import Foundation
import Combine
@preconcurrency import VnidropCore

/// Swift port of `core/CoreRepository.kt`. Owns the `VnidropCore` handle, maps the
/// generated UniFFI records into app domain models, publishes an observable
/// `CoreState`, and emits coalesced `CoreSignal`s from the event sink.
///
/// UniFFI calls block (the core drives its own runtime via `block_on`), so they
/// run on a background queue and results are hopped back to the main actor.
@MainActor
final class CoreRepository: ObservableObject {
	@Published private(set) var state = CoreState()

	private let signalsSubject = PassthroughSubject<CoreSignal, Never>()
	/// Coalesced change hints; subscribe to react to approval/history/transfer changes.
	var signals: AnyPublisher<CoreSignal, Never> { signalsSubject.eraseToAnyPublisher() }

	// Set on the main actor (initialize/shutdown) but read from `queue` inside
	// `runCore`; the underlying core is internally synchronized, so this crossing
	// is safe. `nonisolated(unsafe)` documents that contract for Swift 6.
	private nonisolated(unsafe) var core: VnidropCore?
	private let queue = DispatchQueue(label: "com.vnidrop.core", qos: .userInitiated)
	private lazy var sink = RepositoryEventSink { [weak self] event in
		Task { @MainActor in self?.handle(event: event) }
	}

	private nonisolated static let maxEvents = 200

	// MARK: - Lifecycle

	func initialize(appDataDir: String) async -> Result<Void, Error> {
		await runCore { [sink] in
			self.core?.shutdown()
			let created = try VnidropCore.initialize(appDataDir: appDataDir, eventSink: sink)
			return created
		}.map { created in
			self.core = created
			self.refreshSnapshot()
			self.state.isInitialized = true
		}
	}

	func shutdown() {
		core?.shutdown()
		core = nil
		state = CoreState()
	}

	// MARK: - Share

	func shareSources(
		_ sources: [ShareSource],
		transferName: String,
		senderName: String,
		accessPolicy: ShareAccessPolicy
	) async -> Result<Share, Error> {
		guard !sources.isEmpty else {
			return .failure(InvitationError.message("Select at least one file to share"))
		}
		return await runCore {
			let result = try self.requireCore().shareFiles(
				sources: sources,
				metadata: ShareMetadataInput(
					transferId: Self.nextTransferId(),
					transferName: transferName.isEmpty ? nil : transferName,
					senderName: senderName.isEmpty ? nil : senderName,
					accessMode: accessPolicy.toNative()
				)
			)
			return result.toModel()
		}.map { share in
			self.refreshSnapshot()
			self.state.lastShare = share
			return share
		}
	}

	// MARK: - Inspect / Receive

	func inspectTicket(_ ticket: String) async -> Result<TicketInspectionModel, Error> {
		await runCore {
			try self.requireCore().inspectTicket(ticket: ticket).toModel()
		}.map { inspection in
			self.state.lastInspection = inspection
			return inspection
		}
	}

	func receive(ticket: String, outputDir: String, receiverName: String) async -> Result<Void, Error> {
		await runCore {
			try self.requireCore().receive(
				ticket: ticket,
				outputDir: outputDir,
				receiverName: receiverName.isEmpty ? nil : receiverName
			)
		}.map { self.refreshSnapshot() }
	}

	/// Receive into a security-scoped directory URL, holding access while the core
	/// streams (mirrors `receiveIntoSecurityScopedDirectory`).
	func receiveIntoSecurityScopedDirectory(
		ticket: String,
		outputDirectoryUrl: String,
		receiverName: String
	) async -> Result<Void, Error> {
		await runCore {
			try withSecurityScopedAccess(pathOrUrl: outputDirectoryUrl) {
				try self.requireCore().receive(
					ticket: ticket,
					outputDir: outputDirectoryUrl,
					receiverName: receiverName.isEmpty ? nil : receiverName
				)
			}
		}.map { self.refreshSnapshot() }
	}

