using System;
using System.Collections.Generic;
using System.Linq;
using OpenTK;
using OpenTK.Graphics;
using OpenTK.Graphics.OpenGL4;

namespace SM.OGL.Mesh
{
    /// <summary>
    /// Represents a Vertex Buffer Object used for meshes.
    /// </summary>
    public class VBO : List<float>
    {
        /// <summary>
        /// Specifies the expected usage pattern of the data store.
        /// </summary>
        public BufferUsageHint BufferUsageHint;
        /// <summary>
        /// Specifies the data type of each component in the array.
        /// </summary>
        public VertexAttribPointerType PointerType;
        /// <summary>
        /// Specifies the number of components per generic vertex attribute. Must be 1, 2, 3, 4. 
        /// </summary>
        public int PointerSize;
        /// <summary>
        /// Normalise floats?
        /// </summary>
        public bool Normalised;
        /// <summary>
        /// Specifies the byte offset between consecutive generic vertex attributes.
        /// </summary>
        public int PointerStride;
        /// <summary>
        /// Specifies a offset of the first component of the first generic vertex attribute in the array in the data store of the buffer currently bound to the GL_ARRAY_BUFFER target.
        /// </summary>
        public int PointerOffset;

        /// <summary>
        /// Generates a VBO for inserting mesh data.
        /// </summary>
        /// <param name="bufferUsageHint">Specifies the expected usage pattern of the data store. <para>Default: StaticDraw</para></param>
        /// <param name="pointerType">Specifies the data type of each component in the array. <para>Default: Float</para></param>
        /// <param name="pointerSize">Specifies the number of components per generic vertex attribute. Must be 1, 2, 3, 4. <para>Default: 3</para></param>
        /// <param name="pointerStride">Specifies the byte offset between consecutive generic vertex attributes. <para>Default: 0</para></param>
        /// <param name="pointerOffset">Specifies a offset of the first component of the first generic vertex attribute in the array in the data store of the buffer currently bound to the GL_ARRAY_BUFFER target. <para>Default: 0</para></param>
        /// <param name="normalised">Normalise floats? <para>Default: false</para></param>
        public VBO(BufferUsageHint bufferUsageHint = BufferUsageHint.StaticDraw,
            VertexAttribPointerType pointerType = VertexAttribPointerType.Float, int pointerSize = 3,
            int pointerStride = 0, int pointerOffset = 0, bool normalised = false)
        {
            BufferUsageHint = bufferUsageHint;
            PointerType = pointerType;
            PointerSize = pointerSize;
            PointerStride = pointerStride;
            PointerOffset = pointerOffset;
            Normalised = normalised;
        }

        /// <summary>
        /// Adds two values to the VBO.
        /// </summary>
        public void Add(float x, float y) => AddRange(new[] {x,y});
        /// <summary>
        /// Adds three values to the VBO.
        /// </summary>
        public void Add(float x, float y, float z) => AddRange(new[] {x,y,z});
        /// <summary>
        /// Adds four values to the VBO.
        /// </summary>
        public void Add(float x, float y, float z, float w) => AddRange(new[] {x,y,z,w});
        /// <summary>
        /// Adds a Vector2. 
        /// </summary>
        public void Add(Vector2 vector) => Add(vector.X, vector.Y);
        /// <summary>
        /// Adds a Vector2 and a value.
        /// </summary>
        public void Add(Vector2 vector, float z) => Add(vector.X, vector.Y, z);
        /// <summary>
        /// Adds a Vector2 and two values.
        /// </summary>
        public void Add(Vector2 vector, float z, float w) => Add(vector.X, vector.Y, z, w);
        /// <summary>
        /// Adds a Vector3.
        /// </summary>
        public void Add(Vector3 vector) => Add(vector.X, vector.Y, vector.Z);
        /// <summary>
        /// Adds a Vector3 and a value.
        /// </summary>
        public void Add(Vector3 vector, float w) => Add(vector.X, vector.Y, vector.Z, w);
        /// <summary>
        /// Adds a vector4.
        /// </summary>
        /// <param name="vector"></param>
        public void Add(Vector4 vector) => Add(vector.X, vector.Y, vector.Z, vector.W);
        /// <summary>
        /// Adds a color.
        /// </summary>
        public void Add(Color4 color) => Add(color.R, color.G, color.B, color.A);

        /// <summary>
        /// Binds the buffer to the active VAO.
        /// </summary>
        /// <param name="attribID">The id for the attribute.</param>
        internal void BindBuffer(int attribID)
        {
            float[] data = ToArray();

            int buffer = GL.GenBuffer();
            GL.BindBuffer(BufferTarget.ArrayBuffer, buffer);
            GL.BufferData(BufferTarget.ArrayBuffer, data.Length * sizeof(float), data, BufferUsageHint);

            GL.VertexAttribPointer(attribID, PointerSize, PointerType, Normalised, PointerStride, PointerOffset);
            GL.EnableVertexAttribArray(attribID);
            GL.BindBuffer(BufferTarget.ArrayBuffer, 0);
        }
    }
}