pdfmuse-core 0.1.0

//! PDF parsing.
//!
//! M0 is a **naive path**: lopdf loads the object tree ([`objects`]) and
//! `extract_text` pulls plain text (one paragraph per page, no coordinates). The
//! real value — a self-written content-stream interpreter that emits chars with
//! precise bboxes — replaces the text step in PER-36, building on the page
//! accessors in [`objects`].

mod cmap;
mod content;
mod content_lex;
mod object_parser;
mod lazy;
mod fonts;
mod graphics;
mod objects;
mod tables;

use lopdf::ObjectId;

use crate::error::Result;
use crate::ir::{Document, Metadata, Page, SourceKind, Warning, WarningKind};
use objects::PdfDoc;

/// Parse a PDF into the IR. Pages are extracted independently and in parallel
/// (with the `rayon` feature; sequential otherwise, e.g. WASM), then reassembled
/// in page order so output is identical either way.
pub(crate) fn parse_pdf(data: &[u8], password: Option<&str>) -> Result<Document> {
    // Loading handles decryption (encrypted + wrong/no password → fatal Err).
    let (pdf, warnings) = PdfDoc::load(data, password)?;

    let pages: Vec<(u32, ObjectId)> = pdf.pages().into_iter().collect();
    let mut out = Document {
        source: SourceKind::Pdf,
        metadata: Metadata { page_count: pages.len() as u32, ..Default::default() },
        warnings, // dangling refs / undecodable streams surfaced by the validation pass
        ..Default::default()
    };

    for (page, mut page_warnings) in extract_pages(&pdf, &pages) {
        out.warnings.append(&mut page_warnings);
        out.pages.push(page);
    }

    Ok(out)
}

/// Extract one page — content-stream interpretation plus its own warnings. Purely
/// a function of the page, so it is safe to run for many pages concurrently.
fn extract_one(pdf: &PdfDoc<'_>, page_number: u32, page_id: ObjectId) -> (Page, Vec<Warning>) {
    // lopdf page numbers are 1-based; the IR is 0-based.
    let index = page_number.saturating_sub(1);
    let mut page = Page { index, ..Default::default() };

    // Page dimensions from the (possibly inherited) MediaBox.
    if let Some([x0, y0, x1, y1]) = pdf.media_box(page_id) {
        page.width = (x1 - x0).abs();
        page.height = (y1 - y0).abs();
    }

    // Self-written content-stream interpreter → chars with precise bboxes plus
    // vector rects/rules.
    let pc = content::extract_page(pdf, page_id, index, page.height);
    page.chars = pc.chars;
    page.rects = pc.rects;
    page.rules = pc.rules;
    let mut warnings = pc.warnings;

    // A page with images but no text layer is scanned → needs an OCR backend.
    if page.chars.is_empty() && pdf.page_has_image(page_id) {
        warnings.push(Warning {
            page: Some(index),
            kind: WarningKind::NeedsOcr,
            detail: "page has no text layer (scanned); needs an OCR backend".into(),
        });
    }

    (page, warnings)
}

/// Map every page to `(Page, warnings)` in page order. Parallel across cores with
/// the `rayon` feature; identical output either way (pages are independent).
fn extract_pages(pdf: &PdfDoc<'_>, pages: &[(u32, ObjectId)]) -> Vec<(Page, Vec<Warning>)> {
    #[cfg(feature = "rayon")]
    {
        use rayon::prelude::*;
        pages.par_iter().map(|&(n, id)| extract_one(pdf, n, id)).collect()
    }
    #[cfg(not(feature = "rayon"))]
    {
        pages.iter().map(|&(n, id)| extract_one(pdf, n, id)).collect()
    }
}

#[cfg(test)]
mod tests {
    use super::parse_pdf;
    use crate::ir::{SourceKind, WarningKind};
    use lopdf::content::{Content, Operation};
    use lopdf::{dictionary, Document as LoDoc, Object, Stream};

    /// Synthesize a minimal one-page digital PDF containing `text`.
    fn sample_pdf(text: &str) -> Vec<u8> {
        let mut doc = LoDoc::with_version("1.5");
        let pages_id = doc.new_object_id();
        let font_id = doc.add_object(dictionary! {
            "Type" => "Font", "Subtype" => "Type1", "BaseFont" => "Courier",
        });
        let resources_id = doc.add_object(dictionary! {
            "Font" => dictionary! { "F1" => font_id },
        });
        let content = Content {
            operations: vec![
                Operation::new("BT", vec![]),
                Operation::new("Tf", vec!["F1".into(), 24.into()]),
                Operation::new("Td", vec![100.into(), 700.into()]),
                Operation::new("Tj", vec![Object::string_literal(text)]),
                Operation::new("ET", vec![]),
            ],
        };
        let content_id = doc.add_object(Stream::new(dictionary! {}, content.encode().unwrap()));
        let page_id = doc.add_object(dictionary! {
            "Type" => "Page",
            "Parent" => pages_id,
            "Contents" => content_id,
            "Resources" => resources_id,
            "MediaBox" => vec![0.into(), 0.into(), 612.into(), 792.into()],
        });
        let pages = dictionary! {
            "Type" => "Pages",
            "Kids" => vec![page_id.into()],
            "Count" => 1,
        };
        doc.objects.insert(pages_id, Object::Dictionary(pages));
        let catalog_id = doc.add_object(dictionary! { "Type" => "Catalog", "Pages" => pages_id });
        doc.trailer.set("Root", catalog_id);
        let mut buf = Vec::new();
        doc.save_to(&mut buf).unwrap();
        buf
    }

