#include "engine.hpp"

#include <exception>
#include <glm/trigonometric.hpp>
#include <limits>
#include <ranges>

#include "glm/ext/matrix_clip_space.hpp"
#include <glm/gtc/matrix_transform.hpp>

namespace {
[[nodiscard]] auto load_scene_to_renderer(trb::render::renderer &renderer,
                                          trb::game::scene &scene) {
  const auto is_mesh_node = [](const auto &v) {
    return std::holds_alternative<trb::game::mesh_node>(v);
  };

  const auto upload_mesh_node = [&](const auto &v) {
    return renderer.register_mesh(std::get<trb::game::mesh_node>(v));
  };

  return scene.nodes | std::views::filter(is_mesh_node) |
         std::views::transform(upload_mesh_node) |
         std::ranges::to<std::vector<std::uint32_t>>();
}

[[nodiscard]] std::pair<glm::vec3, glm::vec3>
bounds_of(const trb::game::scene &scene) {
  auto min = glm::vec3(std::numeric_limits<float>::infinity());
  auto max = glm::vec3(-std::numeric_limits<float>::infinity());

  const auto is_mesh_node = [](const auto &v) {
    return std::holds_alternative<trb::game::mesh_node>(v);
  };

  for (const auto &v : scene.nodes | std::views::filter(is_mesh_node)) {
    const auto &mesh = std::get<trb::game::mesh_node>(v);
    for (const auto [position, normal, uv] : mesh.vertices) {
      min = glm::min(min, position);
      max = glm::max(max, position);
    }
  }

  return std::make_pair(min, max);
}

struct level_view {
  glm::mat4 view;
  glm::mat4 projection;
};
[[nodiscard]] level_view calculate_camera_matrices(glm::vec3 min, glm::vec3 max,
                                                   float aspectRatio,
                                                   float zoom = 1.0f) {
  // 1. Calculate the X/Z center. We ignore the Y center per your requirement.
  glm::vec3 center =
      glm::vec3((min.x + max.x) * 0.5f, 0.0f, (min.z + max.z) * 0.5f);

  // 2. Position the camera.
  // For 45 degrees in Y-up: we move 'distance' up (Y) and 'distance' back (Z).
  float distance = 100.0f;
  glm::vec3 cameraPos = center + glm::vec3(0.0f, distance, distance);

  // 3. View Matrix
  // Up is (0, 1, 0). Camera looks at the X/Z center.
  glm::mat4 view = glm::lookAt(cameraPos, center, glm::vec3(0.0f, 1.0f, 0.0f));

  // 4. Determine Ortho Bounds
  // We must check all corners because at 45 degrees, the Y-height
  // of objects affects their projected X/Y position on screen.
  glm::vec3 corners[8] = {{min.x, min.y, min.z}, {max.x, min.y, min.z},
                          {min.x, max.y, min.z}, {max.x, max.y, min.z},
                          {min.x, min.y, max.z}, {max.x, min.y, max.z},
                          {min.x, max.y, max.z}, {max.x, max.y, max.z}};

  float vMinX = FLT_MAX, vMaxX = -FLT_MAX;
  float vMinY = FLT_MAX, vMaxY = -FLT_MAX;

  for (const auto &corner : corners) {
    glm::vec4 vSpace = view * glm::vec4(corner, 1.0f);
    vMinX = glm::min(vMinX, vSpace.x);
    vMaxX = glm::max(vMaxX, vSpace.x);
    vMinY = glm::min(vMinY, vSpace.y);
    vMaxY = glm::max(vMaxY, vSpace.y);
  }

  // 5. Apply Zoom and Aspect Ratio
  float width = (vMaxX - vMinX) / zoom;
  float height = (vMaxY - vMinY) / zoom;
  float midX = (vMinX + vMaxX) * 0.5f;
  float midY = (vMinY + vMaxY) * 0.5f;

  if (aspectRatio > (width / height)) {
    width = height * aspectRatio;
  } else {
    height = width / aspectRatio;
  }

  glm::mat4 projection =
      glm::ortho(midX - width * 0.5f, midX + width * 0.5f, midY - height * 0.5f,
                 midY + height * 0.5f, -1000.0f, 1000.0f);

  return {view, projection};
}

} // namespace

namespace trb::game {
engine::engine()
    : display(&input, {1920, 1080}, "Tanks Reborn"), renderer(&display),
      level_border(load_glb("../assets/models/level_scene.glb")),
      level_border_render_ids(
          ::load_scene_to_renderer(renderer, level_border)) {}

void engine::run() {
  while (!display.should_close()) {
    try {
      const auto [map_min, map_max] = ::bounds_of(level_border);
      const auto [view, projection] =
          ::calculate_camera_matrices(map_min, map_max, 1920.0f / 1080.0f);
      renderer.render(level_border_render_ids, view, projection);
    } catch (const vuk::VkException &ex) {
      if (ex.what() != std::string("Out of date.")) {
        std::rethrow_exception(std::current_exception());
      }
    }

    display.poll_events();
  }
}

} // namespace trb::game