From 25c54a4c1db41dbdca1bdb9f7e709a1c69688eb0 Mon Sep 17 00:00:00 2001
From: Brent Simmons <brent@ranchero.com>
Date: Fri, 13 Dec 2024 08:57:19 -0800
Subject: [PATCH] Add Core module with Cache.

---
 Core/Package.swift                    | 21 +++++++
 Core/Sources/Core/Cache.swift         | 85 +++++++++++++++++++++++++++
 Core/Tests/CoreTests/CoreTests.swift  | 12 ++++
 NetNewsWire.xcodeproj/project.pbxproj |  2 +
 4 files changed, 120 insertions(+)
 create mode 100644 Core/Package.swift
 create mode 100644 Core/Sources/Core/Cache.swift
 create mode 100644 Core/Tests/CoreTests/CoreTests.swift

diff --git a/Core/Package.swift b/Core/Package.swift
new file mode 100644
index 000000000..e1882a15c
--- /dev/null
+++ b/Core/Package.swift
@@ -0,0 +1,21 @@
+// swift-tools-version: 6.0
+
+import PackageDescription
+
+let package = Package(
+    name: "Core",
+	platforms: [.macOS(.v13), .iOS(.v16)],
+    products: [
+        .library(
+            name: "Core",
+            targets: ["Core"]),
+    ],
+    targets: [
+        .target(
+            name: "Core"),
+        .testTarget(
+            name: "CoreTests",
+            dependencies: ["Core"]
+        ),
+    ]
+)
diff --git a/Core/Sources/Core/Cache.swift b/Core/Sources/Core/Cache.swift
new file mode 100644
index 000000000..33ee208b5
--- /dev/null
+++ b/Core/Sources/Core/Cache.swift
@@ -0,0 +1,85 @@
+//
+//  Cache.swift
+//
+//
+//  Created by Brent Simmons on 10/12/24.
+//
+
+import Foundation
+import os
+
+public protocol CacheRecord: Sendable {
+	var dateCreated: Date { get }
+}
+
+public final class Cache<T: CacheRecord>: Sendable {
+
+	public let timeToLive: TimeInterval
+	public let timeBetweenCleanups: TimeInterval
+
+	private struct State: Sendable {
+		var lastCleanupDate = Date()
+		var cache = [String: T]()
+	}
+
+	private let stateLock = OSAllocatedUnfairLock(initialState: State())
+
+	public init(timeToLive: TimeInterval, timeBetweenCleanups: TimeInterval) {
+		self.timeToLive = timeToLive
+		self.timeBetweenCleanups = timeBetweenCleanups
+	}
+
+	public subscript(_ key: String) -> T? {
+		get {
+			stateLock.withLock { state in
+
+				cleanupIfNeeded(&state)
+
+				guard let value = state.cache[key] else {
+					return nil
+				}
+				if value.dateCreated.timeIntervalSinceNow < -timeToLive {
+					state.cache[key] = nil
+					return nil
+				}
+
+				return value
+			}
+		}
+		set {
+			stateLock.withLock { state in
+				state.cache[key] = newValue
+			}
+		}
+	}
+
+	public func cleanup() {
+		stateLock.withLock { state in
+			cleanupIfNeeded(&state)
+		}
+	}
+}
+
+extension Cache {
+
+	private func cleanupIfNeeded(_ state: inout State) {
+
+		let currentDate = Date()
+		guard state.lastCleanupDate.timeIntervalSince(currentDate) < -timeBetweenCleanups else {
+			return
+		}
+
+		var keysToDelete = [String]()
+		for (key, value) in state.cache {
+			if value.dateCreated.timeIntervalSince(currentDate) < -timeToLive {
+				keysToDelete.append(key)
+			}
+		}
+
+		for key in keysToDelete {
+			state.cache[key] = nil
+		}
+
+		state.lastCleanupDate = Date()
+	}
+}
diff --git a/Core/Tests/CoreTests/CoreTests.swift b/Core/Tests/CoreTests/CoreTests.swift
new file mode 100644
index 000000000..3cad2b63f
--- /dev/null
+++ b/Core/Tests/CoreTests/CoreTests.swift
@@ -0,0 +1,12 @@
+import XCTest
+@testable import Core
+
+final class CoreTests: XCTestCase {
+    func testExample() throws {
+        // XCTest Documentation
+        // https://developer.apple.com/documentation/xctest
+
+        // Defining Test Cases and Test Methods
+        // https://developer.apple.com/documentation/xctest/defining_test_cases_and_test_methods
+    }
+}
diff --git a/NetNewsWire.xcodeproj/project.pbxproj b/NetNewsWire.xcodeproj/project.pbxproj
index 942a40d95..9f7020527 100644
--- a/NetNewsWire.xcodeproj/project.pbxproj
+++ b/NetNewsWire.xcodeproj/project.pbxproj
@@ -1029,6 +1029,7 @@
 		8405DDA122168920008CE1BF /* TimelineTableView.xib */ = {isa = PBXFileReference; lastKnownFileType = file.xib; path = TimelineTableView.xib; sourceTree = "<group>"; };
 		8405DDA422168C62008CE1BF /* TimelineContainerViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TimelineContainerViewController.swift; sourceTree = "<group>"; };
 		840BEE4021D70E64009BBAFA /* CrashReportWindowController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CrashReportWindowController.swift; sourceTree = "<group>"; };
+		840C544F2D0C9A4A00A240DB /* Core */ = {isa = PBXFileReference; lastKnownFileType = wrapper; path = Core; sourceTree = "<group>"; };
 		840D617C2029031C009BC708 /* NetNewsWire.app */ = {isa = PBXFileReference; explicitFileType = wrapper.application; includeInIndex = 0; path = NetNewsWire.app; sourceTree = BUILT_PRODUCTS_DIR; };
 		840D617E2029031C009BC708 /* AppDelegate.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AppDelegate.swift; sourceTree = "<group>"; };
 		840D61952029031D009BC708 /* NetNewsWire_iOSTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = NetNewsWire_iOSTests.swift; sourceTree = "<group>"; };
@@ -2028,6 +2029,7 @@
 				51CD32C724D2E06C009ABAEF /* Secrets */,
 				51CD32A824D2CB25009ABAEF /* SyncDatabase */,
 				843E2F152CF2B43700ED170F /* RSWeb */,
+				840C544F2D0C9A4A00A240DB /* Core */,
 			);
 			sourceTree = "<group>";
 			usesTabs = 1;