#include "imm_renderer_impl.h"

#include <gfx/core.h>
#include <gfx/util/shader.h>

#include <math/aabb3.h>

#include <assert.h>
#include <string.h> // memcpy

bool imm_renderer_make(ImmRenderer* renderer, GfxCore* gfxcore) {
  assert(renderer);
  assert(gfxcore);

  const size_t num_triangle_verts = IMM_MAX_NUM_TRIANGLES * 3;

  renderer->gfxcore = gfxcore;

  renderer->triangles = gfx_make_geometry(
      gfxcore, &(GeometryDesc){
                   .type         = Triangles,
                   .buffer_usage = BufferDynamic,
                   .num_verts    = num_triangle_verts,
                   .positions3d  = (BufferView3d){
                        .size_bytes = num_triangle_verts * sizeof(vec3)}});
  if (!renderer->triangles) {
    goto cleanup;
  }

  renderer->shader = gfx_make_immediate_mode_shader(gfxcore);
  if (!renderer->shader) {
    goto cleanup;
  }

  renderer->matrix_stack[0] = mat4_id();
  renderer->stack_pointer   = 0;

  gfx_imm_set_colour(renderer, vec4_make(0.0, 0.0, 0.0, 1.0));

  return true;

cleanup:
  imm_renderer_destroy(renderer);
  return false;
}

void imm_renderer_destroy(ImmRenderer* renderer) {
  assert(renderer);
  assert(renderer->gfxcore);

  if (renderer->triangles) {
    gfx_destroy_geometry(renderer->gfxcore, &renderer->triangles);
    // TODO: Could also destroy the geometry's buffers here.
  }

  if (renderer->shader) {
    gfx_destroy_shader_program(renderer->gfxcore, &renderer->shader);
  }
}

void imm_renderer_flush(ImmRenderer* renderer) {
  assert(renderer);

  if (renderer->num_triangle_verts > 0) {
    gfx_update_geometry(
        renderer->triangles,
        &(GeometryDesc){
            .num_verts   = renderer->num_triangle_verts,
            .positions3d = (BufferView3d){
                                          .data       = renderer->triangle_verts,
                                          .size_bytes = renderer->num_triangle_verts * sizeof(vec3)}
    });

    gfx_apply_uniforms(renderer->shader);
    gfx_render_geometry(renderer->triangles);

    renderer->num_triangle_verts = 0;
  }
}

void gfx_imm_start(ImmRenderer* renderer) {
  assert(renderer);
  // Shader uniforms are applied lazily.
  // TODO: In the event that gfx_activate_shader_program() activates uniforms
  // automatically for convenience, call an overload here that doesn't do so.
  ShaderProgram* shader = renderer->shader;
  gfx_activate_shader_program(shader);
}

void gfx_imm_end(ImmRenderer* renderer) {
  assert(renderer);
  imm_renderer_flush(renderer);
  gfx_deactivate_shader_program(renderer->shader);
}

void gfx_imm_draw_triangles(
    ImmRenderer* renderer, const vec3 verts[], size_t num_triangles) {
  assert(renderer);
  assert(verts);
  const size_t new_verts = num_triangles * 3;
  assert(
      renderer->num_triangle_verts + new_verts < (IMM_MAX_NUM_TRIANGLES * 3));

  memcpy(
      renderer->triangle_verts + renderer->num_triangle_verts, verts,
      new_verts * sizeof(vec3));

  renderer->num_triangle_verts += new_verts;
}

void gfx_imm_draw_triangle(ImmRenderer* renderer, const vec3 verts[3]) {
  gfx_imm_draw_triangles(renderer, verts, 1);
}

void gfx_imm_draw_aabb2(ImmRenderer* renderer, aabb2 box) {
  assert(renderer);

  // clang-format off
  const vec3 verts[4] = {
      vec3_make(box.min.x, box.min.y, 0),    // 3 ---- 2
      vec3_make(box.max.x, box.min.y, 0),    // |      |
      vec3_make(box.max.x, box.max.y, 0),    // |      |
      vec3_make(box.min.x, box.max.y, 0)};   // 0 ---- 1
  // clang-format on

#define tri(i0, i1, i2) verts[i0], verts[i1], verts[i2]
  const vec3 tris[6] = {tri(0, 1, 2), tri(0, 2, 3)};
#undef tri

  gfx_imm_draw_triangles(renderer, tris, 2);
}

void gfx_imm_draw_aabb3(ImmRenderer* renderer, aabb3 box) {
  assert(renderer);

