Add reusable Cache to Core module.

Modules/Core/Sources/Core/Cache.swift

@@ -0,0 +1,79 @@
+//
+//  Cache.swift
+//
+//
+//  Created by Brent Simmons on 10/12/24.
+//
+
+import Foundation
+import os
+
+public protocol CacheRecord: Sendable {
+	var dateCreated: Date { get }
+}
+
+final class Cache: Sendable {
+
+	public let timeToLive: TimeInterval
+	public let timeBetweenCleanups: TimeInterval
+
+	private struct State: Sendable {
+		var lastCleanupDate = Date()
+		var cache = [String: CacheRecord]()
+	}
+
+	private let stateLock = OSAllocatedUnfairLock(initialState: State())
+
+	public init(timeToLive: TimeInterval, timeBetweenCleanups: TimeInterval) {
+		self.timeToLive = timeToLive
+		self.timeBetweenCleanups = timeBetweenCleanups
+	}
+
+	public subscript(_ key: String) -> CacheRecord? {
+		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
+			}
+		}
+	}
+}
+
+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()
+	}
+}