import { useCallback, useMemo } from 'react';
import { useSearchParams } from 'react-router';

// Coin control selection, held in `?coins=txid:vout,txid:vout`.
//
// The Coins section picks the inputs and the Send section spends them — two panels that must agree on a
// set. The URL is how they agree (docs/navigation-audit.md): no channel, no shared store, and the
// selection survives a reload and can be handed to someone as a link.
//
// Outpoints are public transaction data, so there is nothing sensitive about putting them in an address
// bar — unlike anything else this app handles.

const PARAM = 'coins';
const OUTPOINT = /^[0-9a-f]{64}:\d+$/i;

export function useCoinSelection() {
  const [params, setParams] = useSearchParams();

  const raw = params.get(PARAM) ?? '';
  const selected = useMemo(() => raw.split(',').filter((o) => OUTPOINT.test(o)), [raw]);

  const write = useCallback(
    (next: string[]) => {
      setParams(
        (prev) => {
          const updated = new URLSearchParams(prev);
          if (next.length === 0) updated.delete(PARAM);
          else updated.set(PARAM, next.join(','));
          return updated;
        },
        { replace: true },
      );
    },
    [setParams],
  );

  const toggle = useCallback(
    (outpoint: string) =>
      write(selected.includes(outpoint) ? selected.filter((o) => o !== outpoint) : [...selected, outpoint]),
    [selected, write],
  );

  const clear = useCallback(() => write([]), [write]);

  return { selected, toggle, clear, set: write };
}