#include "light_impl.h"
#include "llr_impl.h"
#include "mesh_impl.h"

#include "llr/material_impl.h"
#include "scene/animation_impl.h"

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

#include <cassert.h>

static const int IRRADIANCE_MAP_WIDTH               = 1024;
static const int IRRADIANCE_MAP_HEIGHT              = 1024;
static const int PREFILTERED_ENVIRONMENT_MAP_WIDTH  = 128;
static const int PREFILTERED_ENVIRONMENT_MAP_HEIGHT = 128;
static const int BRDF_INTEGRATION_MAP_WIDTH         = 512;
static const int BRDF_INTEGRATION_MAP_HEIGHT        = 512;

/// Initialize renderer state for IBL.
static bool init_ibl(LLR* renderer) {
  assert(renderer);
  assert(!renderer->ibl);
  assert(!renderer->brdf_integration_map);

  if (!((renderer->ibl = gfx_make_ibl(renderer->gfxcore)))) {
    return false;
  }

  if (!((renderer->brdf_integration_map = gfx_make_brdf_integration_map(
             renderer->ibl, renderer->gfxcore, BRDF_INTEGRATION_MAP_WIDTH,
             BRDF_INTEGRATION_MAP_HEIGHT)))) {
    return false;
  }

  return true;
}

// TODO: Why is this done lazily here? Do it when the environment light is
//  created.
//
/// Compute irradiance and prefiltered environment maps for the light if they
/// have not been already computed.
static bool set_up_environment_light(LLR* renderer, EnvironmentLight* light) {
  assert(renderer);
  assert(light);
  assert(renderer->ibl);
  assert(renderer->brdf_integration_map);

  if (light->irradiance_map) {
    assert(light->prefiltered_environment_map);
    return true;
  }

  // For convenience.
  GfxCore* gfxcore = renderer->gfxcore;

  Texture* irradiance_map              = 0;
  Texture* prefiltered_environment_map = 0;

  if (!((irradiance_map = gfx_make_irradiance_map(
             renderer->ibl, gfxcore, light->environment_map,
             IRRADIANCE_MAP_WIDTH, IRRADIANCE_MAP_HEIGHT)))) {
    goto cleanup;
  }

  int max_mip_level = 0;
  if (!((prefiltered_environment_map = gfx_make_prefiltered_environment_map(
             renderer->ibl, gfxcore, light->environment_map,
             PREFILTERED_ENVIRONMENT_MAP_WIDTH,
             PREFILTERED_ENVIRONMENT_MAP_HEIGHT, &max_mip_level)))) {
    goto cleanup;
  }

  light->irradiance_map              = irradiance_map;
  light->prefiltered_environment_map = prefiltered_environment_map;
  light->max_reflection_lod          = max_mip_level;

  return true;

cleanup:
  if (irradiance_map) {
    gfx_destroy_texture(gfxcore, &irradiance_map);
  }
  if (prefiltered_environment_map) {
    gfx_destroy_texture(gfxcore, &prefiltered_environment_map);
  }
  return false;
}

static void configure_light(LLR* renderer, Light* light) {
  assert(renderer);
  assert(light);

  // For convenience.
  ShaderProgram* const shader = renderer->shader;

  switch (light->type) {
  case EnvironmentLightType: {
    EnvironmentLight* env = &light->environment;

    const bool initialized = set_up_environment_light(renderer, env);
    ASSERT(initialized);
    assert(env->environment_map);
    assert(env->irradiance_map);
    assert(env->prefiltered_environment_map);
    assert(renderer->brdf_integration_map);

    gfx_set_texture_uniform(
        shader, "BRDFIntegrationMap", renderer->brdf_integration_map);
    gfx_set_texture_uniform(shader, "Sky", env->environment_map);
    gfx_set_texture_uniform(shader, "IrradianceMap", env->irradiance_map);
    gfx_set_texture_uniform(
        shader, "PrefilteredEnvironmentMap", env->prefiltered_environment_map);
    gfx_set_float_uniform(
        shader, "MaxReflectionLOD", (float)env->max_reflection_lod);

    break;
  }
  default:
    assert(false); // TODO: Implement other light types.
    break;
  }
}

static void configure_state(LLR* renderer) {
  assert(renderer);

