#include "MetaCoreRender/MetaCoreMesh.h"

#include <glad/glad.h>

namespace MetaCore {

MetaCoreMesh::~MetaCoreMesh() {
    Shutdown();
}

bool MetaCoreMesh::Build(const std::vector<MetaCoreVertex>& vertices, const std::vector<std::uint32_t>& indices, MetaCorePrimitiveType primitiveType) {
    Shutdown();

    PrimitiveType_ = primitiveType;
    IndexCount_ = static_cast<std::uint32_t>(indices.size());

    glGenVertexArrays(1, &VertexArrayHandle_);
    glGenBuffers(1, &VertexBufferHandle_);
    glGenBuffers(1, &IndexBufferHandle_);

    glBindVertexArray(VertexArrayHandle_);

    glBindBuffer(GL_ARRAY_BUFFER, VertexBufferHandle_);
    glBufferData(
        GL_ARRAY_BUFFER,
        static_cast<GLsizeiptr>(vertices.size() * sizeof(MetaCoreVertex)),
        vertices.data(),
        GL_STATIC_DRAW
    );

    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, IndexBufferHandle_);
    glBufferData(
        GL_ELEMENT_ARRAY_BUFFER,
        static_cast<GLsizeiptr>(indices.size() * sizeof(std::uint32_t)),
        indices.data(),
        GL_STATIC_DRAW
    );

    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(MetaCoreVertex), reinterpret_cast<const void*>(offsetof(MetaCoreVertex, Position)));

    glEnableVertexAttribArray(1);
    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(MetaCoreVertex), reinterpret_cast<const void*>(offsetof(MetaCoreVertex, Normal)));

    glEnableVertexAttribArray(2);
    glVertexAttribPointer(2, 4, GL_FLOAT, GL_FALSE, sizeof(MetaCoreVertex), reinterpret_cast<const void*>(offsetof(MetaCoreVertex, Color)));

    glBindVertexArray(0);
    return true;
}

void MetaCoreMesh::Shutdown() {
    if (IndexBufferHandle_ != 0) {
        glDeleteBuffers(1, &IndexBufferHandle_);
        IndexBufferHandle_ = 0;
    }

    if (VertexBufferHandle_ != 0) {
        glDeleteBuffers(1, &VertexBufferHandle_);
        VertexBufferHandle_ = 0;
    }

    if (VertexArrayHandle_ != 0) {
        glDeleteVertexArrays(1, &VertexArrayHandle_);
        VertexArrayHandle_ = 0;
    }

    IndexCount_ = 0;
}

void MetaCoreMesh::Draw() const {
    glBindVertexArray(VertexArrayHandle_);
    glDrawElements(
        PrimitiveType_ == MetaCorePrimitiveType::Triangles ? GL_TRIANGLES : GL_LINES,
        static_cast<GLsizei>(IndexCount_),
        GL_UNSIGNED_INT,
        nullptr
    );
    glBindVertexArray(0);
}

}  // namespace MetaCore