import csv
import json
import sys
from typing import Dict, List, Optional, Tuple


DEFAULT_REFERENCE_PATH = "data/tester.csv"
DEFAULT_PREDICTIONS_PATH = "predictions.csv"


def _safe_float(value, default: float = 0.0) -> float:
    try:
        return float(value)
    except (TypeError, ValueError):
        return default


def _normalize_binary(value) -> int:
    value_str = str(value).strip().lower()
    if value_str in {"1", "true", "yes", "y", "positive", "fail", "failure"}:
        return 1
    return 0


def _read_csv(path: str) -> List[Dict[str, str]]:
    with open(path, "r", encoding="utf-8") as f:
        return list(csv.DictReader(f))


def _find_label_column(fieldnames: List[str]) -> str:
    label_candidates = [col for col in fieldnames if col.startswith("label_")]
    if len(label_candidates) == 1:
        return label_candidates[0]
    if not label_candidates:
        raise ValueError("No label column found. Expected a column starting with 'label_'.")
    raise ValueError(
        f"Multiple label columns found: {label_candidates}. Expected exactly one label column."
    )


def _find_prediction_columns(fieldnames: List[str]) -> Tuple[Optional[str], Optional[str]]:
    pred_label_candidates = [
        "prediction",
        "pred",
        "predicted_label",
        "prediction_label",
        "label_pred",
        "y_pred",
        "output",
    ]
    pred_score_candidates = [
        "prediction_score",
        "pred_score",
        "score",
        "probability",
        "prob",
        "confidence",
        "risk_score",
        "y_score",
    ]

    pred_label_col = next((c for c in pred_label_candidates if c in fieldnames), None)
    pred_score_col = next((c for c in pred_score_candidates if c in fieldnames), None)
    return pred_label_col, pred_score_col


def _index_prediction_rows(
    rows: List[Dict[str, str]], id_column: Optional[str]
) -> Dict[str, Dict[str, str]]:
    if not id_column:
        return {str(i): row for i, row in enumerate(rows)}
    return {str(row[id_column]): row for row in rows}


def _detect_join_key(
    reference_fields: List[str], prediction_fields: List[str]
) -> Optional[str]:
    preferred_keys = ["id", "row_id", "sample_id", "case_id", "record_id"]
    for key in preferred_keys:
        if key in reference_fields and key in prediction_fields:
            return key
    return None


def _build_y_true_y_pred(
    reference_rows: List[Dict[str, str]],
    prediction_rows: List[Dict[str, str]],
    label_col: str,
    pred_label_col: Optional[str],
    pred_score_col: Optional[str],
    threshold: float,
) -> Tuple[List[int], List[int], List[float], Dict[str, int], List[Dict[str, str]]]:
    if not prediction_rows:
        raise ValueError("Predictions file is empty.")

    ref_fields = list(reference_rows[0].keys())
    pred_fields = list(prediction_rows[0].keys())
    join_key = _detect_join_key(ref_fields, pred_fields)
    pred_index = _index_prediction_rows(prediction_rows, join_key)

    y_true: List[int] = []
    y_pred: List[int] = []
    y_score: List[float] = []
    matched_reference_rows: List[Dict[str, str]] = []

    matched_rows = 0
    missing_predictions = 0

    for i, ref_row in enumerate(reference_rows):
        ref_lookup = str(ref_row[join_key]) if join_key else str(i)
        pred_row = pred_index.get(ref_lookup)

        if pred_row is None:
            missing_predictions += 1
            continue

        true_label = _normalize_binary(ref_row.get(label_col, 0))

        if pred_label_col and pred_label_col in pred_row:
            pred_label = _normalize_binary(pred_row.get(pred_label_col, 0))
            pred_score = float(pred_label)
        elif pred_score_col and pred_score_col in pred_row:
            pred_score = _safe_float(pred_row.get(pred_score_col, 0.0))
            pred_label = 1 if pred_score >= threshold else 0
        else:
            raise ValueError(
                "No usable prediction column found. Provide a binary prediction column "
                "or a score column such as prediction_score."
            )

        y_true.append(true_label)
        y_pred.append(pred_label)
        y_score.append(pred_score)
        matched_reference_rows.append(ref_row)
        matched_rows += 1

    support = {
        "reference_rows": len(reference_rows),
        "prediction_rows": len(prediction_rows),
        "matched_rows": matched_rows,
        "missing_predictions": missing_predictions,
        "join_key_used": 0 if join_key is None else 1,
    }

    if matched_rows == 0:
        raise ValueError("No rows could be matched between reference and prediction files.")

    return y_true, y_pred, y_score, support, matched_reference_rows


def _confusion_matrix(y_true: List[int], y_pred: List[int]) -> Dict[str, int]:
    tp = tn = fp = fn = 0
    for truth, pred in zip(y_true, y_pred):
        if truth == 1 and pred == 1:
            tp += 1
        elif truth == 0 and pred == 0:
            tn += 1
        elif truth == 0 and pred == 1:
            fp += 1
        elif truth == 1 and pred == 0:
            fn += 1
    return {"tp": tp, "tn": tn, "fp": fp, "fn": fn}


def _accuracy(tp: int, tn: int, fp: int, fn: int) -> float:
    denom = tp + tn + fp + fn
    return (tp + tn) / denom if denom else 0.0


def _precision(tp: int, fp: int) -> float:
    denom = tp + fp
    return tp / denom if denom else 0.0