  // Check if anything changed first so that we don't call gfx_apply_uniforms()
  // unnecessarily.
  const bool nothing_changed = (renderer->changed_flags == 0);
  if (nothing_changed) {
    return;
  }
  // Setting a null shader is also allowed, in which case there is nothing to
  // configure.
  if (renderer->shader == 0) {
    renderer->shader_changed = false;
    return;
  }

  // For convenience.
  ShaderProgram* const shader = renderer->shader;
  const mat4* const    model = &renderer->matrix_stack[renderer->stack_pointer];

  // TODO: Check to see which ones the shader actually uses and avoid
  //  computing the unnecessary matrices.

  if (renderer->matrix_changed || renderer->shader_changed) {
    renderer->matrix_changed = false;

    gfx_set_mat4_uniform(shader, "Model", model);
    gfx_set_mat4_uniform(shader, "ModelMatrix", model);
  }

  // TODO: camera_changed is not set anywhere. Need to think how imm primitive
  //  rendering and imm mesh rendering work together. We could treat imm
  //  primitive calls like setting a new shader.
  if (renderer->camera_changed || renderer->shader_changed) {
    renderer->camera_changed = false;

    // Set all supported camera-related uniforms. Shaders can choose which ones
    // to use.
    const mat4 modelview = mat4_mul(renderer->view, *model);
    const mat4 view_proj = mat4_mul(renderer->projection, renderer->view);
    const mat4 mvp       = mat4_mul(renderer->projection, modelview);

    gfx_set_mat4_uniform(shader, "Modelview", &modelview);
    gfx_set_mat4_uniform(shader, "View", &renderer->view);
    gfx_set_mat4_uniform(shader, "Projection", &renderer->projection);
    gfx_set_mat4_uniform(shader, "ViewProjection", &view_proj);
    gfx_set_mat4_uniform(shader, "MVP", &mvp);
    gfx_set_vec3_uniform(shader, "CameraPosition", renderer->camera_position);
    gfx_set_mat4_uniform(shader, "CameraRotation", &renderer->camera_rotation);
    gfx_set_float_uniform(shader, "Fovy", renderer->fovy);
    gfx_set_float_uniform(shader, "Aspect", renderer->aspect);
  }

  if (renderer->lights_changed || renderer->shader_changed) {
    renderer->lights_changed = false;

    // TODO: Could do better by only setting the lights that have actually
    //  changed.
    // TODO: Will also need to pass the number of lights to the shader once the
    //  other light types are implemented.
    for (int i = 0; i < renderer->num_lights; ++i) {
      configure_light(renderer, renderer->lights[i]);
    }
  }

  if (renderer->skeleton_changed || renderer->shader_changed) {
    renderer->skeleton_changed = false;

    if (renderer->num_joints > 0) {
      gfx_set_mat4_array_uniform(
          shader, "JointMatrices", renderer->joint_matrices,
          renderer->num_joints);
    }
  }

  if (renderer->shader_changed) {
    renderer->shader_changed = false;
    gfx_activate_shader_program(renderer->shader);
  }

  // Must be called after activating the program.
  gfx_apply_uniforms(renderer->shader);
}

bool gfx_llr_make(LLR* renderer, GfxCore* gfxcore) {
  assert(renderer);
  assert(gfxcore);

  renderer->gfxcore = gfxcore;
  if (!init_ibl(renderer)) {
    goto cleanup;
  }
  gfx_llr_load_identity(renderer);
  renderer->view            = mat4_id();
  renderer->projection      = mat4_id();
  renderer->camera_rotation = mat4_id();
  return true;

cleanup:
  gfx_llr_destroy(renderer);
  return false;
}

void gfx_llr_destroy(LLR* renderer) {
  assert(renderer);
  assert(renderer->gfxcore);

  if (renderer->brdf_integration_map) {
    gfx_destroy_texture(renderer->gfxcore, &renderer->brdf_integration_map);
  }

  // TODO: Do this once the IBL from the scene renderer is gone.
  if (renderer->ibl) {
    // gfx_destroy_ibl(renderer->gfxcore, &renderer->ibl);
  }
}

void gfx_llr_set_shader(LLR* renderer, ShaderProgram* shader) {
  assert(renderer);
  // null shader is allowed, so do not assert it.

