DEV: Make edit sidebar categories modal load more results incrementally (#26761)

app/assets/javascripts/discourse/app/components/sidebar/edit-navigation-menu/categories-modal.gjs

@@ -4,6 +4,7 @@ import { Input } from "@ember/component";
 import { concat, fn, get } from "@ember/helper";
 import { on } from "@ember/modifier";
 import { action } from "@ember/object";
+import didInsert from "@ember/render-modifiers/modifiers/did-insert";
 import { service } from "@ember/service";
 import { gt, includes, not } from "truth-helpers";
 import EditNavigationMenuModal from "discourse/components/sidebar/edit-navigation-menu/modal";
@@ -45,6 +46,19 @@ function findAncestors(categories) {
   return ancestors;
 }
 
+function applyMode(mode, categories, selectedSidebarCategoryIds) {
+  return categories.filter((c) => {
+    switch (mode) {
+      case "everything":
+        return true;
+      case "only-selected":
+        return selectedSidebarCategoryIds.includes(c.id);
+      case "only-unselected":
+        return !selectedSidebarCategoryIds.includes(c.id);
+    }
+  });
+}
+
 export default class extends Component {
   @service currentUser;
   @service site;
@@ -60,18 +74,27 @@ export default class extends Component {
   constructor() {
     super(...arguments);
 
+    this.observer = new IntersectionObserver(
+      (entries) => {
+        if (entries.some((entry) => entry.isIntersecting)) {
+          this.observer.disconnect();
+          this.loadMore();
+        }
+      },
+      {
+        threshold: 1.0,
+      }
+    );
+
     this.processing = false;
     this.setFilterAndMode("", "everything");
   }
 
   setFilteredCategories(categories) {
+    this.filteredCategories = categories;
     const ancestors = findAncestors(categories);
     const allCategories = categories.concat(ancestors).uniqBy((c) => c.id);
 
-    if (this.siteSettings.fixed_category_positions) {
-      allCategories.sort((a, b) => a.position - b.position);
-    }
-
     this.filteredCategoriesGroupings = splitWhere(
       Category.sortCategories(allCategories),
       (category) => category.parent_category_id === undefined
@@ -80,51 +103,69 @@ export default class extends Component {
     this.filteredCategoryIds = categories.map((c) => c.id);
   }
 
+  concatFilteredCategories(categories) {
+    this.setFilteredCategories(this.filteredCategories.concat(categories));
+  }
+
+  setFetchedCategories(mode, categories) {
+    this.setFilteredCategories(
+      applyMode(mode, categories, this.selectedSidebarCategoryIds)
+    );
+  }
+
+  concatFetchedCategories(mode, categories) {
+    this.concatFilteredCategories(
+      applyMode(mode, categories, this.selectedSidebarCategoryIds)
+    );
+  }
+
+  @action
+  didInsert(element) {
+    this.observer.disconnect();
+    this.observer.observe(element);
+  }
+
   async searchCategories(filter, mode) {
     if (filter === "" && mode === "only-selected") {
       this.setFilteredCategories(
         await Category.asyncFindByIds(this.selectedSidebarCategoryIds)
       );
+
+      this.loadedPage = null;
+      this.hasMorePages = false;
     } else {
       const { categories } = await Category.asyncSearch(filter, {
         includeAncestors: true,
         includeUncategorized: false,
       });
 
-      const filteredFetchedCategories = categories.filter((c) => {
-        switch (mode) {
-          case "everything":
-            return true;
-          case "only-selected":
-            return this.selectedSidebarCategoryIds.includes(c.id);
-          case "only-unselected":
-            return !this.selectedSidebarCategoryIds.includes(c.id);
-        }
-      });
+      this.setFetchedCategories(mode, categories);
 
-      this.setFilteredCategories(filteredFetchedCategories);
+      this.loadedPage = 1;
+      this.hasMorePages = true;
     }
   }
 
   async setFilterAndMode(newFilter, newMode) {
-    this.filter = newFilter;
-    this.mode = newMode;
+    this.requestedFilter = newFilter;
+    this.requestedMode = newMode;
 
     if (!this.processing) {
       this.processing = true;
 
       try {
-        while (true) {
-          const filter = this.filter;
-          const mode = this.mode;
+        while (
+          this.loadedFilter !== this.requestedFilter ||
+          this.loadedMode !== this.requestedMode
+        ) {
+          const filter = this.requestedFilter;
+          const mode = this.requestedMode;
 
           await this.searchCategories(filter, mode);
 
