Standard-of-Iron/ui/campaign_map_render_utils.h

#pragma once

#include <QMatrix4x4>
#include <QVector2D>
#include <QVector3D>
#include <QVector4D>
#include <cmath>
#include <vector>

namespace CampaignMapRender {

inline auto catmull_rom(const QVector2D &p0, const QVector2D &p1,
                        const QVector2D &p2, const QVector2D &p3,
                        float t) -> QVector2D {
  const float t2 = t * t;
  const float t3 = t2 * t;

  const float c0 = -0.5F * t3 + t2 - 0.5F * t;
  const float c1 = 1.5F * t3 - 2.5F * t2 + 1.0F;
  const float c2 = -1.5F * t3 + 2.0F * t2 + 0.5F * t;
  const float c3 = 0.5F * t3 - 0.5F * t2;

  return p0 * c0 + p1 * c1 + p2 * c2 + p3 * c3;
}

inline auto catmull_rom_tangent(const QVector2D &p0, const QVector2D &p1,
                                const QVector2D &p2, const QVector2D &p3,
                                float t) -> QVector2D {
  const float t2 = t * t;

  const float c0 = -1.5F * t2 + 2.0F * t - 0.5F;
  const float c1 = 4.5F * t2 - 5.0F * t;
  const float c2 = -4.5F * t2 + 4.0F * t + 0.5F;
  const float c3 = 1.5F * t2 - t;

  return p0 * c0 + p1 * c1 + p2 * c2 + p3 * c3;
}

inline auto
smooth_catmull_rom(const std::vector<QVector2D> &input,
                   int samples_per_segment = 8) -> std::vector<QVector2D> {
  if (input.size() < 2) {
    return input;
  }

  std::vector<QVector2D> result;
  result.reserve(input.size() * static_cast<size_t>(samples_per_segment));

  for (size_t i = 0; i + 1 < input.size(); ++i) {

    const QVector2D &p0 = (i == 0) ? input[0] : input[i - 1];
    const QVector2D &p1 = input[i];
    const QVector2D &p2 = input[i + 1];
    const QVector2D &p3 =
        (i + 2 >= input.size()) ? input[input.size() - 1] : input[i + 2];

    for (int s = 0; s < samples_per_segment; ++s) {
      const float t =
          static_cast<float>(s) / static_cast<float>(samples_per_segment);
      result.push_back(catmull_rom(p0, p1, p2, p3, t));
    }
  }

  result.push_back(input.back());

  return result;
}

struct MiterParams {
  float max_miter_ratio = 3.0F;
  float min_denom = 0.2F;
};

enum class CapStyle { Flat, Round, Square };

enum class JoinStyle { Miter, Round, Bevel };

struct StrokeMeshConfig {
  float width = 4.0F;
  CapStyle start_cap = CapStyle::Round;
  CapStyle end_cap = CapStyle::Round;
  JoinStyle join_style = JoinStyle::Miter;
  MiterParams miter_params;
  int cap_segments = 6;
  int join_segments = 4;
};

inline auto perp_ccw(const QVector2D &v) -> QVector2D {
  return QVector2D(-v.y(), v.x());
}

inline auto safe_normalize(const QVector2D &v,
                           float epsilon = 1e-5F) -> QVector2D {
  const float len = v.length();
  if (len < epsilon) {
    return QVector2D(0.0F, 0.0F);
  }
  return v / len;
}

inline auto generate_round_cap(const QVector2D &center,
                               const QVector2D &direction, float half_width,
                               int segments,
                               bool is_start) -> std::vector<QVector2D> {
  std::vector<QVector2D> verts;
  verts.reserve(static_cast<size_t>((segments + 1) * 2));

  const QVector2D perp = perp_ccw(direction) * half_width;
  const float pi = 3.14159265358979F;

  const float start_angle = is_start ? pi * 0.5F : -pi * 0.5F;
  const float end_angle = is_start ? -pi * 0.5F : pi * 0.5F;

  for (int i = 0; i <= segments; ++i) {
    const float t = static_cast<float>(i) / static_cast<float>(segments);
    const float angle = start_angle + t * (end_angle - start_angle);

    const float cos_a = std::cos(angle);
    const float sin_a = std::sin(angle);

    const QVector2D offset = perp * cos_a - direction * half_width * sin_a;

