using System;
using System.Globalization;
using System.Windows.Data;

namespace XP.Common.Controls.ImageHistogram
{
    /// <summary>
    /// 频次标签转换器：将大数值转为 K/M 缩写格式 | Frequency label converter: converts large values to K/M abbreviation format
    /// 例如：500000 → "500K"，1500000 → "1.5M"，800 → "800"
    /// </summary>
    internal sealed class FrequencyLabelConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            if (value == null) return "0";

            double num;
            if (value is double d)
                num = d;
            else if (value is decimal dec)
                num = (double)dec;
            else if (!double.TryParse(value.ToString(), out num))
                return value.ToString() ?? "0";

            if (num >= 1_000_000)
            {
                double mValue = num / 1_000_000.0;
                return mValue == Math.Floor(mValue)
                    ? $"{(int)mValue}M"
                    : $"{mValue:0.#}M";
            }

            if (num >= 1_000)
            {
                double kValue = num / 1_000.0;
                return kValue == Math.Floor(kValue)
                    ? $"{(int)kValue}K"
                    : $"{kValue:0.#}K";
            }

            return $"{(int)num}";
        }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            throw new NotImplementedException();
        }
    }
}