/*
 *	Karinto Library Project
 *
 *	This software is distributed under a zlib-style license.
 *	See license.txt for more information.
 */

using System;
using System.Collections.Generic;

namespace Karinto
{
    /// <summary>
    ///     範囲を示す
    /// </summary>
    public class Range
    {
        #region constructors
        /// <summary>
        ///     終端を含む範囲
        /// </summary>
        /// <param name="first">最初の要素</param>
        /// <param name="last">最後の要素</param>
        public Range(IComparable first, IComparable last)
            : this(first, last, false)
        {
        }

        /// <summary>
        ///     範囲
        /// </summary>
        /// <param name="first">最初の要素</param>
        /// <param name="last">最後の要素</param>
        /// <param name="isExcludeEnd">終端を含むか否か(含まないときtrue)</param>
        public Range(IComparable first, IComparable last, bool excludeEnd)
        {
            if (first.GetType() != last.GetType())
            {
                throw new ArgumentException("The boundary elements must be same type.");
            }
            First = first;
            Last = last;
            ExcludesEnd = excludeEnd;
        }
        #endregion

        #region properties
        public IComparable First { get; private set; }
        public IComparable Last { get; private set; }
        public bool ExcludesEnd { get; private set; }
        #endregion

        #region public methods
        /// <summary>
        ///     対象が範囲内か調べる
        /// </summary>
        /// <param name="other">対象</param>
        /// <returns>範囲内か否か(範囲内ならtrue)</returns>
        public bool Includes(IComparable other)
        {
            if (other.CompareTo(First) < 0) return false;
            if (other.CompareTo(Last) > 0) return false;
            if (other.CompareTo(Last) == 0) return !ExcludesEnd;
            return true;
        }

        /// <summary>
        ///     両端に値を加算することで範囲を移動させる
        /// </summary>
        /// <param name="delta">変化量</param>
        public void Shift(double delta)
        {
            First = (double)First + delta;
            Last = (double)Last + delta;
        }

        /// <summary>
        ///     両端に値を加算することで範囲を移動させる
        /// </summary>
        /// <param name="delta">変化量</param>
        public void Shift(int delta)
        {
            First = (int)First + delta;
            Last = (int)Last + delta;
        }

        public IEnumerator<Int32> GetEnumerator()
        {
            Int32 cursor = Convert.ToInt32(First);
            Int32 last = Convert.ToInt32(Last);
            while (cursor < last)
            {
                yield return cursor;
                cursor++;
            }
            if (cursor == last)
            {
                if (!ExcludesEnd) yield return cursor;
            }
        }

        /// <summary>
        ///     イテレータブロック
        /// </summary>
        /// <param name="step">刻み</param>
        /// <returns>step刻みの範囲内の要素</returns>
        public IEnumerable<Int32> Step(Int32 step)
        {
            Int32 cursor = Convert.ToInt32(First);
            Int32 last = Convert.ToInt32(Last);
            while (cursor < last)
            {
                yield return cursor;
                cursor += step;
            }
            if (cursor == last)
            {
                if (!ExcludesEnd) yield return cursor;
            }
        }

        /// <summary>
        ///     イテレータブロック
        /// </summary>
        /// <param name="stepWidth">刻み</param>
        /// <returns>step刻みの範囲内の要素</returns>
        public IEnumerable<double> Step(double stepWidth)
        {
            int i = 0;
            double first = Convert.ToDouble(First);
            double last = Convert.ToDouble(Last);
            double cursor = first;
            while (cursor < last)
            {
                yield return cursor;
                i++;
                cursor = first + stepWidth * i;//単純に加算していくと誤差が蓄積する
            }
            if (cursor == last)
            {
                if (!ExcludesEnd) yield return cursor;
            }
        }
        #endregion

    }
}