using DotBased.Logging;
using Manager.App.Services;
using Microsoft.AspNetCore.Components;
using Microsoft.AspNetCore.Components.Web;
using Microsoft.AspNetCore.Components.Web.Virtualization;
using Microsoft.JSInterop;

namespace Manager.App.Components.Application.System;

public partial class EventConsole : ComponentBase
{
    private const int BatchDelayMs = 2000;
    private List<ServiceEvent> _serviceEvents = [];
    private readonly List<ServiceEvent> _batchBuffer = [];
    private readonly SemaphoreSlim _batchLock = new(1, 1);
    private ElementReference _consoleContainer;
    private bool _autoScroll = true;
    private CancellationTokenSource _cts = new();
    private TimeZoneInfo _timeZone = TimeZoneInfo.Local;
    private Virtualize<ServiceEvent>? _virtualize;

    [Parameter]
    public List<ServiceEvent> InitialEvents { get; set; } = [];
    [Parameter]
    public IAsyncEnumerable<ServiceEvent>? AsyncEnumerable { get; set; }

    [Parameter]
    public int Elevation { get; set; }
    [Parameter]
    public string? Class { get; set; }
    [Parameter]
    public string? Style { get; set; }

    protected override async Task OnInitializedAsync()
    {
        _serviceEvents.AddRange(InitialEvents);
        var jsTimeZone = await JsRuntime.InvokeAsync<string>("getUserTimeZone");
        if (!string.IsNullOrEmpty(jsTimeZone))
        {
            _timeZone = TimeZoneInfo.FindSystemTimeZoneById(jsTimeZone);
        }
        _ = Task.Run(() => ReadEventStreamsAsync(_cts.Token));
    }

    private async Task ReadEventStreamsAsync(CancellationToken token)
    {
        if (AsyncEnumerable == null)
        {
            return;
        }
        
        await foreach (var serviceEvent in AsyncEnumerable.WithCancellation(token))
        {
            await _batchLock.WaitAsync(token);
            try
            {
                _batchBuffer.Add(serviceEvent);
            }
            finally
            {
                _batchLock.Release();
            }

            _ = BatchUpdateUi();
        }
    }
    
    private string GetLogClass(ServiceEvent serviceEvent) =>
        serviceEvent.Severity switch
        {
            LogSeverity.Info => "log-info",
            LogSeverity.Warning => "log-warning",
            LogSeverity.Error => "log-error",
            LogSeverity.Debug => "log-debug",
            LogSeverity.Trace => "log-trace",
            LogSeverity.Fatal => "log-fatal",
            LogSeverity.Verbose => "log-error",
            _ => "log-info"
        };
    
    private DateTime _lastBatchUpdate = DateTime.MinValue;
    private bool _updateScheduled;

    private async Task BatchUpdateUi()
    {
        if (_updateScheduled) return;
        _updateScheduled = true;

        while (!_cts.Token.IsCancellationRequested)
        {
            var elapsed = (DateTime.UtcNow - _lastBatchUpdate).TotalMilliseconds;
            if (elapsed < BatchDelayMs)
            {
                await Task.Delay(BatchDelayMs - (int)elapsed, _cts.Token);
            }

            List<ServiceEvent> batch;
            await _batchLock.WaitAsync();
            try
            {
                if (_batchBuffer.Count == 0) continue;
                batch = new List<ServiceEvent>(_batchBuffer);
                _batchBuffer.Clear();
            }
            finally
            {
                _batchLock.Release();
            }

            foreach (var serviceEvent in batch.Where(serviceEvent => !_serviceEvents.Contains(serviceEvent)))
            {
                _serviceEvents.Add(serviceEvent);
            }
            
            _lastBatchUpdate = DateTime.UtcNow;
            
            if (_virtualize != null)
            {
                await _virtualize.RefreshDataAsync();
            }
            
            if (_autoScroll)
            {
                await JsRuntime.InvokeVoidAsync("scrollToBottom", _consoleContainer);
            }
            
            await InvokeAsync(StateHasChanged);

            _updateScheduled = false;
            break;
        }
    }
    
    private void OnUserScroll(WheelEventArgs e)
    {
        _ = UpdateAutoScroll();
    }
    
    private async Task UpdateAutoScroll()
    {
        if (_consoleContainer.Context != null)
        {
            var scrollInfo = await JsRuntime.InvokeAsync<ScrollInfo>("getScrollInfo", _consoleContainer);
            _autoScroll = scrollInfo.ScrollTop + scrollInfo.ClientHeight >= scrollInfo.ScrollHeight - 20;
        }
    }
    
    private ValueTask<ItemsProviderResult<ServiceEvent>> VirtualizedItemsProvider(ItemsProviderRequest request)
    {
        var items = _serviceEvents.Skip(request.StartIndex).Take(request.Count);
        return ValueTask.FromResult(new ItemsProviderResult<ServiceEvent>(items, _serviceEvents.Count));
    }
    
    public void Dispose()
    {
        _batchLock.Dispose();
    }
    
    private class ScrollInfo
    {
        public double ScrollTop { get; set; }
        public double ScrollHeight { get; set; }
        public double ClientHeight { get; set; }
    }
}