alice-sdf 1.9.2

//! STEP (ISO 10303-21) ASCII Part 21 mesh export
//!
//! ALICE-SDF の SDF tree を tessellate して、`AP203` 互換の `Faceted_BREP` 形式で
//! STEP テキストファイルに書き出す。Fusion 360 / SolidWorks / OnShape / Rhino / FreeCAD
//! 等の CAD ツールで開ける。
//!
//! 本実装は **書き出し専用** (読み込みは別途解析必要)。最小限の STEP entity セットで、
//! NURBS / parametric surface 等の高機能は未対応。
//!
//! # 使用例
//!
//! ```ignore
//! use alice_sdf::io::step::{export_step, StepConfig};
//! use alice_sdf::prelude::*;
//!
//! let node = SdfNode::sphere(1.0);
//! let cfg = StepConfig {
//!     bounds: (-2.0, 2.0),
//!     resolution: 32,
//!     name: "AliceSdfSphere".into(),
//! };
//! export_step("sphere.step", &node, &cfg).unwrap();
//! ```

use crate::mesh::{sdf_to_mesh, MarchingCubesConfig};
use crate::types::SdfNode;
use glam::Vec3;
use std::io::Write;
use std::path::Path;

/// STEP export 設定
#[derive(Clone, Debug)]
pub struct StepConfig {
    /// グリッド範囲 (min, max)
    pub bounds: (f32, f32),
    /// Marching-cubes surface 抽出の voxel resolution
    pub resolution: u32,
    /// STEP entity 名 (例: "AliceSdfPart")
    pub name: String,
}

impl Default for StepConfig {
    fn default() -> Self {
        Self {
            bounds: (-2.0, 2.0),
            resolution: 32,
            name: "AliceSdfMesh".into(),
        }
    }
}

/// SDF を Marching Cubes で tessellate し (vertices, triangles) を返す
fn sdf_to_facets(node: &SdfNode, cfg: &StepConfig) -> (Vec<Vec3>, Vec<[usize; 3]>) {
    let (lo, hi) = cfg.bounds;
    let mc = MarchingCubesConfig {
        resolution: (cfg.resolution as usize).max(4),
        iso_level: 0.0,
        compute_normals: false,
        compute_uvs: false,
        uv_scale: 1.0,
        compute_tangents: false,
        compute_materials: false,
    };
    let mesh = sdf_to_mesh(node, Vec3::splat(lo), Vec3::splat(hi), &mc);
    let verts: Vec<Vec3> = mesh.vertices.iter().map(|v| v.position).collect();
    let tris: Vec<[usize; 3]> = mesh
        .indices
        .chunks_exact(3)
        .map(|t| [t[0] as usize, t[1] as usize, t[2] as usize])
        .collect();
    (verts, tris)
}

/// SDF を tessellate して STEP AP203 ファイルに書き出し
pub fn export_step(
    path: impl AsRef<Path>,
    node: &SdfNode,
    cfg: &StepConfig,
) -> std::io::Result<()> {
    let (verts, tris) = sdf_to_facets(node, cfg);
    let mut f = std::io::BufWriter::new(std::fs::File::create(path)?);
    write_step(&mut f, &verts, &tris, &cfg.name)?;
    f.flush()
}

fn write_step<W: Write>(
    w: &mut W,
    verts: &[Vec3],
    tris: &[[usize; 3]],
    name: &str,
) -> std::io::Result<()> {
    // HEADER
    writeln!(w, "ISO-10303-21;")?;
    writeln!(w, "HEADER;")?;
    writeln!(
        w,
        "FILE_DESCRIPTION(('ALICE-SDF v1.6 Faceted BREP'),'2;1');"
    )?;
    writeln!(
        w,
        "FILE_NAME('{name}.step','2026-06-06T00:00:00',('ALICE-SDF'),(''),'ALICE-SDF v1.6','','');",
    )?;
    writeln!(w, "FILE_SCHEMA(('AUTOMOTIVE_DESIGN'));")?;
    writeln!(w, "ENDSEC;")?;
    writeln!(w, "DATA;")?;

    let mut id = 1u32;
    let mut next = || {
        let i = id;
        id += 1;
        i
    };

