Summarize retrieval drift

#!/usr/bin/env python3
"""Summarize a saved retrieval-drift report. Standard library only; no network I/O."""
import argparse
import json
import math
import sys
from pathlib import Path


def summarize(report):
    if not isinstance(report, dict) or not isinstance(report.get("queries"), list):
        raise ValueError("Report must contain a queries array")
    thresholds = report.get("thresholds", {})
    degraded = thresholds.get("degraded", 0.05)
    review = thresholds.get("review", 0.10)
    if any(isinstance(n, bool) or not isinstance(n, (int, float)) or not math.isfinite(n)
           for n in [degraded, review]) or not 0 <= degraded <= review:
        raise ValueError("Thresholds must be finite numbers: 0 <= degraded <= review")
    counts = {"healthy": 0, "degraded": 0, "review_required": 0}
    for index, query in enumerate(report["queries"]):
        if not isinstance(query, dict):
            raise ValueError(f"Query {index + 1} must be an object")
        distances = [query.get("baseline_dist"), query.get("drifted_dist")]
        if any(isinstance(n, bool) or not isinstance(n, (int, float)) or not math.isfinite(n)
               for n in distances):
            raise ValueError(f"Query {index + 1} requires finite numeric distances")
        delta = distances[1] - distances[0]
        state = "review_required" if delta >= review else "degraded" if delta >= degraded else "healthy"
        counts[state] += 1
    return {"query_count": len(report["queries"]), "thresholds": {"degraded": degraded, "review": review}, "summary": counts}


def main():
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("report", type=Path, help="Path to a saved JSON report")
    args = parser.parse_args()
    try:
        result = summarize(json.loads(args.report.read_text(encoding="utf-8-sig")))
    except (OSError, ValueError, TypeError) as error:
        print(f"Cannot summarize report: {error}", file=sys.stderr)
        return 2
    print(json.dumps(result, indent=2))
    return 0


if __name__ == "__main__":
    sys.exit(main())