    verts.push_back(center);
    verts.push_back(center + offset);
  }

  return verts;
}

inline auto generate_square_cap(const QVector2D &center,
                                const QVector2D &direction, float half_width,
                                bool is_start) -> std::vector<QVector2D> {
  const QVector2D perp = perp_ccw(direction) * half_width;
  const QVector2D extension =
      direction * half_width * (is_start ? -1.0F : 1.0F);

  std::vector<QVector2D> verts;
  verts.reserve(4);

  verts.push_back(center + perp);
  verts.push_back(center - perp);
  verts.push_back(center + perp + extension);
  verts.push_back(center - perp + extension);

  return verts;
}

inline auto
build_stroke_mesh(const std::vector<QVector2D> &points,
                  const StrokeMeshConfig &config) -> std::vector<QVector2D> {
  std::vector<QVector2D> result;

  if (points.size() < 2 || config.width <= 0.0F) {
    return result;
  }

  std::vector<QVector2D> cleaned;
  cleaned.reserve(points.size());
  for (const auto &pt : points) {
    if (cleaned.empty()) {
      cleaned.push_back(pt);
      continue;
    }
    const QVector2D delta = pt - cleaned.back();
    if (QVector2D::dotProduct(delta, delta) > 1e-10F) {
      cleaned.push_back(pt);
    }
  }

  if (cleaned.size() < 2) {
    return result;
  }

  const float half_width = config.width * 0.5F;
  result.reserve(cleaned.size() * 2 + 32);

  if (config.start_cap == CapStyle::Round) {
    const QVector2D start_dir = safe_normalize(cleaned[1] - cleaned[0]);
    auto cap_verts = generate_round_cap(cleaned[0], start_dir, half_width,
                                        config.cap_segments, true);
    result.insert(result.end(), cap_verts.begin(), cap_verts.end());
  } else if (config.start_cap == CapStyle::Square) {
    const QVector2D start_dir = safe_normalize(cleaned[1] - cleaned[0]);
    auto cap_verts =
        generate_square_cap(cleaned[0], start_dir, half_width, true);
    result.insert(result.end(), cap_verts.begin(), cap_verts.end());
  }

  for (size_t i = 0; i < cleaned.size(); ++i) {
    QVector2D offset;

    if (i == 0) {

      const QVector2D dir = safe_normalize(cleaned[1] - cleaned[0]);
      offset = perp_ccw(dir) * half_width;
    } else if (i + 1 == cleaned.size()) {

      const QVector2D dir = safe_normalize(cleaned[i] - cleaned[i - 1]);
      offset = perp_ccw(dir) * half_width;
    } else {

      QVector2D dir0 = safe_normalize(cleaned[i] - cleaned[i - 1]);
      QVector2D dir1 = safe_normalize(cleaned[i + 1] - cleaned[i]);

      if (dir0.isNull() && dir1.isNull()) {

        dir0 = QVector2D(1.0F, 0.0F);
        dir1 = QVector2D(1.0F, 0.0F);
      } else if (dir0.isNull()) {
        dir0 = dir1;
      } else if (dir1.isNull()) {
        dir1 = dir0;
      }

      const QVector2D n0 = perp_ccw(dir0);
      const QVector2D n1 = perp_ccw(dir1);
      QVector2D miter = safe_normalize(n0 + n1);

      if (miter.isNull()) {
        miter = n1;
      }

      float denom = QVector2D::dotProduct(miter, n1);
      if (std::abs(denom) < config.miter_params.min_denom) {
        denom = (denom >= 0.0F) ? config.miter_params.min_denom
                                : -config.miter_params.min_denom;
      }

      float miter_len = half_width / denom;

      const float max_len = half_width * config.miter_params.max_miter_ratio;
      if (std::abs(miter_len) > max_len) {
        miter_len = (miter_len < 0.0F) ? -max_len : max_len;
      }

      offset = miter * miter_len;
    }

    result.push_back(cleaned[i] + offset);
    result.push_back(cleaned[i] - offset);
  }

  if (config.end_cap == CapStyle::Round) {
    const QVector2D end_dir =
        safe_normalize(cleaned.back() - cleaned[cleaned.size() - 2]);
    auto cap_verts = generate_round_cap(cleaned.back(), end_dir, half_width,
                                        config.cap_segments, false);
    result.insert(result.end(), cap_verts.begin(), cap_verts.end());
  } else if (config.end_cap == CapStyle::Square) {
    const QVector2D end_dir =
        safe_normalize(cleaned.back() - cleaned[cleaned.size() - 2]);
    auto cap_verts =
        generate_square_cap(cleaned.back(), end_dir, half_width, false);
    result.insert(result.end(), cap_verts.begin(), cap_verts.end());
  }

  return result;
}

struct StrokePass {
  QVector4D color;
  float width_multiplier;
  float z_offset;
};

namespace CartographicStyles {

inline auto get_inked_route_passes(float base_width, int age_factor = 0)
    -> std::vector<StrokePass> {
  const float fade = 1.0F - static_cast<float>(age_factor) * 0.08F;
  const float fade_clamped = std::max(0.3F, fade);

  return {

      {{0.12F * fade_clamped, 0.09F * fade_clamped, 0.07F * fade_clamped,
        0.65F * fade_clamped},
       1.3F,
       0.000F},

