Allow unlimited nesting of item classes

migrations/20240806120210_item_class_unlimited_depth.down.sql

@@ -0,0 +1,28 @@
+-- SPDX-FileCopyrightText: 2024 Simon Bruder <simon@sbruder.de>
+--
+-- SPDX-License-Identifier: AGPL-3.0-or-later
+
+DROP VIEW item_class_tree;
+
+DROP TRIGGER prevent_item_class_cycle ON item_classes;
+DROP FUNCTION check_item_class_cycle;
+
+CREATE FUNCTION check_item_class_recursion_depth()
+RETURNS TRIGGER AS $$
+BEGIN
+  IF NEW.parent IS NULL THEN
+    RETURN NEW;
+  END IF;
+
+  IF (SELECT parent FROM item_classes WHERE id = NEW.parent) IS NULL THEN
+    RETURN NEW;
+  END IF;
+
+  RAISE EXCEPTION 'Item classes may only be nested one level deep';
+END;
+$$ LANGUAGE plpgsql;
+
+CREATE TRIGGER prevent_item_class_recursion
+BEFORE INSERT OR UPDATE ON item_classes
+FOR EACH ROW
+EXECUTE FUNCTION check_item_class_recursion_depth();

migrations/20240806120210_item_class_unlimited_depth.up.sql

@@ -0,0 +1,50 @@
+-- SPDX-FileCopyrightText: 2024 Simon Bruder <simon@sbruder.de>
+--
+-- SPDX-License-Identifier: AGPL-3.0-or-later
+
+DROP TRIGGER prevent_item_class_recursion ON item_classes;
+DROP FUNCTION check_item_class_recursion_depth;
+
+CREATE FUNCTION check_item_class_cycle()
+RETURNS TRIGGER AS $$
+BEGIN
+  IF NEW.parent IS NULL THEN
+    RETURN NEW;
+  END IF;
+
+  IF NEW.id = NEW.parent THEN
+    RAISE EXCEPTION 'Cycle detected';
+  END IF;
+
+  IF (WITH RECURSIVE cte AS (
+    SELECT id, parent
+    FROM item_classes
+    WHERE id = NEW.parent
+
+    UNION ALL
+
+    SELECT item_classes.id, item_classes.parent
+    FROM item_classes, cte
+    WHERE item_classes.id = cte.parent
+  )
+  SELECT 1
+  FROM cte
+  WHERE parent = NEW.id
+  LIMIT 1) THEN
+    RAISE EXCEPTION 'Cycle detected';
+  END IF;
+
+  RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;
+
+CREATE TRIGGER prevent_item_class_cycle
+BEFORE INSERT OR UPDATE ON item_classes
+FOR EACH ROW
+EXECUTE FUNCTION check_item_class_cycle();
+
+CREATE RECURSIVE VIEW item_class_tree (id, parents) AS (
+  SELECT id, ARRAY[]::UUID[] AS parents FROM item_classes WHERE parent IS NULL
+  UNION ALL
+  SELECT item_classes.id, item_class_tree.parents || item_classes.parent FROM item_classes, item_class_tree WHERE item_classes.parent = item_class_tree.id
+);

src/frontend/item_class/show.rs

@@ -44,49 +44,45 @@ async fn get(
     let mut title = item_class.name.clone();
     title.push_str(" – Item Details");
 
-    let mut page_actions = vec![
-        (PageActionGroup::Button {
-            action: PageAction {
-                method: PageActionMethod::Get,
-                target: format!("/items/add?class={}", item_class.id),
-                name: "Add Item".to_string(),
-            },
-            colour: Colour::Success,
-        }),
-    ];
-    if item_class.parent.is_none() {
-        page_actions.push(PageActionGroup::Button {
-            action: PageAction {
-                method: PageActionMethod::Get,
-                target: format!("/item-classes/add?parent={}", item_class.id),
-                name: "Add Child".to_string(),
-            },
-            colour: Colour::Primary,
-        });
-    }
-    page_actions.push(PageActionGroup::Button {
-        action: PageAction {
-            method: PageActionMethod::Get,
-            target: format!("/item-class/{}/edit", item_class.id),
-            name: "Edit".to_string(),
-        },
-        colour: Colour::Warning,
-    });
-    page_actions.push(PageActionGroup::Button {
-        action: PageAction {
-            method: PageActionMethod::Post,
-            target: format!("/item-class/{}/delete", item_class.id),
-            name: "Delete".to_string(),
-        },
-        colour: Colour::Danger,
-    });
-
     Ok(templates::base(
         TemplateConfig {
             path: &format!("/item-class/{}", item_class.id),
             title: Some(&title),
             page_title: Some(Box::new(item_class.name.clone())),
-            page_actions,
+            page_actions: vec![
+                PageActionGroup::Button {
+                    action: PageAction {
+                        method: PageActionMethod::Get,
+                        target: format!("/items/add?class={}", item_class.id),
+                        name: "Add Item".to_string(),
+                    },
+                    colour: Colour::Success,
+                },
+                PageActionGroup::Button {
+                    action: PageAction {
+                        method: PageActionMethod::Get,
+                        target: format!("/item-classes/add?parent={}", item_class.id),
+                        name: "Add Child".to_string(),
+                    },
+                    colour: Colour::Primary,
+                },
+                PageActionGroup::Button {
+                    action: PageAction {
+                        method: PageActionMethod::Get,
+                        target: format!("/item-class/{}/edit", item_class.id),
+                        name: "Edit".to_string(),
+                    },
+                    colour: Colour::Warning,
+                },
+                PageActionGroup::Button {
+                    action: PageAction {
+                        method: PageActionMethod::Post,
+                        target: format!("/item-class/{}/delete", item_class.id),
+                        name: "Delete".to_string(),
+                    },
+                    colour: Colour::Danger,
+                },
+            ],
             user: Some(user),
             ..Default::default()
         },