using System;
using System.Collections.Generic;

namespace ClipForge
{
    public class RingBuffer<T>
    {
        private readonly T[] _buffer;
        private readonly int _capacity;
        private int _head;      // where the next write goes
        private int _count;     // how many slots are filled
        private readonly object _lock = new object();

        public RingBuffer(int capacity)
        {
            _capacity = capacity;
            _buffer = new T[capacity];
            _head = 0;
            _count = 0;
        }

        // Write a new item into the buffer
        public void Write(T item)
        {
            lock (_lock)
            {
                _buffer[_head] = item;
                _head = (_head + 1) % _capacity;
                if (_count < _capacity)
                    _count++;
            }
        }

        // Read the last N items in chronological order
        public List<T> ReadLast(int count)
        {
            lock (_lock)
            {
                // Can't read more than we have
                int available = Math.Min(count, _count);
                var result = new List<T>(available);

                // Work backwards from the most recent write
                int start = (_head - available + _capacity) % _capacity;

                for (int i = 0; i < available; i++)
                {
                    result.Add(_buffer[(start + i) % _capacity]);
                }

                return result;
            }
        }

        // How many items are currently stored
        public int Count
        {
            get { lock (_lock) { return _count; } }
        }

        // Empty the buffer
        public void Clear()
        {
            lock (_lock)
            {
                _head = 0;
                _count = 0;
            }
        }
    }
}