"""Rewrite query validation via BM25 retrieval rank comparison."""

from src.retrieval.bm25_retriever import BM25Retriever
from src.utils import setup_logger

logger = setup_logger(__name__)


def validate_rewrite(
    original_query: str,
    rewrite_query: str,
    ms_label: str,
    retriever: BM25Retriever,
    gold_evidence_ids: set,
    top_k: int = 10,
) -> dict:
    """Validate a rewrite_query by comparing retrieval performance.

    Args:
        original_query: Original user query.
        rewrite_query: Generated rewrite query.
        ms_label: Memory state label.
        retriever: BM25 retriever for this user.
        gold_evidence_ids: Set of gold evidence session IDs.
        top_k: Top-k for recall computation.

    Returns:
        Validation result dict.
    """
    if ms_label == "SM":
        return {"status": "skip", "reason": "SM does not use retrieval"}
    if ms_label == "NM" or rewrite_query == original_query:
        return {"status": "keep", "reason": "NM uses original query"}

    # Compute ranks
    base_rank = retriever.get_rank(original_query, gold_evidence_ids)
    new_rank = retriever.get_rank(rewrite_query, gold_evidence_ids)

    # Compute recall@k
    base_recall = retriever.recall_at_k(original_query, gold_evidence_ids, k=top_k)
    new_recall = retriever.recall_at_k(rewrite_query, gold_evidence_ids, k=top_k)

    validation_result = {
        "base_rank": base_rank,
        "new_rank": new_rank,
        "base_recall_at_k": base_recall,
        "new_recall_at_k": new_recall,
        "rank_improved": new_rank < base_rank,
        "rank_not_worse": new_rank <= base_rank,
    }

    # Decision based on ms_label
    if ms_label == "PM":
        if new_recall and new_rank <= base_rank:
            validation_result["status"] = "keep"
        elif new_recall and new_rank > base_rank:
            validation_result["status"] = "keep_downweight"
        else:
            validation_result["status"] = "discard"
    elif ms_label == "VM":
        if new_recall:
            validation_result["status"] = "keep"
        else:
            validation_result["status"] = "discard"
    else:
        validation_result["status"] = "keep"

    return validation_result