MacMonitor/Sources/History/RollingRingBuffer.swift

import Foundation

public struct HistoricalSample<T>: Identifiable {
    public let id: UUID
    public let timestamp: Date
    public let value: T
    
    public init(timestamp: Date = Date(), value: T) {
        self.id = UUID()
        self.timestamp = timestamp
        self.value = value
    }
}

public final class RollingRingBuffer<T> {
    private var buffer: [HistoricalSample<T>]
    private let capacity: Int
    private let lock = NSLock()
    
    public init(capacity: Int = 60) {
        self.capacity = max(1, capacity)
        self.buffer = []
        self.buffer.reserveCapacity(self.capacity)
    }
    
    public func append(_ value: T, timestamp: Date = Date()) {
        lock.lock()
        defer { lock.unlock() }
        
        let sample = HistoricalSample(timestamp: timestamp, value: value)
        if buffer.count >= capacity {
            buffer.removeFirst()
        }
        buffer.append(sample)
    }
    
    public var samples: [HistoricalSample<T>] {
        lock.lock()
        defer { lock.unlock() }
        return buffer
    }
    
    public var count: Int {
        lock.lock()
        defer { lock.unlock() }
        return buffer.count
    }
    
    public func clear() {
        lock.lock()
        defer { lock.unlock() }
        buffer.removeAll(keepingCapacity: true)
    }
}