#include "riverbank_renderer.h"
#include "../../game/map/visibility_service.h"
#include "../gl/mesh.h"
#include "../gl/resources.h"
#include "../scene_renderer.h"
#include "ground_utils.h"
#include "map/terrain.h"
#include <GL/gl.h>
#include <QVector2D>
#include <QVector3D>
#include <algorithm>
#include <cmath>
#include <cstddef>
#include <memory>
#include <qglobal.h>
#include <qmatrix4x4.h>
#include <qvectornd.h>
#include <utility>
#include <vector>

namespace Render::GL {

RiverbankRenderer::RiverbankRenderer() = default;
RiverbankRenderer::~RiverbankRenderer() = default;

void RiverbankRenderer::configure(
    const std::vector<Game::Map::RiverSegment> &river_segments,
    const Game::Map::TerrainHeightMap &height_map) {
  m_river_segments = river_segments;
  m_tile_size = height_map.getTileSize();
  m_grid_width = height_map.getWidth();
  m_grid_height = height_map.getHeight();
  m_heights = height_map.getHeightData();
  m_visibility_texture.reset();
  m_cached_visibility_version = 0;
  m_visibility_width = 0;
  m_visibility_height = 0;
  build_meshes();
}

void RiverbankRenderer::build_meshes() {
  m_meshes.clear();
  m_visibility_samples.clear();

  if (m_river_segments.empty()) {
    return;
  }

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

    fx = fx * fx * (3.0F - 2.0F * fx);
    fy = fy * fy * (3.0F - 2.0F * fy);

    float const a = Ground::noise_hash(ix, iy);
    float const b = Ground::noise_hash(ix + 1.0F, iy);
    float const c = Ground::noise_hash(ix, iy + 1.0F);
    float const d = Ground::noise_hash(ix + 1.0F, iy + 1.0F);

    return a * (1.0F - fx) * (1.0F - fy) + b * fx * (1.0F - fy) +
           c * (1.0F - fx) * fy + d * fx * fy;
  };

  auto sample_height = [&](float world_x, float world_z) -> float {
    if (m_heights.empty() || m_grid_width == 0 || m_grid_height == 0) {
      return 0.0F;
    }

    float const half_width = m_grid_width * 0.5F - 0.5F;
    float const half_height = m_grid_height * 0.5F - 0.5F;
    float gx = (world_x / m_tile_size) + half_width;
    float gz = (world_z / m_tile_size) + half_height;

    gx = std::clamp(gx, 0.0F, float(m_grid_width - 1));
    gz = std::clamp(gz, 0.0F, float(m_grid_height - 1));

    int const x0 = int(std::floor(gx));
    int const z0 = int(std::floor(gz));
    int const x1 = std::min(x0 + 1, m_grid_width - 1);
    int const z1 = std::min(z0 + 1, m_grid_height - 1);

    float const tx = gx - float(x0);
    float const tz = gz - float(z0);

    float const h00 = m_heights[z0 * m_grid_width + x0];
    float const h10 = m_heights[z0 * m_grid_width + x1];
    float const h01 = m_heights[z1 * m_grid_width + x0];
    float const h11 = m_heights[z1 * m_grid_width + x1];

    float const h0 = h00 * (1.0F - tx) + h10 * tx;
    float const h1 = h01 * (1.0F - tx) + h11 * tx;
    return h0 * (1.0F - tz) + h1 * tz;
  };

  for (const auto &segment : m_river_segments) {
    QVector3D dir = segment.end - segment.start;
    float const length = dir.length();
    if (length < 0.01F) {
      m_meshes.push_back(nullptr);
      m_visibility_samples.emplace_back();
      continue;
    }

    dir.normalize();
    QVector3D const perpendicular(-dir.z(), 0.0F, dir.x());
    float const half_width = segment.width * 0.5F;

    constexpr int k_rings_per_side = 5;
    constexpr int k_total_rings = k_rings_per_side * 2;

    int length_steps =
        static_cast<int>(std::ceil(length / (m_tile_size * 0.5F))) + 1;
    length_steps = std::max(length_steps, 8);

    std::vector<Vertex> vertices;
    std::vector<unsigned int> indices;
    std::vector<QVector3D> samples;

    for (int i = 0; i < length_steps; ++i) {
      float const t =
          static_cast<float>(i) / static_cast<float>(length_steps - 1);
      QVector3D center_pos = segment.start + dir * (length * t);
      float const center_height = sample_height(center_pos.x(), center_pos.z());

