// Copyright (c) 2010-2014 SharpDX - Alexandre Mutel
// 
// 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.

using System;
using System.Globalization;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using SharpDX.Mathematics.Interop;

namespace SharpDX
{
    /// <summary>
    /// Defines the viewport dimensions.
    /// </summary>
    [StructLayout(LayoutKind.Sequential, Pack = 4)]
    public struct Viewport : IEquatable<Viewport>
    {
        /// <summary>
        /// Position of the pixel coordinate of the upper-left corner of the viewport.
        /// </summary>
        public int X;

        /// <summary>
        /// Position of the pixel coordinate of the upper-left corner of the viewport.
        /// </summary>
        public int Y;

        /// <summary>
        /// Width dimension of the viewport.
        /// </summary>
        public int Width;

        /// <summary>
        /// Height dimension of the viewport.
        /// </summary>
        public int Height;

        /// <summary>
        /// Gets or sets the minimum depth of the clip volume.
        /// </summary>
        public float MinDepth;

        /// <summary>
        /// Gets or sets the maximum depth of the clip volume.
        /// </summary>
        public float MaxDepth;

        /// <summary>
        /// Initializes a new instance of the <see cref="Viewport"/> struct.
        /// </summary>
        /// <param name="x">The x coordinate of the upper-left corner of the viewport in pixels.</param>
        /// <param name="y">The y coordinate of the upper-left corner of the viewport in pixels.</param>
        /// <param name="width">The width of the viewport in pixels.</param>
        /// <param name="height">The height of the viewport in pixels.</param>
        public Viewport(int x, int y, int width, int height)
        {
            X = x;
            Y = y;
            Width = width;
            Height = height;
            MinDepth = 0f;
            MaxDepth = 1f;
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="Viewport"/> struct.
        /// </summary>
        /// <param name="x">The x coordinate of the upper-left corner of the viewport in pixels.</param>
        /// <param name="y">The y coordinate of the upper-left corner of the viewport in pixels.</param>
        /// <param name="width">The width of the viewport in pixels.</param>
        /// <param name="height">The height of the viewport in pixels.</param>
        /// <param name="minDepth">The minimum depth of the clip volume.</param>
        /// <param name="maxDepth">The maximum depth of the clip volume.</param>
        public Viewport(int x, int y, int width, int height, float minDepth, float maxDepth)
        {
            X = x;
            Y = y;
            Width = width;
            Height = height;
            MinDepth = minDepth;
            MaxDepth = maxDepth;
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="Viewport"/> struct.
        /// </summary>
        /// <param name="bounds">A bounding box that defines the location and size of the viewport in a render target.</param>
        public Viewport(Rectangle bounds)
        {
            X = bounds.X;
            Y = bounds.Y;
            Width = bounds.Width;
            Height = bounds.Height;
            MinDepth = 0f;
            MaxDepth = 1f;
        }

        /// <summary>
        /// Gets the size of this resource.
        /// </summary>
        /// <value>The bounds.</value>
        public Rectangle Bounds
        {
            get
            {
                return new Rectangle(X, Y, Width, Height);
            }

            set
            {
                X = value.X;
                Y = value.Y;
                Width = value.Width;
                Height = value.Height;
            }
        }

        /// <summary>
        /// Determines whether the specified <see cref="Viewport"/> is equal to this instance.
        /// </summary>
        /// <param name="other">The <see cref="Viewport"/> to compare with this instance.</param>
        /// <returns>
        /// <c>true</c> if the specified <see cref="Viewport"/> is equal to this instance; otherwise, <c>false</c>.
        /// </returns>
        [MethodImpl((MethodImplOptions)0x100)] // MethodImplOptions.AggressiveInlining
        public bool Equals(ref Viewport other)
        {
            return X == other.X && Y == other.Y && Width == other.Width && Height == other.Height && MathUtil.NearEqual(MinDepth, other.MinDepth) && MathUtil.NearEqual(MaxDepth, other.MaxDepth);
        }

        /// <summary>
        /// Determines whether the specified <see cref="Viewport"/> is equal to this instance.
        /// </summary>
        /// <param name="other">The <see cref="Viewport"/> to compare with this instance.</param>
        /// <returns>
        /// <c>true</c> if the specified <see cref="Viewport"/> is equal to this instance; otherwise, <c>false</c>.
        /// </returns>
        [MethodImpl((MethodImplOptions)0x100)] // MethodImplOptions.AggressiveInlining
        public bool Equals(Viewport other)
        {
            return Equals(ref other);
        }

        /// <summary>
        /// Determines whether the specified object is equal to this instance.
        /// </summary>
        /// <param name="obj">The object to compare with this instance.</param>
        /// <returns>
        /// <c>true</c> if the specified object is equal to this instance; otherwise, <c>false</c>.
        /// </returns>
        public override bool Equals(object obj)
        {
            if(!(obj is Viewport))
                return false;

            var strongValue = (Viewport)obj;
            return Equals(ref strongValue);
        }

        /// <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()
        {
            unchecked
            {
                int hashCode = X;
                hashCode = (hashCode * 397) ^ Y;
                hashCode = (hashCode * 397) ^ Width;
                hashCode = (hashCode * 397) ^ Height;
                hashCode = (hashCode * 397) ^ MinDepth.GetHashCode();
                hashCode = (hashCode * 397) ^ MaxDepth.GetHashCode();
                return hashCode;
            }
        }
        
        /// <summary>
        /// Implements the operator ==.
        /// </summary>
        /// <param name="left">The left.</param>
        /// <param name="right">The right.</param>
        /// <returns>The result of the operator.</returns>
        [MethodImpl((MethodImplOptions)0x100)] // MethodImplOptions.AggressiveInlining
        public static bool operator ==(Viewport left, Viewport right)
        {
            return left.Equals(ref right);
        }

