using System.Windows;
using System.Windows.Media;
using System.Windows.Threading;
using Pcie8586Probe.Models;
using Pcie8586Probe.ViewModels;

namespace Pcie8586Probe;

public partial class MainWindow : Window
{
    private const double TableRowHeight = 20.0;
    private const double TableHeaderHeight = 24.0;
    private readonly MainViewModel _viewModel = new();
    private readonly DispatcherTimer _renderTimer;

    public MainWindow()
    {
        InitializeComponent();
        DataContext = _viewModel;

        _renderTimer = new DispatcherTimer
        {
            Interval = TimeSpan.FromMilliseconds(50)
        };
        _renderTimer.Tick += RenderTimer_Tick;
        _renderTimer.Start();
        ConfigurePlot();
    }

    private void ConfigurePlot()
    {
        var fontName = GetChineseFontName();
        WavePlot.Plot.Font.Set(fontName);
        WavePlot.Plot.Title("PCIe8586M \u5B9E\u65F6\u6CE2\u5F62");
        WavePlot.Plot.XLabel("\u6837\u672C\u5E8F\u53F7");
        WavePlot.Plot.YLabel("\u7535\u538B (V)");
        WavePlot.Plot.Axes.SetLimitsY(-5.2, 5.2);
        WavePlot.Refresh();
    }

    private void RenderTimer_Tick(object? sender, EventArgs e)
    {
        if (_viewModel.ConsumePlotClearRequest())
        {
            ClearPlot();
        }

        var frame = _viewModel.ConsumeLatestFrame();
        if (frame is not null)
        {
            _viewModel.AppendTableRows(frame, GetVisibleTableRowCount());
        }

        var plotBlock = _viewModel.ConsumePendingPlotBlock();
        if (plotBlock is not null)
        {
            DrawFrame(plotBlock, _viewModel.ConfiguredRange);
        }
    }

    private void ClearPlot()
    {
        WavePlot.Plot.Clear();
        ConfigurePlot();
    }

    private void DrawFrame(SampleBlock frame, InputRange range)
    {
        WavePlot.Plot.Clear();
        var xLimits = GetDisplayX(frame);
        for (var channel = 0; channel < frame.ChannelCount; channel++)
        {
            var (xs, ys) = Downsample(frame.Channels[channel], frame.StartSampleIndex, 6_000);
            var scatter = WavePlot.Plot.Add.Scatter(xs, ys);
            scatter.LegendText = $"CH{channel}";
        }

        WavePlot.Plot.Axes.SetLimitsX(xLimits.Min, xLimits.Max);

        WavePlot.Plot.Axes.SetLimitsY(
            range == InputRange.PlusMinus5V ? -5.2 : -1.2,
            range == InputRange.PlusMinus5V ? 5.2 : 1.2);
        WavePlot.Plot.ShowLegend();
        WavePlot.Refresh();
    }

    private static (double[] Xs, double[] Ys) Downsample(double[] source, long startSampleIndex, int maxPoints)
    {
        if (source.Length <= maxPoints)
        {
            var xs = new double[source.Length];
            for (var index = 0; index < source.Length; index++)
            {
                xs[index] = startSampleIndex + index;
            }

            return (xs, source);
        }

        var xsDownsampled = new double[maxPoints];
        var ys = new double[maxPoints];
        var step = source.Length / (double)maxPoints;
        for (var index = 0; index < maxPoints; index++)
        {
            var sourceIndex = (int)(index * step);
            xsDownsampled[index] = startSampleIndex + sourceIndex;
            ys[index] = source[sourceIndex];
        }

        return (xsDownsampled, ys);
    }

    private static (double Min, double Max) GetDisplayX(SampleBlock frame)
    {
        var min = frame.StartSampleIndex;
        var max = frame.StartSampleIndex + Math.Max(1, frame.SamplesPerChannel - 1);
        return (min, max);
    }

    private int GetVisibleTableRowCount()
    {
        var usableHeight = Math.Max(0, SampleTable.ActualHeight - TableHeaderHeight - 2);
        return Math.Max(1, (int)Math.Ceiling(usableHeight / TableRowHeight));
    }

    private static string GetChineseFontName()
    {
        string[] candidates =
        [
            "Microsoft YaHei UI",
            "Microsoft YaHei",
            "SimSun",
            "Noto Sans CJK SC",
            "Arial Unicode MS"
        ];

        var installed = Fonts.SystemFontFamilies.Select(static family => family.Source).ToHashSet(StringComparer.OrdinalIgnoreCase);
        return candidates.FirstOrDefault(installed.Contains) ?? "Segoe UI";
    }

    private void Window_Closing(object? sender, System.ComponentModel.CancelEventArgs e)
    {
        _renderTimer.Stop();
        _viewModel.Dispose();
    }
}