def _recall(tp: int, fn: int) -> float:
    denom = tp + fn
    return tp / denom if denom else 0.0


def _f1(precision: float, recall: float) -> float:
    denom = precision + recall
    return 2 * precision * recall / denom if denom else 0.0


def _trajectory_diagnostics(
    reference_rows: List[Dict[str, str]],
    y_true: List[int],
    y_pred: List[int],
) -> Dict[str, float]:
    if not reference_rows or "drift_gradient" not in reference_rows[0]:
        return {
            "trajectory_positive_support": 0,
            "recall_trajectory_deterioration_detection": 0.0,
            "false_stable_trajectory_rate": 0.0,
            "trajectory_label_alignment_rate": 0.0,
        }

    trajectory_positive_support = 0
    trajectory_detected_tp = 0
    trajectory_false_stable = 0
    trajectory_alignment_hits = 0

    for row, truth, pred in zip(reference_rows, y_true, y_pred):
        drift_gradient = _safe_float(row.get("drift_gradient", 0.0))
        worsening_trajectory = 1 if drift_gradient > 0 else 0

        if worsening_trajectory == 1:
            trajectory_positive_support += 1
            if pred == 1:
                trajectory_detected_tp += 1
            if pred == 0:
                trajectory_false_stable += 1

        if worsening_trajectory == truth:
            trajectory_alignment_hits += 1

    recall_trajectory_deterioration_detection = (
        trajectory_detected_tp / trajectory_positive_support
        if trajectory_positive_support
        else 0.0
    )

    false_stable_trajectory_rate = (
        trajectory_false_stable / trajectory_positive_support
        if trajectory_positive_support
        else 0.0
    )

    trajectory_label_alignment_rate = (
        trajectory_alignment_hits / len(reference_rows)
        if reference_rows
        else 0.0
    )

    return {
        "trajectory_positive_support": trajectory_positive_support,
        "recall_trajectory_deterioration_detection": recall_trajectory_deterioration_detection,
        "false_stable_trajectory_rate": false_stable_trajectory_rate,
        "trajectory_label_alignment_rate": trajectory_label_alignment_rate,
    }


def score(
    reference_path: str = DEFAULT_REFERENCE_PATH,
    predictions_path: str = DEFAULT_PREDICTIONS_PATH,
    threshold: float = 0.5,
) -> Dict[str, object]:
    reference_rows = _read_csv(reference_path)
    prediction_rows = _read_csv(predictions_path)

    if not reference_rows:
        raise ValueError("Reference file is empty.")

    label_col = _find_label_column(list(reference_rows[0].keys()))
    pred_label_col, pred_score_col = _find_prediction_columns(list(prediction_rows[0].keys()))

    y_true, y_pred, y_score, support, matched_reference_rows = _build_y_true_y_pred(
        reference_rows=reference_rows,
        prediction_rows=prediction_rows,
        label_col=label_col,
        pred_label_col=pred_label_col,
        pred_score_col=pred_score_col,
        threshold=threshold,
    )

    cm = _confusion_matrix(y_true, y_pred)
    precision = _precision(cm["tp"], cm["fp"])
    recall = _recall(cm["tp"], cm["fn"])
    accuracy = _accuracy(cm["tp"], cm["tn"], cm["fp"], cm["fn"])
    f1 = _f1(precision, recall)

    trajectory_metrics = _trajectory_diagnostics(
        reference_rows=matched_reference_rows,
        y_true=y_true,
        y_pred=y_pred,
    )

    return {
        "label_column": label_col,
        "prediction_label_column": pred_label_col,
        "prediction_score_column": pred_score_col,
        "primary_metric": "recall_trajectory_deterioration_detection",
        "secondary_metric": "false_stable_trajectory_rate",
        "threshold_transparency": {
            "score_threshold_used": threshold if pred_score_col else None,
            "threshold_applied_to_score_column": pred_score_col,
            "predictions_interpreted_as": (
                "binary labels from prediction column"
                if pred_label_col
                else "binary labels thresholded from score column"
            ),
        },
        "support": {
            **support,
            "positive_label_support": sum(y_true),
            "negative_label_support": len(y_true) - sum(y_true),
            "predicted_positive_support": sum(y_pred),
            "predicted_negative_support": len(y_pred) - sum(y_pred),
        },
        "metrics": {
            "accuracy": round(accuracy, 4),
            "precision": round(precision, 4),
            "recall": round(recall, 4),
            "f1": round(f1, 4),
            "recall_trajectory_deterioration_detection": round(
                trajectory_metrics["recall_trajectory_deterioration_detection"], 4
            ),
            "false_stable_trajectory_rate": round(
                trajectory_metrics["false_stable_trajectory_rate"], 4
            ),
            "trajectory_label_alignment_rate": round(
                trajectory_metrics["trajectory_label_alignment_rate"], 4
            ),
        },
        "confusion_matrix": cm,
        "trajectory_support": {
            "trajectory_positive_support": trajectory_metrics["trajectory_positive_support"],
        },
    }


if __name__ == "__main__":
    reference_path = sys.argv[1] if len(sys.argv) > 1 else DEFAULT_REFERENCE_PATH
    predictions_path = sys.argv[2] if len(sys.argv) > 2 else DEFAULT_PREDICTIONS_PATH
    threshold = float(sys.argv[3]) if len(sys.argv) > 3 else 0.5

    output = score(
        reference_path=reference_path,
        predictions_path=predictions_path,
        threshold=threshold,
    )
    print(json.dumps(output, indent=2))