/*
* Copyright 2007 ZXing authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*      http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

using System;

using ZXing.Common.Detector;

namespace ZXing
{
    /// <summary>
    /// Encapsulates a point of interest in an image containing a barcode. Typically, this
    /// would be the location of a finder pattern or the corner of the barcode, for example.
    /// </summary>
    /// <author>Sean Owen</author>
    public class ResultPoint
    {
        private readonly float x;
        private readonly float y;
        private readonly byte[] bytesX;
        private readonly byte[] bytesY;
        private String toString;

        /// <summary>
        /// Initializes a new instance of the <see cref="ResultPoint"/> class.
        /// </summary>
        public ResultPoint()
        {
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="ResultPoint"/> class.
        /// </summary>
        /// <param name="x">The x.</param>
        /// <param name="y">The y.</param>
        public ResultPoint(float x, float y)
        {
            this.x = x;
            this.y = y;
            // calculate only once for GetHashCode
            bytesX = BitConverter.GetBytes(x);
            bytesY = BitConverter.GetBytes(y);
        }

        /// <summary>
        /// Gets the X.
        /// </summary>
        virtual public float X
        {
            get
            {
                return x;
            }
        }

        /// <summary>
        /// Gets the Y.
        /// </summary>
        virtual public float Y
        {
            get
            {
                return y;
            }
        }

        /// <summary>
        /// Determines whether the specified <see cref="System.Object"/> is equal to this instance.
        /// </summary>
        /// <param name="other">The <see cref="System.Object"/> to compare with this instance.</param>
        /// <returns>
        ///   <c>true</c> if the specified <see cref="System.Object"/> is equal to this instance; otherwise, <c>false</c>.
        /// </returns>
        public override bool Equals(Object other)
        {
            var otherPoint = other as ResultPoint;
            if (otherPoint == null)
                return false;
            return x == otherPoint.x && y == otherPoint.y;
        }

        /// <summary>
        /// Returns a hash code for this instance.
        /// </summary>
        /// <returns>
        /// A hash code for this instance, suitable for use in hashing algorithms and data structures like a hash table. 
        /// </returns>
        public override int GetHashCode()
        {
            return 31 * ((bytesX[0] << 24) + (bytesX[1] << 16) + (bytesX[2] << 8) + bytesX[3]) +
                         (bytesY[0] << 24) + (bytesY[1] << 16) + (bytesY[2] << 8) + bytesY[3];
        }

        /// <summary>
        /// Returns a <see cref="System.String"/> that represents this instance.
        /// </summary>
        /// <returns>
        /// A <see cref="System.String"/> that represents this instance.
        /// </returns>
        public override String ToString()
        {
            if (toString == null)
            {
                var result = new System.Text.StringBuilder(25);
                result.AppendFormat(System.Globalization.CultureInfo.CurrentUICulture, "({0}, {1})", x, y);
                toString = result.ToString();
            }
            return toString;
        }

        /// <summary>
        /// Orders an array of three ResultPoints in an order [A,B,C] such that AB is less than AC and
        /// BC is less than AC and the angle between BC and BA is less than 180 degrees.
        /// </summary>
        /// <param name="patterns">array of three <see cref="ResultPoint" /> to order</param>
        public static void orderBestPatterns(ResultPoint[] patterns)
        {
            // Find distances between pattern centers
            float zeroOneDistance = distance(patterns[0], patterns[1]);
            float oneTwoDistance = distance(patterns[1], patterns[2]);
            float zeroTwoDistance = distance(patterns[0], patterns[2]);

            ResultPoint pointA, pointB, pointC;
            // Assume one closest to other two is B; A and C will just be guesses at first
            if (oneTwoDistance >= zeroOneDistance && oneTwoDistance >= zeroTwoDistance)
            {
                pointB = patterns[0];
                pointA = patterns[1];
                pointC = patterns[2];
            }
            else if (zeroTwoDistance >= oneTwoDistance && zeroTwoDistance >= zeroOneDistance)
            {
                pointB = patterns[1];
                pointA = patterns[0];
                pointC = patterns[2];
            }
            else
            {
                pointB = patterns[2];
                pointA = patterns[0];
                pointC = patterns[1];
            }

            // Use cross product to figure out whether A and C are correct or flipped.
            // This asks whether BC x BA has a positive z component, which is the arrangement
            // we want for A, B, C. If it's negative, then we've got it flipped around and
            // should swap A and C.
            if (crossProductZ(pointA, pointB, pointC) < 0.0f)
            {
                ResultPoint temp = pointA;
                pointA = pointC;
                pointC = temp;
            }

            patterns[0] = pointA;
            patterns[1] = pointB;
            patterns[2] = pointC;
        }


        /// <summary>
        /// calculates the distance between two points
        /// </summary>
        /// <param name="pattern1">first pattern</param>
        /// <param name="pattern2">second pattern</param>
        /// <returns>
        /// distance between two points
        /// </returns>
        public static float distance(ResultPoint pattern1, ResultPoint pattern2)
        {
            return MathUtils.distance(pattern1.x, pattern1.y, pattern2.x, pattern2.y);
        }

        /// <summary>
        /// Returns the z component of the cross product between vectors BC and BA.
        /// </summary>
        private static float crossProductZ(ResultPoint pointA, ResultPoint pointB, ResultPoint pointC)
        {
            float bX = pointB.x;
            float bY = pointB.y;
            return ((pointC.x - bX) * (pointA.y - bY)) - ((pointC.y - bY) * (pointA.x - bX));
        }
    }
}