feat: support Podcast generation

src/podcast/graph/builder.py

@@ -0,0 +1,35 @@
+from langgraph.graph import END, START, StateGraph
+
+from .audio_mixer_node import audio_mixer_node
+from .script_writer_node import script_writer_node
+from .state import PodcastState
+from .tts_node import tts_node
+
+
+def build_graph():
+    """Build and return the podcast workflow graph."""
+    # build state graph
+    builder = StateGraph(PodcastState)
+    builder.add_node("script_writer", script_writer_node)
+    builder.add_node("tts", tts_node)
+    builder.add_node("audio_mixer", audio_mixer_node)
+    builder.add_edge(START, "script_writer")
+    builder.add_edge("script_writer", "tts")
+    builder.add_edge("tts", "audio_mixer")
+    builder.add_edge("audio_mixer", END)
+    return builder.compile()
+
+
+if __name__ == "__main__":
+    from dotenv import load_dotenv
+
+    load_dotenv()
+
+    report_content = open("examples/nanjing_tangbao.md").read()
+    workflow = build_graph()
+    final_state = workflow.invoke({"input": report_content})
+    for line in final_state["script"].lines:
+        print("<M>" if line.speaker == "male" else "<F>", line.text)
+
+    with open("final.mp3", "wb") as f:
+        f.write(final_state["output"])