Consolidate update+reader & remove some dead code

Sources/apk/Index/ApkIndexReader.swift

@@ -0,0 +1,102 @@
+/*
+ * darwin-apk © 2024 Gay Pizza Specifications
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import Foundation
+
+public struct ApkIndexReader {
+  static func read(from indexURL: URL) throws -> ApkIndex {
+    let timed = false
+    var timer: ContinuousClock.Instant
+    let durFormat = Duration.UnitsFormatStyle(
+      allowedUnits: [ .seconds, .milliseconds ],
+      width: .condensedAbbreviated,
+      fractionalPart: .show(length: 3))
+
+    if timed {
+      timer = ContinuousClock.now
+    }
+
+    let file = try FileInputStream(indexURL)
+    //var file = try MemoryInputStream(buffer: try Data(contentsOf: indexURL))
+    var gzip = GZipReader()
+    var tarRecords = [TarReader.Entry]()
+    for tarData in try (0..<2).map({ _ in try gzip.read(inStream: file) }) {
+      let tarStream = MemoryInputStream(buffer: tarData)
+      tarRecords += try TarReader.read(tarStream)
+    }
+
+    guard case .file(let signatureName, _) = tarRecords.first else {
+      throw ReadingError.missingSignature
+    }
+    guard let apkIndexFile = tarRecords.firstFile(name: "APKINDEX") else {
+      throw ReadingError.missingIndex
+    }
+    guard let description = tarRecords.firstFile(name: "DESCRIPTION") else {
+      throw ReadingError.missingDescription
+    }
+
+    if timed {
+      print("\(indexURL.lastPathComponent): Extract time:  \((ContinuousClock.now - timer).formatted(durFormat))")
+      timer = ContinuousClock.now
+    }
+
+    let index = try ApkIndex(raw:
+      try ApkRawIndex(lines: MemoryInputStream(buffer: apkIndexFile).lines))
+
+    if timed {
+      print("\(indexURL.lastPathComponent): Index time: \((ContinuousClock.now - timer).formatted(durFormat))")
+    }
+
+    return index
+  }
+
+  public static func resolve<S: Sequence<ApkIndexRepository>>(_ repositories: S, fetch: FetchMode) async throws -> ApkIndex {
+    try await withThrowingTaskGroup(of: ApkIndex.self) { group in
+      for repository in repositories {
+        group.addTask(priority: .userInitiated) {
+          let local: URL
+          switch fetch {
+          case .local:
+            local = URL(filePath: repository.localName)
+          case .lazy:
+            if !FileManager.default.fileExists(atPath: repository.localName) {
+              fallthrough
+            }
+            local = URL(filePath: repository.localName)
+          case .update:
+            //FIXME: Don't call print in the lib
+            print("Fetching \"\(repository.resolved)\"")
+            local = try await ApkIndexDownloader.fetch(repository: repository)
+          }
+          let index = try Self.read(from: local)
+          return index
+        }
+      }
+      return try await ApkIndex.merge(group.reduce(into: []) { $0.append($1) })
+    }
+  }
+}
+
+public extension ApkIndexReader {
+  enum FetchMode: Sendable {
+    case update
+    case lazy
+    case local
+  }
+
+  enum ReadingError: Error, LocalizedError {
+    case missingSignature
+    case missingIndex
+    case missingDescription
+
+    public var errorDescription: String? {
+      switch self {
+      case .missingSignature:   "Missing signature"
+      case .missingIndex:       "APKINDEX missing"
+      case .missingDescription: "DESCRIPTION missing"
+      }
+    }
+  }
+}