  // clang-format off
  const vec3 vertices[8] = {
      vec3_make(box.min.x, box.min.y, box.max.z), //     7 ----- 6
      vec3_make(box.max.x, box.min.y, box.max.z), //    /       /|
      vec3_make(box.max.x, box.max.y, box.max.z), //   3 ----- 2 |
      vec3_make(box.min.x, box.max.y, box.max.z), //   |       | |
      vec3_make(box.min.x, box.min.y, box.min.z), //   | 4 ----- 5
      vec3_make(box.max.x, box.min.y, box.min.z), //   |/      |/
      vec3_make(box.max.x, box.max.y, box.min.z), //   0 ----- 1
      vec3_make(box.min.x, box.max.y, box.min.z)};
  // clang-format on

  gfx_imm_draw_box3(renderer, vertices);
}

void gfx_imm_draw_box3(ImmRenderer* renderer, const vec3 vertices[8]) {
  assert(renderer);
  assert(vertices);

  //     7 ----- 6
  //    /       /|
  //   3 ----- 2 |
  //   |       | |
  //   | 4 ----- 5
  //   |/      |/
  //   0 ----- 1

#define tri(i0, i1, i2) vertices[i0], vertices[i1], vertices[i2]
  const vec3 tris[36] = {// Front.
                         tri(0, 1, 2), tri(0, 2, 3),
                         // Right.
                         tri(1, 5, 6), tri(1, 6, 2),
                         // Back.
                         tri(5, 4, 7), tri(5, 7, 6),
                         // Left.
                         tri(4, 0, 03), tri(4, 3, 7),
                         // Top.
                         tri(3, 2, 6), tri(3, 6, 7),
                         // Bottom.
                         tri(0, 4, 5), tri(0, 5, 1)};

  gfx_imm_draw_triangles(renderer, tris, 12);
}

// Load the top of the matrix stack into the shader.
static void update_shader_model_matrix(ImmRenderer* renderer) {
  assert(renderer);
  imm_renderer_flush(renderer);
  gfx_set_mat4_uniform(
      renderer->shader, "Model",
      &renderer->matrix_stack[renderer->stack_pointer]);
}

void gfx_imm_load_identity(ImmRenderer* renderer) {
  assert(renderer);
  renderer->matrix_stack[0] = mat4_id();
  renderer->stack_pointer   = 0;
  update_shader_model_matrix(renderer);
}

void gfx_imm_push_matrix(ImmRenderer* renderer, const mat4* matrix) {
  assert(renderer);
  assert(matrix);
  assert(renderer->stack_pointer >= 0);
  assert(renderer->stack_pointer < IMM_MAX_NUM_MATRICES); // TODO: hard assert.

  renderer->matrix_stack[renderer->stack_pointer + 1] =
      mat4_mul(*matrix, renderer->matrix_stack[renderer->stack_pointer]);
  renderer->stack_pointer += 1;

  update_shader_model_matrix(renderer);
}

void gfx_imm_pop_matrix(ImmRenderer* renderer) {
  assert(renderer);
  assert(renderer->stack_pointer > 0); // TODO: hard assert.

  // For debugging, zero out the matrix stack as matrices are popped out.
  memset(
      &renderer->matrix_stack[renderer->stack_pointer], 0,
      sizeof(renderer->matrix_stack[0]));

  renderer->stack_pointer -= 1;

  update_shader_model_matrix(renderer);
}

void gfx_imm_translate(ImmRenderer* renderer, vec3 offset) {
  assert(renderer);
  const mat4 mat = mat4_translate(offset);
  gfx_imm_push_matrix(renderer, &mat);
}

void gfx_imm_set_camera(ImmRenderer* renderer, const Camera* camera) {
  assert(renderer);
  assert(renderer->shader);
  imm_renderer_flush(renderer);
  const mat4 view      = spatial3_inverse_transform(&camera->spatial);
  const mat4 view_proj = mat4_mul(camera->projection, view);
  gfx_imm_set_view_projection_matrix(renderer, &view_proj);
}

void gfx_imm_set_model_matrix(ImmRenderer* renderer, const mat4* model) {
  assert(renderer);
  assert(model);
  imm_renderer_flush(renderer);
  renderer->matrix_stack[0] = *model;
  renderer->stack_pointer   = 0;
  update_shader_model_matrix(renderer);
}

void gfx_imm_set_view_projection_matrix(
    ImmRenderer* renderer, const mat4* view_proj) {
  assert(renderer);
  assert(renderer->shader);
  imm_renderer_flush(renderer);
  gfx_set_mat4_uniform(renderer->shader, "ViewProjection", view_proj);
}

void gfx_imm_set_colour(ImmRenderer* renderer, vec4 colour) {
  assert(renderer);
  assert(renderer->shader);
  imm_renderer_flush(renderer);
  gfx_set_vec4_uniform(renderer->shader, "Colour", colour);
}