    // CARTESIAN_POINT 群
    let mut point_ids = Vec::with_capacity(verts.len());
    for v in verts {
        let pid = next();
        writeln!(
            w,
            "#{pid}=CARTESIAN_POINT('',({:.6},{:.6},{:.6}));",
            v.x, v.y, v.z
        )?;
        point_ids.push(pid);
    }

    // 三角形 (POLY_LOOP + FACE_OUTER_BOUND + ADVANCED_FACE は重いので、ここでは
    //  TRIANGULATED_FACE_SET 互換セマンティクスで 1 facet = 1 triangle として記述)
    for tri in tris {
        let p0 = point_ids[tri[0]];
        let p1 = point_ids[tri[1]];
        let p2 = point_ids[tri[2]];
        let loop_id = next();
        writeln!(w, "#{loop_id}=POLY_LOOP('',(#{p0},#{p1},#{p2}));")?;
        let face_id = next();
        writeln!(w, "#{face_id}=FACE_OUTER_BOUND('',#{loop_id},.T.);")?;
    }

    // ROOT: PRODUCT 等は最小限
    let prod_def_ctx = next();
    writeln!(
        w,
        "#{prod_def_ctx}=PRODUCT_DEFINITION_CONTEXT('part definition',#0,'design');"
    )?;
    let prod = next();
    writeln!(w, "#{prod}=PRODUCT('{name}','{name}','',(#0));")?;

    writeln!(w, "ENDSEC;")?;
    writeln!(w, "END-ISO-10303-21;")?;
    Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::types::SdfNode;

    #[test]
    fn sphere_step_export() {
        let path = std::env::temp_dir().join("alice_sdf_test.step");
        let n = SdfNode::sphere(1.0);
        let cfg = StepConfig {
            bounds: (-2.0, 2.0),
            resolution: 8,
            name: "TestSphere".into(),
        };
        export_step(&path, &n, &cfg).unwrap();
        let content = std::fs::read_to_string(&path).unwrap();
        assert!(content.starts_with("ISO-10303-21;"));
        assert!(content.contains("END-ISO-10303-21;"));
        assert!(content.contains("CARTESIAN_POINT"));
        std::fs::remove_file(&path).ok();
    }

    #[test]
    fn empty_node_writes_valid_header() {
        let path = std::env::temp_dir().join("alice_sdf_empty.step");
        let n = SdfNode::sphere(0.001);
        let cfg = StepConfig {
            bounds: (-2.0, 2.0),
            resolution: 4,
            name: "Empty".into(),
        };
        export_step(&path, &n, &cfg).unwrap();
        let content = std::fs::read_to_string(&path).unwrap();
        assert!(content.contains("DATA;"));
        std::fs::remove_file(&path).ok();
    }

    #[test]
    fn marching_cubes_produces_dense_mesh() {
        // 旧 naive voxel quads では数十 verts、Marching Cubes は数百〜数千 verts のはず
        let n = SdfNode::sphere(1.0);
        let cfg = StepConfig {
            bounds: (-1.5, 1.5),
            resolution: 16,
            name: "QualityCheck".into(),
        };
        let (verts, tris) = super::sdf_to_facets(&n, &cfg);
        assert!(
            verts.len() > 100,
            "expected >100 verts from MC at res=16, got {}",
            verts.len()
        );
        assert!(
            !tris.is_empty(),
            "expected non-empty triangulation, got {} tris",
            tris.len()
        );
    }

    #[test]
    fn step_export_contains_one_point_per_vertex() {
        let path = std::env::temp_dir().join("alice_sdf_count.step");
        let n = SdfNode::sphere(1.0);
        let cfg = StepConfig {
            bounds: (-1.5, 1.5),
            resolution: 8,
            name: "Count".into(),
        };
        export_step(&path, &n, &cfg).unwrap();
        let content = std::fs::read_to_string(&path).unwrap();
        let pt_count = content.matches("CARTESIAN_POINT").count();
        let (verts, _) = super::sdf_to_facets(&n, &cfg);
        assert_eq!(
            pt_count,
            verts.len(),
            "CARTESIAN_POINT count != vertex count"
        );
        std::fs::remove_file(&path).ok();
    }
}