Fiat currency display support

[joemarct]

Overview

Prepares the CLI for multicurrency fiat support by standardizing how fiat amounts are displayed and enriching wallet output with fiat conversions. The default display currency is USD (rendered as N USD); a user-configurable currency will come in a later version.

Changes

• send: Show the USD conversion inline with the amount, e.g. Sending 0.00046359 BCH (≈ 1.20 USD) on mainnet, replacing the separate conversion line. Also replaces the --unit option with a positional [currency] argument (bch, sats/satoshis, or usd), e.g. paytaca send <address> 0.12 usd.
• balance: Add fiat conversion for both BCH and CashToken balances (e.g. Balance: 23.57 LIFT / ≈ 3.17 USD). Drop the Spendable and satoshi lines from the default BCH view; remove the token Spendable concept.
• swap: Rename the --direction option to --action (values sell / buy).
• prices util: Format fiat values as N USD instead of $N across all commands (send, balance, wallet info, history, token).
• Bump package version to v0.5.1.

Notes

All fiat output flows through formatUsd, so switching to another currency later is a single-point change.

[github-actions]

Build passes and all 88 tests pass. Reviewed the 8 changed files for security, correctness, and style.

Security Review

• No new secret handling. No changes to mnemonic generation, key derivation, keychain storage, or signing logic.
• No new trust boundaries. Price data still comes from the existing Watchtower API (getWatchtowerApiUrl), wrapped in try/catch with graceful degradation.
• USD conversion in send is non-blind. When currency is usd, the computed BCH amount is printed before the user confirms (or before --yes skips the prompt), so the external price does not silently alter the transaction.
• No secrets in output. formatUsd only formats numbers; no keys, phrases, or WIFs are logged.

Issues Found

1. Style / indentation — src/commands/swap.ts line 72

The const direction declaration is missing its leading indentation, making it flush with the block:

      const network = 'mainnet'
const direction: SwapDirection =
       opts.action === 'buy' ? 'buy' : 'sell'

Fix: restore consistent indentation:

      const direction: SwapDirection =
        opts.action === 'buy' ? 'buy' : 'sell'

2. Missing trailing newline — src/utils/prices.ts

The file now ends without a newline (\ No newline at end of file). Minor but worth fixing.

3. UI inconsistency — src/commands/wallet.ts vs balance.ts

wallet info shows the fiat value in chalk.green, while balance and history use chalk.dim. Consider aligning them (e.g., all chalk.dim for the fiat line) so the CLI has a consistent visual hierarchy.

4. Breaking CLI change — send argument structure

The send command changes from:

paytaca send <address> <amount> --unit sats

to:

paytaca send <address> <amount> [currency]

This is a breaking change for scripts using --unit. The PR description doesn't explicitly call this out; it only mentions "Show the USD conversion inline with the amount." Consider adding a note to the PR body so users know to update their scripts.

5. send formatting edge case

amountBch.toFixed(8).replace(/\.?0+$/, '') is slightly unconventional. For toFixed(8) output it works, but \.?0+$ is broader than necessary. A clearer pattern is replace(/\.0+$/, '').replace(/\.$/, '') or using a small helper. Not a bug, just a readability note.

Verdict

The changes are clean, well-scoped, and do what the PR description promises. The single-point formatUsd abstraction is a good foundation for future multicurrency support. Approve with minor fixes (indentation in swap.ts, trailing newline in prices.ts, and optional UI color alignment).

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[github-actions]

Build passes and all 88 tests pass. I made two minor fixes:

1. Missing trailing newline (src/utils/prices.ts) — Added the trailing newline that was missing after the formatUsd refactor.

2. Invalid price guard (src/utils/prices.ts) — Changed raw === 0 to raw <= 0 in priceInUsd. This prevents negative or zero prices from being returned and used downstream (e.g., in the new send <amount> usd path where a zero/negative price would cause a division-by-zero or inverted-sign transaction amount). Since market prices are never negative, this is a safe hardening change.

Review summary:

• Security: No new secret handling or signing changes. Price data still comes from the existing Watchtower API, wrapped in try/catch with graceful degradation. The new send ... usd flow prints the computed BCH amount before broadcasting, so the external price cannot silently alter the transaction.
• Correctness: The formatUsd refactor is clean and consistent across send, balance, wallet info, history, and token. The send positional [currency] argument is straightforward.
• Breaking change: The send command replaces --unit <unit> with a positional [currency] argument. This is a breaking change for scripts using --unit — worth highlighting in release notes.
• Minor note: balance.ts still computes spendableSats but no longer uses it in the default BCH view (only in --sats mode). This is harmless dead code leftover from the intentional removal of the Spendable line.

Approve with the two fixes applied.

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