pdfcraft/crates/xfa/src/lib.rs

//! pdfcraft-xfa — XFA forms (L3). See the README.
//!
//! A dynamic XFA form is a PDF shell around an XML template; viewers without an XFA engine
//! show its one placeholder page ("requires Adobe Reader"). This crate reads the template,
//! lays it out and writes ordinary pages and AcroForm fields into the document, so the rest
//! of PdfCraft (rendering, filling, saving, printing, tools) works on it unchanged.

#![deny(clippy::unwrap_used, clippy::expect_used, clippy::panic, clippy::unimplemented, clippy::todo, clippy::unreachable)]

pub mod data;
pub mod fixtures;
pub mod layout;
pub mod model;
pub mod packets;
pub mod parse;
pub mod pdf;
pub mod script;
pub mod text;

use pdfcraft_cos::Document;

pub use data::{
    DataNode, DataOp, DataPath, DatasetsWrite, FieldData, FieldDatum, add_data_instances, build_data, iso_to_pattern, parse_datasets, pattern_to_iso,
    read_values, remove_data_instance, som_to_path, write_data_ops, write_data_value, write_datasets, write_datasets_reusing,
};
pub use layout::{Action, BorderShape, Form, Item, MAX_PAGES, Page, Widget, WidgetKind, layout};
pub use packets::{Encoding, Packets, decode as decode_packet, encode as encode_packet, read_packets};
pub use parse::{measure, parse};
pub use pdf::{CLICK_KEY, LAYOUT_KEY, SOM_KEY, existing_layout};
pub use script::{
    FormNode, LiveForm, MAX_FORM_NODES, NodeKind, OVERRIDES_KEY, Overrides, ScriptEvent, apply_overrides, data_of, fields_by_som, form_tree,
    has_scripts, overrides, rerender, set_overrides, template_of,
};

#[derive(Debug, thiserror::Error)]
pub enum XfaError {
    #[error("the document is not an XFA form")]
    NotXfa,
    #[error("the XFA template could not be read: {0}")]
    Malformed(String),
    #[error("{0}")]
    TooLarge(String),
    #[error("{0}")]
    Cos(#[from] pdfcraft_cos::CosError),
}

/// What laying out a form produced.
#[derive(Clone, Debug, Default, PartialEq)]
pub struct Report {
    pub pages: usize,
    pub fields: usize,
    /// Template bytes read.
    pub template_bytes: usize,
    /// What was approximated or left out, for the user.
    pub warnings: Vec<String>,
}

/// Is this a dynamic XFA form still showing its placeholder pages (one PdfCraft has not laid
/// out yet)?
pub fn is_dynamic(doc: &Document) -> bool {
    existing_layout(doc).is_none() && matches!(read_packets(doc), Ok(Some(p)) if p.needs_rendering || !p.has_fields)
}

/// Lay a template packet (or whole XDP, whose datasets then fill the fields) out.
pub fn layout_xml(xml: &str) -> Result<Form, XfaError> {
    let (tpl, warnings) = parse(xml)?;
    let data = parse_datasets(xml);
    let mut form = layout(&tpl, data.as_ref())?;
    form.warnings.splice(0..0, warnings);
    Ok(form)
}

/// Lay a dynamic XFA form out into its own document: its placeholder pages are replaced by the
/// laid-out pages and its fields join the AcroForm, holding the values of the datasets packet.
/// The XFA packets stay, so Adobe's viewers keep rendering it their way. Widget appearances are
/// left for the forms layer to generate.
pub fn render_into(doc: &mut Document) -> Result<Report, XfaError> {
    if !is_dynamic(doc) {
        return Err(XfaError::NotXfa);
    }
    let packets = read_packets(doc)?.ok_or(XfaError::NotXfa)?;
    if packets.xdp.trim().is_empty() {
        return Err(XfaError::Malformed("the XFA packets hold no template".into()));
    }
    let (tpl, parse_warnings) = parse(&packets.xdp)?;
    let data = parse_datasets(&packets.xdp);
    let laid = apply_overrides(&tpl, &overrides(doc));
    let mut form = layout(&laid, data.as_ref())?;
    form.warnings.splice(0..0, parse_warnings);
    if form.pages.is_empty() {
        return Err(XfaError::Malformed("the template laid out to no pages".into()));
    }
    let written = pdf::write_form(doc, &form)?;
    let mut warnings = form.warnings;
    warnings.extend(written.warnings);
    warnings.dedup();
    Ok(Report { pages: written.pages, fields: written.fields, template_bytes: packets.xdp.len(), warnings })
}

#[cfg(test)]
mod tests;