import AppKit
import Darwin
import Foundation
import ShotdeckCore

/// Result of composing a send PDF. Kept so the self-test can drive the share
/// outcome without presenting a real AirDrop sheet.
struct ComposedSend: Sendable {
    let fileName: String
    let fileURL: URL
    let pageCount: Int
}

extension AppModel: SendCapable {
    public func send(anchor: NSView?) async {
        guard !session.isEmpty, !isSending else { return }
        setSending(true)

        let transport = TransportSettings.transport()

        // OneDrive mode: verify the real destination exists RIGHT NOW, before composing
        // anything. `outboxURL` is kept in sync with the resolved OneDrive folder by
        // bootstrap/chooseTransport/chooseOneDriveFolder, but this is re-resolved fresh
        // here (never trusted stale) so a folder that vanished since then (OneDrive
        // signed out, external volume unmounted, folder deleted) is caught instead of
        // silently writing into whatever `outboxURL` happens to hold.
        if transport == .oneDrive {
            guard let folder = OneDriveLocator.resolveOneDriveFolder(),
                  Self.directoryExists(at: folder)
            else {
                let path = OneDriveLocator.resolveOneDriveFolder()?.path
                    ?? TransportSettings.storedOneDriveFolderPath()
                    ?? "no OneDrive folder found"
                setStatus(ShotdeckError.oneDriveFolderUnavailable(path: path).errorDescription)
                setSending(false)
                return
            }
            if outboxURL != folder || watchFolderURL != folder {
                setFolderURLs(outbox: folder, watch: folder)
                try? await watcher.updateWatchFolder(folder)
            }
        }

        let pending: ComposedSend
        do {
            pending = try await composePDFForSend()
        } catch {
            // Never unlink the published PDF, and never unlink the temp file either:
            // a rename failure would leave the complete document at the temp name.
            setStatus((error as? ShotdeckError)?.errorDescription ?? "The PDF could not be built.")
            setSending(false)
            return
        }

        switch transport {
        case .oneDrive:
            // No AirDrop, no anchor needed — the PDF is already in the watched
            // OneDrive folder. Archive immediately; the iPad marks it up in place.
            await handleDidShareItems(fileName: pending.fileName, pageCount: pending.pageCount)
            let pageWord = pending.pageCount == 1 ? "page" : "pages"
            setStatus(
                "Saved to OneDrive — \(pending.pageCount) \(pageWord). Open it in Files on your iPad."
            )
            setSending(false)

        case .airDrop:
            guard let anchor else {
                handleDidFailToShareItems(fileName: pending.fileName)
                setSending(false)
                return
            }

            do {
                try Sharing.airDrop(fileURL: pending.fileURL, from: anchor) { [weak self] success in
                    guard let self else { return }
                    if success {
                        await self.handleDidShareItems(
                            fileName: pending.fileName,
                            pageCount: pending.pageCount
                        )
                    } else {
                        self.handleDidFailToShareItems(fileName: pending.fileName)
                    }
                    self.setSending(false)
                }
            } catch {
                // canPerform false, no service, or no visible window: same as cancel.
                handleDidFailToShareItems(fileName: pending.fileName)
                setSending(false)
            }
        }
    }

    private static func directoryExists(at url: URL) -> Bool {
        var isDirectory: ObjCBool = false
        let exists = FileManager.default.fileExists(atPath: url.path, isDirectory: &isDirectory)
        return exists && isDirectory.boolValue
    }

    /// Writes the PDF to the outbox and records its path. Does not archive the session
    /// and does not present AirDrop — that happens only after the share completes.
    func composePDFForSend() async throws -> ComposedSend {
        let workingSession = session
        let composer = self.composer
        // Live outbox (FolderSettings), not `paths.outbox` — Settings changes take effect.
        let outboxDir = outboxURL
        let sourceDir = paths.sessionDirectory(workingSession.id)
        let fileName = PDFComposer.fileName(for: workingSession)
        let finalURL = outboxDir.appendingPathComponent(fileName)
        // Same directory as the final target so the rename below is same-volume (atomic).
        let tempURL = outboxDir.appendingPathComponent(".shotdeck-\(UUID().uuidString).pdf")
        let title = "Redline – \(DubaiTime.stamp(workingSession.createdAt))"

        // D-13: build off the main actor. Only Sendable values cross into the
        // detached task — never `anchor` (NSView is not Sendable).
        try await Task.detached(priority: .userInitiated) {
            _ = try composer.compose(
                session: workingSession,
                imageURL: { capture in sourceDir.appendingPathComponent(capture.fileName) },
                title: title,
                to: tempURL
            )
            // POSIX rename onto `finalURL` replaces any same-name file in one
            // directory operation; there is never a window where the PDF is gone.
            if Darwin.rename(tempURL.path, finalURL.path) != 0 {
                throw ShotdeckError.pdfCompositionFailed(
                    reason: "could not publish the PDF: \(String(cString: strerror(errno)))"
                )
            }
            try AtomicFile.fsyncDirectory(at: outboxDir)
        }.value

        guard FileManager.default.fileExists(atPath: finalURL.path) else {
            throw ShotdeckError.pdfCompositionFailed(reason: "the PDF was not written to disk")
        }
        rememberLastComposedPDF(finalURL)
        return ComposedSend(
            fileName: fileName,
            fileURL: finalURL,
            pageCount: workingSession.captures.count
        )
    }

    /// `NSSharingServiceDelegate.sharingService(_:didShareItems:)` seam.
    func handleDidShareItems(fileName: String, pageCount: Int) async {
        guard !session.isEmpty else { return }
        do {
            _ = try await spool.archiveCurrent(pdfFileName: fileName)
            replaceSession(try await spool.currentSession())
            let pageWord = pageCount == 1 ? "page" : "pages"
            setStatus("Sent — \(pageCount) \(pageWord).")
        } catch {
            setStatus((error as? ShotdeckError)?.errorDescription ?? "Could not archive the session.")
        }
    }

    /// `NSSharingServiceDelegate.sharingService(_:didFailToShareItems:error:)` seam,
    /// also used when `canPerform` is false or the user cancels. Does not archive.
    func handleDidFailToShareItems(fileName: String) {
        setStatus(
            "AirDrop didn't complete — nothing was sent. Your captures are still here; the PDF is on your \(outboxDisplayName) as \(fileName)."
        )
    }
}