"""
Backfill script to populate currency_id for capex and opex rows using existing currency_code.

Usage:
  python scripts/backfill_currency.py --dry-run
  python scripts/backfill_currency.py --create-missing

This script is intentionally cautious: it defaults to dry-run mode and will refuse to run
if DATABASE_URL is not set. It supports creating missing currency rows when `--create-missing`
is provided. Always run against a development/staging database first.
"""
from __future__ import annotations
import os
import argparse
from sqlalchemy import text, create_engine


def load_env_dburl() -> str:
    db = os.environ.get("DATABASE_URL")
    if not db:
        raise RuntimeError(
            "DATABASE_URL not set — set it to your dev/staging DB before running this script")
    return db


def backfill(db_url: str, dry_run: bool = True, create_missing: bool = False) -> None:
    engine = create_engine(db_url)
    with engine.begin() as conn:
        # Ensure currency table exists
        res = conn.execute(text("SELECT name FROM sqlite_master WHERE type='table' AND name='currency';")) if db_url.startswith(
            'sqlite:') else conn.execute(text("SELECT to_regclass('public.currency');"))
        # Note: we don't strictly depend on the above - we assume migration was already applied

        # Helper: find or create currency by code
        def find_currency_id(code: str):
            r = conn.execute(text("SELECT id FROM currency WHERE code = :code"), {
                             "code": code}).fetchone()
            if r:
                return r[0]
            if create_missing:
                # insert and return id
                conn.execute(text("INSERT INTO currency (code, name, symbol, is_active) VALUES (:c, :n, NULL, TRUE)"), {
                             "c": code, "n": code})
                if db_url.startswith('sqlite:'):
                    r2 = conn.execute(text("SELECT id FROM currency WHERE code = :code"), {
                                      "code": code}).fetchone()
                else:
                    r2 = conn.execute(text("SELECT id FROM currency WHERE code = :code"), {
                                      "code": code}).fetchone()
                return r2[0]
            return None

        # Process tables capex and opex
        for table in ("capex", "opex"):
            # Check if currency_id column exists
            try:
                cols = conn.execute(text(f"SELECT 1 FROM information_schema.columns WHERE table_name = '{table}' AND column_name = 'currency_id'")) if not db_url.startswith(
                    'sqlite:') else [(1,)]
            except Exception:
                cols = [(1,)]

            if not cols:
                print(f"Skipping {table}: no currency_id column found")
                continue

            # Find rows where currency_id IS NULL but currency_code exists
            rows = conn.execute(text(
                f"SELECT id, currency_code FROM {table} WHERE currency_id IS NULL OR currency_id = ''"))
            changed = 0
            for r in rows:
                rid = r[0]
                code = (r[1] or "USD").strip().upper()
                cid = find_currency_id(code)
                if cid is None:
                    print(
                        f"Row {table}:{rid} has unknown currency code '{code}' and create_missing=False; skipping")
                    continue
                if dry_run:
                    print(
                        f"[DRY RUN] Would set {table}.currency_id = {cid} for row id={rid} (code={code})")
                else:
                    conn.execute(text(f"UPDATE {table} SET currency_id = :cid WHERE id = :rid"), {
                                 "cid": cid, "rid": rid})
                    changed += 1

            print(f"{table}: processed, changed={changed} (dry_run={dry_run})")


def main() -> None:
    parser = argparse.ArgumentParser(
        description="Backfill currency_id from currency_code for capex/opex tables")
    parser.add_argument("--dry-run", action="store_true",
                        default=True, help="Show actions without writing")
    parser.add_argument("--create-missing", action="store_true",
                        help="Create missing currency rows in the currency table")
    args = parser.parse_args()

    db = load_env_dburl()
    backfill(db, dry_run=args.dry_run, create_missing=args.create_missing)


if __name__ == "__main__":
    main()