import Foundation

/// The only type in the app that knows the on-disk directory layout.
public struct AppSupportPaths: Sendable {
    public let root: URL
    public let spool: URL
    public let archive: URL
    public let outbox: URL
    public let watchFolder: URL

    /// Production paths.
    public static func standard() throws -> AppSupportPaths {
        let fileManager = FileManager.default
        let desktop = try fileManager.url(
            for: .desktopDirectory,
            in: .userDomainMask,
            appropriateFor: nil,
            create: true
        )
        let downloads = try fileManager.url(
            for: .downloadsDirectory,
            in: .userDomainMask,
            appropriateFor: nil,
            create: true
        )
        let root = try standardRoot(fileManager: fileManager)
        return try AppSupportPaths(root: root, outbox: desktop, watchFolder: downloads)
    }

    /// The standard `~/Library/Application Support/Shotdeck` root. Shared by
    /// `standard()`, `FolderSettings.resolvedAppSupportPaths()`, and
    /// `TransportSettings.resolvedAppSupportPaths()` so all three agree on where the
    /// root lives — the folder-resolution logic (AirDrop-only vs transport-aware)
    /// differs between those, the root computation never should.
    public static func standardRoot(fileManager: FileManager = .default) throws -> URL {
        let appSupportParent = try fileManager.url(
            for: .applicationSupportDirectory,
            in: .userDomainMask,
            appropriateFor: nil,
            create: true
        )
        return appSupportParent.appendingPathComponent("Shotdeck", isDirectory: true)
    }

    /// Test paths rooted anywhere. Every directory is created if missing.
    public init(root: URL, outbox: URL, watchFolder: URL) throws {
        self.root = root
        self.spool = root.appendingPathComponent("spool", isDirectory: true)
        self.archive = root.appendingPathComponent("archive", isDirectory: true)
        self.outbox = outbox
        self.watchFolder = watchFolder

        try Self.createDirectory(self.root)
        try Self.createDirectory(self.spool)
        try Self.createDirectory(self.archive)
        try Self.createDirectory(self.outbox)
        try Self.createDirectory(self.watchFolder)
    }

    public func sessionDirectory(_ id: UUID) -> URL {
        spool.appendingPathComponent(id.uuidString, isDirectory: true)
    }

    public func archiveDirectory(_ id: UUID) -> URL {
        archive.appendingPathComponent(id.uuidString, isDirectory: true)
    }

    private static func createDirectory(_ url: URL) throws {
        try FileManager.default.createDirectory(
            at: url,
            withIntermediateDirectories: true
        )
    }
}