#include <plot/render/buffer.hpp>

namespace plot::render {
namespace detail {

bool InstanceStore::create(Status* st) noexcept {
  // plot::gl::Buffer::create() already reports Unsupported while the entry
  // points are unresolved and GLFailure when the driver hands out no name, so
  // the wrapper only has to propagate its answer.
  if (!buffer_.create(st)) {
    return false;
  }
  capacity_ = 0;
  return true;
}

void InstanceStore::upload(const void* data, u32 count, usize instance_bytes) noexcept {
  if (buffer_.id() == 0 || count == 0 || instance_bytes == 0) {
    return;
  }
  if (count > capacity_) {
    // Only a workload larger than anything staged so far pays for an
    // allocation; a frame that repeats the previous one writes into the store
    // that is already there.
    buffer_.upload(nullptr, static_cast<usize>(count) * instance_bytes, gl::GL_STREAM_DRAW);
    capacity_ = count;
  }
  buffer_.upload_sub(data, static_cast<usize>(count) * instance_bytes, 0);
}

}  // namespace detail
}  // namespace plot::render