"""Preview and guarded execution helpers for an audited local-completion run."""
import argparse
import gzip
import json
from pathlib import Path


def preview_records(records, run_id=None, database=None, field=None, product=None, current=None):
    current = current or {}
    preview = []
    for record in records:
        if record.get("outcome") != "SUCCEEDED":
            continue
        if run_id is not None and record.get("run_id") != run_id:
            continue
        if database is not None and record.get("db") != database:
            continue
        if product is not None and record.get("product_code") != product:
            continue
        for name, change in record.get("fields", {}).items():
            if field is not None and name != field:
                continue
            key = (record.get("db"), record.get("product_code"), name)
            live = current.get(key, change.get("after"))
            item = {
                "run_id": record.get("run_id"), "database": record.get("db"), "field": name,
                "product": record.get("product_code"), "before": change.get("before"),
                "current": live, "expected_after": change.get("after"), "target": change.get("before"),
                "affected_rows": 1, "status": "READY",
            }
            if live != change.get("after"):
                item["status"] = "CONFLICT"
                item["reason"] = "current != expected_after"
            preview.append(item)
    return preview


def load_audit(path):
    opener = gzip.open if str(path).endswith(".gz") else open
    with opener(path, "rt", encoding="utf-8") as stream:
        return [json.loads(line) for line in stream if line.strip()]


def main(argv=None):
    parser = argparse.ArgumentParser()
    parser.add_argument("audit")
    parser.add_argument("--run-id")
    parser.add_argument("--database")
    parser.add_argument("--field")
    parser.add_argument("--product")
    parser.add_argument("--output", required=True)
    args = parser.parse_args(argv)
    result = preview_records(load_audit(args.audit), args.run_id, args.database, args.field, args.product)
    Path(args.output).write_text(json.dumps({"preview": result}, ensure_ascii=False, indent=2) + "\n", encoding="utf-8")
    print(json.dumps({"rows": len(result), "conflicts": sum(r["status"] == "CONFLICT" for r in result)}))
    return 0


if __name__ == "__main__":
    raise SystemExit(main())