chendandan_homework/app/graph/builder.py

from __future__ import annotations
"""需求解析阶段子图：从用户原始输入解析为结构化TravelRequest，路由到澄清/就绪/错误节点。"""

from langgraph.graph import (
    END,
    START,
    StateGraph,
)

from app.agents.requirement_agent import (
    RequirementAgent,
)
from app.graph.nodes import (
    clarification_node,
    error_node,
    make_parse_request_node,
    ready_node,
    route_after_parse,
)
from app.graph.state import TravelState


def build_requirement_graph(
    agent: RequirementAgent | None = None,
):
    """构建需求解析阶段的LangGraph。"""

    requirement_agent = (
        agent or RequirementAgent()
    )

    builder = StateGraph(TravelState)

    builder.add_node(
        "parse_request",
        make_parse_request_node(
            requirement_agent
        ),
    )

    builder.add_node(
        "clarify",
        clarification_node,
    )

    builder.add_node(
        "ready",
        ready_node,
    )

    builder.add_node(
        "error",
        error_node,
    )

    builder.add_edge(
        START,
        "parse_request",
    )

    builder.add_conditional_edges(
        "parse_request",
        route_after_parse,
        {
            "clarify": "clarify",
            "ready": "ready",
            "error": "error",
        },
    )

    builder.add_edge("clarify", END)
    builder.add_edge("ready", END)
    builder.add_edge("error", END)

    return builder.compile()