/* SPDX-License-Identifier: GPL-2.0-or-later
 * Copyright 2016 by Mike Erwin. All rights reserved. */

/** \file
 * \ingroup gpu
 */

#include "gpu_shader_interface.hh"
#include "gpu_vertex_buffer_private.hh"

#include "gl_batch.hh"
#include "gl_context.hh"
#include "gl_index_buffer.hh"
#include "gl_storage_buffer.hh"
#include "gl_vertex_buffer.hh"

#include "gl_vertex_array.hh"

namespace blender::gpu {

/* -------------------------------------------------------------------- */
/** \name Vertex Array Bindings
 * \{ */

/** Returns enabled vertex pointers as a bit-flag (one bit per attribute). */
static uint16_t vbo_bind(const ShaderInterface *interface,
                         const GPUVertFormat *format,
                         uint v_first,
                         uint v_len,
                         const bool use_instancing)
{
  uint16_t enabled_attrib = 0;
  const uint attr_len = format->attr_len;
  uint stride = format->stride;
  uint offset = 0;
  GLuint divisor = (use_instancing) ? 1 : 0;

  for (uint a_idx = 0; a_idx < attr_len; a_idx++) {
    const GPUVertAttr *a = &format->attrs[a_idx];

    if (format->deinterleaved) {
      offset += ((a_idx == 0) ? 0 : format->attrs[a_idx - 1].size) * v_len;
      stride = a->size;
    }
    else {
      offset = a->offset;
    }

    /* This is in fact an offset in memory. */
    const GLvoid *pointer = (const GLubyte *)(intptr_t)(offset + v_first * stride);
    const GLenum type = to_gl(static_cast<GPUVertCompType>(a->comp_type));

    for (uint n_idx = 0; n_idx < a->name_len; n_idx++) {
      const char *name = GPU_vertformat_attr_name_get(format, a, n_idx);
      const ShaderInput *input = interface->attr_get(name);

      if (input == nullptr || input->location == -1) {
        continue;
      }

      enabled_attrib |= (1 << input->location);

      if (ELEM(a->comp_len, 16, 12, 8)) {
        BLI_assert(a->fetch_mode == GPU_FETCH_FLOAT);
        BLI_assert(a->comp_type == GPU_COMP_F32);
        for (int i = 0; i < a->comp_len / 4; i++) {
          glEnableVertexAttribArray(input->location + i);
          glVertexAttribDivisor(input->location + i, divisor);
          glVertexAttribPointer(
              input->location + i, 4, type, GL_FALSE, stride, (const GLubyte *)pointer + i * 16);
        }
      }
      else {
        glEnableVertexAttribArray(input->location);
        glVertexAttribDivisor(input->location, divisor);

        switch (a->fetch_mode) {
          case GPU_FETCH_FLOAT:
          case GPU_FETCH_INT_TO_FLOAT:
            glVertexAttribPointer(input->location, a->comp_len, type, GL_FALSE, stride, pointer);
            break;
          case GPU_FETCH_INT_TO_FLOAT_UNIT:
            glVertexAttribPointer(input->location, a->comp_len, type, GL_TRUE, stride, pointer);
            break;
          case GPU_FETCH_INT:
            glVertexAttribIPointer(input->location, a->comp_len, type, stride, pointer);
            break;
        }
      }
    }
  }
  return enabled_attrib;
}

void GLVertArray::update_bindings(const GLuint vao,
                                  const GPUBatch *batch_, /* Should be GLBatch. */
                                  const ShaderInterface *interface,
                                  const int base_instance)
{
  const GLBatch *batch = static_cast<const GLBatch *>(batch_);
  uint16_t attr_mask = interface->enabled_attr_mask_;

  glBindVertexArray(vao);

  /* Reverse order so first VBO'S have more prevalence (in term of attribute override). */
  for (int v = GPU_BATCH_VBO_MAX_LEN - 1; v > -1; v--) {
    GLVertBuf *vbo = batch->verts_(v);
    if (vbo) {
      vbo->bind();
      attr_mask &= ~vbo_bind(interface, &vbo->format, 0, vbo->vertex_len, false);
    }
  }

  for (int v = GPU_BATCH_INST_VBO_MAX_LEN - 1; v > -1; v--) {
    GLVertBuf *vbo = batch->inst_(v);
    if (vbo) {
      vbo->bind();
      attr_mask &= ~vbo_bind(interface, &vbo->format, base_instance, vbo->vertex_len, true);
    }
  }

  if (batch->resource_id_buf) {
    const ShaderInput *input = interface->attr_get("drw_ResourceID");
    if (input) {
      dynamic_cast<GLStorageBuf *>(unwrap(batch->resource_id_buf))->bind_as(GL_ARRAY_BUFFER);
      glEnableVertexAttribArray(input->location);
      glVertexAttribDivisor(input->location, 1);
      glVertexAttribIPointer(
          input->location, 1, to_gl(GPU_COMP_I32), sizeof(uint32_t), (GLvoid *)nullptr);
      attr_mask &= ~(1 << input->location);
    }
  }

  if (attr_mask != 0 && GLContext::vertex_attrib_binding_support) {
    for (uint16_t mask = 1, a = 0; a < 16; a++, mask <<= 1) {
      if (attr_mask & mask) {
        GLContext *ctx = GLContext::get();
        /* This replaces glVertexAttrib4f(a, 0.0f, 0.0f, 0.0f, 1.0f); with a more modern style.
         * Fix issues for some drivers (see T75069). */
        glBindVertexBuffer(a, ctx->default_attr_vbo_, (intptr_t)0, (intptr_t)0);
        glEnableVertexAttribArray(a);
        glVertexAttribFormat(a, 4, GL_FLOAT, GL_FALSE, 0);
        glVertexAttribBinding(a, a);
      }
    }
  }

  if (batch->elem) {
    /* Binds the index buffer. This state is also saved in the VAO. */
    static_cast<GLIndexBuf *>(unwrap(batch->elem))->bind();
  }
}

void GLVertArray::update_bindings(const GLuint vao,
                                  const uint v_first,
                                  const GPUVertFormat *format,
                                  const ShaderInterface *interface)
{
  glBindVertexArray(vao);

  vbo_bind(interface, format, v_first, 0, false);
}

/** \} */

}  // namespace blender::gpu