+          this.loadedFilter = filter;
+          this.loadedMode = mode;
           this.initialLoad = false;
-
-          if (filter === this.filter && mode === this.mode) {
-            break;
-          }
         }
       } finally {
         this.processing = false;
@@ -132,28 +173,65 @@ export default class extends Component {
     }
   }
 
+  async loadMore() {
+    if (!this.processing && this.hasMorePages) {
+      this.processing = true;
+
+      try {
+        const page = this.loadedPage + 1;
+        const { categories } = await Category.asyncSearch(
+          this.requestedFilter,
+          {
+            includeAncestors: true,
+            includeUncategorized: false,
+            page,
+          }
+        );
+        this.loadedPage = page;
+
+        if (categories.length === 0) {
+          this.hasMorePages = false;
+        } else {
+          this.concatFetchedCategories(this.requestedMode, categories);
+        }
+      } finally {
+        this.processing = false;
+      }
+
+      if (
+        this.loadedFilter !== this.requestedFilter ||
+        this.loadedMode !== this.requestedMode
+      ) {
+        await this.setFilterAndMode(this.requestedFilter, this.requestedMode);
+      }
+    }
+  }
+
   debouncedSetFilterAndMode(filter, mode) {
     discourseDebounce(this, this.setFilterAndMode, filter, mode, INPUT_DELAY);
   }
 
   @action
   resetFilter() {
-    this.debouncedSetFilterAndMode(this.filter, "everything");
+    this.debouncedSetFilterAndMode(this.requestedFilter, "everything");
   }
 
   @action
   filterSelected() {
-    this.debouncedSetFilterAndMode(this.filter, "only-selected");
+    this.debouncedSetFilterAndMode(this.requestedFilter, "only-selected");
   }
 
   @action
   filterUnselected() {
-    this.debouncedSetFilterAndMode(this.filter, "only-unselected");
+    this.debouncedSetFilterAndMode(this.requestedFilter, "only-unselected");
   }
 
   @action
   onFilterInput(filter) {
-    this.debouncedSetFilterAndMode(filter.toLowerCase().trim(), this.mode);
+    this.debouncedSetFilterAndMode(
+      filter.toLowerCase().trim(),
+      this.requestedMode
+    );
   }
 
   @action
@@ -234,6 +312,7 @@ export default class extends Component {
             <div
               class="sidebar-categories-form__row"
               style={{borderColor (get categories "0.color") "left"}}
+              {{didInsert this.didInsert}}
             >
 
               {{#each categories as |category|}}

spec/system/editing_sidebar_categories_navigation_spec.rb

@@ -225,6 +225,43 @@ RSpec.describe "Editing sidebar categories navigation", type: :system do
     expect(modal).to have_checkbox(category2_subcategory)
   end
 
+  context "when there are more categories than the page limit" do
+    around(:each) do |example|
+      search_calls = 0
+
+      spy =
+        CategoriesController.clone.prepend(
+          Module.new do
+            define_method :search do
+              search_calls += 1
+              super()
+            end
+          end,
+        )
+
+      @get_search_calls = lambda { search_calls }
+
+      stub_const(Object, :CategoriesController, spy) do
+        stub_const(CategoriesController, :MAX_CATEGORIES_LIMIT, 1) { example.run }
+      end
+    end
+
+    it "loads all the categories eventually" do
+      visit "/latest"
+
+      expect(sidebar).to have_categories_section
+
+      modal = sidebar.click_edit_categories_button
+      modal.filter("category")
+
+      expect(modal).to have_categories(
+        [category2, category2_subcategory, category, category_subcategory2, category_subcategory],
+      )
+
+      expect(@get_search_calls.call).to eq(6)
+    end
+  end
+
   describe "when max_category_nesting has been set to 3" do
     before_all { SiteSetting.max_category_nesting = 3 }