"""Assembles the VeriScite LangGraph state machine."""

from langgraph.graph import StateGraph, END

from app.graph.state import GraphState
from app.graph import nodes


def build_graph():
    graph = StateGraph(GraphState)

    graph.add_node("extract_claims", nodes.extract_claims)
    graph.add_node("fetch_citation", nodes.fetch_citation)
    graph.add_node("verify_dual", nodes.verify_dual)
    graph.add_node("handle_unresolved_citation", nodes.handle_unresolved_citation)
    graph.add_node("escalate", nodes.escalate)
    graph.add_node("explain", nodes.explain)
    graph.add_node("next_claim", nodes.next_claim)
    graph.add_node("build_report", nodes.build_report)

    graph.set_entry_point("extract_claims")
    graph.add_edge("extract_claims", "fetch_citation")

    graph.add_conditional_edges(
        "fetch_citation",
        nodes.route_after_fetch,
        {"verify": "verify_dual", "unresolved": "handle_unresolved_citation"},
    )

    graph.add_conditional_edges(
        "verify_dual",
        nodes.route_after_verify,
        {"escalate": "escalate", "explain": "explain"},
    )
    graph.add_edge("escalate", "explain")

    graph.add_conditional_edges(
        "explain",
        nodes.advance_or_report,
        {"next_claim": "next_claim", "report": "build_report"},
    )
    graph.add_conditional_edges(
        "handle_unresolved_citation",
        nodes.advance_or_report,
        {"next_claim": "next_claim", "report": "build_report"},
    )
    graph.add_edge("next_claim", "fetch_citation")
    graph.add_edge("build_report", END)

    return graph.compile()