facturx

# Changelog

All notable changes to this project are documented here.
Format based on [Keep a Changelog](https://keepachangelog.com/).

## [0.3.0] - 2026-07-30

Support of the two data items the French e-invoicing mandate requires on top of
plain EN 16931. Both fields default to `nil` and emit nothing, so **generated
output is unchanged** for callers that don't set them.

### Changed
- `parse/1` now populates `business_process` (BT-23), which in 0.2.0 was always
  `nil`. Emitting is unaffected: the French closed-list check is **opt-in**, so
  `Facturx.parse(xml) |> Facturx.build()` still succeeds on a non-French document
  (a German ZUGFeRD or Peppol invoice carrying its own BT-23).

### Added
- `Facturx.Invoice.business_process` — **BT-23** "cadre de facturation"
  (`ram:BusinessProcessSpecifiedDocumentContextParameter/ram:ID`), mandatory
  `1..1` for the mandate and previously not emitted at all. This is the field
  that carries the nature of the transaction (goods / services / mixed) and
  therefore VAT chargeability.
- `Facturx.Invoice.tax_due_date_type_code` — **BT-8** VAT point date code
  (`ram:ApplicableTradeTax/ram:DueDateTypeCode`), i.e. the option to pay VAT on
  debits. Document-level and replicated onto every VAT breakdown entry, which
  satisfies rule S1.13 by construction.
- `Facturx.business_processes/0` — the closed list of 13 BT-23 codes of rule
  G1.02 (`B1`/`S1`/`M1`, `B2`/`S2`/`M2`, `B4`/`S4`/`M4`, `S5`, `S6`, `B7`/`S7`).
- `Facturx.vat_point_date_codes/0` — the BT-8 code list, `5` (invoice date, VAT on
  debits) / `29` (delivery date, goods) / `72` (payment date, VAT on collection).
  BT-8 is validated against it **by default** (`:validate_vat_point_date`, set it
  to `false` to reproduce a nonconformant third-party document), returning
  `{:error, {:invalid_vat_point_date_code, code}}`. The restriction comes from
  EN 16931 (`BR-CL-06`), not from France, and the enumeration ships in
  `priv/schematron/en16931/FACTUR-X_EN16931_codedb.xml` (code list `id=28`). Note
  that `3`/`35`/`432` are the **UBL** (UNTDID 2005) values and are invalid in CII
  — the XSD accepts them (unrestricted `xs:token`) but the Schematron does not.
- Per-entry BT-8: a `tax_breakdown` entry may carry its own `:due_date_type_code`,
  which overrides the document-level field. EN 16931 allows the code to differ
  between VAT breakdown entries even though French rule S1.13 does not, so parsing
  hoists a uniform code to the document level and keeps divergent codes per entry
  instead of collapsing them onto one value.

### Fixed
- A `:tax_due_date_type_code` with an empty `:tax_breakdown` had nowhere to be
  emitted and was dropped silently; `build/2` now returns
  `{:error, {:vat_point_date_unemittable, code}}`.
- `""` in `:business_process` or `:tax_due_date_type_code` produced an empty
  element that parsed back as `nil`, breaking the round-trip invariant. Empty
  strings are now treated as absent, like `nil`.
- `Facturx.CII.build/2` output is now covered against the bundled XSD by the test
  suite. That path had never been exercised: element order had only ever been
  checked by reading the schema.
- `:validate_business_process` option on `build/2` (and therefore `generate/3`),
  **defaulting to `false`**, also settable once via
  `config :facturx, Facturx.CII, validate_business_process: true` (the option
  overrides the config in both directions). Enabled, an unknown BT-23 code
  returns `{:error, {:invalid_business_process, code}}`. It is opt-in because
  BT-23 is an EN 16931 term whose values are *not* restricted to the French list
  — Peppol, Chorus Pro and other national specifications use their own.
- `parse/1` reads both fields back, preserving the `parse(build(inv)) == inv`
  round-trip invariant.
- Documentation, sourced against the **v3.2 (2026-04-30)** external
  specifications: `docs/reference/reforme-fr.md` (business reference, primary
  sources, and three widely repeated claims that the sources contradict),
  `docs/reference/mapping-cii-flux1.md` (all 116 regulatory Flux 1 data items
  mapped to CII, with coverage status — 50 emitted), and ADR 0002.

### Notes
- No new schema is bundled: BT-23 and BT-8 are already declared `minOccurs="0"`
  in the EN 16931 XSD shipped since 0.2.0.
- Rule **G1.60** (a `B4`/`S4`/`M4` framework forbids `type_code` `386`/`500`/`503`)
  is **not** enforced — the closed list is not full BT-23 conformance.
- There is no `:extended_ctc_fr` profile, deliberately. The PPF profile is
  declared by the transmitted file's name prefix (`Base_`/`Full_`, rule S1.06),
  which is the caller's responsibility; the URN
  `…#conformant#urn.cpro.gouv.fr:1p0:extended-ctc-fr` found in much secondary
  writing does not appear anywhere in the official specifications.

