import csv
import re
import subprocess
import sys
from decimal import Decimal
from pathlib import Path
# extract transaction from izpisek pdf
TRANSACTION_START = re.compile(r"^\d{2}\.\d{2}\.\d{2}\s")
TRANSACTION_LINE = re.compile(
    r"^(?P<date>\d{2}\.\d{2}\.\d{2})\s+"
    r"(?P<middle>.*?)\s+"
    r"(?P<amount>[+-][\d.,]+)\s+"
    r"(?P<balance>-?[\d.,]+-?)\s*$"
)
CONTINUATION_INDENT = 15
FIELD_SPLIT = re.compile(r"\s{4,}")
ACCOUNT = re.compile(r"^SI\d{2}(?:\s?\d{4}){3}\s?\d{3}$")


def pdf_to_text(pdf_path):
    result = subprocess.run(
        ["pdftotext", "-layout", str(pdf_path), "-"],
        capture_output=True, text=True, check=True,
    )
    return result.stdout


def to_number(text):
    """Statements write 1.234,56 and mark a negative balance with a trailing minus."""
    text = text.strip()
    if text.endswith("-"):
        text = "-" + text[:-1]
    return Decimal(text.replace(".", "").replace(",", "."))


def parse_transaction(line):
    m = TRANSACTION_LINE.match(line.rstrip())
    account = ""
    desc_parts = []
    for f in FIELD_SPLIT.split(m.group("middle").strip()):
        if ACCOUNT.match(f):
            account = f
        else:
            desc_parts.append(f)
    return {
        "date": m.group("date"),
        "desc": " ".join(desc_parts),
        "account": account,
        "amount": f"{to_number(m.group('amount')):+.2f}",
        "balance": f"{to_number(m.group('balance')):.2f}",
        "currency": "EUR",
    }


def extract_transactions(pdf_path):
    print(pdf_path)
    rows = []
    full_text = pdf_to_text(pdf_path)
    for page_text in full_text.split("\f"):
        page_start = len(rows)
        for line in page_text.split("\n"):
            if not line.strip():
                continue
            if TRANSACTION_START.match(line):
                rows.append(parse_transaction(line))
                continue
            if len(rows) <= page_start:
                continue
            indent = len(line) - len(line.lstrip(" "))
            if indent < CONTINUATION_INDENT:
                continue
            parts = FIELD_SPLIT.split(line.strip())
            rows[-1]["desc"] += " " + parts[0]
            if len(parts) > 1:
                rows[-1]["account"] = (rows[-1]["account"] + " " + parts[1]).strip()
    return rows


def check_balances(rows, path):
    """Every balance must be the previous one plus the transaction amount."""
    for prev, row in zip(rows, rows[1:]):
        expected = Decimal(prev["balance"]) + Decimal(row["amount"])
        if expected != Decimal(row["balance"]):
            print(f"  warning: {path.name} {row['date']} {row['desc'][:40]!r} "
                  f"balance {row['balance']} != {expected}")


def main():
    pdf_dir = Path(sys.argv[1])
    out_path = pdf_dir.with_suffix(".csv")

    all_rows = []
    for pdf_path in sorted(pdf_dir.glob("*.pdf")):
        rows = extract_transactions(pdf_path)
        # consecutive izpiski of one account, so the chain carries over the file boundary
        check_balances(all_rows[-1:] + rows, pdf_path)
        all_rows.extend(rows)

    with open(out_path, "w", newline="") as f:
        writer = csv.DictWriter(f, fieldnames=["date", "desc", "account", "amount", "balance", "currency"])
        writer.writeheader()
        writer.writerows(all_rows)

    print(f"Wrote {len(all_rows)} transactions to {out_path}")


if __name__ == "__main__":
    main()