"""Synthetic example only: transform the documented local catalogue schema."""
import argparse
import csv
from decimal import Decimal, InvalidOperation
import json
from pathlib import Path


def convert(source, destination, report_path):
    accepted = []
    rejected = []
    seen = set()
    with source.open(encoding="utf-8-sig", newline="") as handle:
        reader = csv.DictReader(handle, delimiter=";")
        if reader.fieldnames != ["Artikelnummer", "Titel", "Preis", "Bestand"]:
            raise ValueError("Input headers differ from the documented example schema")
        rows = list(reader)
    for index, row in enumerate(rows, start=2):
        sku = (row.get("Artikelnummer") or "").strip()
        title = (row.get("Titel") or "").strip()
        reason = None
        if None in row or any(value is None for value in row.values()):
            reason = "column_count"
        elif not sku or not title:
            reason = "required_field"
        elif sku in seen:
            reason = "duplicate_sku"
        else:
            try:
                price = Decimal(row["Preis"].strip().replace(",", "."))
                stock_text = row["Bestand"].strip()
                if not price.is_finite() or price < 0 or price != price.quantize(Decimal("0.01")):
                    raise ValueError("Price must be nonnegative with at most two decimal places")
                if not stock_text.isascii() or not stock_text.isdigit():
                    raise ValueError("Stock must be a nonnegative integer")
                stock = int(stock_text)
            except (InvalidOperation, ValueError):
                reason = "invalid_scalar"
        if reason:
            rejected.append({"source_line": index, "sku": sku, "reason": reason})
        else:
            seen.add(sku)
            accepted.append({"sku": sku, "title": title, "price_eur": format(price, ".2f"), "stock": stock})
    with destination.open("w", encoding="utf-8", newline="") as handle:
        writer = csv.DictWriter(handle, fieldnames=["sku", "title", "price_eur", "stock"], lineterminator="\n")
        writer.writeheader()
        writer.writerows(accepted)
    report = {"synthetic_example": True, "input_records": len(rows), "accepted_records": len(accepted),
              "rejected_records": len(rejected), "counts_reconcile": len(rows) == len(accepted) + len(rejected),
              "duplicate_policy": "Reject subsequent duplicate of an accepted SKU; do not infer or merge", "rejections": rejected}
    report_path.write_text(json.dumps(report, ensure_ascii=False, indent=2) + "\n", encoding="utf-8")
    return accepted, report


if __name__ == "__main__":
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("source", type=Path)
    parser.add_argument("destination", type=Path)
    parser.add_argument("report", type=Path)
    options = parser.parse_args()
    convert(options.source, options.destination, options.report)