first async refactor of fetch/index

Sources/apk/Common/ApkRepositoriesConfig.swift

@@ -0,0 +1,37 @@
+/*
+ * darwin-apk © 2024 Gay Pizza Specifications
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import Foundation
+import ArgumentParser
+
+public struct ApkRepositoriesConfig {
+  public let repositories: [ApkIndexRepository]
+
+  public init() async throws(ExitCode) {
+    do {
+      self.repositories = try await Self.readConfig(name: "repositories").flatMap { repo in
+        Self.readConfig(name: "arch").map { arch in
+          ApkIndexRepository(name: repo, arch: arch)
+        }
+      }.reduce(into: []) { $0.append($1) }
+    } catch {
+      print("Failed to read repository configurations, \(error.localizedDescription)")
+      throw .failure
+    }
+  }
+
+  private static func readConfig(name: String)
+      -> AsyncFilterSequence<AsyncMapSequence<AsyncLineSequence<URL.AsyncBytes>, String>> {
+    return URL(filePath: name, directoryHint: .notDirectory).lines
+      .map { $0.trimmingCharacters(in: .whitespaces) }
+      .filter { !$0.isEmpty && $0.first != "#" }  // Ignore empty & commented lines
+  }
+}
+
+public extension ApkIndex {
+  @inlinable static func resolve(_ config: ApkRepositoriesConfig, fetch: ApkIndexFetchMode) async throws -> Self {
+    try await Self.resolve(config.repositories, fetch: fetch)
+  }
+}