Create mermaid_renderer.py

engine_03/flow/mermaid_renderer.py

@@ -0,0 +1,21 @@
+from .graph_models import FlowGraph
+
+
+def build_mermaid(flow: FlowGraph) -> str:
+    """
+    Build a Mermaid graph string from a FlowGraph.
+    """
+    lines = ["graph TD"]
+
+    for node in flow.nodes:
+        safe_label = node.label or node.id
+        lines.append(f"  {node.id}[{safe_label}]")
+
+    for edge in flow.edges:
+        if edge.label:
+            lines.append(f"  {edge.source} -->|{edge.label}| {edge.target}")
+        else:
+            lines.append(f"  {edge.source} --> {edge.target}")
+
+    mermaid = "```mermaid\n" + "\n".join(lines) + "\n```"
+    return mermaid