Debounce send input validation

[gringokiwi]

First, only run LN URL verification if the string begins with lnurl, or if the user pastes.

Second, only check for a Lightning address if it's full address with TLD (e.g. user@example.xxx), and debounce the validation by ~400ms or so to allow for scenarios where someone is typing in the address.

debouncing.mp4

[arkanaai]

Codebase context

This touches two files:

src/screens/Wallet/Send/Form.tsx — the parseRecipient useEffect (line ~186) runs on every keystroke with no debouncing. It calls isValidLnUrl() on every change, and a second useEffect (line ~349) fires checkLnUrlConditions() (a network request) the moment sendInfo.lnUrl is set.

src/lib/lnurl.ts — isLnUrl() already gates bech32 decoding behind a startsWith('lnurl') check, so that's fine. isLnAddress() uses a broad email regex that matches incomplete strings like user@domain (no TLD requirement).

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Acceptance criteria

• LNURL bech32 decoding is only attempted when the input starts with lnurl (already true in isLnUrl), or when the value was set via paste — no change needed here unless there's a regression path
• Lightning address validation (isLnAddress) requires a proper TLD: the domain part must contain at least one dot with 2+ alpha chars after it (e.g. user@example.com passes, user@localhost or user@domain does not)
• parseRecipient is debounced (suggested: ~400 ms) so network-bound checks (checkLnUrlConditions) don't fire on every keystroke — paste events should bypass the debounce and resolve immediately
• Existing address types (Ark, BTC, bolt11, BIP21) are unaffected — they short-circuit before the LNURL/LN-address branch

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Suggested approach

1. TLD fix in src/lib/lnurl.ts — tighten the isLnAddress regex (or add a post-check) to require .[a-zA-Z]{2,} at the end of the domain segment.

2. Debounce in Form.tsx — wrap parseRecipient() in a useDebounce / setTimeout ref (~400 ms). Pass an isPaste flag (detectable via the existing Paste component's onPaste callback or a React synthetic paste event on the input) to skip the delay when the value came from clipboard.

3. LNURL-specific gate — as a belt-and-suspenders improvement, only enter the isValidLnUrl branch if lowerCaseData.startsWith('lnurl') OR isPaste is true; otherwise skip it entirely while the user is still typing. The LN address branch can stay but is protected by the TLD check above.