import Foundation

/// The two ways a composed PDF can reach the iPad and come back marked up.
public enum SendTransport: String, Codable, Sendable, CaseIterable {
    case airDrop
    case oneDrive

    public var displayName: String {
        switch self {
        case .airDrop: return "AirDrop"
        case .oneDrive: return "OneDrive folder"
        }
    }
}

/// User-configurable transport choice plus the OneDrive folder override, backed by
/// UserDefaults the same way `FolderSettings` is. See `FolderSettings` for why a plain
/// path (not a security-scoped bookmark) is correct for this unsandboxed app.
public enum TransportSettings {
    public static let transportDefaultsKey = "ai.flowmaster.shotdeck.transport"
    public static let oneDriveFolderDefaultsKey = "ai.flowmaster.shotdeck.oneDriveFolder"

    /// Defaults to `.airDrop` when unset or when the stored value cannot be parsed.
    public static func transport(defaults: UserDefaults = .standard) -> SendTransport {
        guard let raw = defaults.string(forKey: transportDefaultsKey),
              let value = SendTransport(rawValue: raw)
        else { return .airDrop }
        return value
    }

    public static func setTransport(_ value: SendTransport, defaults: UserDefaults = .standard) {
        defaults.set(value.rawValue, forKey: transportDefaultsKey)
    }

    /// Raw stored path (or nil if never set / cleared). Does NOT validate that the
    /// directory still exists.
    public static func storedOneDriveFolderPath(defaults: UserDefaults = .standard) -> String? {
        defaults.string(forKey: oneDriveFolderDefaultsKey)
    }

    public static func setOneDriveFolder(_ url: URL, defaults: UserDefaults = .standard) {
        defaults.set(url.path, forKey: oneDriveFolderDefaultsKey)
    }

    public static func resetOneDriveFolder(defaults: UserDefaults = .standard) {
        defaults.removeObject(forKey: oneDriveFolderDefaultsKey)
    }

    /// The outbox/watch folders Redline should actually use right now, for the current
    /// transport. AirDrop mode delegates to `FolderSettings.resolve()` unchanged.
    /// OneDrive mode uses the SAME folder for both outbox and watch — see
    /// `OneDriveLocator.resolveOneDriveFolder`. When no OneDrive folder can be resolved
    /// at all (no sync root, no override), this falls back to the AirDrop folders so the
    /// app always has somewhere to write; `send(anchor:)` performs its own live
    /// existence check before ever composing into a OneDrive send, so that fallback is
    /// never mistaken for a valid OneDrive destination.
    public static func effectiveFolders(
        defaults: UserDefaults = .standard,
        fileManager: FileManager = .default
    ) -> (outbox: URL, watch: URL, transport: SendTransport) {
        let transport = transport(defaults: defaults)
        switch transport {
        case .airDrop:
            let folders = FolderSettings.resolve(defaults: defaults, fileManager: fileManager)
            return (folders.outbox, folders.watch, transport)
        case .oneDrive:
            if let folder = OneDriveLocator.resolveOneDriveFolder(
                defaults: defaults,
                home: fileManager.homeDirectoryForCurrentUser,
                fileManager: fileManager
            ) {
                return (folder, folder, transport)
            }
            let folders = FolderSettings.resolve(defaults: defaults, fileManager: fileManager)
            return (folders.outbox, folders.watch, transport)
        }
    }

    /// Builds an `AppSupportPaths` using `root` (defaults to the standard
    /// `~/Library/Application Support/Shotdeck` when nil) plus whatever
    /// `effectiveFolders()` returns for outbox/watch. Unlike
    /// `FolderSettings.resolvedAppSupportPaths()` (AirDrop-only), this is
    /// transport-aware — it is the ONLY function launch code should use to build its
    /// paths, so the watcher it feeds is never seeded with a stale AirDrop folder while
    /// OneDrive is the persisted transport. `root` is exposed purely so tests (and the
    /// ONEDRIVE-SELFTEST relaunch simulation) can point it at a temporary directory
    /// instead of the user's real Application Support folder.
    public static func resolvedAppSupportPaths(
        root: URL? = nil,
        defaults: UserDefaults = .standard,
        fileManager: FileManager = .default
    ) throws -> AppSupportPaths {
        let resolvedRoot = try root ?? AppSupportPaths.standardRoot(fileManager: fileManager)
        let folders = effectiveFolders(defaults: defaults, fileManager: fileManager)
        return try AppSupportPaths(root: resolvedRoot, outbox: folders.outbox, watchFolder: folders.watch)
    }
}

