#pragma once

#include <cstddef>
#include <cstdint>
#include <vector>

namespace fn::gfx {

// CPU-side mesh: positions interleaved with normals stride 3 floats each,
// indexed by `indices`.
struct Mesh {
    std::vector<float>    positions;  // x,y,z stride=3 (count = num_vertices*3)
    std::vector<float>    normals;    // x,y,z stride=3 (same length as positions)
    std::vector<uint32_t> indices;    // tri-list (count multiple of 3)
};

// Parse Wavefront .obj from a text buffer. Pure: no I/O.
// Supports: v, vn, f (triangles and quads). Ignores: vt, mtllib, usemtl, o, g, s.
// If the file has no vn, normals are generated per-face (flat shading).
// Quads in `f` are split into 2 triangles (fan). N-gons (>4 verts) are not supported.
//
// Returns an empty Mesh ({}, {}, {}) on parse failure (no vertices found).
Mesh mesh_obj_parse(const char* obj_text, size_t len);

// Read file from disk and parse. IMPURE (file I/O).
// Returns empty Mesh on read or parse failure.
Mesh mesh_obj_load(const char* path);

} // namespace fn::gfx