using System.Buffers.Binary;
using System.Text.Json;
using System.Text.Json.Serialization;
using SSPCTester.Devices.Interfaces;
using SSPCTester.Logic.Models;

namespace SSPCTester.Logic.Storage;

public static class WaveformStore
{
    public static async Task<string?> SaveAsync(
        Project project, int channel, string phase, CurveData curve, CancellationToken ct = default)
    {
        if (string.IsNullOrWhiteSpace(project.FolderPath)) return null;

        string folder = Path.Combine(project.FolderPath, "curves");
        Directory.CreateDirectory(folder);
        string stem = $"CH{channel:00}_{phase}_{DateTime.Now:yyyyMMdd_HHmmssfff}";
        string binPath = Path.Combine(folder, stem + ".bin");
        string jsonPath = Path.Combine(folder, stem + ".json");
        var channels = curve.EngineeringChannels.Count > 0
            ? curve.EngineeringChannels
            : new[] { new CurveChannelData(0, DaqChannelRole.OutputVoltage, "输出电压", "V", 1, 0, curve.Voltage) };
        int samples = channels.Min(x => x.Samples.Length);
        byte[] buffer = new byte[channels.Count * sizeof(float) * Math.Min(samples, 4096)];

        await using (var stream = File.Create(binPath))
        {
            for (int offset = 0; offset < samples;)
            {
                int take = Math.Min(4096, samples - offset);
                int byteOffset = 0;
                for (int sample = 0; sample < take; sample++)
                foreach (var item in channels)
                {
                    BinaryPrimitives.WriteSingleLittleEndian(
                        buffer.AsSpan(byteOffset, sizeof(float)),
                        (float)item.Samples[offset + sample]);
                    byteOffset += sizeof(float);
                }
                await stream.WriteAsync(buffer.AsMemory(0, byteOffset), ct);
                offset += take;
            }
        }

        await File.WriteAllTextAsync(jsonPath, JsonSerializer.Serialize(new
        {
            format = "float32-little-endian-interleaved",
            sample_rate_hz = curve.SampleRateHz,
            trigger_sample_index = curve.TriggerSampleIndex,
            trigger_time_sec = curve.TriggerTimeSec,
            samples_per_channel = samples,
            channels = channels.Select(x => new
            {
                physical_channel = x.PhysicalChannel,
                role = x.Role.ToString(),
                name = x.Name,
                unit = x.Unit,
                scale = x.Scale,
                offset = x.Offset
            })
        }, new JsonSerializerOptions { WriteIndented = true }), ct);

        return Path.GetRelativePath(project.FolderPath, jsonPath);
    }

    public static async Task<CurveData?> LoadAsync(
        Project project, string? relativeJsonPath, CancellationToken ct = default)
    {
        if (string.IsNullOrWhiteSpace(project.FolderPath) ||
            string.IsNullOrWhiteSpace(relativeJsonPath))
        {
            return null;
        }

        string jsonPath = Path.IsPathRooted(relativeJsonPath)
            ? relativeJsonPath
            : Path.Combine(project.FolderPath, relativeJsonPath);
        if (!File.Exists(jsonPath)) return null;

        await using var jsonStream = File.OpenRead(jsonPath);
        var metadata = await JsonSerializer.DeserializeAsync<WaveformMetadata>(
            jsonStream, cancellationToken: ct);
        if (metadata == null) return null;

        string binPath = Path.ChangeExtension(jsonPath, ".bin");
        if (!File.Exists(binPath)) return null;

        int channelCount = metadata.Channels.Length;
        int samples = metadata.SamplesPerChannel;
        if (channelCount <= 0 || samples <= 0) return null;

        var values = Enumerable.Range(0, channelCount)
            .Select(_ => new double[samples]).ToArray();
        byte[] buffer = new byte[channelCount * sizeof(float) * Math.Min(samples, 4096)];

        await using (var stream = File.OpenRead(binPath))
        {
            for (int offset = 0; offset < samples;)
            {
                int take = Math.Min(4096, samples - offset);
                int expectedBytes = channelCount * sizeof(float) * take;
                int read = 0;
                while (read < expectedBytes)
                {
                    int n = await stream.ReadAsync(buffer.AsMemory(read, expectedBytes - read), ct);
                    if (n == 0)
                        throw new InvalidDataException($"Waveform data ended early: {binPath}");
                    read += n;
                }

                int byteOffset = 0;
                for (int sample = 0; sample < take; sample++)
                for (int channel = 0; channel < channelCount; channel++)
                {
                    values[channel][offset + sample] =
                        BinaryPrimitives.ReadSingleLittleEndian(buffer.AsSpan(byteOffset, sizeof(float)));
                    byteOffset += sizeof(float);
                }

                offset += take;
            }
        }

        var channels = metadata.Channels.Select((x, index) => new CurveChannelData(
            x.PhysicalChannel,
            Enum.TryParse<DaqChannelRole>(x.Role, true, out var role) ? role : DaqChannelRole.Unconfigured,
            x.Name,
            x.Unit,
            x.Scale,
            x.Offset,
            values[index])).ToArray();

        var voltage = channels.FirstOrDefault(x => x.Role == DaqChannelRole.OutputVoltage)?.Samples
            ?? channels.First().Samples;
        var current = channels.FirstOrDefault(x => x.Role == DaqChannelRole.OutputCurrent)?.Samples;

        return new CurveData
        {
            SampleRateHz = metadata.SampleRateHz,
            TriggerSampleIndex = metadata.TriggerSampleIndex,
            TriggerTimeSec = metadata.TriggerTimeSec,
            Voltage = voltage,
            Current = current,
            EngineeringChannels = channels
        };
    }

    private sealed class WaveformMetadata
    {
        [JsonPropertyName("sample_rate_hz")]
        public int SampleRateHz { get; set; }
        [JsonPropertyName("trigger_sample_index")]
        public int TriggerSampleIndex { get; set; }
        [JsonPropertyName("trigger_time_sec")]
        public double TriggerTimeSec { get; set; }
        [JsonPropertyName("samples_per_channel")]
        public int SamplesPerChannel { get; set; }
        [JsonPropertyName("channels")]
        public WaveformChannelMetadata[] Channels { get; set; } = Array.Empty<WaveformChannelMetadata>();
    }

    private sealed class WaveformChannelMetadata
    {
        [JsonPropertyName("physical_channel")]
        public int PhysicalChannel { get; set; }
        [JsonPropertyName("role")]
        public string Role { get; set; } = "";
        [JsonPropertyName("name")]
        public string Name { get; set; } = "";
        [JsonPropertyName("unit")]
        public string Unit { get; set; } = "";
        [JsonPropertyName("scale")]
        public double Scale { get; set; }
        [JsonPropertyName("offset")]
        public double Offset { get; set; }
    }
}