feat: scaffold mindmap core and layout engine

src/lib/mindmap/layout/engines/logicalStructure.ts

@@ -0,0 +1,62 @@
+import {
+  LayoutEngine,
+  LayoutNode,
+  LayoutOptions,
+  LayoutResult,
+  MindmapNode,
+  MindmapTree,
+} from '@/lib/mindmap/types';
+
+interface PositionedNode {
+  node: MindmapNode;
+  depth: number;
+  index: number;
+}
+
+export class LogicalStructureLayout implements LayoutEngine {
+  readonly name = 'logical' as const;
+
+  compute(tree: MindmapTree, options: LayoutOptions = {}): LayoutResult {
+    const horizontalSpacing = options.horizontalSpacing ?? 280;
+    const verticalSpacing = options.verticalSpacing ?? 96;
+
+    const positioned: PositionedNode[] = [];
+    walk(tree, 0, positioned);
+
+    const nodes: LayoutNode[] = positioned.map((item) => ({
+      id: item.node.id,
+      parentId: item.node.parentId,
+      depth: item.depth,
+      data: item.node.data,
+      position: {
+        x: item.depth * horizontalSpacing,
+        y: item.index * verticalSpacing,
+      },
+    }));
+
+    const edges = nodes
+      .filter((n) => n.parentId)
+      .map((n) => ({
+        id: `${n.parentId}-${n.id}`,
+        source: n.parentId!,
+        target: n.id,
+      }));
+
+    const bounds = {
+      width: Math.max(...nodes.map((n) => n.position.x), 0) + horizontalSpacing,
+      height:
+        Math.max(...nodes.map((n) => n.position.y), 0) + verticalSpacing,
+    };
+
+    return { nodes, edges, bounds };
+  }
+}
+
+function walk(node: MindmapNode, depth: number, acc: PositionedNode[], nextIndex = { value: 0 }) {
+  acc.push({ node, depth, index: nextIndex.value++ });
+  node.children?.forEach((child) => {
+    child.parentId = node.id;
+    walk(child, depth + 1, acc, nextIndex);
+  });
+}
+