/// Pure path logic for locating a OneDrive sync root under
/// `~/Library/CloudStorage` and the Redline folder inside it. No side effects — never
/// creates a directory. Fully unit-testable with a fake home tree.
public enum OneDriveLocator {
    /// Every directory directly under `<home>/Library/CloudStorage` whose name starts
    /// with "OneDrive-", sorted so a name containing "MMD" (case-insensitive) sorts
    /// first, then alphabetically. Empty when CloudStorage does not exist.
    public static func syncRoots(
        home: URL = FileManager.default.homeDirectoryForCurrentUser,
        fileManager: FileManager = .default
    ) -> [URL] {
        let cloudStorage = home.appendingPathComponent("Library/CloudStorage", isDirectory: true)
        var isDirectory: ObjCBool = false
        guard fileManager.fileExists(atPath: cloudStorage.path, isDirectory: &isDirectory),
              isDirectory.boolValue
        else { return [] }

        let items = (try? fileManager.contentsOfDirectory(
            at: cloudStorage,
            includingPropertiesForKeys: [.isDirectoryKey],
            options: [.skipsHiddenFiles]
        )) ?? []

        let roots = items.filter { url in
            guard url.lastPathComponent.hasPrefix("OneDrive-") else { return false }
            var itemIsDirectory: ObjCBool = false
            let exists = fileManager.fileExists(atPath: url.path, isDirectory: &itemIsDirectory)
            return exists && itemIsDirectory.boolValue
        }

        return roots.sorted { a, b in
            let aName = a.lastPathComponent
            let bName = b.lastPathComponent
            let aIsMMD = aName.localizedCaseInsensitiveContains("MMD")
            let bIsMMD = bName.localizedCaseInsensitiveContains("MMD")
            if aIsMMD != bIsMMD { return aIsMMD }
            return aName.localizedStandardCompare(bName) == .orderedAscending
        }
    }

    /// First sync root's "Redline" subfolder, or nil when there is no sync root at all.
    public static func defaultRedlineFolder(
        home: URL = FileManager.default.homeDirectoryForCurrentUser,
        fileManager: FileManager = .default
    ) -> URL? {
        guard let first = syncRoots(home: home, fileManager: fileManager).first else { return nil }
        return first.appendingPathComponent("Redline", isDirectory: true)
    }

    /// The stored override when it is set AND still exists as a directory; otherwise
    /// `defaultRedlineFolder`. Never creates anything.
    public static func resolveOneDriveFolder(
        defaults: UserDefaults = .standard,
        home: URL = FileManager.default.homeDirectoryForCurrentUser,
        fileManager: FileManager = .default
    ) -> URL? {
        if let storedPath = TransportSettings.storedOneDriveFolderPath(defaults: defaults) {
            var isDirectory: ObjCBool = false
            let exists = fileManager.fileExists(atPath: storedPath, isDirectory: &isDirectory)
            if exists, isDirectory.boolValue {
                return URL(fileURLWithPath: storedPath, isDirectory: true)
            }
        }
        return defaultRedlineFolder(home: home, fileManager: fileManager)
    }

    /// True when `url` exists as a directory AND is writable by the current process.
    /// The live check `send(anchor:)` performs before ever composing into a OneDrive
    /// destination — a directory that exists but has had its permissions revoked (e.g.
    /// `chmod 500`) must be treated as unavailable, not silently attempted and
    /// surfaced as a generic PDF-composition failure.
    public static func isWritableDirectory(
        at url: URL,
        fileManager: FileManager = .default
    ) -> Bool {
        var isDirectory: ObjCBool = false
        let exists = fileManager.fileExists(atPath: url.path, isDirectory: &isDirectory)
        guard exists, isDirectory.boolValue else { return false }
        return fileManager.isWritableFile(atPath: url.path)
    }

    /// Writes a tiny probe file into `folder`, fsyncs it, then removes it — the only
    /// reliable way to catch a OneDrive Files-On-Demand directory whose provider domain
    /// is signed out: such a directory can report as existing and POSIX-writable
    /// (`isWritableDirectory` returns true) while an actual write fails. True only when
    /// the write, fsync, AND removal of the probe file all succeed; any failure at any
    /// of those steps means false, so the caller treats the folder as unavailable
    /// rather than proceeding to compose a real PDF into it.
    public static func probeWritable(
        at folder: URL,
        fileManager: FileManager = .default
    ) -> Bool {
        let probeURL = folder.appendingPathComponent(".redline-probe-\(UUID().uuidString)")
        do {
            try AtomicFile.write(Data(), to: probeURL)
        } catch {
            return false
        }
        do {
            try fileManager.removeItem(at: probeURL)
        } catch {
            return false
        }
        return true
    }
}