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 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)?
    /// True for the duration of any appcast check (manual or scheduled).
    public private(set) var isCheckingForUpdates: Bool = false

    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 FolderSettings.resolve() via resolvedAppSupportPaths — never .standard().
        let folders = FolderSettings.resolve()
        self.outboxURL = folders.outbox
        self.watchFolderURL = folders.watch
        self.outboxDisplayName = folders.outbox.lastPathComponent
        self.watchFolderDisplayName = folders.watch.lastPathComponent
        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)
            }
        }
        self.updateChecker.onCheckingChanged = { [weak self] checking in
            self?.isCheckingForUpdates = checking
        }
    }

    /// CFBundleShortVersionString of the running app.
    public var appVersion: String { UpdateChecker.currentVersion() }
    /// Version recorded in the app-managed rollback copy, when one exists.
    public var previousVersion: String? { updateChecker.previousVersion() }
    /// Most recent status text — shared with the general status line by design
    /// (Redline has one status channel, not a separate update-only one).
    public var updateStatusMessage: String? { statusLine }

    // 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 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.
        }

        do {
            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.")
        }

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

        let skipSchedule =
            ProcessInfo.processInfo.environment["SHOTDECK_PICKER_SELFTEST"] != nil
            || ProcessInfo.processInfo.environment["SHOTDECK_SNAPSHOT_DIR"] != nil
            || ProcessInfo.processInfo.environment["SHOTDECK_UPDATE_SELFTEST"] != nil
        if !skipSchedule {
            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()
    }

    /// User-initiated appcast check ("Check for updates" menu row).
    public func checkForUpdates() {
        Task { @MainActor in
            await updateChecker.checkNow(manual: true)
        }
    }

    /// Reverts `/Applications/Redline.app` to the app-managed rollback copy and relaunches.
    /// Does nothing unless a `Redline.app.previous` exists and the user clicked the row.
    public func revertToPreviousVersion() {
        updateChecker.revertToPrevious()
    }

    /// 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
    }
}