Fix a multi-currency brokerage ledger codebase with interacting planted bugs

# Fix the multi-currency brokerage ledger The working directory contains a small ledger codebase (`solve.py` and the `ledger/` package, about 290 lines) plus sample inputs. Its output does not follow the specification below: **several bugs are planted, and some interact**. Fix the code (you may restructure it freely, Python 3 standard library only) so that `python solve.py input.json answer.json` follows this specification exactly. Hidden checks also run it on freshly generated inputs. ## Inputs `input.json`: `base` (base currency), `as_of` (valuation date), file names for `transactions`, `rates`, `prices`. CSV files may start with a UTF-8 BOM, contain `#` comment lines and blank lines (ignored), padded header names (case-insensitive) and quoted fields with commas. Transaction rows are numbered from 0 = first data row after the header, counting only non-comment, non-blank rows (`line`). - `rates.csv` `date,currency,rate`: units of base per 1 unit of currency. Not every currency has a rate every day. - `prices.csv` `date,symbol,close,currency`. - `transactions.csv` `date,type,account,amount,currency,symbol,qty,memo`. ## Rules 1. All money is exact decimal (no binary floats in calculations). "Round" means to 0.01, **half away from zero for .5 cases (ROUND_HALF_UP)**. 2. FX rate for (currency, date) = the rate with the latest date **on or before** that date (a rate dated exactly that day counts). The base currency's rate is always 1. No such rate means none. 3. Numbers: surrounding spaces and `_` are ignored; `(x)` means -x. A non-number in amount/qty -> reject `bad_number`. Empty amount/qty = 0. Empty currency = base. 4. Validation order per row, first failure wins: unknown type (case-insensitive DEPOSIT, WITHDRAW, TRANSFER, BUY, SELL, DIV, FEE) -> `bad_type`; empty account -> `bad_account`; `bad_number`; amount or qty < 0 -> `negative_value`; no FX rate for the row's currency on its date -> `no_rate`. Then the type-specific checks below. A rejected row changes nothing. Rejects are `{"line", "reason"}` in file order; `applied` counts rows not rejected. 5. Cash is kept per account **per currency** (never converted). 6. DEPOSIT adds cash. WITHDRAW: needs cash in that currency >= amount, else `insufficient_cash`. 7. TRANSFER: memo must be `to:<account>` (prefix case-insensitive, account trimmed, non-empty, different from the source) else `bad_transfer`; needs cash >= amount else `insufficient_cash`; moves the amount **in the same currency** to the destination account (which is created if new). 8. BUY: symbol (upper-cased) non-empty and qty > 0 else `bad_trade`; needs cash >= amount else `insufficient_cash`; pays `amount` (total cost) in the row currency; adds a lot of qty with cost basis = round(amount * rate on the trade date) in base. 9. SELL: symbol/qty as BUY (`bad_trade`); held qty in that account must be >= qty else `insufficient_qty`. Lots are relieved **FIFO** (oldest first). A fully used lot relieves its whole remaining cost; a partly used lot relieves round(lot_cost * take / lot_qty) and keeps the rest (so cost always sums exactly). Proceeds in base = round(amount * rate); realized gain += proceeds - relieved cost. Cash += amount in the row currency. 10. DIV: cash += amount; income += round(amount * rate). FEE: cash -= amount (may go negative); income -= round(amount * rate). 11. Valuation at `as_of`: each holding (qty > 0) uses the last close on or before `as_of` in its quote currency; value_base = round(qty * close * rate(currency, as_of)), or null if no price. Cash in base = sum over currencies of round(balance * rate(currency, as_of)). total_value_base = round(cash in base + sum of holding values). grand_total_base = sum of account totals. ## answer.json `{"accounts": {account: {"cash": {ccy: balance (non-zero only, sorted)}, "holdings": {SYMBOL: {"qty", "cost_base", "value_base"}} (qty > 0 only), "realized_base", "income_base", "total_value_base"}}, "rejects": [...], "applied": n, "grand_total_base"}`. Accounts are every account that ever had cash, lots, gains or income. Money is written as a JSON number with 2 decimals. ## Scoring Hidden checks (partial credit = fraction passed; all must pass): `rejects_and_applied`, `cash_balances`, `holdings_quantities`, `cost_basis`, `realized_gains`, `income`, `valuation` (account totals and grand total) on the given input; `fresh_run_1`, `fresh_run_2` (the whole answer) on fresh inputs. All values exact. 30-second limit per run.