acadrust 0.3.4

A pure Rust library for reading and writing CAD files in DXF format (ASCII and Binary) and DWG format (Binary).
Documentation 
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//! ACIS/SAT solid modeler data parser and writer.
//!
//! This module provides support for parsing and generating ACIS SAT (Save And
//! Restore) format data, which is the text-based geometry representation used
//! by 3DSOLID, BODY, and REGION entities in DXF/DWG files.
//!
//! # Supported Versions
//!
//! - **ACIS 1.5–6.0** (SAT versions 400–600): Legacy format without explicit
//!   record indices.
//! - **ACIS 7.0** (SAT version 700): Adds explicit negative record indices,
//!   `asmheader` entity, and `@`-prefixed counted strings.
//! - **ACIS 21.0+** (SAT version 21800): Modern format with extended entity types.
//!
//! # Format Overview
//!
//! A SAT file consists of:
//! 1. A **header** (3–4 lines): version, product info, tolerances
//! 2. **Entity records**: each terminated by `#`, representing the B-rep
//!    topology (body → lump → shell → face → loop → coedge → edge → vertex)
//!    and associated geometry (surfaces, curves, points, transforms).
//!
//! # Example
//!
//! ```rust
//! use acadrust::entities::acis::{SatDocument, SatVersion};
//!
//! // Parse SAT text from a 3DSOLID entity
//! let sat_text = "700 0 1 0\n\
//!     @12 Spatial Corp @7 ACIS 7.0 @24 Thu Jan 01 00:00:00 2023\n\
//!     1e-06 9.9999999999999995e-07\n\
//!     -0 asmheader $-1 -1 @12 700 7 0 0 @5 ACIS @3 7.0 @24 Thu Jan 01 00:00:00 2023 #\n\
//!     -1 body $-1 $-1 $-1 $-1 #\n\
//!     End-of-ACIS-data\n";
//!
//! let doc = SatDocument::parse(sat_text).unwrap();
//! assert_eq!(doc.header.version, SatVersion::new(7, 0, 0));
//! assert_eq!(doc.records.len(), 2);
//!
//! // Write back to SAT text
//! let output = doc.to_sat_string();
//! assert!(output.contains("700"));
//! ```

pub mod types;
pub mod parser;
pub mod writer;
pub mod sab;
pub mod primitives;

pub use types::*;
pub use parser::SatParser;
pub use writer::SatWriter;
pub use sab::{SabWriter, SabReader};

/// Downgrade ACIS v600+ record token layouts to v400 format.
///
/// ACIS 6.0 added extra fields to some entity types (most notably `edge`).
/// When downgrading SAT output for DXF compatibility, these extra fields
/// must be stripped.
///
/// Detection is based on actual token count rather than version header,
/// because some SAT data has a v400 header but v600 record layouts
/// (e.g., "ACIS 6.00" builder with version=400 header).
///
/// **edge** layout change (after sentinel normalization):
/// - v400 (6 tokens): `$sentinel $sv $ev $coedge $curve sense`
/// - v600 (9 tokens): `$sentinel $sv start_param $ev end_param $coedge $curve sense "unknown"`
///
/// The v600 "unknown" string becomes `7 unknown` in legacy SAT (counted string),
/// which BricsCAD's v400 parser misinterprets as extra tokens.
pub fn downgrade_records_to_v400(records: &mut Vec<SatRecord>) {
    for record in records.iter_mut() {
        if record.entity_type == "edge" {
            // v600 edge tokens (after sentinel normalization):
            //   [0] sentinel $-1
            //   [1] $sv
            //   [2] start_param (Float)      ← remove
            //   [3] $ev
            //   [4] end_param (Float)        ← remove
            //   [5] $coedge
            //   [6] $curve
            //   [7] sense (Enum)
            //   [8] "unknown" (String)       ← remove
            // Result: [0]sentinel [1]$sv [2]$ev [3]$coedge [4]$curve [5]sense
            let len = record.tokens.len();
            if len >= 9 {
                // Remove from end first to preserve indices
                record.tokens.truncate(len - 1); // remove "unknown" string
                record.tokens.remove(4); // remove end_param (was index 4)
                record.tokens.remove(2); // remove start_param (was index 2)
            }
        }
    }
}