Add CustomCollection.reconcile

Sources/App/Models/CustomCollection.swift

@@ -64,3 +64,34 @@ final class CustomCollection: @unchecked Sendable, Model, Content {
     }
 
 }
+
+
+extension CustomCollection {
+    func reconcile(on database: Database, packageURLs: [URL]) async throws {
+        let incoming: [Package.Id: Package] = .init(
+            packages: try await Package.query(on: database)
+                .filter(by: packageURLs)
+                .all()
+        )
+        try await $packages.load(on: database)
+        let existing: [Package.Id: Package] = .init(packages: packages)
+        let newIDs = Set(incoming.keys).subtracting(Set(existing.keys))
+        try await $packages.attach(incoming[newIDs], on: database)
+        let removedIDs = Set(existing.keys).subtracting(Set(incoming.keys))
+        try await $packages.detach(existing[removedIDs], on: database)
+    }
+}
+
+
+private extension [Package.Id: Package] {
+    init(packages: [Package]) {
+        self.init(
+            packages.compactMap({ pkg in pkg.id.map({ ($0, pkg) }) }),
+            uniquingKeysWith: { (first, second) in first }
+        )
+    }
+
+    subscript(ids: some Collection<Package.Id>) -> [Package] {
+        Array(ids.compactMap { self[$0] })
+    }
+}

Tests/AppTests/CustomCollectionTests.swift

@@ -200,4 +200,59 @@ class CustomCollectionTests: AppTestCase {
         }
     }
 
+    func test_CustomCollection_reconcile() async throws {
+        // Test reconciliation of a custom collection against a list of package URLs
+        let collection = CustomCollection(id: .id0, name: "List", url: "https://github.com/foo/bar/list.json")
+        try await collection.save(on: app.db)
+        try await Package(id: .id1, url: URL("https://a")).save(on: app.db)
+        try await Package(id: .id2, url: URL("https://b")).save(on: app.db)
+
+        do { // Initial set of URLs
+            // MUT
+            try await collection.reconcile(on: app.db, packageURLs: [URL("https://a")])
+
+            do { // validate
+                let count = try await CustomCollectionPackage.query(on: app.db).count()
+                XCTAssertEqual(count, 1)
+                let collection = try await CustomCollection.find(.id0, on: app.db).unwrap()
+                try await collection.$packages.load(on: app.db)
+                XCTAssertEqual(collection.packages.map(\.url), ["https://a"])
+            }
+        }
+
+        do { // Add more URLs
+            // MUT
+            try await collection.reconcile(on: app.db, packageURLs: [
+                URL("https://a"),
+                URL("https://b")
+            ])
+
+            do { // validate
+                let count = try await CustomCollectionPackage.query(on: app.db).count()
+                XCTAssertEqual(count, 2)
+                let collection = try await CustomCollection.find(.id0, on: app.db).unwrap()
+                try await collection.$packages.load(on: app.db)
+                XCTAssertEqual(collection.packages.map(\.url).sorted(), [
+                    "https://a",
+                    "https://b"
+                ])
+            }
+        }
+
+        do { // Remove URLs
+            // MUT
+            try await collection.reconcile(on: app.db, packageURLs: [
+                URL("https://b")
+            ])
+
+            do { // validate
+                let count = try await CustomCollectionPackage.query(on: app.db).count()
+                XCTAssertEqual(count, 1)
+                let collection = try await CustomCollection.find(.id0, on: app.db).unwrap()
+                try await collection.$packages.load(on: app.db)
+                XCTAssertEqual(collection.packages.map(\.url), ["https://b"])
+            }
+        }
+    }
+
 }