Initial commit: Chat-to-diagram v1.0

- Chat interface with OpenAI GPT integration
- Automatic diagram generation from text descriptions
- Tldraw canvas with Dagre layout engine
- REST API instead of WebSocket approach

🤖 Generated with Claude Code (https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/lib/diagram-parser.ts

@@ -0,0 +1,99 @@
+/**
+ * Diagram Parser Utility
+ *
+ * Extracts and validates diagram JSON from AI responses
+ */
+
+import { GraphModel } from '@/types/graph';
+
+/**
+ * Extract diagram JSON from AI response text
+ * Looks for content between [DIAGRAM_START] and [DIAGRAM_END] markers
+ */
+export function extractDiagramFromResponse(response: string): GraphModel | null {
+  try {
+    const startMarker = '[DIAGRAM_START]';
+    const endMarker = '[DIAGRAM_END]';
+
+    const startIndex = response.indexOf(startMarker);
+    const endIndex = response.indexOf(endMarker);
+
+    if (startIndex === -1 || endIndex === -1) {
+      console.log('No diagram markers found in response');
+      return null;
+    }
+
+    const jsonStr = response.substring(
+      startIndex + startMarker.length,
+      endIndex
+    ).trim();
+
+    const diagram = JSON.parse(jsonStr) as GraphModel;
+
+    // Validate diagram structure
+    if (!validateDiagram(diagram)) {
+      console.error('Invalid diagram structure');
+      return null;
+    }
+
+    return diagram;
+  } catch (error) {
+    console.error('Failed to extract diagram from response:', error);
+    return null;
+  }
+}
+
+/**
+ * Validate diagram structure
+ */
+export function validateDiagram(diagram: any): diagram is GraphModel {
+  if (!diagram || typeof diagram !== 'object') {
+    return false;
+  }
+
+  if (!Array.isArray(diagram.nodes) || !Array.isArray(diagram.edges)) {
+    return false;
+  }
+
+  // Validate nodes
+  for (const node of diagram.nodes) {
+    if (!node.id || !node.label || !node.type) {
+      console.error('Invalid node structure:', node);
+      return false;
+    }
+
+    const validTypes = ['start', 'process', 'decision', 'end', 'data', 'default'];
+    if (!validTypes.includes(node.type)) {
+      console.error('Invalid node type:', node.type);
+      return false;
+    }
+  }
+
+  // Validate edges
+  for (const edge of diagram.edges) {
+    if (!edge.id || !edge.source || !edge.target) {
+      console.error('Invalid edge structure:', edge);
+      return false;
+    }
+
+    // Check that source and target nodes exist
+    const sourceExists = diagram.nodes.some((n: any) => n.id === edge.source);
+    const targetExists = diagram.nodes.some((n: any) => n.id === edge.target);
+
+    if (!sourceExists || !targetExists) {
+      console.error('Edge references non-existent node:', edge);
+      return false;
+    }
+  }
+
+  return true;
+}
+
+/**
+ * Remove diagram markers from response text (for display)
+ */
+export function stripDiagramMarkers(response: string): string {
+  return response
+    .replace(/\[DIAGRAM_START\][\s\S]*?\[DIAGRAM_END\]/g, '[Diagram generated]')
+    .trim();
+}