      constexpr float k_edge_noise_freq_1 = 2.0F;
      constexpr float k_edge_noise_freq_2 = 5.0F;
      constexpr float k_edge_noise_freq_3 = 10.0F;

      float const edge_noise1 = noise(center_pos.x() * k_edge_noise_freq_1,
                                      center_pos.z() * k_edge_noise_freq_1);
      float const edge_noise2 = noise(center_pos.x() * k_edge_noise_freq_2,
                                      center_pos.z() * k_edge_noise_freq_2);
      float const edge_noise3 = noise(center_pos.x() * k_edge_noise_freq_3,
                                      center_pos.z() * k_edge_noise_freq_3);

      float combined_noise =
          edge_noise1 * 0.5F + edge_noise2 * 0.3F + edge_noise3 * 0.2F;
      combined_noise = (combined_noise - 0.5F) * 2.0F;

      float const width_variation = combined_noise * half_width * 0.35F;

      float const meander = noise(t * 3.0F, length * 0.1F) * 0.3F;
      QVector3D const center_offset = perpendicular * meander;
      center_pos += center_offset;

      struct RingProfile {
        float distance_from_water;
        float height_offset;
      };

      constexpr RingProfile k_left_rings[k_rings_per_side] = {{0.0F, 0.02F},
                                                              {0.125F, 0.175F},
                                                              {0.25F, 0.3F},
                                                              {0.375F, 0.125F},
                                                              {0.5F, -0.15F}};

      float const ring_noise =
          noise(center_pos.x() * 3.0F, center_pos.z() * 3.0F) * 0.075F;
      float const base_bank_width = 0.5F + ring_noise;

      unsigned int const ring_start_idx =
          static_cast<unsigned int>(vertices.size());

      for (int ring = 0; ring < k_rings_per_side; ++ring) {
        float const ring_dist =
            k_left_rings[ring].distance_from_water * base_bank_width;
        float const ring_height = k_left_rings[ring].height_offset;

        QVector3D const ring_pos =
            center_pos -
            perpendicular * (half_width + width_variation + ring_dist);
        float const terrain_height = sample_height(ring_pos.x(), ring_pos.z());
        float const clamped_height =
            std::min(terrain_height, center_height + 0.05F);

        if (ring == 0) {
          samples.push_back(ring_pos);
        }

        Vertex vtx{};
        vtx.position[0] = ring_pos.x();
        vtx.position[1] = clamped_height + ring_height;
        vtx.position[2] = ring_pos.z();

        QVector3D normal;
        if (ring == 0) {

          QVector3D const next_ring_pos =
              center_pos -
              perpendicular *
                  (half_width + width_variation +
                   k_left_rings[1].distance_from_water * base_bank_width);
          float const next_terrain =
              sample_height(next_ring_pos.x(), next_ring_pos.z());
          float const next_clamped =
              std::min(next_terrain, center_height + 0.05F);
          QVector3D slope_vec(next_ring_pos.x() - ring_pos.x(),
                              (next_clamped + k_left_rings[1].height_offset) -
                                  (clamped_height + ring_height),
                              next_ring_pos.z() - ring_pos.z());
          normal = QVector3D::crossProduct(slope_vec, dir).normalized();
        } else if (ring == k_rings_per_side - 1) {

          unsigned int prev_idx = ring_start_idx + ring - 1;
          QVector3D prev_pos(vertices[prev_idx].position[0],
                             vertices[prev_idx].position[1],
                             vertices[prev_idx].position[2]);
          QVector3D slope_vec(ring_pos.x() - prev_pos.x(),
                              (clamped_height + ring_height) - prev_pos.y(),
                              ring_pos.z() - prev_pos.z());
          normal = QVector3D::crossProduct(slope_vec, dir).normalized();
        } else {

          unsigned int prev_idx = ring_start_idx + ring - 1;
          QVector3D prev_pos(vertices[prev_idx].position[0],
                             vertices[prev_idx].position[1],
                             vertices[prev_idx].position[2]);

          QVector3D const next_ring_pos =
              center_pos -
              perpendicular * (half_width + width_variation +
                               k_left_rings[ring + 1].distance_from_water *
                                   base_bank_width);
          float const next_terrain =
              sample_height(next_ring_pos.x(), next_ring_pos.z());
          float const next_clamped =
              std::min(next_terrain, center_height + 0.05F);