      {{0.18F * fade_clamped, 0.14F * fade_clamped, 0.10F * fade_clamped,
        0.55F * fade_clamped},
       1.05F,
       0.001F},

      {{0.70F * fade_clamped, 0.58F * fade_clamped, 0.32F * fade_clamped,
        0.65F * fade_clamped},
       0.8F,
       0.002F},

      {{0.62F * fade_clamped, 0.22F * fade_clamped, 0.18F * fade_clamped,
        0.75F * fade_clamped},
       0.6F,
       0.003F}};
}

inline auto get_coastline_passes(float base_width) -> std::vector<StrokePass> {
  return {

      {{0.12F, 0.10F, 0.08F, 0.95F}, 1.8F, 0.000F},

      {{0.25F, 0.22F, 0.18F, 0.85F}, 1.4F, 0.001F},

      {{0.55F, 0.50F, 0.42F, 0.75F}, 1.0F, 0.002F}};
}

inline auto get_border_passes(float base_width) -> std::vector<StrokePass> {
  return {

      {{0.18F, 0.15F, 0.12F, 0.55F}, 1.6F, 0.000F},

      {{0.32F, 0.28F, 0.24F, 0.70F}, 1.0F, 0.001F}};
}

inline auto get_river_passes(float base_width) -> std::vector<StrokePass> {
  return {

      {{0.25F, 0.32F, 0.40F, 0.75F}, 1.6F, 0.000F},

      {{0.35F, 0.48F, 0.58F, 0.90F}, 1.0F, 0.001F},

      {{0.55F, 0.68F, 0.78F, 0.50F}, 0.4F, 0.002F}};
}

} // namespace CartographicStyles

inline auto compute_normal_from_heights(float h_left, float h_right,
                                        float h_down, float h_up,
                                        float scale = 1.0F) -> QVector3D {
  const float dx = (h_right - h_left) * scale;
  const float dz = (h_up - h_down) * scale;
  QVector3D normal(-dx, 2.0F, -dz);
  normal.normalize();
  return normal;
}

inline auto hash_2d(float x, float y) -> float {
  const float h = std::sin(x * 12.9898F + y * 78.233F) * 43758.5453123F;
  return h - std::floor(h);
}

inline auto value_noise_2d(float x, float y) -> float {
  const float ix = std::floor(x);
  const float iy = std::floor(y);
  const float fx = x - ix;
  const float fy = y - iy;

  const float sx = fx * fx * (3.0F - 2.0F * fx);
  const float sy = fy * fy * (3.0F - 2.0F * fy);

  const float c00 = hash_2d(ix, iy);
  const float c10 = hash_2d(ix + 1.0F, iy);
  const float c01 = hash_2d(ix, iy + 1.0F);
  const float c11 = hash_2d(ix + 1.0F, iy + 1.0F);

  const float x0 = c00 * (1.0F - sx) + c10 * sx;
  const float x1 = c01 * (1.0F - sx) + c11 * sx;
  return x0 * (1.0F - sy) + x1 * sy;
}

inline auto fbm_noise_2d(float x, float y, int octaves = 4,
                         float lacunarity = 2.0F,
                         float persistence = 0.5F) -> float {
  float value = 0.0F;
  float amplitude = 1.0F;
  float frequency = 1.0F;
  float max_value = 0.0F;

  for (int i = 0; i < octaves; ++i) {
    value += amplitude * value_noise_2d(x * frequency, y * frequency);
    max_value += amplitude;
    amplitude *= persistence;
    frequency *= lacunarity;
  }

  return value / max_value;
}

inline auto compute_hillshade(const QVector3D &normal,
                              const QVector3D &light_dir,
                              float ambient = 0.3F) -> float {
  const float ndotl = QVector3D::dotProduct(normal, light_dir);
  return ambient + (1.0F - ambient) * std::max(0.0F, ndotl);
}

