"""
Cause graph API — explain why a node/action made its decisions.
"""

from fastapi import APIRouter
from typing import Optional

from backend.api.api import cause_graph

router = APIRouter(prefix="/api/cause", tags=["cause"])


@router.get("/explain/{node}")
def explain_node(node: str, action: Optional[str] = None):
    """Explain the causal chain for a given node (+ optional action)."""
    chain = cause_graph.explain(node, action)
    return {
        "node": node,
        "action": action,
        "events": len(chain),
        "chain": chain,
    }


@router.get("/trace")
def full_trace():
    """Return the entire cause graph as a dict."""
    return {
        "nodes_tracked": len(cause_graph.graph),
        "events_seen": len(cause_graph.events),
        "trace": {str(k): v for k, v in cause_graph.full_trace().items()},
    }


@router.get("/events")
def recent_events(limit: int = 100):
    """Return the most recent N ingested events."""
    events = cause_graph.events[-limit:]
    return {
        "count": len(events),
        "events": events,
    }


# Legacy wrappers (kept for api.py facade)
def explain_node_legacy(cause_graph_instance, node, action=None):
    return cause_graph_instance.explain(node, action)


def full_cause_trace(cause_graph_instance):
    return cause_graph_instance.full_trace()