  // It's important to not set shader_changed unnecessarily, since that would
  // re-trigger the setting of uniforms.
  if (renderer->shader != shader) {
    renderer->shader         = shader;
    renderer->shader_changed = true;
  }
}

void gfx_llr_push_light(LLR* renderer, Light* light) {
  assert(renderer);
  assert(light);
  assert(renderer->num_lights >= 0);
  ASSERT(renderer->num_lights < GFX_LLR_MAX_NUM_LIGHTS);

  renderer->lights[renderer->num_lights++] = light;
  renderer->lights_changed                 = true;
}

void gfx_llr_pop_light(LLR* renderer) {
  assert(renderer);
  ASSERT(renderer->num_lights > 0);

  renderer->lights[--renderer->num_lights] = 0;
  renderer->lights_changed                 = true;
}

void gfx_llr_set_skeleton(
    LLR* renderer, const Anima* anima, const Skeleton* skeleton) {
  assert(renderer);
  assert(anima);
  assert(skeleton);
  assert(skeleton->num_joints <= GFX_MAX_NUM_JOINTS);

  for (size_t i = 0; i < skeleton->num_joints; ++i) {
    const joint_idx joint_index = skeleton->joints[i];
    const Joint*    joint       = &anima->joints[joint_index];
    renderer->joint_matrices[i] = joint->joint_matrix;
  }
  renderer->num_joints       = skeleton->num_joints;
  renderer->skeleton_changed = true;
}

void gfx_llr_clear_skeleton(LLR* renderer) {
  assert(renderer);

  renderer->num_joints       = 0;
  renderer->skeleton_changed = true;
}

void gfx_llr_set_camera(LLR* renderer, const Camera* camera) {
  assert(renderer);

  renderer->camera_position = camera->spatial.p;
  renderer->camera_rotation =
      mat4_rotation(spatial3_transform(&camera->spatial));
  renderer->view       = spatial3_inverse_transform(&camera->spatial);
  renderer->projection = camera->projection;
  // Assuming a perspective matrix.
  renderer->fovy = (R)atan(1.0 / (mat4_at(camera->projection, 1, 1))) * 2;
  renderer->camera_changed = true;
}

void gfx_llr_set_aspect(LLR* renderer, float aspect) {
  assert(renderer);

  renderer->aspect         = aspect;
  renderer->camera_changed = true;
}

void gfx_llr_render_geometry(LLR* renderer, const Geometry* geometry) {
  assert(renderer);
  assert(geometry);

  configure_state(renderer);
  gfx_render_geometry(geometry);
}

void gfx_llr_render_mesh(LLR* renderer, const Mesh* mesh) {
  assert(renderer);
  assert(renderer->shader);
  assert(mesh);
  assert(mesh->geometry);
  assert(mesh->material);

  gfx_material_activate(renderer->shader, mesh->material);
  gfx_llr_render_geometry(renderer, mesh->geometry);
}

void gfx_llr_load_identity(LLR* renderer) {
  assert(renderer);

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

void gfx_llr_push_matrix(LLR* renderer, const mat4* matrix) {
  assert(renderer);
  assert(matrix);
  assert(renderer->stack_pointer >= 0);
  ASSERT(renderer->stack_pointer < GFX_LLR_MAX_NUM_MATRICES);

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

void gfx_llr_pop_matrix(LLR* renderer) {
  assert(renderer);
  ASSERT(renderer->stack_pointer > 0);

  // 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;
  renderer->matrix_changed = true;
}

void gfx_llr_translate(LLR* renderer, vec3 offset) {
  assert(renderer);

  const mat4 mat = mat4_translate(offset);
  gfx_llr_push_matrix(renderer, &mat);
}

void gfx_llr_set_model_matrix(LLR* renderer, const mat4* model) {
  assert(renderer);
  assert(model);

  renderer->matrix_stack[0] = *model;
  renderer->stack_pointer   = 0;
  renderer->matrix_changed  = true;
}