import AppKit
import Foundation
import Observation
import SwiftUI
import ShotdeckCore

@MainActor
public protocol SendCapable: AnyObject {
    func send(anchor: NSView?) async
}

@MainActor
public protocol SettingsWindowPresenting: AnyObject {
    func presentSettingsWindow()
}

@MainActor
public protocol ReturnsSectionProviding: AnyObject {
    @ViewBuilder func returnsSection() -> AnyView
}

@MainActor
@Observable
public final class AppModel {
    public private(set) var session: CaptureSession
    public private(set) var region: CaptureRegion?
    public private(set) var screenRecordingGranted: Bool
    public private(set) var allReturns: [ReturnedDocument] = []
    public private(set) var commentedReturns: [ReturnedDocument] = []
    public private(set) var statusLine: String?
    public private(set) var isCapturing: Bool = false
    public private(set) var isSending: Bool = false
    public private(set) var outboxDisplayName: String
    public private(set) var watchFolderDisplayName: String
    /// Live transport choice; WP-onedrive reads this to pick the send path and to drive
    /// the Settings "Send via" picker and the menu's "Send…" label.
    public private(set) var transport: SendTransport
    /// Ground truth for the Settings OneDrive row: nil means "no OneDrive folder found".
    /// Views read this instead of calling `OneDriveLocator.resolveOneDriveFolder()`
    /// directly, so state (and testing with a fake home) flows through the model like
    /// everything else — never a View reaching past the model for real UserDefaults/home.
    public private(set) var resolvedOneDriveFolder: URL?
    /// Live outbox; WP-4b reads this (not `paths.outbox`) so Settings folder changes take effect.
    public private(set) var outboxURL: URL
    /// Live watch folder; WP-4c updates this alongside `ReturnWatcher.updateWatchFolder`.
    public private(set) var watchFolderURL: URL
    /// Absolute URL of the PDF composed this run, if any. Used by "Reveal last PDF".
    public private(set) var lastComposedPDFURL: URL?
    /// Currently bound capture combo (the last one Carbon accepted, or the preferred load).
    private(set) var captureHotkey: HotkeyPreference
    var hotkeyDisplayString: String { captureHotkey.displayString }
    /// Staged update offered in the menu. Set only after checksum + payload validation.
    public private(set) var updateAvailable: (version: String, notes: String)?

    let paths: AppSupportPaths
    let spool: SpoolStore
    let composer: PDFComposer
    let capturer: ScreenCapturer
    let hotkeys: HotkeyCenter
    let picker: RegionPickerController
    let ledger: ReturnLedger
    let watcher: ReturnWatcher
    let updateChecker: UpdateChecker

    public init(
        paths: AppSupportPaths,
        spool: SpoolStore,
        composer: PDFComposer,
        capturer: ScreenCapturer,
        hotkeys: HotkeyCenter,
        picker: RegionPickerController,
        ledger: ReturnLedger,
        watcher: ReturnWatcher
    ) {
        self.paths = paths
        self.spool = spool
        self.composer = composer
        self.capturer = capturer
        self.hotkeys = hotkeys
        self.picker = picker
        self.ledger = ledger
        self.watcher = watcher
        self.session = CaptureSession(
            id: UUID(),
            createdAt: Date(),
            state: .open,
            captures: [],
            pdfFileName: nil
        )
        self.region = Self.loadPersistedRegion()
        self.screenRecordingGranted = ScreenCapturer.isScreenRecordingGranted
        // Seeded from TransportSettings.effectiveFolders() — the one place that combines
        // the transport choice with FolderSettings/OneDriveLocator. Never call
        // FolderSettings.resolve() directly outside that function.
        let folders = TransportSettings.effectiveFolders()
        self.outboxURL = folders.outbox
        self.watchFolderURL = folders.watch
        self.outboxDisplayName = folders.outbox.lastPathComponent
        self.watchFolderDisplayName = folders.watch.lastPathComponent
        self.transport = folders.transport
        self.resolvedOneDriveFolder = OneDriveLocator.resolveOneDriveFolder()
        self.captureHotkey = HotkeyPreference.load()
        self.updateChecker = UpdateChecker()
        self.updateChecker.onChecked = { [weak self] in
            guard let self else { return }
            self.updateAvailable = self.updateChecker.availableUpdate
            if let message = self.updateChecker.statusMessage {
                self.setStatus(message)
            }
        }
    }