inline auto elevation_to_tint(float elevation, bool is_water) -> QVector4D {
  if (is_water) {

    const float depth_factor =
        1.0F - std::min(1.0F, std::abs(elevation) * 2.0F);
    return QVector4D(0.6F * depth_factor + 0.2F, 0.7F * depth_factor + 0.2F,
                     0.85F * depth_factor + 0.15F, 1.0F);
  }

  if (elevation < 0.2F) {

    return QVector4D(0.95F, 1.0F, 0.92F, 1.0F);
  }
  if (elevation < 0.5F) {

    const float t = (elevation - 0.2F) / 0.3F;
    return QVector4D(1.0F, 0.98F - t * 0.05F, 0.95F - t * 0.08F, 1.0F);
  }

  const float t = (elevation - 0.5F) / 0.5F;
  return QVector4D(0.95F - t * 0.1F, 0.88F - t * 0.15F, 0.82F - t * 0.12F,
                   1.0F);
}

inline auto parchment_pattern(float u, float v, float scale = 8.0F) -> float {

  const float n1 = fbm_noise_2d(u * scale, v * scale, 3, 2.0F, 0.5F);
  const float n2 = fbm_noise_2d(u * scale * 2.5F + 100.0F,
                                v * scale * 2.5F + 100.0F, 2, 2.0F, 0.4F);

  const float combined = n1 * 0.6F + n2 * 0.4F;
  return 0.85F + combined * 0.15F;
}

namespace CinematicCameraDefaults {

inline constexpr float k_default_yaw = 185.0F;
inline constexpr float k_default_pitch = 52.0F;
inline constexpr float k_default_distance = 1.35F;

struct RegionFocus {
  float u;
  float v;
  float distance;
  float pitch;
  float yaw;
};

inline constexpr RegionFocus k_focus_carthage = {0.35F, 0.55F, 1.0F, 48.0F,
                                                 200.0F};
inline constexpr RegionFocus k_focus_rome = {0.55F, 0.35F, 0.9F, 50.0F, 175.0F};
inline constexpr RegionFocus k_focus_spain = {0.18F, 0.42F, 1.1F, 45.0F,
                                              195.0F};
inline constexpr RegionFocus k_focus_alps = {0.52F, 0.28F, 0.85F, 55.0F,
                                             180.0F};
inline constexpr RegionFocus k_focus_sicily = {0.58F, 0.48F, 0.75F, 52.0F,
                                               185.0F};

} // namespace CinematicCameraDefaults

enum class BadgeStyle { Standard, Seal, Banner, Shield, Medallion };

struct MissionBadgeConfig {
  BadgeStyle style = BadgeStyle::Standard;
  QVector4D primary_color{0.75F, 0.18F, 0.12F, 1.0F};
  QVector4D secondary_color{0.95F, 0.85F, 0.45F, 1.0F};
  QVector4D border_color{0.15F, 0.10F, 0.08F, 1.0F};
  float size = 24.0F;
  float border_width = 2.0F;
  bool show_shadow = true;
  float shadow_offset = 2.0F;
  float shadow_opacity = 0.4F;
};

inline auto generate_shield_badge(const QVector2D &center, float size,
                                  int segments = 16) -> std::vector<QVector2D> {
  std::vector<QVector2D> verts;
  verts.reserve(static_cast<size_t>(segments * 2 + 4));

  const float w = size * 0.5F;
  const float h = size * 0.6F;
  const float pi = 3.14159265358979F;

  verts.push_back(center + QVector2D(-w, -h * 0.4F));
  verts.push_back(center + QVector2D(w, -h * 0.4F));

  for (int i = 0; i <= segments / 2; ++i) {
    const float t = static_cast<float>(i) / static_cast<float>(segments / 2);
    const float angle = pi * 0.5F * t;
    const float x = w * std::cos(angle);
    const float y = -h * 0.4F + h * 0.9F * std::sin(angle) + h * 0.5F * t * t;
    verts.push_back(center + QVector2D(x, y));
  }

  verts.push_back(center + QVector2D(0.0F, h * 0.6F));

  for (int i = segments / 2; i >= 0; --i) {
    const float t = static_cast<float>(i) / static_cast<float>(segments / 2);
    const float angle = pi * 0.5F * t;
    const float x = -w * std::cos(angle);
    const float y = -h * 0.4F + h * 0.9F * std::sin(angle) + h * 0.5F * t * t;
    verts.push_back(center + QVector2D(x, y));
  }