    #[test]
    fn extracts_positioned_chars_from_digital_pdf() {
        let bytes = sample_pdf("Hello pdfmuse");
        let doc = parse_pdf(&bytes, None).expect("parses a digital PDF");
        assert_eq!(doc.source, SourceKind::Pdf);
        assert_eq!(doc.pages.len(), 1);
        assert_eq!(doc.metadata.page_count, 1);
        assert!(doc.warnings.is_empty(), "unexpected warnings: {:?}", doc.warnings);
        assert_eq!((doc.pages[0].width, doc.pages[0].height), (612.0, 792.0));

        let chars = &doc.pages[0].chars;
        let text: String = chars.iter().map(|c| c.text.as_str()).collect();
        assert_eq!(text, "Hello pdfmuse");

        // The content stream places text at "100 700 Td" with 24pt Courier.
        // First glyph starts at x≈100; top-left origin means y grows downward.
        let first = &chars[0];
        assert_eq!(first.text, "H");
        assert_eq!(first.size, 24.0);
        assert!((first.bbox.x0 - 100.0).abs() < 0.5, "x0 = {}", first.bbox.x0);
        assert!(first.bbox.y1 > first.bbox.y0, "bbox should have positive height");
        // Courier is monospace 600/1000 em → 14.4pt advance; 'e' is the 2nd char.
        assert!((chars[1].bbox.x0 - 114.4).abs() < 0.5, "second glyph x0 = {}", chars[1].bbox.x0);
    }

    /// A one-page PDF whose content stream draws a single stroked rectangle.
    fn sample_pdf_with_rect() -> Vec<u8> {
        let mut doc = LoDoc::with_version("1.5");
        let pages_id = doc.new_object_id();
        let content = Content {
            operations: vec![
                Operation::new("re", vec![100.into(), 100.into(), 200.into(), 50.into()]),
                Operation::new("S", vec![]),
            ],
        };
        let content_id = doc.add_object(Stream::new(dictionary! {}, content.encode().unwrap()));
        let page_id = doc.add_object(dictionary! {
            "Type" => "Page",
            "Parent" => pages_id,
            "Contents" => content_id,
            "MediaBox" => vec![0.into(), 0.into(), 612.into(), 792.into()],
        });
        let pages = dictionary! { "Type" => "Pages", "Kids" => vec![page_id.into()], "Count" => 1 };
        doc.objects.insert(pages_id, Object::Dictionary(pages));
        let catalog_id = doc.add_object(dictionary! { "Type" => "Catalog", "Pages" => pages_id });
        doc.trailer.set("Root", catalog_id);
        let mut buf = Vec::new();
        doc.save_to(&mut buf).unwrap();
        buf
    }

    #[test]
    fn collects_vector_rectangles() {
        let doc = parse_pdf(&sample_pdf_with_rect(), None).expect("parses");
        let rects = &doc.pages[0].rects;
        assert_eq!(rects.len(), 1);
        // "re 100 100 200 50" → user corners (100,100)-(300,150); identity CTM.
        // Y flips on a 792-high page: y_user 100→692, 150→642.
        let b = rects[0].bbox;
        assert!((b.x0 - 100.0).abs() < 0.5, "x0 = {}", b.x0);
        assert!((b.x1 - 300.0).abs() < 0.5, "x1 = {}", b.x1);
        assert!((b.y0 - 642.0).abs() < 0.5 && (b.y1 - 692.0).abs() < 0.5, "y = {},{}", b.y0, b.y1);
    }

    /// A one-page PDF whose only content is an image XObject (a "scanned" page).
    fn sample_pdf_scanned() -> Vec<u8> {
        let mut doc = LoDoc::with_version("1.5");
        let pages_id = doc.new_object_id();
        let img = doc.add_object(Stream::new(
            dictionary! {
                "Type" => "XObject", "Subtype" => "Image",
                "Width" => 1, "Height" => 1, "BitsPerComponent" => 8, "ColorSpace" => "DeviceGray",
            },
            vec![0u8],
        ));
        let resources_id = doc.add_object(dictionary! { "XObject" => dictionary! { "Im1" => img } });
        let content = Content {
            operations: vec![
                Operation::new("q", vec![]),
                Operation::new("Do", vec![Object::Name(b"Im1".to_vec())]),
                Operation::new("Q", vec![]),
            ],
        };
        let content_id = doc.add_object(Stream::new(dictionary! {}, content.encode().unwrap()));
        let page_id = doc.add_object(dictionary! {
            "Type" => "Page", "Parent" => pages_id, "Contents" => content_id,
            "Resources" => resources_id,
            "MediaBox" => vec![0.into(), 0.into(), 612.into(), 792.into()],
        });
        let pages = dictionary! { "Type" => "Pages", "Kids" => vec![page_id.into()], "Count" => 1 };
        doc.objects.insert(pages_id, Object::Dictionary(pages));
        let catalog_id = doc.add_object(dictionary! { "Type" => "Catalog", "Pages" => pages_id });
        doc.trailer.set("Root", catalog_id);
        let mut buf = Vec::new();
        doc.save_to(&mut buf).unwrap();
        buf
    }

    #[test]
    fn scanned_page_warns_needs_ocr() {
        let doc = parse_pdf(&sample_pdf_scanned(), None).expect("parses");
        assert!(doc.pages[0].chars.is_empty(), "scanned page should have no text");
        assert!(
            doc.warnings.iter().any(|w| w.kind == WarningKind::NeedsOcr),
            "expected NeedsOcr; got {:?}",
            doc.warnings
        );
    }
}