dpp-rules

Pure #![no_std], zero-dependency EU ESPR cross-field regulatory rules.

These are rules that JSON Schema cannot express — "fibre percentages must sum to ~100%", "SVHC concentration > 0.1% triggers disclosure", "surfactant band must be one of the four EU-standard labels". They live here, once, and are consumed by both dpp-domain (standalone validation, no Wasm host) and the Wasm sector plugins (via dpp-plugin-sdk::rules). Every regulatory rule has exactly one implementation.

See docs/architecture/SECTOR-MODEL-CONSOLIDATION.md §7 for the design rationale.

No-std constraint

This crate must remain #![no_std] + alloc with zero dependencies. That is the whole reason C1 extracted it from dpp-domain: sector plugins compile to wasm32-wasip1 and cannot pull in the heavier domain crate. If a rule needs std or an external crate, the rule is in the wrong place.

The CI cargo check target verifies this. Do not break it.

Module structure

src/
├── lib.rs                    re-exports everything at the crate root (backward compat)
│
├── common/
│   ├── country.rs            ISO 3166-1 alpha-2 validation ✅
│   ├── numeric.rs            percentage helpers, sum checks      (placeholder)
│   └── units.rs              unit conversion helpers              (placeholder)
│
├── chemicals/                REACH / RoHS / EU 2026/405  (cross-sector — never under one sector)
│   ├── svhc.rs               REACH Art. 33 concentration validation ✅
│   └── surfactants.rs        EU 2026/405 band validation ✅
│
├── textiles/                 EU ESPR textile sector
│   ├── fibre.rs              fibre_sum_ok, validate_fibre_composition ✅
│   └── care.rs               ISO 3758 care symbols                (placeholder)
│
├── batteries/                EU Regulation 2023/1542, Annex XIII
│   ├── chemistry.rs          allowed chemistries, voltage ranges  (placeholder)
│   ├── degradation.rs        SOH estimation, cycle life           (placeholder)
│   └── recycled_content.rs   Co / Li / Ni split thresholds       (placeholder)
│
├── electronics/              EU Ecodesign Regulation (ESPR)
│   └── spare_parts.rs        availability periods                 (placeholder)
│                             NOTE: repairability scoring → dpp-calc, not here
│
├── metals/                   CBAM (EU Regulation 2023/956)
│   ├── aluminium.rs          alloy grade, CO₂e per route          (placeholder)
│   └── steel.rs              BF-BOF / EAF / DRI-EAF, scrap ratio (placeholder)
│
├── construction/             EU CPR 2024/3110                     (placeholder)
└── toys/                     EN 71 / REACH / EU 2025/2509         (placeholder)

Active sectors are batteries, textiles, and electronics. All others have placeholder modules with field documentation; rules will be added as the delegated acts finalise and the sector plugins mature.

Adding a rule

1. Find the right module (sector + sub-concern). If the rule applies to more than one sector, it belongs in chemicals/ or common/, not under any single sector.
2. Write a pure function with primitive borrowing inputs (&str, f64, &[T]). No owned allocations in function arguments.
3. Return Result<(), String> for validators, bool for predicates.
4. Add a #[cfg(test)] mod tests block in the same file.
5. If the symbol needs to be accessible from dpp-domain or dpp-plugin-sdk callers without the module path, add a pub use line in lib.rs.
6. Run cargo test -p dpp-rules and then cargo test --workspace before committing.

Invariants