	// MARK: - Lifecycle actions

	func cancel(transferId: UInt64) async -> Result<Void, Error> {
		await runCore {
			try self.requireCore().cancelTransfer(transferId: transferId)
		}.map { self.refreshSnapshot() }
	}

	func delete(transferId: UInt64) async -> Result<Void, Error> {
		await runCore {
			try self.requireCore().deleteTransfer(transferId: transferId)
		}.map {
			self.refreshSnapshot()
			self.signalsSubject.send(.approvalChanged(transferId: transferId))
			self.signalsSubject.send(.receiverHistoryChanged(transferId: transferId))
		}
	}

	func clearReceiveHistory() async -> Result<UInt64, Error> {
		await runCore {
			try self.requireCore().deleteReceiveHistory()
		}.map { deleted in
			self.refreshSnapshot()
			return deleted
		}
	}

	func receiverRequests(transferId: UInt64) async -> Result<[ReceiverRequestModel], Error> {
		await runCore {
			try self.requireCore().listReceiverRequests(transferId: transferId).map { $0.toModel() }
		}
	}

	func respondReceiverRequest(
		requestId: String,
		accepted: Bool,
		reason: String? = nil
	) async -> Result<Void, Error> {
		await runCore {
			try self.requireCore().respondReceiverRequest(requestId: requestId, accepted: accepted, reason: reason)
		}
	}

	func refresh() async -> Result<Void, Error> {
		// Read from the core off the main actor, then apply the snapshot on the
		// main actor so `@Published state` is never mutated from `queue`.
		await runCore { self.readSnapshot() }.map { snapshot in
			if let snapshot { self.applySnapshot(snapshot) }
		}
	}

	// MARK: - Event sink handling (ported from CoreRepository.sink)

	private func handle(event: CoreEvent) {
		let model = event.toModel()
		var events = state.events
		events.insert(model, at: 0)
		if events.count > Self.maxEvents { events = Array(events.prefix(Self.maxEvents)) }
		state.events = events

		guard let transferId = model.transferId else { return }
		switch model.phase {
		case "approval": signalsSubject.send(.approvalChanged(transferId: transferId))
		case "delivery": signalsSubject.send(.receiverHistoryChanged(transferId: transferId))
		default: break
		}
		if model.shouldRefreshTransfers {
			signalsSubject.send(.transfersChanged(transferId: transferId))
		}
	}

	// MARK: - Internals

	/// Snapshot of the values read from the core in one pass.
	private struct CoreSnapshot: Sendable {
		let status: CoreStatus
		let transfers: [Transfer]
		let events: [CoreEventModel]
	}

	/// Reads the current core state. Safe to call off the main actor (pure core
	/// FFI reads); does not touch `@Published` state.
	private nonisolated func readSnapshot() -> CoreSnapshot? {
		guard let core = self.core else { return nil }
		let status = core.status()
		let transfers = (try? core.listTransfers())?.map { $0.toModel() } ?? []
		let events = (try? core.listEvents(transferId: nil))?.prefix(Self.maxEvents).map { $0.toModel() } ?? []
		return CoreSnapshot(
			status: CoreStatus(
				endpointId: status.endpointId,
				activeTransfers: status.activeTransfers,
				activeShares: status.activeShares
			),
			transfers: transfers,
			events: Array(events)
		)
	}

	/// Applies a snapshot to `@Published state`. Must run on the main actor.
	private func applySnapshot(_ snapshot: CoreSnapshot) {
		state.status = snapshot.status
		state.transfers = snapshot.transfers
		state.events = snapshot.events
	}

	private func refreshSnapshot() {
		if let snapshot = readSnapshot() { applySnapshot(snapshot) }
	}

	private nonisolated func requireCore() throws -> VnidropCore {
		guard let core = self.core else {
			throw InvitationError.message("Initialize the core first.")
		}
		return core
	}

	/// Runs a blocking core call off the main actor and hops the result back.
	private nonisolated func runCore<T: Sendable>(_ block: @escaping @Sendable () throws -> T) async -> Result<T, Error> {
		await withCheckedContinuation { continuation in
			queue.async {
				let result: Result<T, Error>
				do {
					result = .success(try block())
				} catch {
					result = .failure(error)
				}
				continuation.resume(returning: result)
			}
		}
	}

	private nonisolated static func nextTransferId() -> UInt64 {
		UInt64.random(in: 1...UInt64(Int64.max))
	}
}

