              let bitmap = NSBitmapImageRep(data: tiff),
              let jpeg = bitmap.representation(using: .jpeg, properties: [.compressionFactor: 0.5])
        else { return nil }
        return jpeg
    }

    private func buildTaskContext() -> [String: Any] {
        var ctx: [String: Any] = [:]
        guard let task = activeTask else { return ctx }
        ctx["task_title"] = task.title
        ctx["task_goal"] = task.description ?? task.title
        ctx["steps"] = activeSteps.map { step -> [String: Any] in
            var s: [String: Any] = [
                "id": step.id,
                "sort_order": step.sortOrder,
                "title": step.title,
                "status": step.status
            ]
            if let note = step.checkpointNote { s["checkpoint_note"] = note }
            return s
        }
        return ctx
    }

    private func applyDistractionResult(_ result: DistractionAnalysisResponse) {
        // 1. Apply step side-effects (always)
        for completedId in result.stepsCompleted {
            if let idx = activeSteps.firstIndex(where: { $0.id == completedId }) {
                activeSteps[idx].status = "done"
            }
        }
        if let note = result.checkpointNoteUpdate,
           let stepId = result.currentStepId,
           let idx = activeSteps.firstIndex(where: { $0.id == stepId }) {
            activeSteps[idx].checkpointNote = note
        }
        if let stepId = result.currentStepId,
           let idx = activeSteps.firstIndex(where: { $0.id == stepId }) {
            currentStepIndex = idx
        }

        // 2. Notification priority (design spec §1.5):
        //    Proactive friction help → Context resume → Gentle nudge
        //    NEVER nudge when the system could help instead.
        if let friction = result.friction, friction.isActionable {
            if friction.isResumption {
                // Task resumption detected — auto-surface resume card without button press
                Task { await fetchResumeCard() }
            } else if proactiveCard == nil {
                proactiveCard = ProactiveCard(source: .vlmFriction(
                    frictionType: friction.type,
                    description: friction.description,
                    actions: friction.proposedActions
                ))
            }
        } else if !result.onTask, result.confidence > 0.7, let nudge = result.gentleNudge {
            // Only nudge if VLM found no actionable friction
            distractionCount += 1
            lastNudge = nudge
            sendNudgeNotification(nudge)
        }
    }

    // MARK: - Notifications

    private func handleArgusStatus(_ event: String) {
        switch event {
        case "screenshot_captured":
            argusStatus = "📸 Screenshot captured — sending to VLM…"
            sendDebugNotification(title: "📸 Screenshot Captured", body: "Sending to VLM for analysis…")
        case "vlm_running":
            argusStatus = "🤖 VLM analyzing screen…"
            sendDebugNotification(title: "🤖 VLM Running", body: "Gemini is analyzing your screen…")
        case "vlm_done":
            argusStatus = "🧠 VLM done — applying result…"
            sendDebugNotification(title: "🧠 VLM Done", body: "Analysis complete, processing result…")
        default:
            break
        }
    }

    private func sendDebugNotification(title: String, body: String) {
        let content = UNMutableNotificationContent()
        content.title = title
        content.body = body
        let req = UNNotificationRequest(
            identifier: "debug-\(UUID().uuidString)",
            content: content,
            trigger: nil
        )
        UNUserNotificationCenter.current().add(req)
    }

    private func sendNudgeNotification(_ nudge: String) {
        let content = UNMutableNotificationContent()
        content.title = "Hey, quick check-in!"
        content.body = nudge
        content.sound = .default
        let req = UNNotificationRequest(
            identifier: UUID().uuidString,
            content: content,
            trigger: nil
        )
        UNUserNotificationCenter.current().add(req)
    }

    private func requestNotificationPermission() async {
        try? await UNUserNotificationCenter.current()
            .requestAuthorization(options: [.alert, .sound])
    }
}