#!/usr/bin/env python3

import csv
from decimal import Decimal, InvalidOperation
import sys
from pathlib import Path
from datetime import datetime


def clean_money(value: str) -> Decimal | None:
    if not value:
        return None

    value = (
        value.replace("£", "")
             .replace(",", "")
             .strip()
    )

    if not value:
        return None

    try:
        return Decimal(value)
    except InvalidOperation:
        return None

def parse_date(value: str) -> str | None:
    """
    Convert '01 Dec 2025' → '12/01/2025'
    """
    value = value.strip()
    if not value:
        return None

    try:
        dt = datetime.strptime(value, "%d %b %Y")
        return dt.strftime("%m/%d/%Y")
    except ValueError:
        return None

def convert(in_path: Path, out_path: Path):
    with open(in_path, newline="", encoding="latin-1") as f_in, \
         open(out_path, "w", newline="", encoding="utf-8") as f_out:

        reader = csv.reader(f_in)

        # Skip metadata lines until we hit the header
        for row in reader:
            if row and row[0] == "Date":
                header = row
                break
        else:
            raise RuntimeError("Could not find Nationwide CSV header row")

        dict_reader = csv.DictReader(f_in, fieldnames=header)

        fieldnames = ["Date", "Payee", "Description", "Amount"]
        writer = csv.DictWriter(f_out, fieldnames=fieldnames)
        writer.writeheader()

        for row in dict_reader:
            raw_date = row.get("Date") or ""
            date = parse_date(raw_date)
            if not date:
                continue

            desc = (row.get("Description") or "").strip()
            payee = desc

            paid_out = clean_money(row.get("Paid out", ""))
            paid_in = clean_money(row.get("Paid in", ""))

            if paid_out is not None:
                amount = -paid_out
            elif paid_in is not None:
                amount = paid_in
            else:
                continue

            writer.writerow({
                "Date": date,
                "Payee": payee,
                "Description": desc,
                "Amount": f"{amount:.2f}",
            })


def main():
    if len(sys.argv) < 2:
        print("Usage: python nationwide-cleaner.py input.csv [output.csv]")
        sys.exit(1)

    in_path = Path(sys.argv[1])
    out_path = Path(sys.argv[2]) if len(sys.argv) >= 3 else in_path.with_name(
        in_path.stem + "_actual.csv"
    )

    convert(in_path, out_path)
    print(f"Written cleaned file to {out_path}")


if __name__ == "__main__":
    main()