namespace Admin.NET.Plugin.AiDOP.Infrastructure;

/// <summary>
/// 期量差与绿黄红（见 doc/plan/关键定义说明/期量差说明.md）。
/// 达成比例 = 实际 ÷ 目标 × 100%。
/// higher_is_better 默认黄 95 / 严重红 80；lower_is_better 默认黄 110 / 严重红 120。
/// YellowThreshold 分绿黄红；RedThreshold 仅决定红色是否严重告警（闪烁）。
/// </summary>
public static class AidopS4KpiMerge
{
    public const string Green = "green";
    public const string Yellow = "yellow";
    public const string Red = "red";

    public const decimal DefaultHigherYellow = 95m;
    public const decimal DefaultHigherRed = 80m;
    public const decimal DefaultLowerYellow = 110m;
    public const decimal DefaultLowerRed = 120m;

    public sealed record KpiAchievementEvaluation(
        string Status,
        decimal? RatioPercent,
        bool IsBeyondRedThreshold,
        decimal EffectiveYellowThreshold,
        decimal EffectiveRedThreshold);

    public static bool IsLowerBetter(string? direction) =>
        string.Equals(direction, "lower_is_better", StringComparison.OrdinalIgnoreCase);

    /// <summary>
    /// 保存校验。两个阈值都为空时通过；只配一个时另一个按方向默认值参与组合校验。
    /// 不交换配置值。
    /// </summary>
    public static bool TryValidateThresholds(
        string? direction,
        decimal? yellowThreshold,
        decimal? redThreshold,
        out string? error)
    {
        error = null;
        if (yellowThreshold == null && redThreshold == null)
            return true;

        var lower = IsLowerBetter(direction);
        var yellow = yellowThreshold ?? (lower ? DefaultLowerYellow : DefaultHigherYellow);
        var red = redThreshold ?? (lower ? DefaultLowerRed : DefaultHigherRed);

        if (lower)
        {
            if (yellow >= 100m && yellow <= red)
                return true;
            error = "lower_is_better 阈值不合法，应满足 100 <= YellowThreshold <= RedThreshold。";
            return false;
        }

        if (red > 0m && red <= yellow && yellow <= 100m)
            return true;
        error = "higher_is_better 阈值不合法，应满足 0 < RedThreshold <= YellowThreshold <= 100。";
        return false;
    }

    public static KpiAchievementEvaluation Evaluate(
        decimal? current,
        decimal? target,
        string? direction,
        decimal? yellowThreshold = null,
        decimal? redThreshold = null)
    {
        var (yellow, red) = ResolveEffectiveThresholds(direction, yellowThreshold, redThreshold);
        if (current == null || target == null || target.Value == 0)
            return new KpiAchievementEvaluation(Yellow, null, false, yellow, red);

        var ratio = current.Value / target.Value * 100m;
        if (IsLowerBetter(direction))
        {
            var status = ratio <= 100m ? Green : ratio <= yellow ? Yellow : Red;
            var blink = status == Red && ratio > red;
            return new KpiAchievementEvaluation(status, ratio, blink, yellow, red);
        }

        {
            var status = ratio >= 100m ? Green : ratio >= yellow ? Yellow : Red;
            var blink = status == Red && ratio < red;
            return new KpiAchievementEvaluation(status, ratio, blink, yellow, red);
        }
    }

    public static string AchievementLevel(
        decimal? current, decimal? target, string direction,
        decimal? yellowThreshold = null, decimal? redThreshold = null) =>
        Evaluate(current, target, direction, yellowThreshold, redThreshold).Status;

    public static bool IsBeyondRedThreshold(
        decimal? current,
        decimal? target,
        string? direction,
        decimal? yellowThreshold = null,
        decimal? redThreshold = null) =>
        Evaluate(current, target, direction, yellowThreshold, redThreshold).IsBeyondRedThreshold;

    /// <summary>期量差数值（当前−目标）；展示用箭头与符号在调用方处理。</summary>
    public static decimal? GapValue(decimal? current, decimal? target)
    {
        if (current == null || target == null) return null;
        return current.Value - target.Value;
    }

    public static string GapArrow(decimal? gap)
    {
        if (gap == null) return "flat";
        return gap.Value >= 0 ? "up" : "down";
    }

    private static (decimal Yellow, decimal Red) ResolveEffectiveThresholds(
        string? direction,
        decimal? yellowThreshold,
        decimal? redThreshold)
    {
        var lower = IsLowerBetter(direction);
        var defaults = lower
            ? (DefaultLowerYellow, DefaultLowerRed)
            : (DefaultHigherYellow, DefaultHigherRed);
        if (!TryValidateThresholds(direction, yellowThreshold, redThreshold, out _))
            return defaults;
        return (
            yellowThreshold ?? defaults.Item1,
            redThreshold ?? defaults.Item2);
    }
}