## [0.2.0] - 2026-07-24

### Added
- `Facturx.XSD.validate/2` + `Facturx.validate_xsd/2`: validate CII XML against
  the EN 16931 **XSD**, in **pure Elixir, in-process** via OTP `:xmerl_xsd` — no
  external tool, no network, no Port. Catches missing mandatory elements, wrong
  data types, unexpected elements, wrong order and cardinality. Bundled schema:
  `priv/xsd/en16931/`.
- `Facturx.XSD.Cache` (supervised): compiles each bundled schema once and shares
  it via `:persistent_term`, so validation runs in the caller process — in
  parallel, ~0.6 ms/call (vs ~5 ms recompiling per call). Falls back to per-call
  compilation in a short-lived task when no cached schema is available.

### Security
- XSD validation treats input as untrusted: a `<!DOCTYPE>` is rejected and
  external entity/DTD fetching is disabled, preventing XXE and entity-expansion
  ("billion laughs") attacks.

### Notes
- `:xmerl_xsd` is a partial XSD 1.0 implementation; it validates the CII EN 16931
  schema well but is not a guarantee of full XSD 1.0 conformance. Business-rule
  validation remains in `Facturx.Validate` (Schematron).

## [0.1.0] - 2026-07-24

First public release. Pure-Elixir generation and extraction of Factur-X /
ZUGFeRD invoices (EN 16931), with optional Schematron validation.

### Added
- Project skeleton and scope ADR.
- Public API surface: `Facturx.generate/3`, `extract/1`, `parse/1`, `build/2`, `validate/2`.
- `Facturx.Extract.extract/1`: locate and decode the embedded CII XML from a
  Factur-X PDF (classic xref), with profile detection and refc-binary-safe
  results (`:binary.copy`). Validated against a real EN 16931 fixture.
- `Facturx.Embed.embed/3` + `Facturx.generate/3`: embed CII XML into a PDF/A-2
  or PDF/A-3 base via an incremental update (embedded-file stream, `/Filespec`,
  `/AF`, `EmbeddedFiles` name tree, overridden catalog + XMP). Promotes PDF/A-2
  → PDF/A-3; refuses PDF/A-1 and non-PDF/A input. Output verified
  **PDF/A-3b-compliant by veraPDF** and semantically identical to the Python
  reference (`akretion/factur-x`).
- `Facturx.Xmp.promote/3`: bump `pdfaid:part` 2 → 3 and inject the Factur-X
  extension schema + `fx:*` properties.
- `Facturx.CII.build/2` + `parse/1`: map `Facturx.Invoice` (Decimal amounts) to
  and from EN 16931 CII XML (header, seller/buyer/ship-to, lines, VAT breakdown,
  monetary totals). Output validated against the CII XSD; `build`/`parse`
  round-trip the modelled fields (`build` fills conventional defaults — unit
  `C62`, legal scheme `0002` — which `parse` reads back).
  `Facturx.generate/3` now accepts an `Invoice` struct
  directly (struct → CII → embed → veraPDF-valid Factur-X).
- `Facturx.Validate.validate/2`: optional EN 16931 Schematron validation. Sends
  the XML + bundled compiled schematron (`priv/schematron/`) to a Saxon server
  over `multipart/form-data` (via optional `:req`) and interprets the SVRL report
  into violations. Supports a `:xsl` override for custom rule sets. Proven
  end-to-end against a live Saxon server. Note: the EN 16931 XSLT resolves a
  code-list DB via `document(...)`; the Saxon server must be configured to allow
  that URI (`:codedb_url` overrides the location).

### Known limitations
- Classic cross-reference tables only; object/xref streams (`/Type /ObjStm`,
  `/Type /XRef`) are not yet handled (`Extract` reports
  `:object_streams_unsupported`, `Embed` `:xref_streams_unsupported`).
- `Embed` uses an incremental update, so the pre-promotion (part-2) XMP remains
  earlier in the file; conformant readers resolve the latest object (veraPDF
  confirms). A full-rewrite mode may be added later.
- `Embed` merges `/AF`, `/Names` and `/PageMode` into the existing catalog
  (preserving e.g. `/Dests`). Shapes it cannot safely merge in place are
  refused, never corrupted: an indirect `/AF`/`/Names` reference, or a base that
  already carries embedded files (re-embedding into a Factur-X).