    // MARK: Seam mutators — the only way a WP-4b/4c extension changes state.

    func setStatus(_ text: String?) { statusLine = text }
    func setSending(_ value: Bool) { isSending = value }
    func setCapturing(_ value: Bool) { isCapturing = value }
    func replaceSession(_ new: CaptureSession) { session = new }
    func replaceRegion(_ new: CaptureRegion?) { region = new }
    func setReturns(all: [ReturnedDocument], commented: [ReturnedDocument]) {
        allReturns = all
        commentedReturns = commented
    }
    func setFolderDisplayNames(outbox: String, watch: String) {
        outboxDisplayName = outbox
        watchFolderDisplayName = watch
    }
    func setFolderURLs(outbox: URL, watch: URL) {
        outboxURL = outbox
        watchFolderURL = watch
        setFolderDisplayNames(outbox: outbox.lastPathComponent, watch: watch.lastPathComponent)
    }
    func setTransport(_ value: SendTransport) { transport = value }
    func setResolvedOneDriveFolder(_ value: URL?) { resolvedOneDriveFolder = value }

    /// Bumped by chooseTransport/chooseOneDriveFolder (SettingsView.swift) before each
    /// spawns its async watcher-reconcile Task; that Task checks its own snapshot
    /// against the live value before every mutating step, so rapid toggling always
    /// lets the LAST choice win instead of applying stale, superseded work. Not
    /// `@Observable`-relevant state — pure internal bookkeeping, never read by a View.
    var reconcileGeneration = 0
    /// The MOST RECENT watcher-reconcile Task spawned by chooseTransport/
    /// chooseOneDriveFolder, if one is still (or was just) in flight. send() awaits
    /// this BEFORE snapshotting transport/folder, so a toggle immediately followed by
    /// Send can never race ahead of the reconcile it depends on (the watcher's
    /// recordUncommented flag briefly lagging the just-chosen transport, for example).
    /// `Task<Void, Never>` never throws; awaiting an already-completed task's `.value`
    /// returns immediately. Not `@Observable`-relevant — pure internal bookkeeping.
    var pendingReconcileTask: Task<Void, Never>?
    func rememberLastComposedPDF(_ url: URL) { lastComposedPDFURL = url }

    /// True when a last-composed PDF path is known this run, or the newest
    /// `Redline-*.pdf` in the outbox exists on disk.
    var canRevealLastPDF: Bool { revealablePDFURL() != nil }

    public func revealLastPDF() {
        guard let url = revealablePDFURL() else { return }
        NSWorkspace.shared.activateFileViewerSelecting([url])
    }

    func revealablePDFURL() -> URL? {
        if let last = lastComposedPDFURL, FileManager.default.fileExists(atPath: last.path) {
            return last
        }
        return newestOutboxRedlinePDF()
    }

    func newestOutboxRedlinePDF() -> URL? {
        let fm = FileManager.default
        let items = (try? fm.contentsOfDirectory(
            at: outboxURL,
            includingPropertiesForKeys: [.contentModificationDateKey],
            options: [.skipsHiddenFiles]
        )) ?? []
        let matches = items.filter {
            $0.lastPathComponent.hasPrefix("Redline-") && $0.pathExtension.lowercased() == "pdf"
        }
        return matches.max { a, b in
            let da = (try? a.resourceValues(forKeys: [.contentModificationDateKey])
                .contentModificationDate) ?? .distantPast
            let db = (try? b.resourceValues(forKeys: [.contentModificationDateKey])
                .contentModificationDate) ?? .distantPast
            return da < db
        }
    }

    public var iconState: MenuIconState {
        if !screenRecordingGranted { return .recordingMissing }
        if isCapturing { return .capturing }
        if region == nil { return .noRegion }
        if session.captures.isEmpty { return .regionEmpty }
        return .hasCaptures(session.captures.count)
    }

    public func bootstrap() async {
        if let data = UserDefaults.standard.data(forKey: CaptureRegion.defaultsKey),
           let decoded = try? JSONDecoder().decode(CaptureRegion.self, from: data),
           decoded.isStillValid {
            replaceRegion(decoded)
        }

        do {
            let recovered = try await spool.currentSession()
            replaceSession(recovered)
        } catch {
            setStatus((error as? ShotdeckError)?.errorDescription ?? "Could not open the spool.")
        }

        do {
            let initial = try await ledger.all()
            let commented = try await ledger.commented()
            setReturns(all: initial, commented: commented)
        } catch {
            // Empty ledger on first run is not an error.
        }

