parse-qr.ts

/**
 * Parses scanned QR code strings into Stellar payment data.
 *
 * Supports:
 *  1. SEP-0007 pay URI — web+stellar:pay?destination=...&amount=...&memo=...
 *  2. Raw G-address (56-char Stellar public key)
 *  3. Invoisio deep-link — invoisio://pay?...  (same query params as SEP-0007)
 */

export type MemoType = "text" | "id" | "hash" | "return";

export interface ParsedPayment {
  destination: string;
  amount?: string;
  assetCode?: string;
  assetIssuer?: string;
  memo?: string;
  memoType: MemoType;
  /** Reconstructed SEP-0007 URI ready to deep-link into a Stellar wallet */
  sep0007Uri: string;
}

/**
 * A typed parse failure. `code` lets the UI tailor the message and recovery
 * actions, while `message` is a plain-language explanation for the user.
 */
export type ParseQrErrorCode =
  | "unsupported-format"
  | "missing-destination"
  | "invalid-destination";

export interface ParseQrError {
  code: ParseQrErrorCode;
  message: string;
}

const G_ADDRESS_RE = /^G[A-Z2-7]{55}$/;

function isValidGAddress(addr: string): boolean {
  return G_ADDRESS_RE.test(addr);
}

function parseMemoType(raw: string | null): MemoType {
  switch (raw?.toLowerCase()) {
    case "text":
      return "text";
    case "id":
      return "id";
    case "hash":
      return "hash";
    case "return":
      return "return";
    default:
      return "text";
  }
}

function buildSep0007Uri(p: Omit<ParsedPayment, "sep0007Uri">): string {
  const parts = [`destination=${encodeURIComponent(p.destination)}`];
  if (p.amount) parts.push(`amount=${encodeURIComponent(p.amount)}`);
  if (p.assetCode) parts.push(`asset_code=${encodeURIComponent(p.assetCode)}`);
  if (p.assetIssuer)
    parts.push(`asset_issuer=${encodeURIComponent(p.assetIssuer)}`);
  if (p.memo) {
    parts.push(`memo=${encodeURIComponent(p.memo)}`);
    parts.push(`memo_type=${p.memoType}`);
  }
  return `web+stellar:pay?${parts.join("&")}`;
}

/**
 * @returns ParsedPayment on success, or a ParseQrError describing what went
 * wrong so the UI can offer a clear recovery path.
 */
export function parseQrCode(raw: string): ParsedPayment | ParseQrError {
  const trimmed = raw.trim();

  // 1. Raw G-address
  if (isValidGAddress(trimmed)) {
    const parsed: Omit<ParsedPayment, "sep0007Uri"> = {
      destination: trimmed,
      memoType: "text",
    };
    return { ...parsed, sep0007Uri: buildSep0007Uri(parsed) };
  }

  // 2. SEP-0007 or Invoisio deep-link
  const isSep0007 = trimmed.startsWith("web+stellar:pay?");
  const isInvoisio = trimmed.startsWith("invoisio://pay?");

  if (!isSep0007 && !isInvoisio) {
    return {
      code: "unsupported-format",
      message:
        "This QR code isn't a Stellar payment request. Expected a Stellar address (G...) or a web+stellar: payment link.",
    };
  }

  let queryString: string;
  if (isSep0007) {
    queryString = trimmed.slice("web+stellar:pay?".length);
  } else {
    queryString = trimmed.slice("invoisio://pay?".length);
  }

  // URLSearchParams works in React Native (Hermes supports it)
  const params = new URLSearchParams(queryString);
  const destination = params.get("destination");

  if (!destination) {
    return {
      code: "missing-destination",
      message:
        "This QR code doesn't include a destination address. Ask the merchant to regenerate the payment QR code.",
    };
  }

  if (!isValidGAddress(destination)) {
    return {
      code: "invalid-destination",
      message: `Invalid destination address: ${destination}. It must be a valid Stellar public key that starts with "G".`,
    };
  }

  const memoType = parseMemoType(params.get("memo_type"));

  const amount = params.get("amount");
  const assetCode = params.get("asset_code");
  const assetIssuer = params.get("asset_issuer");
  const memo = params.get("memo");

  const parsed: Omit<ParsedPayment, "sep0007Uri"> = {
    destination,
    memoType,
    ...(amount !== null && { amount }),
    ...(assetCode !== null && { assetCode }),
    ...(assetIssuer !== null && { assetIssuer }),
    ...(memo !== null && { memo }),
  };

  return { ...parsed, sep0007Uri: buildSep0007Uri(parsed) };
}