  return verts;
}

inline auto generate_banner_badge(const QVector2D &center, float size,
                                  int segments = 12) -> std::vector<QVector2D> {
  std::vector<QVector2D> verts;
  const float w = size * 0.4F;
  const float h = size * 0.7F;

  verts.push_back(center + QVector2D(-w, -h * 0.5F));
  verts.push_back(center + QVector2D(w, -h * 0.5F));
  verts.push_back(center + QVector2D(w, h * 0.3F));
  verts.push_back(center + QVector2D(0.0F, h * 0.5F));
  verts.push_back(center + QVector2D(-w, h * 0.3F));

  return verts;
}

inline auto
generate_medallion_badge(const QVector2D &center, float size,
                         int segments = 24) -> std::vector<QVector2D> {
  std::vector<QVector2D> verts;
  verts.reserve(static_cast<size_t>(segments + 1));

  const float radius = size * 0.5F;
  const float pi = 3.14159265358979F;

  for (int i = 0; i <= segments; ++i) {
    const float angle =
        2.0F * pi * static_cast<float>(i) / static_cast<float>(segments);
    verts.push_back(
        center + QVector2D(radius * std::cos(angle), radius * std::sin(angle)));
  }

  return verts;
}

enum class CartographicSymbol { Mountain, City, Port, Fort, Temple };

inline auto generate_mountain_icon(const QVector2D &center, float size,
                                   int peaks = 2) -> std::vector<QVector2D> {
  std::vector<QVector2D> verts;
  const float h = size * 0.5F;
  const float w = size * 0.3F;

  if (peaks == 1) {

    verts.push_back(center + QVector2D(-w, h * 0.3F));
    verts.push_back(center + QVector2D(0.0F, -h * 0.5F));
    verts.push_back(center + QVector2D(w, h * 0.3F));
  } else if (peaks == 2) {

    verts.push_back(center + QVector2D(-w * 1.5F, h * 0.3F));
    verts.push_back(center + QVector2D(-w * 0.5F, -h * 0.4F));
    verts.push_back(center + QVector2D(0.0F, h * 0.1F));
    verts.push_back(center + QVector2D(w * 0.5F, -h * 0.5F));
    verts.push_back(center + QVector2D(w * 1.5F, h * 0.3F));
  } else {

    verts.push_back(center + QVector2D(-w * 2.0F, h * 0.3F));
    verts.push_back(center + QVector2D(-w, -h * 0.35F));
    verts.push_back(center + QVector2D(-w * 0.3F, h * 0.1F));
    verts.push_back(center + QVector2D(0.0F, -h * 0.5F));
    verts.push_back(center + QVector2D(w * 0.3F, h * 0.0F));
    verts.push_back(center + QVector2D(w, -h * 0.4F));
    verts.push_back(center + QVector2D(w * 2.0F, h * 0.3F));
  }

  return verts;
}

inline auto generate_city_marker(const QVector2D &center, float size,
                                 int importance = 1) -> std::vector<QVector2D> {
  std::vector<QVector2D> verts;
  const float h = size * 0.5F;
  const float w = size * 0.2F;

  verts.push_back(center + QVector2D(-w * 2.0F, h * 0.3F));
  verts.push_back(center + QVector2D(w * 2.0F, h * 0.3F));

  if (importance >= 2) {

    verts.push_back(center + QVector2D(w * 2.0F, -h * 0.2F));
    verts.push_back(center + QVector2D(w * 1.5F, -h * 0.2F));
    verts.push_back(center + QVector2D(w * 1.5F, -h * 0.5F));
    verts.push_back(center + QVector2D(w * 0.5F, -h * 0.5F));
    verts.push_back(center + QVector2D(w * 0.5F, -h * 0.3F));
    verts.push_back(center + QVector2D(-w * 0.5F, -h * 0.3F));
    verts.push_back(center + QVector2D(-w * 0.5F, -h * 0.6F));
    verts.push_back(center + QVector2D(-w * 1.5F, -h * 0.6F));
    verts.push_back(center + QVector2D(-w * 1.5F, -h * 0.2F));
    verts.push_back(center + QVector2D(-w * 2.0F, -h * 0.2F));
  } else {

    verts.push_back(center + QVector2D(w * 2.0F, -h * 0.1F));
    verts.push_back(center + QVector2D(w, -h * 0.1F));
    verts.push_back(center + QVector2D(w, -h * 0.4F));
    verts.push_back(center + QVector2D(-w, -h * 0.4F));
    verts.push_back(center + QVector2D(-w, -h * 0.1F));
    verts.push_back(center + QVector2D(-w * 2.0F, -h * 0.1F));
  }

