import type { Asset, Chain } from './types';
import { CHAIN_ASSET } from './types';
import { pegCryptoAmount } from './peg';
import { applyCentDust } from './dust';
import { deriveBaseAddress, deriveTronAddress } from './derivation';

export interface WalletSource {
  kind: 'xpub' | 'static';
  xpub?: string | null;
  staticAddress?: string | null;
  /** Next unused derivation index (xpub wallets). */
  nextIndex: number;
}

export interface BuildOptionInput {
  chain: Chain;
  /** Decimal string, e.g. "100" or "99.50". */
  fiatAmount: string;
  /** Fiat per whole token, 1e6-scaled (RateQuote.rateUnits). */
  rateUnits: bigint;
  wallet: WalletSource;
  /** Static mode: reports whether a candidate dusted amount collides with an active invoice on the same address. */
  isAmountTaken?: (candidate: bigint) => boolean;
  random?: () => number;
}

export interface BuiltOption {
  chain: Chain;
  asset: Asset;
  cryptoAmount: bigint;
  address: string;
  derivationIndex: number | null;
  dustApplied: boolean;
}

/**
 * Build one invoice option (address + pegged amount) for the asset the payer selected.
 * Options are created lazily — the caller invokes this only on first selection.
 */
export function buildInvoiceOption(input: BuildOptionInput): BuiltOption {
  const asset = CHAIN_ASSET[input.chain];
  const baseAmount = pegCryptoAmount(input.fiatAmount, input.rateUnits);

  if (input.wallet.kind === 'xpub') {
    if (!input.wallet.xpub) throw new Error('xpub wallet is missing its extended public key');
    const index = input.wallet.nextIndex;
    const address =
      input.chain === 'base'
        ? deriveBaseAddress(input.wallet.xpub, index)
        : deriveTronAddress(input.wallet.xpub, index);
    return { chain: input.chain, asset, cryptoAmount: baseAmount, address, derivationIndex: index, dustApplied: false };
  }

  if (!input.wallet.staticAddress) throw new Error('static wallet is missing its address');
  const cryptoAmount = applyCentDust(baseAmount, input.isAmountTaken ?? (() => false), input.random);
  return {
    chain: input.chain,
    asset,
    cryptoAmount,
    address: input.wallet.staticAddress,
    derivationIndex: null,
    dustApplied: true,
  };
}