From 2bbd1fca2a2477fd89aaab9631fbeb0883eb8208 Mon Sep 17 00:00:00 2001
From: RumovZ <gp5glkw78@relay.firefox.com>
Date: Wed, 6 Jul 2022 11:26:14 +0200
Subject: [PATCH] Skip card generation if fronts remain unchanged (#1949)

Closes #1945
---
 rslib/src/notetype/mod.rs          |  2 +-
 rslib/src/notetype/schemachange.rs | 88 +++++++++++++++++++-----------
 2 files changed, 57 insertions(+), 33 deletions(-)

diff --git a/rslib/src/notetype/mod.rs b/rslib/src/notetype/mod.rs
index 419ecb78f..be45b6eba 100644
--- a/rslib/src/notetype/mod.rs
+++ b/rslib/src/notetype/mod.rs
@@ -695,7 +695,7 @@ impl Collection {
                 original.config.sort_field_idx,
                 normalize,
             )?;
-            self.update_cards_for_changed_templates(notetype, original.templates.len())?;
+            self.update_cards_for_changed_templates(notetype, &original.templates)?;
             self.update_notetype_undoable(notetype, original)?;
         } else {
             // adding with existing id for old undo code, bypass undo
diff --git a/rslib/src/notetype/schemachange.rs b/rslib/src/notetype/schemachange.rs
index c3d9310d6..d5168407f 100644
--- a/rslib/src/notetype/schemachange.rs
+++ b/rslib/src/notetype/schemachange.rs
@@ -5,7 +5,7 @@
 
 use std::collections::HashMap;
 
-use super::{CardGenContext, Notetype};
+use super::{CardGenContext, CardTemplate, Notetype};
 use crate::{
     prelude::*,
     search::{JoinSearches, SortMode, TemplateKind},
@@ -52,6 +52,10 @@ impl TemplateOrdChanges {
 
         changes
     }
+
+    fn is_empty(&self) -> bool {
+        *self == Self::default()
+    }
 }
 
 impl Collection {
@@ -130,47 +134,67 @@ impl Collection {
     pub(crate) fn update_cards_for_changed_templates(
         &mut self,
         nt: &Notetype,
-        previous_template_count: usize,
+        old_templates: &[CardTemplate],
     ) -> Result<()> {
-        let ords: Vec<_> = nt.templates.iter().map(|f| f.ord).collect();
         let usn = self.usn()?;
-        if ords_changed(&ords, previous_template_count) {
+        let ords: Vec<_> = nt.templates.iter().map(|f| f.ord).collect();
+        let changes = TemplateOrdChanges::new(ords, old_templates.len() as u32);
+
+        if !changes.is_empty() {
             self.set_schema_modified()?;
-            let changes = TemplateOrdChanges::new(ords, previous_template_count as u32);
-
-            // remove any cards where the template was deleted
-            if !changes.removed.is_empty() {
-                let ords =
-                    SearchBuilder::any(changes.removed.into_iter().map(TemplateKind::Ordinal));
-                self.search_cards_into_table(nt.id.and(ords), SortMode::NoOrder)?;
-                for card in self.storage.all_searched_cards()? {
-                    self.remove_card_and_add_grave_undoable(card, usn)?;
-                }
-                self.storage.clear_searched_cards_table()?;
-            }
-
-            // update ordinals for cards with a repositioned template
-            if !changes.moved.is_empty() {
-                let ords =
-                    SearchBuilder::any(changes.moved.keys().cloned().map(TemplateKind::Ordinal));
-                self.search_cards_into_table(nt.id.and(ords), SortMode::NoOrder)?;
-                for mut card in self.storage.all_searched_cards()? {
-                    let original = card.clone();
-                    card.template_idx = *changes.moved.get(&card.template_idx).unwrap();
-                    self.update_card_inner(&mut card, original, usn)?;
-                }
-                self.storage.clear_searched_cards_table()?;
-            }
         }
 
-        let last_deck = self.get_last_deck_added_to_for_notetype(nt.id);
-        let ctx = CardGenContext::new(nt, last_deck, usn);
-        self.generate_cards_for_notetype(&ctx)?;
+        // remove any cards where the template was deleted
+        if !changes.removed.is_empty() {
+            let ords =
+                SearchBuilder::any(changes.removed.iter().cloned().map(TemplateKind::Ordinal));
+            self.search_cards_into_table(nt.id.and(ords), SortMode::NoOrder)?;
+            for card in self.storage.all_searched_cards()? {
+                self.remove_card_and_add_grave_undoable(card, usn)?;
+            }
+            self.storage.clear_searched_cards_table()?;
+        }
+        // update ordinals for cards with a repositioned template
+        if !changes.moved.is_empty() {
+            let ords = SearchBuilder::any(changes.moved.keys().cloned().map(TemplateKind::Ordinal));
+            self.search_cards_into_table(nt.id.and(ords), SortMode::NoOrder)?;
+            for mut card in self.storage.all_searched_cards()? {
+                let original = card.clone();
+                card.template_idx = *changes.moved.get(&card.template_idx).unwrap();
+                self.update_card_inner(&mut card, original, usn)?;
+            }
+            self.storage.clear_searched_cards_table()?;
+        }
+
+        if should_generate_cards(&changes, nt, old_templates) {
+            let last_deck = self.get_last_deck_added_to_for_notetype(nt.id);
+            let ctx = CardGenContext::new(nt, last_deck, usn);
+            self.generate_cards_for_notetype(&ctx)?;
+        }
 
         Ok(())
     }
 }
 
+fn should_generate_cards(
+    changes: &TemplateOrdChanges,
+    nt: &Notetype,
+    old_templates: &[CardTemplate],
+) -> bool {
+    // must regenerate if any front side has changed, but also in the (unlikely)
+    // case that a template has been replaced by one with an identical front
+    !(changes.added.is_empty() && nt.template_fronts_are_identical(old_templates))
+}
+
+impl Notetype {
+    fn template_fronts_are_identical(&self, other_templates: &[CardTemplate]) -> bool {
+        self.templates
+            .iter()
+            .map(|t| &t.config.q_format)
+            .eq(other_templates.iter().map(|t| &t.config.q_format))
+    }
+}
+
 #[cfg(test)]
 mod test {
     use super::{ords_changed, TemplateOrdChanges};