Add Disk Cache

Author: jkmassel

Modules/Sources/WordPressCore/DataStore/DiskCache.swift

@@ -0,0 +1,52 @@
+import Foundation
+
+public actor DiskCache {
+
+    struct Wrapper<T>: Codable where T: Codable {
+        let date: Date
+        let data: T
+    }
+
+    public func store<T>(object: T, for key: String) throws where T: Codable {
+        try self.ensureCacheDirectoryExists()
+
+        let wrapper = Wrapper(date: Date(), data: object)
+        let data = try JSONEncoder().encode(wrapper)
+
+        FileManager.default.createFile(atPath: self.cacheURL(for: key).path(), contents: data)
+    }
+
+    public func retrieve<T>(for key: String, notOlderThan date: Date? = nil) throws -> T? where T: Codable {
+        try self.ensureCacheDirectoryExists()
+
+        let path = self.cacheURL(for: key)
+        guard FileManager.default.fileExists(at: path) else {
+            return nil
+        }
+
+        let data = try Data(contentsOf: path)
+        let wrapper = try JSONDecoder().decode(Wrapper<T>.self, from: data)
+
+        if let date {
+            if wrapper.date > date {
+                return nil
+            }
+        }
+
+        return wrapper.data
+    }
+
+    private func ensureCacheDirectoryExists() throws {
+        try FileManager.default.createDirectory(
+            at: cacheURL(for: "").deletingLastPathComponent(),
+            withIntermediateDirectories: true
+        )
+    }
+
+    private func cacheURL(for key: String) -> URL {
+        URL.cachesDirectory
+            .appendingPathComponent("object-cache")
+            .appendingPathComponent(key)
+            .appendingPathExtension("json")
+    }
+}