        /// <summary>
        /// Implements the operator !=.
        /// </summary>
        /// <param name="left">The left.</param>
        /// <param name="right">The right.</param>
        /// <returns>The result of the operator.</returns>
        [MethodImpl((MethodImplOptions)0x100)] // MethodImplOptions.AggressiveInlining
        public static bool operator !=(Viewport left, Viewport right)
        {
            return !left.Equals(ref right);
        }

        /// <summary>
        /// Retrieves a string representation of this object.
        /// </summary>
        /// <returns>A <see cref="System.String" /> that represents this instance.</returns>
        public override string ToString()
        {
            return string.Format(CultureInfo.CurrentCulture, "{{X:{0} Y:{1} Width:{2} Height:{3} MinDepth:{4} MaxDepth:{5}}}", X, Y, Width, Height, MinDepth, MaxDepth);
        }

        /// <summary>
        /// Projects a 3D vector from object space into screen space.
        /// </summary>
        /// <param name="source">The vector to project.</param>
        /// <param name="projection">The projection matrix.</param>
        /// <param name="view">The view matrix.</param>
        /// <param name="world">The world matrix.</param>
        /// <returns>The projected vector.</returns>
        public Vector3 Project(Vector3 source, Matrix projection, Matrix view, Matrix world)
        {
            Matrix matrix;
            Matrix.Multiply(ref world, ref view, out matrix);
            Matrix.Multiply(ref matrix, ref projection, out matrix);

            Vector3 vector;
            Project(ref source, ref matrix, out vector);
            return vector;
        }

        /// <summary>
        /// Projects a 3D vector from object space into screen space.
        /// </summary>
        /// <param name="source">The vector to project.</param>
        /// <param name="matrix">A combined WorldViewProjection matrix.</param>
        /// <param name="vector">The projected vector.</param>
        public void Project(ref Vector3 source, ref Matrix matrix, out Vector3 vector)
        {
            Vector3.Transform(ref source, ref matrix, out vector);
            float a = (((source.X * matrix.M14) + (source.Y * matrix.M24)) + (source.Z * matrix.M34)) + matrix.M44;

            if (!MathUtil.IsOne(a))
            {
                vector = (vector / a);
            }

            vector.X = (((vector.X + 1f) * 0.5f) * Width) + X;
            vector.Y = (((-vector.Y + 1f) * 0.5f) * Height) + Y;
            vector.Z = (vector.Z * (MaxDepth - MinDepth)) + MinDepth;
        }

        /// <summary>
        /// Converts a screen space point into a corresponding point in world space.
        /// </summary>
        /// <param name="source">The vector to project.</param>
        /// <param name="projection">The projection matrix.</param>
        /// <param name="view">The view matrix.</param>
        /// <param name="world">The world matrix.</param>
        /// <returns>The unprojected Vector.</returns>
        public Vector3 Unproject(Vector3 source, Matrix projection, Matrix view, Matrix world)
        {
            Matrix matrix;
            Matrix.Multiply(ref world, ref view, out matrix);
            Matrix.Multiply(ref matrix, ref projection, out matrix);
            Matrix.Invert(ref matrix, out matrix);

            Vector3 vector;
            Unproject(ref source, ref matrix, out vector);
            return vector;
        }

        /// <summary>
        /// Converts a screen space point into a corresponding point in world space.
        /// </summary>
        /// <param name="source">The vector to project.</param>
        /// <param name="matrix">An inverted combined WorldViewProjection matrix.</param>
        /// <param name="vector">The unprojected vector.</param>
        public void Unproject(ref Vector3 source, ref Matrix matrix, out Vector3 vector)
        {
            vector.X = (((source.X - X) / (Width)) * 2f) - 1f;
            vector.Y = -((((source.Y - Y) / (Height)) * 2f) - 1f);
            vector.Z = (source.Z - MinDepth) / (MaxDepth - MinDepth);

            float a = (((vector.X * matrix.M14) + (vector.Y * matrix.M24)) + (vector.Z * matrix.M34)) + matrix.M44;
            Vector3.Transform(ref vector, ref matrix, out vector);

            if (!MathUtil.IsOne(a))
            {
                vector = (vector / a);
            }
        }

        /// <summary>
        /// Gets the aspect ratio used by the viewport.
        /// </summary>
        /// <value>The aspect ratio.</value>
        public float AspectRatio
        {
            get
            {
                if (Height != 0)
                {
                    return Width / (float)Height;
                }
                return 0f;
            }
        }

        /// <summary>
        /// Performs an implicit conversion from <see cref="Viewport"/> to <see cref="RawViewport"/>.
        /// </summary>
        /// <param name="value">The value.</param>
        /// <returns>The result of the conversion.</returns>
        public unsafe static implicit operator RawViewport(Viewport value)
        {
            return *(RawViewport*)&value;
        }

        /// <summary>
        /// Performs an implicit conversion from <see cref="Viewport"/> to <see cref="RawViewport"/>.
        /// </summary>
        /// <param name="value">The value.</param>
        /// <returns>The result of the conversion.</returns>
        public unsafe static implicit operator RawViewportF(Viewport value)
        {
            var viewportF = (ViewportF)value;
            return *(RawViewportF*)&viewportF;
        }

        /// <summary>
        /// Performs an implicit conversion from <see cref="RawViewport"/> to <see cref="Viewport"/>.
        /// </summary>
        /// <param name="value">The value.</param>
        /// <returns>The result of the conversion.</returns>
        public unsafe static implicit operator Viewport(RawViewport value)
        {
            return *(Viewport*)&value;
        }
    }
}