        // OneDrive mode: outbox == watch folder, so a freshly written, unmarked PDF must
        // never show up as a return; only a document that already carries a mark does.
        // Also make sure the resolved OneDrive folder actually exists before the
        // watcher starts watching it (bootstrap is the other creation trigger besides
        // chooseTransport/chooseOneDriveFolder — see TransportSettings.effectiveFolders).
        if transport == .oneDrive {
            try? FileManager.default.createDirectory(at: outboxURL, withIntermediateDirectories: true)
        }
        setResolvedOneDriveFolder(OneDriveLocator.resolveOneDriveFolder())
        await watcher.setRecordUncommented(transport == .airDrop)

        do {
            // BLOCKER fix: reconcile the watcher's internal watchFolder with the live
            // watchFolderURL UNCONDITIONALLY, before it ever starts. `paths` (and so the
            // watcher's initial folder, set in its own init) now comes from the same
            // transport-aware TransportSettings.effectiveFolders() as watchFolderURL, so
            // in the normal case this is a no-op — but it is the only thing that would
            // have caught the old bug (launch paths built AirDrop-only while OneDrive was
            // the persisted transport, leaving the watcher's FSEvents stream pointed at a
            // stale folder for the whole session) and it stays cheap insurance against
            // that class of drift ever recurring. Calling it before start() only updates
            // the stored folder — no FSEvents stream exists yet to restart.
            try await watcher.updateWatchFolder(watchFolderURL)
            try await watcher.start { [weak self] _ in
                Task { @MainActor in
                    guard let self else { return }
                    let all = (try? await self.ledger.all()) ?? []
                    let commented = (try? await self.ledger.commented()) ?? []
                    self.setReturns(all: all, commented: commented)
                }
            }
        } catch {
            setStatus((error as? ShotdeckError)?.errorDescription ?? "Could not watch the return folder.")
        }

        // Env-var-flagged self-test/headless runs (PickerSelfTest's phases, PanelSnapshot,
        // and the new ShotdeckTests launch-wiring regression test) skip two real-world
        // side effects that are unsafe or meaningless in that context: the update-check
        // schedule (a real network call), and binding the REAL, process-wide Carbon
        // global hotkey — which is not safe to exercise in an automated/parallel test
        // process (it can collide with ShotdeckCoreTests' own HotkeyCenterCarbonTests
        // running in the same test binary) and was never meaningfully exercised by any
        // self-test anyway. A real user launch never sets these env vars, so production
        // behavior is unchanged.
        let isSelfTestRun =
            ProcessInfo.processInfo.environment["SHOTDECK_PICKER_SELFTEST"] != nil
            || ProcessInfo.processInfo.environment["SHOTDECK_SNAPSHOT_DIR"] != nil
            || ProcessInfo.processInfo.environment["SHOTDECK_UPDATE_SELFTEST"] != nil
            || ProcessInfo.processInfo.environment["SHOTDECK_ONEDRIVE_SELFTEST"] != nil
            || ProcessInfo.processInfo.environment["REDLINE_SELFTEST_PHASE"] != nil

        let pref = HotkeyPreference.load()
        captureHotkey = pref
        if !isSelfTestRun, !bindCaptureHotkey(pref) {
            setStatus("\(pref.displayString) is already used by another app — capture only works from the menu.")
        }

        if !isSelfTestRun {
            updateChecker.startSchedule()
        }
    }

    /// Installs the staged update over `/Applications/Redline.app` and relaunches.
    /// Does nothing unless the user clicked the menu row.
    public func installUpdate() {
        updateChecker.installStaged()
    }

    /// Unregisters `capture` and binds `HotkeyPreference.load()`. If Carbon rejects the new
    /// combo, restores the previous preference (UserDefaults + Carbon) so the old one keeps working.
    func reRegisterHotkey() {
        let previous = captureHotkey
        let next = HotkeyPreference.load()
        hotkeys.unregister(id: "capture")
        if bindCaptureHotkey(next) {
            captureHotkey = next
            return
        }
        setStatus("That combination is taken — pick another.")
        previous.save()
        if bindCaptureHotkey(previous) {
            captureHotkey = previous
        }
    }

