#region --- License ---
/* Copyright (c) 2006, 2007 Stefanos Apostolopoulos
 * See license.txt for license info
 */
#endregion

using System;
using System.Runtime.InteropServices;
namespace OpenTK
{
    /// <summary>
    /// Defines a 2d box (rectangle).
    /// </summary>
    [StructLayout(LayoutKind.Sequential)]
    public struct Box2d
    {
        /// <summary>
        /// The left boundary of the structure.
        /// </summary>
        public double Left;

        /// <summary>
        /// The right boundary of the structure.
        /// </summary>
        public double Right;

        /// <summary>
        /// The top boundary of the structure.
        /// </summary>
        public double Top;

        /// <summary>
        /// The bottom boundary of the structure.
        /// </summary>
        public double Bottom;

        /// <summary>
        /// Constructs a new Box2d with the specified dimensions.
        /// </summary>
        /// <param name="topLeft">An OpenTK.Vector2d describing the top-left corner of the Box2d.</param>
        /// <param name="bottomRight">An OpenTK.Vector2d describing the bottom-right corner of the Box2d.</param>
        public Box2d(Vector2d topLeft, Vector2d bottomRight)
        {
            Left = topLeft.X;
            Top = topLeft.Y;
            Right = bottomRight.X;
            Bottom = bottomRight.Y;
        }

        /// <summary>
        /// Constructs a new Box2d with the specified dimensions.
        /// </summary>
        /// <param name="left">The position of the left boundary.</param>
        /// <param name="top">The position of the top boundary.</param>
        /// <param name="right">The position of the right boundary.</param>
        /// <param name="bottom">The position of the bottom boundary.</param>
        public Box2d(double left, double top, double right, double bottom)
        {
            Left = left;
            Top = top;
            Right = right;
            Bottom = bottom;
        }

        /// <summary>
        /// Creates a new Box2d with the specified dimensions.
        /// </summary>
        /// <param name="top">The position of the top boundary.</param>
        /// <param name="left">The position of the left boundary.</param>
        /// <param name="right">The position of the right boundary.</param>
        /// <param name="bottom">The position of the bottom boundary.</param>
        /// <returns>A new OpenTK.Box2d with the specfied dimensions.</returns>
        public static Box2d FromTLRB(double top, double left, double right, double bottom)
        {
            return new Box2d(left, top, right, bottom);
        }

        /// <summary>
        /// Creates a new Box2d with the specified dimensions.
        /// </summary>
        /// <param name="top">The position of the top boundary.</param>
        /// <param name="left">The position of the left boundary.</param>
        /// <param name="width">The width of the box.</param>
        /// <param name="height">The height of the box.</param>
        /// <returns>A new OpenTK.Box2d with the specfied dimensions.</returns>
        public static Box2d FromDimensions(double left, double top, double width, double height)
        {
            return new Box2d(left, top, left + width, top + height);
        }

        /// <summary>
        /// Creates a new Box2d with the specified dimensions.
        /// </summary>
        /// <param name="position">The position of the top left corner.</param>
        /// <param name="size">The size of the box.</param>
        /// <returns>A new OpenTK.Box2d with the specfied dimensions.</returns>
        public static Box2d FromDimensions(Vector2d position, Vector2d size)
        {
            return FromDimensions(position.X, position.Y, size.X, size.Y);
        }

        /// <summary>
        /// Creates a new Box2d from the specified corners.
        /// </summary>
        /// <param name="corner1">One of the corners of the box.</param>
        /// <param name="corner2">The opposite corner of the box.</param>
        /// <returns></returns>
        public static Box2d FromCorners(Vector2d corner1, Vector2d corner2)
        {
            Box2d box;
            if (corner1.X < corner2.X)
            {
                box.Left = corner1.X;
                box.Right = corner2.X;
            }
            else
            {
                box.Left = corner2.X;
                box.Right = corner1.X;
            }

            if (corner1.Y < corner2.Y)
            {
                box.Top = corner1.Y;
                box.Bottom = corner2.Y;
            }
            else
            {
                box.Top = corner2.Y;
                box.Bottom = corner1.Y;
            }

            return box;
        }

        /// <summary>
        /// Gets a double describing the width of the Box2d structure.
        /// </summary>
        public double Width { get { return (double)System.Math.Abs(Right - Left); } }

        /// <summary>
        /// Gets a double describing the height of the Box2d structure.
        /// </summary>
        public double Height { get { return (double)System.Math.Abs(Bottom - Top); } }

        /// <summary>
        /// Returns whether the box contains the specified point.
        /// </summary>
        /// <param name="point">The point to query.</param>
        /// <returns>Whether this box contains the point.</returns>
        public bool Contains(Vector2d point)
        {
            return (point.X >= Left != point.X > Right) && (point.Y >= Top != point.Y > Bottom);
        }

        /// <summary>
        /// Returns a Box2d translated by the given amount.
        /// </summary>
        /// <param name="point"></param>
        /// <returns></returns>
        public Box2d Translate(Vector2d point)
        {
            return new Box2d(Left + point.X, Top + point.Y, Right + point.X, Bottom + point.Y);
        }

        /// <summary>
        /// Equality comparator.
        /// </summary>
        public static bool operator ==(Box2d left, Box2d right)
        {
            return left.Bottom == right.Bottom && left.Top == right.Top &&
                left.Left == right.Left && left.Right == right.Right;
        }

        /// <summary>
        /// Inequality comparator.
        /// </summary>
        public static bool operator !=(Box2d left, Box2d right)
        {
            return !(left == right);
        }

        /// <summary>
        /// Functional equality comparator.
        /// </summary>
        public bool Equals(Box2d other)
        {
            return this == other;
        }

        /// <summary>
        /// Implements Object.Equals.
        /// </summary>
        public override bool Equals(object obj)
        {
            return obj is Box2d && Equals((Box2d) obj);
        }

        /// <summary>
        /// Gets the hash code for this Box2d.
        /// </summary>
        /// <returns></returns>
        public override int GetHashCode()
        {
            return Left.GetHashCode() ^ Right.GetHashCode() ^ Top.GetHashCode() ^ Bottom.GetHashCode();
        }

        private static string listSeparator = System.Globalization.CultureInfo.CurrentCulture.TextInfo.ListSeparator;
        /// <summary>
        /// Returns a <see cref="System.String"/> describing the current instance.
        /// </summary>
        /// <returns></returns>
        public override string ToString()
        {
            return String.Format("({0}{4} {1}) - ({2}{4} {3})", Left, Top, Right, Bottom, listSeparator);
        }
    }
}