recent_conversations: Improve sorting behavior.

Refine sorting algorithm of recent conversation list so that
it works like spreadsheet sorting, with previous sorting orders
remembered.

Fixes #33289.

web/src/list_widget.ts

@@ -11,6 +11,7 @@ type SortingFunction<T> = (a: T, b: T) => number;
 
 type ListWidgetMeta<Key, Item = Key> = {
     sorting_function: SortingFunction<Item> | null;
+    applied_sorting_functions: [SortingFunction<Item>, boolean][]; // This is used to keep track of the sorting functions applied.
     sorting_functions: Map<string, SortingFunction<Item>>;
     filter_value: string;
     offset: number;
@@ -280,6 +281,7 @@ export function create<Key, Item = Key>(
 
     const meta: ListWidgetMeta<Key, Item> = {
         sorting_function: null,
+        applied_sorting_functions: [],
         sorting_functions: new Map(),
         offset: 0,
         list,
@@ -303,11 +305,26 @@ export function create<Key, Item = Key>(
             meta.filtered_list = get_filtered_items(meta.filter_value, meta.list, opts);
 
             if (meta.sorting_function) {
-                meta.filtered_list.sort(meta.sorting_function);
+                // If the sorting function is already applied, remove it to avoid duplicate sorting.
-            }
+                const existing_sorting_function_index = meta.applied_sorting_functions.findIndex(
+                    ([sorting_function, _]) => sorting_function === meta.sorting_function,
+                );
+                if (existing_sorting_function_index !== -1) {
+                    meta.applied_sorting_functions.splice(existing_sorting_function_index, 1);
+                }
 
-            if (meta.reverse_mode) {
+                meta.applied_sorting_functions.push([meta.sorting_function, meta.reverse_mode]);
-                meta.filtered_list.reverse();
+                meta.filtered_list.sort((a, b) => {
+                    for (let i = meta.applied_sorting_functions.length - 1; i >= 0; i -= 1) {
+                        const sorting_function = meta.applied_sorting_functions[i]![0];
+                        const is_reverse = meta.applied_sorting_functions[i]![1];
+                        const result = sorting_function(a, b);
+                        if (result !== 0) {
+                            return is_reverse ? -result : result;
+                        }
+                    }
+                    return 0;
+                });
             }
         },
 

web/tests/list_widget.test.cjs

@@ -527,6 +527,105 @@ run_test("sorting", () => {
     assert.ok(cleared);
     expected_html = html_for([ellen, alice, bob, cal, dave]);
     assert.deepEqual($container.$appended_data.html(), expected_html);
+});
+
+run_test("Apply consecutive sorts", () => {
+    const $container = make_container();
+    const $scroll_container = make_scroll_container();
+    const $sort_container = make_sort_container();
+
+    let cleared;
+    $container.empty = () => {
+        cleared = true;
+    };
+
+    const alice = {name: "alice", salary: 50};
+    const bob = {name: "bob", salary: 40};
+    const cal = {name: "cal", salary: 30};
+    const dave = {name: "dave", salary: 20};
+    const ellen = {name: "ellen", salary: 95};
+    const bob_2 = {name: "bob", salary: 20};
+    const cal_2 = {name: "cal", salary: 60};
+
+    const list = [alice, bob, cal, dave, ellen, bob_2, cal_2];
+
+    const opts = {
+        name: "sorting-list",
+        $parent_container: $sort_container,
+        modifier_html: (item) => div(item.name) + div(item.salary),
+        get_item: (item) => item,
+        filter: {
+            predicate: () => true,
+        },
+        sort_fields: {
+            ...ListWidget.generic_sort_functions("alphabetic", ["name"]),
+            ...ListWidget.generic_sort_functions("numeric", ["salary"]),
+        },
+        $simplebar_container: $scroll_container,
+    };
+
+    function html_for(people) {
+        return people.map((item) => opts.modifier_html(item)).join("");
+    }
+
+    ListWidget.create($container, list, opts);
+
+    let button_opts;
+    let $button;
+    let expected_html;
+
+    // Apply sorting by salary first, then by name
+    button_opts = {
+        sort_type: "numeric",
+        prop_name: "salary",
+        list_name: "my-list",
+        active: false,
+    };
+
+    $button = sort_button(button_opts);
+
+    $sort_container.f.apply($button);
+
+    button_opts = {
+        sort_type: "alphabetic",
+        prop_name: "name",
+        list_name: "my-list",
+        active: false,
+    };
+
+    $button = sort_button(button_opts);
+
+    $sort_container.f.apply($button);
+
+    assert.ok(cleared);
+    assert.ok($button.siblings_deactivated);
+
+    expected_html = html_for([alice, bob_2, bob, cal, cal_2, dave, ellen]);
+    assert.deepEqual($container.$appended_data.html(), expected_html);
+
+    // Apply sorting by salary again, the previous sort by salary should be removed
+    button_opts = {
+        sort_type: "numeric",
+        prop_name: "salary",
+        list_name: "my-list",
+        active: false,
+    };
+
+    $button = sort_button(button_opts);
+
+    cleared = false;
+    $sort_container.f.apply($button);
+    assert.ok(cleared);
+    expected_html = html_for([bob_2, dave, cal, bob, alice, cal_2, ellen]);
+    assert.deepEqual($container.$appended_data.html(), expected_html);
+    assert.ok(!$button.hasClass("descend"));
+
+    // Hit the salary field again to reverse the salary sorting
+    cleared = false;
+    $sort_container.f.apply($button);
+    assert.ok(cleared);
+    expected_html = html_for([ellen, cal_2, alice, bob, cal, bob_2, dave]);
+    assert.deepEqual($container.$appended_data.html(), expected_html);
     assert.ok($button.hasClass("descend"));
 });