  return verts;
}

inline auto generate_anchor_icon(const QVector2D &center,
                                 float size) -> std::vector<QVector2D> {
  std::vector<QVector2D> verts;
  const float h = size * 0.5F;
  const float w = size * 0.4F;

  verts.push_back(center + QVector2D(0.0F, -h * 0.6F));
  verts.push_back(center + QVector2D(0.0F, h * 0.4F));

  const float ring_r = size * 0.12F;
  const int ring_segs = 8;
  const float pi = 3.14159265358979F;
  const QVector2D ring_center = center + QVector2D(0.0F, -h * 0.6F - ring_r);
  for (int i = 0; i <= ring_segs; ++i) {
    const float angle =
        2.0F * pi * static_cast<float>(i) / static_cast<float>(ring_segs);
    verts.push_back(ring_center + QVector2D(ring_r * std::cos(angle),
                                            ring_r * std::sin(angle)));
  }

  verts.push_back(center + QVector2D(-w * 0.6F, -h * 0.2F));
  verts.push_back(center + QVector2D(w * 0.6F, -h * 0.2F));

  verts.push_back(center + QVector2D(-w, h * 0.1F));
  verts.push_back(center + QVector2D(0.0F, h * 0.4F));
  verts.push_back(center + QVector2D(w, h * 0.1F));

  return verts;
}

struct MediterraneanTerrainConfig {

  static constexpr float alps_u_min = 0.48F;
  static constexpr float alps_u_max = 0.58F;
  static constexpr float alps_v_min = 0.22F;
  static constexpr float alps_v_max = 0.32F;
  static constexpr float alps_height = 0.85F;

  static constexpr float pyrenees_u_min = 0.20F;
  static constexpr float pyrenees_u_max = 0.32F;
  static constexpr float pyrenees_v_min = 0.30F;
  static constexpr float pyrenees_v_max = 0.38F;
  static constexpr float pyrenees_height = 0.65F;

  static constexpr float apennines_u_min = 0.52F;
  static constexpr float apennines_u_max = 0.62F;
  static constexpr float apennines_v_min = 0.35F;
  static constexpr float apennines_v_max = 0.55F;
  static constexpr float apennines_height = 0.55F;

  static constexpr float atlas_u_min = 0.30F;
  static constexpr float atlas_u_max = 0.55F;
  static constexpr float atlas_v_min = 0.62F;
  static constexpr float atlas_v_max = 0.72F;
  static constexpr float atlas_height = 0.60F;

  static constexpr float sea_level = 0.0F;
  static constexpr float max_depth = -0.35F;
};

inline auto compute_mountain_contribution(float u, float v, float u_min,
                                          float u_max, float v_min, float v_max,
                                          float peak_height) -> float {
  if (u < u_min || u > u_max || v < v_min || v > v_max) {
    return 0.0F;
  }

  float dist_u =
      1.0F - 2.0F * std::abs(u - (u_min + u_max) * 0.5F) / (u_max - u_min);
  float dist_v =
      1.0F - 2.0F * std::abs(v - (v_min + v_max) * 0.5F) / (v_max - v_min);
  float falloff = dist_u * dist_v;
  falloff = falloff * falloff;
  return peak_height * falloff;
}

inline auto generate_terrain_height(float u, float v) -> float {
  using Config = MediterraneanTerrainConfig;

  float height = 0.05F;

  height += compute_mountain_contribution(
      u, v, Config::alps_u_min, Config::alps_u_max, Config::alps_v_min,
      Config::alps_v_max, Config::alps_height);

  height += compute_mountain_contribution(
      u, v, Config::pyrenees_u_min, Config::pyrenees_u_max,
      Config::pyrenees_v_min, Config::pyrenees_v_max, Config::pyrenees_height);

  height += compute_mountain_contribution(
      u, v, Config::apennines_u_min, Config::apennines_u_max,
      Config::apennines_v_min, Config::apennines_v_max,
      Config::apennines_height);

  height += compute_mountain_contribution(
      u, v, Config::atlas_u_min, Config::atlas_u_max, Config::atlas_v_min,
      Config::atlas_v_max, Config::atlas_height);

  float noise = fbm_noise_2d(u * 8.0F, v * 8.0F, 4, 2.0F, 0.5F);
  height += (noise - 0.5F) * 0.15F;

  return height;
}

inline auto compute_terrain_normal(float u, float v,
                                   float sample_dist = 0.01F) -> QVector3D {
  float h_left = generate_terrain_height(u - sample_dist, v);
  float h_right = generate_terrain_height(u + sample_dist, v);
  float h_down = generate_terrain_height(u, v - sample_dist);
  float h_up = generate_terrain_height(u, v + sample_dist);

  float dx = (h_right - h_left) / (2.0F * sample_dist);
  float dz = (h_up - h_down) / (2.0F * sample_dist);

