#pragma once
#include "vde/mesh/halfedge_mesh.h"
#include <cmath>
#include <vector>
#include <string>

namespace vde::mesh {
using core::Point2D;
using core::Point3D;
using core::Vector3D;

// ── Triangle quality ────────────────────────────────

struct MeshQuality {
    double min_angle_deg = 0;
    double max_angle_deg = 0;
    double avg_aspect_ratio = 0;
    double max_aspect_ratio = 0;
    size_t degenerate_faces = 0;
};

MeshQuality evaluate_mesh_quality(const HalfedgeMesh& mesh);

// ── Tetrahedron quality ─────────────────────────────

struct TetQuality {
    double min_jacobian = 0.0;          // scaled Jacobian (normalised, 0=b−ad … 1=regular)
    double max_jacobian = 0.0;
    double avg_jacobian = 0.0;
    double min_dihedral_deg = 0.0;      // minimum dihedral angle (degrees)
    double max_dihedral_deg = 0.0;      // maximum dihedral angle
    double max_aspect_ratio = 0.0;      // circumsphere-radius / shortest-edge
    size_t degenerate_tets = 0;
    size_t total_tets = 0;
};

/// Evaluate tetrahedron quality from a triangle mesh.
/// This function interprets the mesh as a tetrahedral mesh where
/// each face belongs to a tet defined by the face vertices + face centroid
/// (suitable for closed triangle surfaces interpreted as volume boundaries).
TetQuality evaluate_tet_quality(const HalfedgeMesh& mesh);

// ── Generic element quality ─────────────────────────

enum class ElementType { Tri, Quad, Tet, Hex };

struct ElemQuality {
    double min_jacobian = 0.0;
    double max_jacobian = 0.0;
    double avg_jacobian = 0.0;
    size_t total_elements = 0;
    size_t degenerate = 0;
};

/// Dispatch by element type; implemented for Tri and Tet (Quad/Hex return stub).
ElemQuality evaluate_element_quality(const HalfedgeMesh& mesh, ElementType type);

// ── Quality report ──────────────────────────────────

struct QualityReport {
    std::string element_type;           // "triangle" / "tetrahedron"
    size_t total     = 0;
    size_t degenerate = 0;

    // Binned histogram (quality ∈ [0,1])
    static constexpr int kBins = 10;
    std::array<size_t, kBins> histogram{};

    // Grade counts  (A=excellent  B=good  C=acceptable  D=poor  F=fail)
    size_t grade_A = 0, grade_B = 0, grade_C = 0, grade_D = 0, grade_F = 0;

    double min_quality = 0.0;
    double max_quality = 0.0;
    double avg_quality = 0.0;
    double stddev_quality = 0.0;
};

/// Generate a full quality report from a triangle surface mesh.
QualityReport mesh_quality_report(const HalfedgeMesh& mesh);

/// Generate a full quality report from a tetrahedral mesh.
/// The mesh is treated as having 4-vertex faces (tets) in the
/// same index order as the surface-mesh face loop.
QualityReport mesh_quality_report_tet(const HalfedgeMesh& mesh);

// ── Utility ─────────────────────────────────────────

/// Compute the scaled Jacobian (determinant / (product of edge-lengths))
/// for a triangle; returns [−1,1], 1 = equilateral.
double tri_scaled_jacobian(const Point3D& a, const Point3D& b, const Point3D& c);

/// Compute the scaled Jacobian for a tetrahedron; returns [0,1].
double tet_scaled_jacobian(const Point3D& a, const Point3D& b,
                           const Point3D& c, const Point3D& d);

}  // namespace vde::mesh