using System;

namespace Cryville.Common {
	public struct Qualified<T> : IFormattable where T : IConvertible {
		static readonly string _prefixes = "yzafpnμm kMGTPEZY";
		public T Value { get; set; }
		public string Unit { get; set; }

		public Qualified(string unit) : this(default, unit) { }
		public Qualified(T value, string unit) {
			Value = value;
			Unit = unit;
		}

		public override readonly string ToString() { return ToString("G3"); }
		public readonly string ToString(string format) { return ToString(format, null); }
		public readonly string ToString(string format, IFormatProvider formatProvider) {
			double value = Value.ToDouble(formatProvider);
			int expIndex = (int)System.Math.Log10(value) / 3;
			if (expIndex == 0) {
				return value.ToString(format, formatProvider) + Unit;
			}
			int prefixIndex = System.Math.Clamp(expIndex + 8, 0, _prefixes.Length - 1);
			value /= System.Math.Pow(1e3, prefixIndex - 8);
			return value.ToString(format, formatProvider) + _prefixes[prefixIndex] + Unit;
		}
	}
}