// Copyright 2021 Benjamin Barenblat
//
// 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
//
//     https://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.

// Vertex array objects.

#ifndef GLPLANET_SRC_GL_VERTEX_ARRAY_H_
#define GLPLANET_SRC_GL_VERTEX_ARRAY_H_

#include <stdint.h>

#include <utility>

#include "src/gl/buffer.h"
#include "src/gl/error.h"
#include "third_party/abseil/absl/types/optional.h"
#include "third_party/glew/include/GL/glew.h"

namespace gl {

enum class VertexAttributeType : GLenum {
  kByte = GL_BYTE,
  kShort = GL_SHORT,
  kInt = GL_INT,
  kFixed = GL_FIXED,
  kFloat = GL_FLOAT,
  kHalfFloat = GL_HALF_FLOAT,
  kDouble = GL_DOUBLE,
  kUnsignedByte = GL_UNSIGNED_BYTE,
  kUnsignedShort = GL_UNSIGNED_SHORT,
  kUnsignedInt = GL_UNSIGNED_INT,
  kInt2x10x10x10Rev = GL_INT_2_10_10_10_REV,
  kUnsignedInt2x10x10x10Rev = GL_UNSIGNED_INT_2_10_10_10_REV,
  kUnsignedInt10f11f11fRev = GL_UNSIGNED_INT_10F_11F_11F_REV,
};

// A VAO.
class VertexArray final {
 public:
  explicit VertexArray() noexcept(!(gl_internal::kThreadSafetyChecks ||
                                    gl_internal::kAggressiveErrorChecking)) {
    gl_internal::CheckThreadSafety();
    glCreateVertexArrays(1, &array_);
    gl_internal::UnnecessaryErrorCheck();
  }

  VertexArray(VertexArray&&) noexcept = default;
  VertexArray& operator=(VertexArray&&) noexcept = default;

  ~VertexArray() noexcept(!(gl_internal::kThreadSafetyChecks ||
                            gl_internal::kAggressiveErrorChecking)) {
    gl_internal::CheckThreadSafety();
    glDeleteVertexArrays(1, &array_);
    gl_internal::UnnecessaryErrorCheck();
  }

  // Attaches the specified vertex buffer to the VAO.
  void SetVertexBuffer(VertexBuffer vertices) {
    gl_internal::CheckThreadSafety();
    glVertexArrayVertexBuffer(array_, /*bindingindex=*/0, vertices.id(),
                              /*offset=*/0, vertices.element_size());
    // This error check is necessary because the elements of the VBO might be
    // too large for the implementation to handle.
    gl_internal::ErrorCheck();
    vertices_ = std::move(vertices);
  }

  // Specifies the organization of data in the attached VAO.
  void SetVertexAttributeFormat(int index, int size, VertexAttributeType type,
                                int offset, bool normalized = false);

  // Attaches the specified element buffer to the VAO. The element buffer must
  // outlive this VAO.
  void SetElementBuffer(ElementBuffer elements) noexcept(
      !(gl_internal::kThreadSafetyChecks ||
        gl_internal::kAggressiveErrorChecking)) {
    gl_internal::CheckThreadSafety();
    glVertexArrayElementBuffer(array_, elements.id());
    gl_internal::UnnecessaryErrorCheck();
    elements_ = std::move(elements);
  }

  // Returns the element buffer attached to this VAO.
  const ElementBuffer& element_buffer() const noexcept { return elements_; }

  // The GL identifier for this VAO.
  unsigned int id() const noexcept { return array_; }

 private:
  GLuint array_;

  VertexBuffer vertices_;
  ElementBuffer elements_;
};

}  // namespace gl

#endif  // GLPLANET_SRC_GL_VERTEX_ARRAY_H_