viewer/services/itemComparators: make the orders linear

By using the item path as a tie-breaker.

GitHub: closes #255

2 files changed, 30 insertions, 6 deletions

diff --git a/viewer/ldgallery-viewer.7.md b/viewer/ldgallery-viewer.7.md
index 9ac1512..6b31879 100644
--- a/viewer/ldgallery-viewer.7.md
+++ b/viewer/ldgallery-viewer.7.md
@@ -2,7 +2,7 @@
 pagetitle: Viewer user manual - ldgallery
 title: LDGALLERY-VIEWER(7) ldgallery
 author: Pacien TRAN-GIRARD, Guillaume FOUET
-date: 2020-09-19 (v2.0)
+date: 2020-09-24 (v2.0)
 ---
 
 
@@ -79,6 +79,7 @@ initialItemSort
   Possible values are "title_asc", "date_asc", "date_desc".
   Defaults to "title_asc".
   Titles are sorted using a human-friendly _natural sort order_ which treats multi-digit numbers atomically.
+  The item path is used as a tie-breaker for all the defined orders.
 
 <!-- https://github.com/pacien/ldgallery/issues/27
 initialSearchQuery
diff --git a/viewer/src/services/itemComparators.ts b/viewer/src/services/itemComparators.ts
index e131b8b..ab1036d 100644
--- a/viewer/src/services/itemComparators.ts
+++ b/viewer/src/services/itemComparators.ts
@@ -23,18 +23,34 @@ export type ItemComparator = (left: Gallery.Item, right: Gallery.Item) => number
 export type ItemSort = { name: Gallery.ItemSortStr; text: TranslateResult; fn: ItemComparator };
 
 export default class ItemComparators {
-  static readonly DEFAULT = ItemComparators.sortByTitleAsc;
-
   static readonly ITEM_SORTS: ItemSort[] = [
-    { name: "title_asc", text: i18n.t("command.sort.byTitleAsc"), fn: ItemComparators.sortByTitleAsc },
-    { name: "date_asc", text: i18n.t("command.sort.byDateAsc"), fn: ItemComparators.sortByDateAsc },
+    {
+      name: "title_asc",
+      text: i18n.t("command.sort.byTitleAsc"),
+      fn: ItemComparators.chain(ItemComparators.sortByTitleAsc, ItemComparators.sortByPathAsc),
+    },
+    {
+      name: "date_asc",
+      text: i18n.t("command.sort.byDateAsc"),
+      fn: ItemComparators.chain(ItemComparators.sortByDateAsc, ItemComparators.sortByPathAsc),
+    },
     {
       name: "date_desc",
       text: i18n.t("command.sort.byDateDesc"),
-      fn: ItemComparators.reverse(ItemComparators.sortByDateAsc),
+      fn: ItemComparators.reverse(ItemComparators.chain(ItemComparators.sortByDateAsc, ItemComparators.sortByPathAsc)),
     },
   ];
 
+  static readonly DEFAULT = ItemComparators.ITEM_SORTS[0].fn;
+
+  static sortByPathAsc(left: Gallery.Item, right: Gallery.Item): number {
+    return left.path.localeCompare(right.path, undefined, {
+      sensitivity: "base",
+      ignorePunctuation: true,
+      numeric: true,
+    });
+  }
+
   static sortByTitleAsc(left: Gallery.Item, right: Gallery.Item): number {
     return left.title.localeCompare(right.title, undefined, {
       sensitivity: "base",
@@ -50,4 +66,11 @@ export default class ItemComparators {
   static reverse(fn: ItemComparator): ItemComparator {
     return (l, r) => -fn(l, r);
   }
+
+  static chain(primary: ItemComparator, tieBreaker: ItemComparator): ItemComparator {
+    return (l, r) => {
+      const primaryComparison = primary(l, r);
+      return primaryComparison !== 0 ? primaryComparison : tieBreaker(l, r);
+    };
+  }
 }