    @discardableResult
    private func bindCaptureHotkey(_ pref: HotkeyPreference) -> Bool {
        hotkeys.register(
            id: "capture",
            keyCode: pref.keyCode,
            modifiers: pref.modifiers
        ) { [weak self] in
            Task { await self?.captureNow() }
        }
    }

    public func captureNow() async {
        guard !isCapturing else { return }
        setCapturing(true)
        defer { setCapturing(false) }

        var target = region
        if target == nil {
            target = await withCheckedContinuation { (cont: CheckedContinuation<CaptureRegion?, Never>) in
                picker.pick { picked in cont.resume(returning: picked) }
            }
            guard let picked = target else {
                setStatus("No region selected.")
                return
            }
            persistRegion(picked)
        }
        guard let region = target else { return }

        do {
            let image = try await capturer.capture(region)
            let capture = try await spool.append(
                pngData: image.pngData,
                pixelWidth: image.pixelWidth,
                pixelHeight: image.pixelHeight,
                scale: image.scale,
                capturedAt: Date()
            )
            replaceSession(try await spool.currentSession())
            setStatus("Captured page \(capture.sequence).")
        } catch {
            screenRecordingGranted = ScreenCapturer.isScreenRecordingGranted
            setStatus((error as? ShotdeckError)?.errorDescription ?? "The screenshot could not be taken.")
        }
    }

    public func rePickRegion() async {
        let picked = await withCheckedContinuation { (cont: CheckedContinuation<CaptureRegion?, Never>) in
            picker.pick { cont.resume(returning: $0) }
        }
        guard let picked else { return }
        persistRegion(picked)
        setStatus("Region set: \(Int(picked.rect.width)) × \(Int(picked.rect.height)).")
    }

    public func removeCapture(id: UUID) async {
        do {
            // D-11: SpoolStore.remove MOVES the PNG to <session>/removed/; it is never unlinked.
            replaceSession(try await spool.remove(captureID: id))
        } catch {
            setStatus((error as? ShotdeckError)?.errorDescription ?? "Could not remove that capture.")
        }
    }

    public func copyCommentedLinks() async {
        do {
            let text = try await ledger.clipboardText()
            let pasteboard = NSPasteboard.general
            pasteboard.clearContents()
            pasteboard.setString(text, forType: .string)
            let count = commentedReturns.count
            setStatus("Copied \(count) link\(count == 1 ? "" : "s").")
        } catch {
            setStatus((error as? ShotdeckError)?.errorDescription ?? "Nothing to copy.")
        }
    }

    public func openSpoolFolder() {
        NSWorkspace.shared.open(paths.spool)
    }

    public func openScreenRecordingSettings() {
        guard let url = URL(string:
            "x-apple.systempreferences:com.apple.preference.security?Privacy_ScreenCapture") else {
            setStatus("Could not open System Settings.")
            return
        }
        NSWorkspace.shared.open(url)
    }

    static func loadPersistedRegion() -> CaptureRegion? {
        guard let data = UserDefaults.standard.data(forKey: CaptureRegion.defaultsKey),
              let decoded = try? JSONDecoder().decode(CaptureRegion.self, from: data),
              decoded.isStillValid
        else { return nil }
        return decoded
    }

    private func persistRegion(_ picked: CaptureRegion) {
        replaceRegion(picked)
        if let encoded = try? JSONEncoder().encode(picked) {
            UserDefaults.standard.set(encoded, forKey: CaptureRegion.defaultsKey)
        }
    }
}

public enum MenuIconState: Equatable {
    case noRegion, regionEmpty, hasCaptures(Int), capturing, recordingMissing

    public var symbolName: String {
        switch self {
        case .noRegion: return "viewfinder"
        case .regionEmpty: return "viewfinder.rectangular"
        case .hasCaptures: return "viewfinder.rectangular"
        case .capturing: return "viewfinder.circle.fill"
        case .recordingMissing: return "exclamationmark.triangle"
        }
    }

    public var countText: String? {
        if case .hasCaptures(let n) = self { return "\(n)" }
        return nil
    }
}