  QVector3D normal(-dx, 1.0F, -dz);
  normal.normalize();
  return normal;
}

inline auto
generate_terrain_mesh(int resolution = 64,
                      float height_scale = 0.05F) -> std::vector<float> {
  std::vector<float> vertices;
  const int vertex_floats = 8;
  vertices.reserve(
      static_cast<size_t>(resolution * resolution * 6 * vertex_floats));

  const float step = 1.0F / static_cast<float>(resolution - 1);

  for (int y = 0; y < resolution - 1; ++y) {
    for (int x = 0; x < resolution - 1; ++x) {
      float u0 = static_cast<float>(x) * step;
      float v0 = static_cast<float>(y) * step;
      float u1 = static_cast<float>(x + 1) * step;
      float v1 = static_cast<float>(y + 1) * step;

      float h00 = generate_terrain_height(u0, v0) * height_scale;
      float h10 = generate_terrain_height(u1, v0) * height_scale;
      float h01 = generate_terrain_height(u0, v1) * height_scale;
      float h11 = generate_terrain_height(u1, v1) * height_scale;

      QVector3D n00 = compute_terrain_normal(u0, v0);
      QVector3D n10 = compute_terrain_normal(u1, v0);
      QVector3D n01 = compute_terrain_normal(u0, v1);
      QVector3D n11 = compute_terrain_normal(u1, v1);

      auto add_vertex = [&](float u, float v, float h, const QVector3D &n) {
        vertices.push_back(u);
        vertices.push_back(v);
        vertices.push_back(u);
        vertices.push_back(v);
        vertices.push_back(h);
        vertices.push_back(n.x());
        vertices.push_back(n.y());
        vertices.push_back(n.z());
      };

      add_vertex(u0, v0, h00, n00);
      add_vertex(u1, v0, h10, n10);
      add_vertex(u0, v1, h01, n01);

      add_vertex(u1, v0, h10, n10);
      add_vertex(u1, v1, h11, n11);
      add_vertex(u0, v1, h01, n01);
    }
  }

  return vertices;
}

struct HillshadeConfig {
  QVector3D light_direction{0.35F, 0.85F, 0.40F};
  float ambient = 0.25F;
  float intensity = 1.0F;
  float z_factor = 2.5F;
};

inline auto compute_hillshade_at(float u, float v,
                                 const HillshadeConfig &config) -> float {
  QVector3D normal = compute_terrain_normal(u, v, 0.005F);

  normal.setY(normal.y() * config.z_factor);
  normal.normalize();

  QVector3D light = config.light_direction.normalized();
  float shade = QVector3D::dotProduct(normal, light);
  shade = config.ambient + (1.0F - config.ambient) * std::max(0.0F, shade);
  return std::min(1.0F, shade * config.intensity);
}

inline auto
generate_hillshade_texture(int width, int height,
                           const HillshadeConfig &config = HillshadeConfig{})
    -> std::vector<unsigned char> {
  std::vector<unsigned char> pixels;
  pixels.reserve(static_cast<size_t>(width * height * 4));

  for (int y = 0; y < height; ++y) {
    for (int x = 0; x < width; ++x) {
      float u = static_cast<float>(x) / static_cast<float>(width - 1);
      float v = static_cast<float>(y) / static_cast<float>(height - 1);

      float shade = compute_hillshade_at(u, v, config);
      auto byte_val = static_cast<unsigned char>(shade * 255.0F);

      pixels.push_back(byte_val);
      pixels.push_back(byte_val);
      pixels.push_back(byte_val);
      pixels.push_back(255);
    }
  }

  return pixels;
}

struct GlyphMetrics {
  float advance;
  float bearing_x;
  float bearing_y;
  float width;
  float height;
  float uv_x;
  float uv_y;
  float uv_w;
  float uv_h;
};

