using System.Buffers.Binary;
using System.IO;
using System.Text.Json;
using Pcie8586Probe.Models;

namespace Pcie8586Probe.Acquisition;

public static class WaveformWriter
{
    public static async Task<RecordingResult> WriteAsync(SampleBlock block, string outputDirectory, string name, InputRange range, CancellationToken cancellationToken)
    {
        Directory.CreateDirectory(outputDirectory);

        var safeName = string.Join("_", name.Split(Path.GetInvalidFileNameChars(), StringSplitOptions.RemoveEmptyEntries));
        if (string.IsNullOrWhiteSpace(safeName))
        {
            safeName = "capture";
        }

        var basePath = Path.Combine(outputDirectory, safeName);
        var binaryPath = basePath + ".bin";
        var metadataPath = basePath + ".json";

        await using (var stream = File.Create(binaryPath))
        {
            var bytes = new byte[4];
            for (var sample = 0; sample < block.SamplesPerChannel; sample++)
            {
                for (var channel = 0; channel < block.ChannelCount; channel++)
                {
                    BinaryPrimitives.WriteSingleLittleEndian(bytes, (float)block.Channels[channel][sample]);
                    await stream.WriteAsync(bytes, cancellationToken);
                }
            }
        }

        var duration = TimeSpan.FromSeconds(block.SamplesPerChannel / block.SampleRateHz);
        var metadata = new
        {
            channel_count = block.ChannelCount,
            sample_rate_hz = block.SampleRateHz,
            input_range = range == InputRange.PlusMinus5V ? "5V" : "1V",
            samples_per_channel = block.SamplesPerChannel,
            dtype = "float32",
            layout = "interleaved",
            unit = "volt",
            recorded_at = DateTimeOffset.Now.ToString("O"),
            duration_ms = duration.TotalMilliseconds
        };

        var json = JsonSerializer.Serialize(metadata, new JsonSerializerOptions { WriteIndented = true });
        await File.WriteAllTextAsync(metadataPath, json, cancellationToken);

        return new RecordingResult(block, basePath, binaryPath, metadataPath, duration);
    }
}