Cache registry managers by base URL

Author: mattt

Sources/PackageRegistry/RegistryManager.swift

@@ -38,6 +38,8 @@ public final class RegistryManager {
         return HTTPClient(configuration: configuration, handler: nil, diagnosticsEngine: nil)
     }
 
+    private static var cache = ThreadSafeKeyValueStore<URL, RegistryManager>()
+
     let registryBaseURL: Foundation.URL
 
     init(registryBaseURL: Foundation.URL) {
@@ -52,32 +54,34 @@ public final class RegistryManager {
             return completion(.failure(RegistryError.invalidURL))
         }
 
-        let request = HTTPClient.Request(
-            method: .head,
-            url: url,
-            headers: [
-                "Accept": "application/vnd.swift.registry.v1",
-                "User-Agent": userAgent
-            ]
-        )
+        do {
+            let manager = try cache.memoize(url) {
+                let request = HTTPClient.Request(
+                    method: .head,
+                    url: url,
+                    headers: [
+                        "Accept": "application/vnd.swift.registry.v1",
+                        "User-Agent": userAgent
+                    ]
+                )
 
-        let client = clientFactory()
-        client.execute(request) { result in
-            switch result {
-            case .success(let response):
+                let client = clientFactory()
+
+                let response = try tsc_await { client.execute(request, callback: $0) }
                 if response.statusCode == 303,
                    response.headers.get("Content-Version").first == "1",
                    let location = response.headers.get("Location").first,
                    let redirectedURL = URL(string: location, relativeTo: url)
                 {
-                    let manager = RegistryManager(registryBaseURL: redirectedURL)
-                    completion(.success(manager))
+                    return RegistryManager(registryBaseURL: redirectedURL)
                 } else {
-                    completion(.failure(RegistryError.invalidResponse))
+                    throw RegistryError.invalidResponse
                 }
-            case .failure(let error):
-                completion(.failure(error))
             }
+
+            completion(.success(manager))
+        } catch {
+            completion(.failure(error))
         }
     }