struct LabelStyle {
  float font_size = 14.0F;
  QVector4D fill_color{0.18F, 0.14F, 0.10F, 1.0F};
  QVector4D stroke_color{0.95F, 0.92F, 0.88F, 0.85F};
  float stroke_width = 1.5F;
  bool use_small_caps = true;
  float letter_spacing = 0.05F;
  float line_height = 1.2F;
};

namespace LabelStyles {

inline auto province_label() -> LabelStyle {
  return {.font_size = 12.0F,
          .fill_color = QVector4D(0.25F, 0.20F, 0.15F, 0.95F),
          .stroke_color = QVector4D(0.98F, 0.96F, 0.92F, 0.75F),
          .stroke_width = 1.2F,
          .use_small_caps = true,
          .letter_spacing = 0.08F,
          .line_height = 1.15F};
}

inline auto city_label() -> LabelStyle {
  return {.font_size = 10.0F,
          .fill_color = QVector4D(0.30F, 0.25F, 0.18F, 0.90F),
          .stroke_color = QVector4D(0.98F, 0.96F, 0.92F, 0.70F),
          .stroke_width = 1.0F,
          .use_small_caps = false,
          .letter_spacing = 0.03F,
          .line_height = 1.1F};
}

inline auto region_label() -> LabelStyle {
  return {.font_size = 16.0F,
          .fill_color = QVector4D(0.20F, 0.16F, 0.12F, 1.0F),
          .stroke_color = QVector4D(0.95F, 0.92F, 0.88F, 0.80F),
          .stroke_width = 2.0F,
          .use_small_caps = true,
          .letter_spacing = 0.12F,
          .line_height = 1.25F};
}

inline auto sea_label() -> LabelStyle {
  return {.font_size = 11.0F,
          .fill_color = QVector4D(0.25F, 0.38F, 0.50F, 0.85F),
          .stroke_color = QVector4D(0.92F, 0.95F, 0.98F, 0.65F),
          .stroke_width = 1.0F,
          .use_small_caps = true,
          .letter_spacing = 0.15F,
          .line_height = 1.2F};
}

} // namespace LabelStyles

inline auto
generate_label_quads(const QVector2D &position, const std::string &text,
                     const LabelStyle &style,
                     float base_font_size = 12.0F) -> std::vector<float> {
  std::vector<float> vertices;
  if (text.empty()) {
    return vertices;
  }

  const float scale = style.font_size / base_font_size;
  const float char_width = 0.006F * scale;
  const float char_height = 0.012F * scale;
  const float spacing = char_width * style.letter_spacing;

  const float total_width =
      static_cast<float>(text.length()) * (char_width + spacing);
  float x_offset = -total_width * 0.5F;

  for (size_t i = 0; i < text.length(); ++i) {
    char c = text[i];
    if (c == ' ') {
      x_offset += char_width * 0.5F;
      continue;
    }

    float atlas_u = static_cast<float>(c % 16) / 16.0F;
    float atlas_v = static_cast<float>(c / 16) / 16.0F;
    float atlas_w = 1.0F / 16.0F;
    float atlas_h = 1.0F / 16.0F;

    float x0 = position.x() + x_offset;
    float y0 = position.y() - char_height * 0.5F;
    float x1 = x0 + char_width;
    float y1 = y0 + char_height;

    vertices.insert(vertices.end(), {x0, y0, atlas_u, atlas_v, 0.0F, 0.0F});
    vertices.insert(vertices.end(),
                    {x1, y0, atlas_u + atlas_w, atlas_v, 1.0F, 0.0F});
    vertices.insert(vertices.end(),
                    {x0, y1, atlas_u, atlas_v + atlas_h, 0.0F, 1.0F});

    vertices.insert(vertices.end(),
                    {x1, y0, atlas_u + atlas_w, atlas_v, 1.0F, 0.0F});
    vertices.insert(vertices.end(),
                    {x1, y1, atlas_u + atlas_w, atlas_v + atlas_h, 1.0F, 1.0F});
    vertices.insert(vertices.end(),
                    {x0, y1, atlas_u, atlas_v + atlas_h, 0.0F, 1.0F});

    x_offset += char_width + spacing;
  }

  return vertices;
}

inline auto compute_label_scale(float viewport_height, float camera_distance,
                                float base_size = 12.0F) -> float {

  const float fov_rad = 0.7854F;
  const float view_height = 2.0F * camera_distance * std::tan(fov_rad * 0.5F);
  const float px_to_uv = view_height / viewport_height;
  return base_size * px_to_uv;
}

} // namespace CampaignMapRender