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 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
        }

        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)
        }
    }

    /// 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)."
        )
    }
}