          QVector3D slope_from_prev(ring_pos.x() - prev_pos.x(),
                                    (terrain_height + ring_height) -
                                        prev_pos.y(),
                                    ring_pos.z() - prev_pos.z());
          QVector3D slope_to_next(
              next_ring_pos.x() - ring_pos.x(),
              (next_clamped + k_left_rings[ring + 1].height_offset) -
                  (clamped_height + ring_height),
              next_ring_pos.z() - ring_pos.z());

          QVector3D n1 =
              QVector3D::crossProduct(slope_from_prev, dir).normalized();
          QVector3D n2 =
              QVector3D::crossProduct(slope_to_next, dir).normalized();
          normal = ((n1 + n2) * 0.5F).normalized();
        }

        vtx.normal[0] = normal.x();
        vtx.normal[1] = normal.y();
        vtx.normal[2] = normal.z();
        vtx.tex_coord[0] = static_cast<float>(ring) / (k_rings_per_side - 1);
        vtx.tex_coord[1] = t;
        vertices.push_back(vtx);
      }

      for (int ring = 0; ring < k_rings_per_side; ++ring) {
        float const ring_dist =
            k_left_rings[ring].distance_from_water * base_bank_width;
        float const ring_height = k_left_rings[ring].height_offset;

        QVector3D const ring_pos =
            center_pos +
            perpendicular * (half_width + width_variation + ring_dist);
        float const terrain_height = sample_height(ring_pos.x(), ring_pos.z());
        float const clamped_height =
            std::min(terrain_height, center_height + 0.05F);

        if (ring == 0) {
          samples.push_back(ring_pos);
        }

        Vertex vtx{};
        vtx.position[0] = ring_pos.x();
        vtx.position[1] = clamped_height + ring_height;
        vtx.position[2] = ring_pos.z();

        QVector3D normal;
        if (ring == 0) {
          QVector3D const next_ring_pos =
              center_pos +
              perpendicular *
                  (half_width + width_variation +
                   k_left_rings[1].distance_from_water * base_bank_width);
          float const next_terrain =
              sample_height(next_ring_pos.x(), next_ring_pos.z());
          float const next_clamped =
              std::min(next_terrain, center_height + 0.05F);
          QVector3D slope_vec(next_ring_pos.x() - ring_pos.x(),
                              (next_clamped + k_left_rings[1].height_offset) -
                                  (clamped_height + ring_height),
                              next_ring_pos.z() - ring_pos.z());
          normal = QVector3D::crossProduct(dir, slope_vec).normalized();
        } else if (ring == k_rings_per_side - 1) {
          unsigned int prev_idx = ring_start_idx + k_rings_per_side + ring - 1;
          QVector3D prev_pos(vertices[prev_idx].position[0],
                             vertices[prev_idx].position[1],
                             vertices[prev_idx].position[2]);
          QVector3D slope_vec(ring_pos.x() - prev_pos.x(),
                              (clamped_height + ring_height) - prev_pos.y(),
                              ring_pos.z() - prev_pos.z());
          normal = QVector3D::crossProduct(dir, slope_vec).normalized();
        } else {
          unsigned int prev_idx = ring_start_idx + k_rings_per_side + ring - 1;
          QVector3D prev_pos(vertices[prev_idx].position[0],
                             vertices[prev_idx].position[1],
                             vertices[prev_idx].position[2]);

          QVector3D const next_ring_pos =
              center_pos +
              perpendicular * (half_width + width_variation +
                               k_left_rings[ring + 1].distance_from_water *
                                   base_bank_width);
          float const next_terrain =
              sample_height(next_ring_pos.x(), next_ring_pos.z());
          float const next_clamped =
              std::min(next_terrain, center_height + 0.05F);

          QVector3D slope_from_prev(ring_pos.x() - prev_pos.x(),
                                    (clamped_height + ring_height) -
                                        prev_pos.y(),
                                    ring_pos.z() - prev_pos.z());
          QVector3D slope_to_next(
              next_ring_pos.x() - ring_pos.x(),
              (next_clamped + k_left_rings[ring + 1].height_offset) -
                  (clamped_height + ring_height),
              next_ring_pos.z() - ring_pos.z());

