using System;
using System.IO;
using System.Text;
using System.Text.RegularExpressions;
using UnityEngine.Networking;

public class ServerSentEventHandler : DownloadHandlerScript
{
    private readonly MemoryStream dataStream = new MemoryStream(1024);

    private readonly Regex eventRegex = new Regex(@"event:?(.*)");
    private readonly Regex dataRegex = new Regex(@"data:?(.*)");
    
    protected override bool ReceiveData(byte[] newData, int dataLength)
    {
        foreach (var character in newData)
        {
            dataStream.WriteByte(character);
            if (character != '\n') continue;

            var stringData = new byte[dataStream.Length];
            Array.Copy(dataStream.GetBuffer(), stringData, dataStream.Length);
            
            HandleLine(Encoding.UTF8.GetString(stringData));

            dataStream.SetLength(0);
        }

        return true;
    }

    private ServerSentEventType? currentType;
    private string currentData;
    
    protected void HandleLine(string newLine)
    {
        var eventMatch = eventRegex.Match(newLine);
        if (eventMatch.Success)
        {
            currentType = ServerSentEventTypeExt.FromName(eventMatch.Groups[1].Value);
        }
        
        var dataMatch = dataRegex.Match(newLine);
        if (dataMatch.Success)
        {
            currentData = dataMatch.Groups[1].Value;
        }

        if (currentData == null || currentType == null) return;
        
        OnServerSentEventReceived?.Invoke(new ServerSentEvent
        {
            Data = currentData,
            Type = currentType.Value
        });
        currentData = null;
        currentType = null;
    }

    public event Action<ServerSentEvent> OnServerSentEventReceived;

}