Substation/XToysPattern.cs

using System.Net.Http;
using System.Text;
using System.Text.Json;
using System.Text.RegularExpressions;

namespace Substation;

public record XToysPattern(string Name, List<WaveFrame> ChannelA, List<WaveFrame> ChannelB);

public static class XToysPatternImporter
{
    static readonly HttpClient Http = new();

    public static async Task<XToysPattern> ImportAsync(string url)
    {
        var patternId = ExtractPatternId(url);
        if (patternId == null)
            throw new ArgumentException("Could not extract pattern ID from URL. Expected format: https://xtoys.app/patterns/<ID>");

        var body = JsonSerializer.Serialize(new { data = new { patternID = patternId } });
        var content = new StringContent(body, Encoding.UTF8, "application/json");
        var response = await Http.PostAsync("https://xtoys.app/api/getPatternv2", content);
        response.EnsureSuccessStatusCode();

        var json = await response.Content.ReadAsStringAsync();
        return Parse(json);
    }

    static int FreqPctToMs(byte freqPct)
    {
        // xToys frequency: 0% = deep (1000ms), 100% = buzzy (10ms)
        // freqPct is the raw 0-100 value from the pattern (already clamped in EvaluatePattern)
        return (int)Math.Round(1000 - 9.9 * freqPct);
    }

    static string? ExtractPatternId(string url)
    {
        var match = Regex.Match(url, @"/patterns/([A-Za-z0-9_-]+)");
        return match.Success ? match.Groups[1].Value : null;
    }

    static XToysPattern Parse(string json)
    {
        using var doc = JsonDocument.Parse(json);

        var pattern = doc.RootElement.GetProperty("result").GetProperty("pattern");
        var name = pattern.GetProperty("name").GetString() ?? "Unknown";
        var patternData = pattern.GetProperty("patternData");

        // Resolve slider defaults
        var sliders = new Dictionary<string, double>();
        if (patternData.TryGetProperty("ma", out var ma))
        {
            foreach (var slider in ma.EnumerateArray())
            {
                var key = slider.GetProperty("key").GetString()!;
                var value = slider.GetProperty("value").GetDouble();
                sliders[key] = value;
            }
        }

        // Evaluate patterns to per-tick value arrays
        var int1 = EvaluatePattern(patternData, "Int1", sliders);
        var int2 = EvaluatePattern(patternData, "Int2", sliders);
        var freq1 = EvaluatePattern(patternData, "Freq1", sliders);
        var freq2 = EvaluatePattern(patternData, "Freq2", sliders);

        // All patterns in a group should have the same total duration.
        // Use the max length to be safe.
        int tickCount = Math.Max(int1.Length, Math.Max(int2.Length, Math.Max(freq1.Length, freq2.Length)));

        var channelA = new List<WaveFrame>(tickCount);
        var channelB = new List<WaveFrame>(tickCount);

        for (int i = 0; i < tickCount; i++)
        {
            byte intA = i < int1.Length ? int1[i] : (byte)0;
            byte intB = i < int2.Length ? int2[i] : (byte)0;
            // Freq patterns output 0-100 (percentage). Map: 0% = 1000ms deep, 100% = 10ms buzzy.
            byte freqA = i < freq1.Length ? Freq.Compress(FreqPctToMs(freq1[i])) : Freq.Compress(10);
            byte freqB = i < freq2.Length ? Freq.Compress(FreqPctToMs(freq2[i])) : Freq.Compress(10);

            channelA.Add(new WaveFrame(
                new[] { freqA, freqA, freqA, freqA },
                new[] { intA, intA, intA, intA }));

            channelB.Add(new WaveFrame(
                new[] { freqB, freqB, freqB, freqB },
                new[] { intB, intB, intB, intB }));
        }

        return new XToysPattern(name, channelA, channelB);
    }

    static byte[] EvaluatePattern(JsonElement patternData, string patternName, Dictionary<string, double> sliders)
    {
        if (!patternData.TryGetProperty("patterns", out var patterns))
            return Array.Empty<byte>();
        if (!patterns.TryGetProperty(patternName, out var patternArr))
            return Array.Empty<byte>();

        var values = new List<byte>();
        double lastEnd = 0;

        foreach (var loop in patternArr.EnumerateArray())
        {
            var steps = loop.GetProperty("steps");
            foreach (var step in steps.EnumerateArray())
            {
                var type = step.GetProperty("type").GetString() ?? "straight";
                var time = ResolveExpr(GetStepValue(step, "time"), sliders);
                var startVal = step.TryGetProperty("start", out var s)
                    ? (s.ValueKind == JsonValueKind.Null ? lastEnd : ResolveExpr(GetStepValue(step, "start"), sliders))
                    : lastEnd;
                var endVal = ResolveExpr(GetStepValue(step, "end"), sliders);

                int ticks = Math.Max(1, (int)Math.Round(time / 0.1));

                for (int t = 0; t < ticks; t++)
                {
                    double frac = (double)t / ticks;
                    double v;
                    if (type == "sine")
                        v = startVal + (endVal - startVal) * (1 - Math.Cos(frac * Math.PI)) / 2;
                    else
                        v = startVal + (endVal - startVal) * frac;

                    values.Add((byte)Math.Clamp((int)Math.Round(v), 0, 100));
                }

                lastEnd = endVal;
            }
        }

        return values.ToArray();
    }

    static string GetStepValue(JsonElement step, string propName)
    {
        if (!step.TryGetProperty(propName, out var el))
            return "0";
        return el.ValueKind switch
        {
            JsonValueKind.String => el.GetString() ?? "0",
            JsonValueKind.Number => el.GetDouble().ToString(),
            _ => "0"
        };
    }

    static double ResolveExpr(string expr, Dictionary<string, double> sliders)
    {
        // Replace {var} references, then evaluate simple expressions like "ramp/2"
        var resolved = Regex.Replace(expr, @"\{(\w+)\}", m =>
            sliders.TryGetValue(m.Groups[1].Value, out var val) ? val.ToString() : "0");

        // Parse simple arithmetic: number, or number/number
        var parts = resolved.Split('/');
        if (parts.Length == 2 && double.TryParse(parts[0], out var a) && double.TryParse(parts[1], out var b))
            return a / b;
        return double.TryParse(resolved, out var result) ? result : 0;
    }
}