          QVector3D n1 =
              QVector3D::crossProduct(dir, slope_from_prev).normalized();
          QVector3D n2 =
              QVector3D::crossProduct(dir, slope_to_next).normalized();
          normal = ((n1 + n2) * 0.5F).normalized();
        }

        vtx.normal[0] = normal.x();
        vtx.normal[1] = normal.y();
        vtx.normal[2] = normal.z();
        vtx.tex_coord[0] = static_cast<float>(ring) / (k_rings_per_side - 1);
        vtx.tex_coord[1] = t;
        vertices.push_back(vtx);
      }

      {
        Vertex const &water_edge_left = vertices[ring_start_idx];
        Vertex skirt_vtx = water_edge_left;
        skirt_vtx.position[1] = -0.05F;
        skirt_vtx.normal[0] = -perpendicular.x();
        skirt_vtx.normal[1] = 0.0F;
        skirt_vtx.normal[2] = -perpendicular.z();
        vertices.push_back(skirt_vtx);
      }

      {
        Vertex const &water_edge_right =
            vertices[ring_start_idx + k_rings_per_side];
        Vertex skirt_vtx = water_edge_right;
        skirt_vtx.position[1] = -0.05F;
        skirt_vtx.normal[0] = perpendicular.x();
        skirt_vtx.normal[1] = 0.0F;
        skirt_vtx.normal[2] = perpendicular.z();
        vertices.push_back(skirt_vtx);
      }

      if (i < length_steps - 1) {
        unsigned int const base_idx = ring_start_idx;
        unsigned int const next_base_idx = base_idx + k_total_rings + 2;

        for (int ring = 0; ring < k_rings_per_side - 1; ++ring) {
          unsigned int idx0 = base_idx + ring;
          unsigned int idx1 = base_idx + ring + 1;
          unsigned int idx2 = next_base_idx + ring;
          unsigned int idx3 = next_base_idx + ring + 1;

          indices.push_back(idx0);
          indices.push_back(idx2);
          indices.push_back(idx1);

          indices.push_back(idx1);
          indices.push_back(idx2);
          indices.push_back(idx3);
        }

        for (int ring = 0; ring < k_rings_per_side - 1; ++ring) {
          unsigned int idx0 = base_idx + k_rings_per_side + ring;
          unsigned int idx1 = base_idx + k_rings_per_side + ring + 1;
          unsigned int idx2 = next_base_idx + k_rings_per_side + ring;
          unsigned int idx3 = next_base_idx + k_rings_per_side + ring + 1;

          indices.push_back(idx0);
          indices.push_back(idx1);
          indices.push_back(idx2);

          indices.push_back(idx1);
          indices.push_back(idx3);
          indices.push_back(idx2);
        }

        {
          unsigned int left_top = base_idx;
          unsigned int left_bottom = base_idx + k_total_rings;
          unsigned int left_top_next = next_base_idx;
          unsigned int left_bottom_next = next_base_idx + k_total_rings;

          indices.push_back(left_top);
          indices.push_back(left_bottom);
          indices.push_back(left_top_next);

          indices.push_back(left_bottom);
          indices.push_back(left_bottom_next);
          indices.push_back(left_top_next);

          unsigned int right_top = base_idx + k_rings_per_side;
          unsigned int right_bottom = base_idx + k_total_rings + 1;
          unsigned int right_top_next = next_base_idx + k_rings_per_side;
          unsigned int right_bottom_next = next_base_idx + k_total_rings + 1;

          indices.push_back(right_top);
          indices.push_back(right_top_next);
          indices.push_back(right_bottom);

          indices.push_back(right_bottom);
          indices.push_back(right_top_next);
          indices.push_back(right_bottom_next);
        }
      }
    }

    if (!vertices.empty() && !indices.empty()) {
      m_meshes.push_back(std::make_unique<Mesh>(vertices, indices));
      m_visibility_samples.push_back(std::move(samples));
    } else {
      m_meshes.push_back(nullptr);
      m_visibility_samples.emplace_back();
    }
  }
}

void RiverbankRenderer::submit(Renderer &renderer, ResourceManager *resources) {
  if (m_meshes.empty() || m_river_segments.empty()) {
    return;
  }

