// --------------------------------------------------------------------------------------------------------------------

// <copyright file="FractionHelper.cs" company="OxyPlot">

//   The MIT License (MIT)

//

//   Copyright (c) 2012 Oystein Bjorke

//

//   Permission is hereby granted, free of charge, to any person obtaining a

//   copy of this software and associated documentation files (the

//   "Software"), to deal in the Software without restriction, including

//   without limitation the rights to use, copy, modify, merge, publish,

//   distribute, sublicense, and/or sell copies of the Software, and to

//   permit persons to whom the Software is furnished to do so, subject to

//   the following conditions:

//

//   The above copyright notice and this permission notice shall be included

//   in all copies or substantial portions of the Software.

//

//   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS

//   OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF

//   MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.

//   IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY

//   CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,

//   TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE

//   SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

// </copyright>

// <summary>

//   Generates fraction strings from double values.

// </summary>

// --------------------------------------------------------------------------------------------------------------------

namespace OxyPlot

{

    using System;

    using System.Globalization;

    /// <summary>

    /// Provides functionality to generate fraction strings from double values.

    /// </summary>

    /// <remarks>

    /// Examples: "3/4", "PI/2"

    /// </remarks>

    public static class FractionHelper

    {

        /// <summary>

        /// Converts a double to a fraction string.

        /// </summary>

        /// <param name="value">

        /// The value.

        /// </param>

        /// <param name="unit">

        /// The unit.

        /// </param>

        /// <param name="unitSymbol">

        /// The unit symbol.

        /// </param>

        /// <param name="eps">

        /// The tolerance.

        /// </param>

        /// <param name="formatProvider">

        /// The format Provider.

        /// </param>

        /// <returns>

        /// The convert to fraction string.

        /// </returns>

        public static string ConvertToFractionString(

            double value,

            double unit = 1,

            string unitSymbol = null,

            double eps = 1e-6,

            IFormatProvider formatProvider = null)

        {

            if (Math.Abs(value) < eps)

            {

                return "0";

            }

            // ½, ⅝, ¾

            value /= unit;

            // int whole = (int)(value - (int) value);

            // int N = 10000;

            // int frac = (int) ((value - whole)*N);

            // var d = GCF(N,frac);

            for (int d = 1; d <= 64; d++)

            {

                double n = value * d;

                var ni = (int)Math.Round(n);

                if (Math.Abs(n - ni) < eps)

                {

                    string nis = unitSymbol == null || ni != 1 ? ni.ToString(CultureInfo.InvariantCulture) : string.Empty;

                    if (d == 1)

                    {

                        return string.Format("{0}{1}", nis, unitSymbol);

                    }

                    return string.Format("{0}{1}/{2}", nis, unitSymbol, d);

                }

            }

            return string.Format(formatProvider ?? CultureInfo.CurrentCulture, "{0}{1}", value, unitSymbol);

        }

        /// <summary>

        /// Finds the greates common divisor.

        /// </summary>

        /// <param name="a">

        /// The a.

        /// </param>

        /// <param name="b">

        /// The b.

        /// </param>

        /// <returns>

        /// The gcd.

        /// </returns>

        public static int gcd(int a, int b)

        {

            if (b == 0)

            {

                return a;

            }

            return gcd(b, a % b);

        }

        /// <summary>

        /// Finds the greatest common factor.

        /// </summary>

        /// <param name="x">

        /// The x.

        /// </param>

        /// <param name="y">

        /// The y.

        /// </param>

        /// <returns>

        /// The gcf.

        /// </returns>

        private static int GCF(int x, int y)

        {

            x = Math.Abs(x);

            y = Math.Abs(y);

            int z;

            do

            {

                z = x % y;

                if (z == 0)

                {

                    return y;

                }

                x = y;

                y = z;

            }

            while (true);

        }

    }

}