using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

/// <summary>
/// Class to convert/manage units of information.
/// https://en.wikipedia.org/wiki/Units_of_information
/// </summary>
public static class DataUnitConvert {

    public static double Measurement = DataUnitMeasurement.Decimal;

    /// <summary>
    /// Converts data from one unit of information to another to another.
    /// </summary>
    public static double UnitConvert(this double input, DataUnit originalType, DataUnit outputType) {

        if (originalType == DataUnit.None || outputType == DataUnit.None)
            return double.NaN;

        double difference = Math.Abs(outputType - originalType);

        if (difference == 0)
            return input;

        double multiplicative = Math.Pow(Measurement, difference);

        if (difference > 0) // divide
            return input / multiplicative;

        if (difference < 0) // multiply
            return input * multiplicative;

        return double.NaN;

    }

    /// <summary>
    /// Gets the best unit of information to display data in.
    /// </summary>
    public static DataUnit GetDataUnit(this double input, DataUnit type = DataUnit.Byte) {

        DataUnit unit = DataUnit.Byte;

        while (true) {

            double test = input.UnitConvert(type, unit);

            if (test > Measurement)
                unit++;
            else
                break;

        }

        return unit;

    }

    /// <summary>
    /// Converts input to a string, appending the specified units abbreviaton.
    /// Will also round the nubmer for cleaner display.
    /// </summary>
    public static string ToString(this double input, DataUnit unit, int decimalPoints = 2) {
        string abbr = unit.GetAbbreviation().ToUpper();
        decimal dec = Convert.ToDecimal(input);
        dec = decimal.Round(dec, decimalPoints, MidpointRounding.AwayFromZero);
        if (unit == DataUnit.None)
            return Convert.ToString(dec);
        else
            return Convert.ToString(dec) + " " + abbr;
    }

    /// <summary>
    /// Converts a string to it's original data.
    /// Specifying 'unit' will convert it to another unit of information automatically.
    /// </summary>
    public static double ToDouble(this string input, DataUnit unit = DataUnit.None) {
        string[] pieces = input.Split(new[] { ' ' });
        double number = Convert.ToDouble(pieces[0]);
        DataUnit originalUnit = GetDataUnit(pieces[1]);
        if (unit == DataUnit.None)
            return number;
        else
            return number.UnitConvert(originalUnit, unit);
    }

    /// <summary>
    /// Returns an abbreviation of a specified DataUnit.
    /// </summary>
    public static string GetAbbreviation(this DataUnit unit) {
        switch (unit) {
            case DataUnit.Byte: return "b";
            case DataUnit.Kilobyte: return "kb";
            case DataUnit.Megabyte: return "mb";
            case DataUnit.Gigabyte: return "gb";
            case DataUnit.Terabyte: return "tb";
            case DataUnit.Petabyte: return "pb";
            case DataUnit.Exabyte: return "eb";
            case DataUnit.Zettabyte: return "zb";
            case DataUnit.Yottabyte: return "yb";   
        }
        return string.Empty;
    }

    /// <summary>
    /// Returns a DataUnit based on the specified abbreviation.
    /// </summary>
    public static DataUnit GetDataUnit(this string unit) {
        switch (unit.ToLower()) {
            case "b": return DataUnit.Byte;
            case "kb": return DataUnit.Kilobyte;
            case "mb": return DataUnit.Megabyte;
            case "gb": return DataUnit.Gigabyte;
            case "tb": return DataUnit.Terabyte;
            case "pb": return DataUnit.Petabyte;
            case "eb": return DataUnit.Exabyte;
            case "zb": return DataUnit.Zettabyte;
            case "yb": return DataUnit.Yottabyte;
        }
        return DataUnit.None;
    }

    // === CONVERTED FUNCTION ===

    /// <summary>
    /// Converts data from one unit of information to another to another.
    /// </summary>
    public static double UnitConvert(this long input, DataUnit originalType, DataUnit outputType) {
        double converted = Convert.ToDouble(input);
        return converted.UnitConvert(originalType, outputType);
    }

    /// <summary>
    /// Gets the best unit of information to display data in.
    /// </summary>
    public static DataUnit GetDataUnit(this long bytes) {
        double converted = Convert.ToDouble(bytes);
        return converted.GetDataUnit();
    }

}

/// <summary>
/// List of supported units of information.
/// In order, least to greatest.
/// </summary>
public enum DataUnit {
    None,
    Byte,
    Kilobyte,
    Megabyte,
    Gigabyte,
    Terabyte,
    Petabyte,
    Exabyte,
    Zettabyte,
    Yottabyte
}

/// <summary>
/// Measurements to convert data.
/// Note: Decimal is more common, and should be used for displaying data.
/// </summary>
public struct DataUnitMeasurement {
    public const double Binary = 1024.0;
    public const double Decimal = 1000.0;
}