Opening documents: index lookups in Document::check and the format-1 style upgrade (#2218)

* fix(doc): index items, threads and styles when opening a document

* Apply review fixes

- crates/doc/src/tests.rs

* address review: borrow style names in pin_para_default

---------

Co-authored-by: aiongg <67543387+aiongg@users.noreply.github.com>
Co-authored-by: autocraft-bot[bot] <354215646+autocraft-bot[bot]@users.noreply.github.com>

crates/format/src/lib.rs

@@ -312,12 +312,14 @@ fn upgrade(doc: &mut Document, from: u32) {
 /// is missing.
 fn pin_para_default<T: Clone>(doc: &mut Document, field: fn(&mut ParaAttrs) -> &mut Option<T>, old: T) {
     let unset = |a: &ParaAttrs| field(&mut a.clone()).is_none();
+    // Every style is looked up by name: through one index, not a search of all styles each time.
+    let index = doc.styles.para_index();
     let roots: std::collections::HashSet<String> = doc
         .styles
         .paragraph
         .iter()
         .filter_map(|s| {
-            let chain = doc.styles.para_chain(&s.name);
+            let chain = designcraft_doc::Styles::para_chain_by(&s.name, |n| index.get(n).copied());
             if chain.iter().all(|c| unset(&c.para)) { chain.first().map(|c| c.name.clone()) } else { None }
         })
         .collect();
@@ -326,9 +328,10 @@ fn pin_para_default<T: Clone>(doc: &mut Document, field: fn(&mut ParaAttrs) -> &
             *field(&mut s.para) = Some(old.clone());
         }
     }
-    let styles = doc.styles.clone();
+    // Borrowed names: one entry per style already in memory, so no copy and no extra bound needed.
+    let names: std::collections::HashSet<&str> = doc.styles.paragraph.iter().map(|s| s.name.as_str()).collect();
     let mut pin = |st: &mut Story| {
-        for p in st.paras.iter_mut().filter(|p| styles.para(&p.style).is_none()) {
+        for p in st.paras.iter_mut().filter(|p| !names.contains(p.style.as_str())) {
             let v = field(&mut p.para);
             if v.is_none() {
                 *v = Some(old.clone());

crates/format/src/tests.rs

@@ -355,6 +355,23 @@ fn format_1_keep_lines_without_mode_stays_all_lines() {
     assert!(!designcraft_doc::ParaProps::default().keep_all_lines);
 }
 
+/// A format-1 file with many styles upgrades in time linear in them (each style's chain was
+/// found by searching every style, twice over).
+#[test]
+fn format_1_upgrade_of_many_styles_is_linear() {
+    let mut d = Document::new(&NewDocument::default());
+    let st = d.styles_mut();
+    for i in 0..20_000 {
+        st.paragraph.push(para_style(&format!("S{i}"), (i % 2 == 1).then(|| format!("S{}", i - 1)).as_deref(), None));
+    }
+    let bytes = save_v1(&d);
+    let t = std::time::Instant::now();
+    let back = load(&bytes).unwrap();
+    assert!(t.elapsed() < std::time::Duration::from_secs(10), "{:?}", t.elapsed());
+    assert_eq!(back.styles.para("S0").unwrap().para.keep_all_lines, Some(true));
+    assert_eq!(back.styles.para("S1").unwrap().para.keep_all_lines, None, "based on S0, which is pinned");
+}
+
 /// Format 1 wrote paragraph rules, text frame options and numbered lists in full, so their
 /// old defaults (black rules, auto-size from the top centre, lists continuing across stories)
 /// load as saved. New documents take InDesign's.