add more comments

Author: ardaatahan

Sources/Hub/Downloader.swift

@@ -58,6 +58,16 @@ class Downloader: NSObject, ObservableObject {
         setupDownload(from: url, with: authToken, resumeSize: resumeSize, headers: headers, expectedSize: expectedSize, timeout: timeout, numRetries: numRetries)
     }
 
+    /// Sets up and initiates a file download operation
+    ///
+    /// - Parameters:
+    ///   - url: Source URL to download from
+    ///   - authToken: Bearer token for authentication with Hugging Face
+    ///   - resumeSize: Number of bytes already downloaded for resuming interrupted downloads
+    ///   - headers: Additional HTTP headers to include in the request
+    ///   - expectedSize: Expected file size in bytes for validation
+    ///   - timeout: Time interval before the request times out
+    ///   - numRetries: Number of retry attempts for failed downloads
     private func setupDownload(
         from url: URL,
         with authToken: String?,

Tests/HubTests/DownloaderTests.swift

@@ -6,12 +6,15 @@
 //
 
 import XCTest
-@testable import Hub
 import Combine
+@testable import Hub
+
+/// Errors that can occur during the download process
 enum DownloadError: Error {
     case invalidDownloadLocation
     case unexpectedError
 }
+
 final class DownloaderTests: XCTestCase {
     var tempDir: URL!
 
@@ -26,6 +29,7 @@ final class DownloaderTests: XCTestCase {
         super.tearDown()
     }
 
+    /// This test downloads a known config file, verifies the download completes, checks the content matches expected value
     func testSuccessfulDownload() async throws {
         // Create a test file
         let url = URL(string: "https://huggingface.co/coreml-projects/Llama-2-7b-chat-coreml/resolve/main/config.json")!
@@ -75,6 +79,7 @@ final class DownloaderTests: XCTestCase {
         XCTAssertEqual(try String(contentsOf: destination, encoding: .utf8), fileContent)
     }
 
+    /// This test attempts to download with incorrect expected file, verifies the download fails, ensures no partial file is left behind
     func testDownloadFailsWithIncorrectSize() async throws {
         let url = URL(string: "https://huggingface.co/coreml-projects/Llama-2-7b-chat-coreml/resolve/main/config.json")!
         let destination = tempDir.appendingPathComponent("config.json")
@@ -97,6 +102,8 @@ final class DownloaderTests: XCTestCase {
         XCTAssertFalse(FileManager.default.fileExists(atPath: destination.path))
     }
 
+    /// This test downloads an LFS file, interrupts the download at 50% and 75% progress,
+    /// verifies the download can resume and complete successfully, checks the final file exists and has content
     func testSuccessfulInterruptedDownload() async throws {
         let url = URL(string: "https://huggingface.co/coreml-projects/sam-2-studio/resolve/main/SAM%202%20Studio%201.1.zip")!
         let destination = tempDir.appendingPathComponent("SAM%202%20Studio%201.1.zip")
@@ -108,18 +115,23 @@ final class DownloaderTests: XCTestCase {
         let downloader = Downloader(
             from: url,
             to: destination,
-            expectedSize: 73194001
+            expectedSize: 73194001 // Correct size for verification
         )
+        
+        // First interruption point at 50%
         var threshold = 0.5
 
         var subscriber: AnyCancellable?
 
         do {
+            // Monitor download progress and interrupt at thresholds to test if
+            // download continues from where it left off
             try await withCheckedThrowingContinuation { (continuation: CheckedContinuation<Void, Error>) in
                 subscriber = downloader.downloadState.sink { state in
                     switch state {
                     case .downloading(let progress):
                         if threshold != 1.0 && progress >= threshold {
+                            // Move to next threshold and interrupt
                             threshold = threshold == 0.5 ? 0.75 : 1.0
                             downloader.cancel()
                         }