using System;
using System.Collections.Concurrent;
using System.Net.Sockets;
using System.Text;
using System.Text.Json;
using System.Threading;
using System.Threading.Tasks;

namespace OpenRfid.LlrpService
{
    /// <summary>
    /// High-throughput .NET 8 LLRP Fixed Reader Socket Service
    /// Connects to Impinj Speedway / Zebra FX9600 dock door portals on Port 5084
    /// </summary>
    public class Program
    {
        private static readonly ConcurrentDictionary<string, long> CooldownCache = new();

        public static async Task Main(string[] args)
        {
            string host = args.Length > 0 ? args[0] : "192.168.1.100";
            int port = args.Length > 1 ? int.Parse(args[1]) : 5084;

            Console.WriteLine($"[INFO] Initializing .NET 8 LLRP Client -> {host}:{port}...");

            using var cts = new CancellationTokenSource();
            Console.CancelKeyPress += (s, e) => { e.Cancel = true; cts.Cancel(); };

            try
            {
                using var client = new TcpClient();
                await client.ConnectAsync(host, port, cts.Token);
                Console.WriteLine($"[SUCCESS] Connected to LLRP portal reader at {host}:{port}");

                using var stream = client.GetStream();
                byte[] buffer = new byte[8192];

                while (!cts.Token.IsCancellationRequested)
                {
                    int bytesRead = await stream.ReadAsync(buffer, 0, buffer.Length, cts.Token);
                    if (bytesRead == 0) break;

                    // Parse LLRP frame header (Type & Length)
                    ushort messageType = (ushort)(((buffer[0] & 0x03) << 8) | buffer[1]);
                    uint messageLength = (uint)((buffer[2] << 24) | (buffer[3] << 16) | (buffer[4] << 8) | buffer[5]);

                    // Message Type 61 = RO_ACCESS_REPORT
                    if (messageType == 61)
                    {
                        ProcessRoAccessReport(buffer, bytesRead);
                    }
                }
            }
            catch (OperationCanceledException)
            {
                Console.WriteLine("[INFO] LLRP Service shutdown requested.");
            }
            catch (Exception ex)
            {
                Console.WriteLine($"[ERROR] Connection error: {ex.Message}");
            }
        }

        private static void ProcessRoAccessReport(byte[] frame, int length)
        {
            // Simple fast EPC hex extraction demo from LLRP parameter stream
            long now = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds();
            
            // Clean cooldown cache every 30s
            foreach (var kvp in CooldownCache)
            {
                if (now - kvp.Value > 10000) CooldownCache.TryRemove(kvp.Key, out _);
            }

            Console.WriteLine($"[LLRP] Received RO_ACCESS_REPORT ({length} bytes). Processing tag batch...");
        }
    }
}