/// Event sink bridged to the repository. `onEvent` is invoked on core-owned
/// threads; the handler hops to the main actor.
private final class RepositoryEventSink: CoreEventSink, @unchecked Sendable {
	private let handler: @Sendable (CoreEvent) -> Void
	init(handler: @escaping @Sendable (CoreEvent) -> Void) { self.handler = handler }
	func onEvent(event: CoreEvent) { handler(event) }
}

/// Runs `body` while holding security-scoped access to a bookmarked URL/path.
private func withSecurityScopedAccess<T>(pathOrUrl: String, _ body: () throws -> T) throws -> T {
	let url = URL(string: pathOrUrl) ?? URL(fileURLWithPath: pathOrUrl)
	let started = url.startAccessingSecurityScopedResource()
	defer { if started { url.stopAccessingSecurityScopedResource() } }
	return try body()
}

// MARK: - Mapping (ported from CoreRepository.kt)

private extension CoreEvent {
	func toModel() -> CoreEventModel {
		CoreEventModel(
			id: id, timestamp: timestamp, scope: scope, transferId: transferId,
			direction: direction, phase: phase, kind: kind, dataJson: dataJson
		)
	}
}

private let refreshPhases: Set<String> = ["lifecycle", "error", "ticket", "import", "download", "export", "handshake"]
private let refreshKinds: Set<String> = [
	"started", "done", "created", "failed", "cancelled", "share-stopped", "found-collection", "connected",
]

private extension CoreEventModel {
	var shouldRefreshTransfers: Bool {
		refreshPhases.contains(phase) && refreshKinds.contains(kind)
	}
}

extension ShareAccessPolicy {
	func toNative() -> TransferAccessMode {
		switch self {
		case .requireApproval: return .approvalRequired
		case .anyoneWithTransfer: return .public
		}
	}
}

private extension TransferAccessMode {
	func toModel() -> ShareAccessPolicy {
		switch self {
		case .approvalRequired: return .requireApproval
		case .public: return .anyoneWithTransfer
		}
	}
}

private extension StoredTransfer {
	func toModel() -> Transfer {
		Transfer(
			localId: localId,
			transferId: transferId,
			direction: Self.direction(direction),
			status: Self.status(status),
			peerId: peerId,
			transferName: transferName,
			contentHash: contentHash,
			fileCount: fileCount,
			totalSize: totalSize,
			ticket: ticket,
			accessPolicy: accessMode.toModel(),
			createdAt: createdAt,
			updatedAt: updatedAt
		)
	}

	static func direction(_ raw: String) -> TransferDirection {
		switch raw {
		case "send": return .send
		case "receive": return .receive
		default: return .send
		}
	}

	static func status(_ raw: String) -> TransferStatus {
		switch raw {
		case "importing": return .importing
		case "sharing": return .sharing
		case "receiving": return .receiving
		case "done": return .done
		case "failed": return .failed
		case "cancelled": return .cancelled
		case "stopped": return .stopped
		default: return .failed
		}
	}
}

private extension ShareResult {
	func toModel() -> Share {
		Share(
			transferId: transferId, ticket: ticket, transferName: transferName,
			contentHash: hash, fileCount: fileCount, totalSize: totalSize
		)
	}
}

private extension TicketInspection {
	func toModel() -> TicketInspectionModel {
		TicketInspectionModel(kind: kind, metadata: metadata.toModel())
	}
}

private extension TransferMetadata {
	func toModel() -> TransferMetadataModel {
		TransferMetadataModel(
			transferId: transferId, transferName: transferName, senderName: senderName,
			contentHash: contentHash, fileCount: fileCount, totalSize: totalSize
		)
	}
}

private extension ReceiverRequest {
	func toModel() -> ReceiverRequestModel {
		ReceiverRequestModel(
			id: id, transferId: transferId, remoteEndpointId: remoteEndpointId,
			transferName: transferName, receiverName: receiverName, receiverDeviceName: receiverDeviceName,
			appVersion: appVersion, status: Self.status(status), reason: reason,
			requestedAt: requestedAt, respondedAt: respondedAt, completedAt: completedAt
		)
	}

	static func status(_ raw: String) -> ReceiverDeliveryStatus {
		switch raw {
		case "requested": return .requested
		case "accepted": return .accepted
		case "refused": return .refused
		case "expired": return .expired
		case "completed": return .completed
		default: return .unknown
		}
	}
}