/// @file
/// @brief Task3: implementation

#include "task3.hpp" // task3::generate_double_annulus
#include "task2.hpp" // task2::select, task2::select_union

#include "TriangleMesh.hpp" // ex5::TriangleMesh

#include <cmath> // for std::sqrt

namespace task3 {

using namespace task2;


/// @todo Implement function 'generate_double_annulus' as declared and specified in task3.hpp
/// Implementation Hints:
///   - calculate the required bounding box for the annuluses using the centers coordinates +- outer radius
///   - create a triangle mesh using the desired bounding box and resolution (h)
///   - use the source code of task2.test.cpp for ideas how to create the boolean functions for circular regions
///   - select the union of the two inner circles and remove the triangles using the following functions:
///      mesh.getVertices
///      task2::select_union(...)
///      mesh.remove_vertices(...)
///   - analoguously, select the union of the two outer circles and remove the INVERSE of this union using
///      - mesh.getVertices()
///      - task2::select_union(..., true)
///      - mesh.remove_vertices(...)


/// @brief Generates a triangle mesh placed of two (potentially merged) annuluses (Kreisringe)
/// @param c1 Center coordinate of the first annulus
/// @param c2 Center coordinate of the second annulus
/// @param r inner radius of both annuluses
/// @param R outer radius of both annuluses
/// @param h lower bound for the triangle egde length of the resulting mesh
/// @return Resulting triangle mesh
ex5::TriangleMesh generate_double_annulus(task2::Vec2d c1, task2::Vec2d c2, double r, double R, double h) {
  // Calculate bounding box based on center coordinates, radii and a small offset
  double offset = h / 2.0;  // Adjust as needed

  auto bb_min = task2::Vec2d{std::min(c1[0], c2[0]) - R - offset,
                             std::min(c1[1], c2[1]) - R - offset};
  auto bb_max = task2::Vec2d{std::max(c1[0], c2[0]) + R + offset,
                             std::max(c1[1], c2[1]) + R + offset};

  // Create triangle mesh using bounding box and edge length
  ex5::TriangleMesh mesh(ex5::TriangleMesh::BBox{bb_min, bb_max}, h);

  // Function to select points within circles (assuming select_union is defined in task2)
  auto in_circle = [&](const task2::Vec2d& p, task2::Vec2d center, double radius) {
    return std::sqrt(std::pow(p[0] - center[0], 2) + std::pow(p[1] - center[1], 2)) <= radius;
  };

  // Select and remove vertices inside both inner circles (union)
  std::unordered_set<size_t> remove_inner;
  for (size_t i = 0; i < mesh.getVertices().size(); ++i) {
    const auto& v = mesh.getVertices()[i];
    if (in_circle(v, c1, r) && in_circle(v, c2, r)) {
      remove_inner.insert(i);
    }
  }
  mesh.remove_vertices(remove_inner);

  // Select and remove vertices outside both outer circles (union - inverted)
  std::unordered_set<size_t> remove_outer;
  for (size_t i = 0; i < mesh.getVertices().size(); ++i) {
    const auto& v = mesh.getVertices()[i];
    if (!in_circle(v, c1, R) && !in_circle(v, c2, R)) {
      remove_outer.insert(i);
    }
  }
  mesh.remove_vertices(remove_outer);

  return mesh;
}

} // namespace task3