using SSPCTester.Devices.Interfaces;

namespace SSPCTester.Logic.Calculation;

/// <summary>
/// 曲线指标计算（纯函数，可单测）。
/// 覆盖开发文档 §6.4 中 1.1-1.6 指标。
/// </summary>
public static class CurveMetrics
{
    /// <summary>查找第一个达到 vTarget 的样点索引；找不到返回 -1。</summary>
    public static int FirstReachIndex(double[] v, double vTarget, bool rising = true, int startIndex = 0)
    {
        if (v == null || v.Length == 0) return -1;
        if (startIndex < 0) startIndex = 0;
        for (int i = startIndex; i < v.Length; i++)
        {
            if (rising ? v[i] >= vTarget : v[i] <= vTarget) return i;
        }
        return -1;
    }

    /// <summary>
    /// 开启时间（ms）：控制信号发出（curve.TriggerTimeSec）到电压达到 Vmax 的 thresholdRatio。
    /// </summary>
    public static double OnTimeMs(CurveData curve, double vMax, double thresholdRatio = 0.9)
    {
        int idx = FirstReachIndex(curve.Voltage, vMax * thresholdRatio, rising: true);
        if (idx < 0) return double.NaN;
        double t = curve.TimeAt(idx) - curve.TriggerTimeSec;
        return t * 1000.0;
    }

    /// <summary>
    /// 关闭时间（ms）：控制信号撤销到电压降到 Vmax 的 thresholdRatio（如 10%）。
    /// </summary>
    public static double OffTimeMs(CurveData curve, double vMax, double thresholdRatio = 0.1)
    {
        int idx = FirstReachIndex(curve.Voltage, vMax * thresholdRatio, rising: false);
        if (idx < 0) return double.NaN;
        double t = curve.TimeAt(idx) - curve.TriggerTimeSec;
        return t * 1000.0;
    }

    /// <summary>
    /// 上升时间（ms）：电压从 Vmax * low 到 Vmax * high 的时间（默认 10% → 90%）。
    /// </summary>
    public static double RiseTimeMs(CurveData curve, double vMax, double lowRatio = 0.1, double highRatio = 0.9)
    {
        var mark = AnalyzeRising(curve, vMax, lowRatio, highRatio);
        return mark.IsValid ? mark.DurationMs : double.NaN;
    }

    /// <summary>
    /// 下降时间（ms）：电压从 Vmax * high 到 Vmax * low 的时间（默认 90% → 10%）。
    /// </summary>
    public static double FallTimeMs(CurveData curve, double vMax, double highRatio = 0.9, double lowRatio = 0.1)
    {
        var mark = AnalyzeFalling(curve, vMax, highRatio, lowRatio);
        return mark.IsValid ? mark.DurationMs : double.NaN;
    }

    /// <summary>Rising curve 10% - 90% transition mark.</summary>
    public static CurveTransitionMark AnalyzeRising(CurveData curve, double vMax, double lowRatio = 0.1, double highRatio = 0.9)
    {
        double startThreshold = 0;
        double endThreshold = vMax * highRatio;
        int triggerIndex = TriggerIndex(curve);
        int endIndex = FirstReachIndex(curve.Voltage, endThreshold, rising: true, startIndex: triggerIndex);
        if (endIndex < 0) return CurveTransitionMark.Invalid(startThreshold, endThreshold);

        int startIndex = LastReachIndex(curve.Voltage, startThreshold, rising: false, startIndex: triggerIndex, endIndex: endIndex);
        if (startIndex < 0) startIndex = FirstReachIndex(curve.Voltage, startThreshold, rising: true, startIndex: triggerIndex);
        if (startIndex < 0 || startIndex > endIndex) return CurveTransitionMark.Invalid(startThreshold, endThreshold);

        return BuildTransitionMark(curve, startIndex, endIndex, startThreshold, endThreshold);
    }

    /// <summary>Falling curve 90% - 10% transition mark.</summary>
    public static CurveTransitionMark AnalyzeFalling(CurveData curve, double vMax, double highRatio = 0.9, double lowRatio = 0.1)
    {
        double startThreshold = vMax;
        double endThreshold = vMax * lowRatio;
        int triggerIndex = TriggerIndex(curve);
        int endIndex = FirstReachIndex(curve.Voltage, endThreshold, rising: false, startIndex: triggerIndex);
        if (endIndex < 0) return CurveTransitionMark.Invalid(startThreshold, endThreshold);

        int startIndex = LastReachIndex(curve.Voltage, vMax * 0.98, rising: true, startIndex: triggerIndex, endIndex: endIndex);
        if (startIndex < 0) startIndex = triggerIndex;
        if (startIndex > endIndex) return CurveTransitionMark.Invalid(startThreshold, endThreshold);

        return BuildTransitionMark(curve, startIndex, endIndex, startThreshold, endThreshold);
    }

    private static int TriggerIndex(CurveData curve)
    {
        if (curve.TriggerSampleIndex > 0)
            return Math.Min(curve.TriggerSampleIndex, Math.Max(curve.Voltage.Length - 1, 0));

        if (curve.SampleRateHz <= 0)
            return 0;

        int index = (int)Math.Round(curve.TriggerTimeSec * curve.SampleRateHz);
        return Math.Clamp(index, 0, Math.Max(curve.Voltage.Length - 1, 0));
    }

    private static int LastReachIndex(double[] v, double vTarget, bool rising, int startIndex, int endIndex)
    {
        if (v == null || v.Length == 0) return -1;
        startIndex = Math.Clamp(startIndex, 0, v.Length - 1);
        endIndex = Math.Clamp(endIndex, 0, v.Length - 1);
        for (int i = endIndex; i >= startIndex; i--)
        {
            if (rising ? v[i] >= vTarget : v[i] <= vTarget) return i;
        }
        return -1;
    }

    private static CurveTransitionMark BuildTransitionMark(
        CurveData curve,
        int startIndex,
        int endIndex,
        double startThreshold,
        double endThreshold)
    {
        double startTimeMs = (curve.TimeAt(startIndex) - curve.TriggerTimeSec) * 1000.0;
        double endTimeMs = (curve.TimeAt(endIndex) - curve.TriggerTimeSec) * 1000.0;
        return new CurveTransitionMark(
            startIndex,
            endIndex,
            startTimeMs,
            endTimeMs,
            endTimeMs - startTimeMs,
            startThreshold,
            endThreshold,
            true);
    }

    /// <summary>从波形最大值估算 Vmax（去掉前后噪声，取 95 百分位以上的均值）。</summary>
    public static double EstimateVMax(double[] v)
    {
        if (v == null || v.Length == 0) return 0;
        var sorted = (double[])v.Clone();
        Array.Sort(sorted);
        int from = (int)(sorted.Length * 0.95);
        double sum = 0; int n = 0;
        for (int i = from; i < sorted.Length; i++) { sum += sorted[i]; n++; }
        return n > 0 ? sum / n : sorted[^1];
    }
}

public readonly record struct CurveTransitionMark(
    int StartIndex,
    int EndIndex,
    double StartTimeMs,
    double EndTimeMs,
    double DurationMs,
    double StartThresholdV,
    double EndThresholdV,
    bool IsValid)
{
    public static CurveTransitionMark Invalid(double startThresholdV, double endThresholdV) =>
        new(
            -1,
            -1,
            double.NaN,
            double.NaN,
            double.NaN,
            startThresholdV,
            endThresholdV,
            false);
}