refactoring of note changes / cloning

services/tree.js

@@ -0,0 +1,84 @@
+"use strict";
+
+const sql = require('./sql');
+
+async function validateParentChild(res, parentNoteId, childNoteId, noteTreeId = null) {
+    const existing = await getExistingNoteTree(parentNoteId, childNoteId);
+
+    if (existing && (noteTreeId === null || existing.note_tree_id !== noteTreeId)) {
+        res.send({
+            success: false,
+            message: 'This note already exists in the target.'
+        });
+
+        return false;
+    }
+
+    if (!await checkTreeCycle(parentNoteId, childNoteId)) {
+        res.send({
+            success: false,
+            message: 'Moving note here would create cycle.'
+        });
+
+        return false;
+    }
+
+    return true;
+}
+
+async function getExistingNoteTree(parentNoteId, childNoteId) {
+    return await sql.getFirst('SELECT * FROM notes_tree WHERE note_id = ? AND parent_note_id = ? AND is_deleted = 0', [childNoteId, parentNoteId]);
+}
+
+/**
+ * Tree cycle can be created when cloning or when moving existing clone. This method should detect both cases.
+ */
+async function checkTreeCycle(parentNoteId, childNoteId) {
+    const subTreeNoteIds = [];
+
+    // we'll load the whole sub tree - because the cycle can start in one of the notes in the sub tree
+    await loadSubTreeNoteIds(childNoteId, subTreeNoteIds);
+
+    async function checkTreeCycleInner(parentNoteId) {
+        if (parentNoteId === 'root') {
+            return true;
+        }
+
+        if (subTreeNoteIds.includes(parentNoteId)) {
+            // while towards the root of the tree we encountered noteId which is already present in the subtree
+            // joining parentNoteId with childNoteId would then clearly create a cycle
+            return false;
+        }
+
+        const parentNoteIds = await sql.getFirstColumn("SELECT DISTINCT parent_note_id FROM notes_tree WHERE note_id = ? AND is_deleted = 0", [parentNoteId]);
+
+        for (const pid of parentNoteIds) {
+            if (!await checkTreeCycleInner(pid)) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
+    return await checkTreeCycleInner(parentNoteId);
+}
+
+async function getNoteTree(noteTreeId) {
+    return sql.getFirst("SELECT * FROM notes_tree WHERE note_tree_id = ?", [noteTreeId]);
+}
+
+async function loadSubTreeNoteIds(parentNoteId, subTreeNoteIds) {
+    subTreeNoteIds.push(parentNoteId);
+
+    const children = await sql.getFirstColumn("SELECT note_id FROM notes_tree WHERE parent_note_id = ? AND is_deleted = 0", [parentNoteId]);
+
+    for (const childNoteId of children) {
+        await loadSubTreeNoteIds(childNoteId, subTreeNoteIds);
+    }
+}
+
+module.exports = {
+    validateParentChild,
+    getNoteTree
+};