/**
 * Copyright (c) 2023 Dominic Masters
 * 
 * This software is released under the MIT License.
 * https://opensource.org/licenses/MIT
 */

#pragma once
#include "dawn.h"
#include "dawnopengl.h"
#include "colorgl.h"

extern int32_t MESH_ACTIVE_COUNT;

/** Indice that references a specific vertice */
typedef int32_t meshindice_t;

typedef enum {
  /** Draw the mesh as a list of points */
  MESH_DRAW_MODE_POINTS = GL_POINTS,
  /** Draw the mesh as a list of lines */
  MESH_DRAW_MODE_LINES = GL_LINES,
  /** Draw the mesh as a list of triangles */
  MESH_DRAW_MODE_TRIANGLES = GL_TRIANGLES
} meshdrawmode_t;

typedef struct {
  /** Pointer to the vertex buffer on the GPU */
  GLuint vertexBuffer;
  /** Pointer to the index buffer on the GPU */
  GLuint indexBuffer;
  /** Pointer to the vertex buffer on the GPU */
  GLuint vertexArray;

  /** How many vertices are in the mesh */
  int32_t verticeCount;
  /** How many indices are in the mesh */
  int32_t indiceCount;
} mesh_t;

/**
 * Initializes a mesh to a default state. Mesh's must be initialized and 
 * destroyed.
 * 
 * @param mesh Mesh to initialize.
 */
void meshInit(mesh_t *mesh);

/**
 * Create a new set of buffers for the mesh to use.
 * 
 * @param mesh Mesh to create buffers for.
 * @param verticeCount How many Vertices will this buffer support.
 * @param indiceCount How many Indices will this buffer support.
 */
void meshCreateBuffers(
  mesh_t *mesh,
  const int32_t verticeCount,
  const int32_t indiceCount
);

/**
 * Cleanup the buffers on a given mesh. This is useful if you intend to expand
 * the count of vertices your mesh supports.
 * 
 * @param mesh Mesh to destroy buffers for.
 */
void meshDestroyBuffers(mesh_t *mesh);

/**
 * Write vertice coordinates to the mesh.
 * 
 * @param mesh Mesh to write to.
 * @param positions Array of coordinates to write.
 * @param position Position, within the buffer, to write to.
 * @param count How many coordinates are in the array.
 */
void meshBufferPositions(
  const mesh_t *mesh,
  const vec3_t *positions,
  const size_t position,
  const size_t count
);

/**
 * Write texture coordinates to the mesh.
 * 
 * @param mesh Mesh to write to.
 * @param coordinates Array of coordinates to write.
 * @param position Position, within the buffer, to write to.
 * @param count How many coordinates are in the array.
 */
void meshBufferCoordinates(
  const mesh_t *mesh,
  const vec2_t *coordinates,
  const size_t position,
  const size_t count
);

/**
 * Write colors to the mesh.
 * 
 * @param mesh Mesh to write to.
 * @param colors Array of colors to write.
 * @param position Position, within the buffer, to write to.
 * @param count How many colors are in the array.
 */
void meshBufferColors(
  const mesh_t *mesh,
  const color4f_t *colors,
  const size_t position,
  const size_t count
);

/**
 * Write indices to the mesh.
 * 
 * @param mesh Mesh to write to.
 * @param indices Array of indices to write.
 * @param position Position, within the buffer, to write to.
 * @param count How many indices are in the array.
 */
void meshBufferIndices(
  const mesh_t *mesh,
  const meshindice_t *indices,
  const size_t position,
  const size_t count
);

/**
 * Draw a mesh. Meshes are drawn by their indices.
 * 
 * @param mesh Mesh to draw.
 * @param mode Which drawing mode to use to draw the mesh.
 * @param indiceStart Start indice (index) to draw.
 * @param indiceCount Count of indices to draw. Use -1 to draw all.
 */
void meshDraw(
  const mesh_t *mesh,
  const meshdrawmode_t mode,
  const int32_t indiceStart,
  const int32_t indiceCount
);

/**
 * Cleanup a mesh. This will destroy the buffers and free the mesh.
 * 
 * @param mesh Mesh to cleanup.
 */
void meshDispose(mesh_t *mesh);