  Q_UNUSED(resources);

  auto *shader = renderer.get_shader("riverbank");
  if (shader == nullptr) {
    return;
  }

  renderer.set_current_shader(shader);

  auto *backend = renderer.backend();
  auto &visibility = Game::Map::VisibilityService::instance();
  const bool use_visibility = visibility.is_initialized();
  const std::uint64_t visibility_version =
      use_visibility ? visibility.version() : 0;
  Game::Map::VisibilityService::Snapshot visibility_snapshot;
  if (use_visibility) {
    visibility_snapshot = visibility.snapshot();
  }

  Texture *visibility_tex = nullptr;
  QVector2D visibility_size(0.0F, 0.0F);

  if (use_visibility) {
    const int vis_w = visibility_snapshot.width;
    const int vis_h = visibility_snapshot.height;
    bool const size_changed =
        (vis_w != m_visibility_width) || (vis_h != m_visibility_height);

    if (!m_visibility_texture || size_changed) {
      m_visibility_texture = std::make_unique<Texture>();
      m_visibility_texture->create_empty(vis_w, vis_h, Texture::Format::RGBA);
      m_visibility_texture->set_filter(Texture::Filter::Nearest,
                                       Texture::Filter::Nearest);
      m_visibility_texture->set_wrap(Texture::Wrap::ClampToEdge,
                                     Texture::Wrap::ClampToEdge);
      m_visibility_width = vis_w;
      m_visibility_height = vis_h;
      m_cached_visibility_version = 0;
    }

    if (visibility_version != m_cached_visibility_version || size_changed) {
      const auto &cells = visibility_snapshot.cells;
      std::vector<unsigned char> texels(
          static_cast<std::size_t>(vis_w * vis_h * 4), 0U);

      for (int z = 0; z < vis_h; ++z) {
        for (int x = 0; x < vis_w; ++x) {
          int const idx = z * vis_w + x;
          unsigned char val = 0U;
          switch (static_cast<Game::Map::VisibilityState>(cells[idx])) {
          case Game::Map::VisibilityState::Visible:
            val = 255U;
            break;
          case Game::Map::VisibilityState::Explored:
            val = 128U;
            break;
          case Game::Map::VisibilityState::Unseen:
          default:
            val = 0U;
            break;
          }
          texels[static_cast<std::size_t>(idx * 4)] = val;
          texels[static_cast<std::size_t>(idx * 4 + 3)] = 255;
        }
      }

      m_visibility_texture->bind();
      glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, vis_w, vis_h, GL_RGBA,
                      GL_UNSIGNED_BYTE, texels.data());
      visibility_tex = m_visibility_texture.get();
      m_cached_visibility_version = visibility_version;
    } else {
      visibility_tex = m_visibility_texture.get();
    }

    visibility_size =
        QVector2D(static_cast<float>(vis_w), static_cast<float>(vis_h));
  }

  if (backend != nullptr) {
    backend->set_riverbank_visibility(
        use_visibility && visibility_tex != nullptr, visibility_tex,
        visibility_size, m_tile_size, m_explored_dim_factor);
  }

  QMatrix4x4 model;
  model.setToIdentity();

  size_t mesh_index = 0;
  for (const auto &segment : m_river_segments) {
    if (mesh_index >= m_meshes.size()) {
      break;
    }

    auto *mesh = m_meshes[mesh_index].get();
    ++mesh_index;

    if (mesh == nullptr) {
      continue;
    }

    float segment_visibility = 1.0F;
    if (use_visibility) {
      enum class SegmentState { Hidden, Explored, Visible };
      SegmentState state = SegmentState::Hidden;

      const auto &samples = m_visibility_samples[mesh_index - 1];
      if (samples.empty()) {
        state = SegmentState::Visible;
      }
      for (const auto &sample : samples) {
        if (visibility_snapshot.isVisibleWorld(sample.x(), sample.z())) {
          state = SegmentState::Visible;
          break;
        }
        if ((state == SegmentState::Hidden) &&
            visibility_snapshot.isExploredWorld(sample.x(), sample.z())) {
          state = SegmentState::Explored;
        }
      }

      if (state == SegmentState::Hidden) {
        continue;
      }

      segment_visibility =
          (state == SegmentState::Visible) ? 1.0F : m_explored_dim_factor;
    }

    renderer.mesh(mesh, model, QVector3D(1.0F, 1.0F, 1.0F), nullptr,
                  segment_visibility);
  }

  renderer.set_current_shader(nullptr);
}

} // namespace Render::GL