Yattee v2 rewrite

Yattee/Services/Downloads/DownloadError.swift

@@ -0,0 +1,31 @@
+//
+//  DownloadError.swift
+//  Yattee
+//
+//  Error types for download operations.
+//
+
+import Foundation
+
+enum DownloadError: LocalizedError {
+    case notSupported
+    case alreadyDownloading
+    case alreadyDownloaded
+    case noStreamAvailable
+    case downloadFailed(String)
+
+    var errorDescription: String? {
+        switch self {
+        case .notSupported:
+            return "Downloads are not supported on this platform."
+        case .alreadyDownloading:
+            return "This video is already downloading."
+        case .alreadyDownloaded:
+            return "This video has already been downloaded."
+        case .noStreamAvailable:
+            return "No downloadable stream available."
+        case .downloadFailed(let reason):
+            return "Download failed: \(reason)"
+        }
+    }
+}