payment_identifier: factor out bip21 functions to bip21.py to break cyclic dependencies,

parse bolt11 only once, store invoice internally instead of bolt11 string
add is_onchain method to indicate if payment identifier can be paid onchain

electrum/bip21.py

@@ -0,0 +1,127 @@
+import urllib
+import re
+from decimal import Decimal
+from typing import Optional
+
+from . import bitcoin
+from .util import format_satoshis_plain
+from .bitcoin import COIN, TOTAL_COIN_SUPPLY_LIMIT_IN_BTC
+from .lnaddr import lndecode, LnDecodeException
+
+# note: when checking against these, use .lower() to support case-insensitivity
+BITCOIN_BIP21_URI_SCHEME = 'bitcoin'
+LIGHTNING_URI_SCHEME = 'lightning'
+
+
+class InvalidBitcoinURI(Exception):
+    pass
+
+
+def parse_bip21_URI(uri: str) -> dict:
+    """Raises InvalidBitcoinURI on malformed URI."""
+
+    if not isinstance(uri, str):
+        raise InvalidBitcoinURI(f"expected string, not {repr(uri)}")
+
+    if ':' not in uri:
+        if not bitcoin.is_address(uri):
+            raise InvalidBitcoinURI("Not a bitcoin address")
+        return {'address': uri}
+
+    u = urllib.parse.urlparse(uri)
+    if u.scheme.lower() != BITCOIN_BIP21_URI_SCHEME:
+        raise InvalidBitcoinURI("Not a bitcoin URI")
+    address = u.path
+
+    # python for android fails to parse query
+    if address.find('?') > 0:
+        address, query = u.path.split('?')
+        pq = urllib.parse.parse_qs(query)
+    else:
+        pq = urllib.parse.parse_qs(u.query)
+
+    for k, v in pq.items():
+        if len(v) != 1:
+            raise InvalidBitcoinURI(f'Duplicate Key: {repr(k)}')
+
+    out = {k: v[0] for k, v in pq.items()}
+    if address:
+        if not bitcoin.is_address(address):
+            raise InvalidBitcoinURI(f"Invalid bitcoin address: {address}")
+        out['address'] = address
+    if 'amount' in out:
+        am = out['amount']
+        try:
+            m = re.match(r'([0-9.]+)X([0-9])', am)
+            if m:
+                k = int(m.group(2)) - 8
+                amount = Decimal(m.group(1)) * pow(Decimal(10), k)
+            else:
+                amount = Decimal(am) * COIN
+            if amount > TOTAL_COIN_SUPPLY_LIMIT_IN_BTC * COIN:
+                raise InvalidBitcoinURI(f"amount is out-of-bounds: {amount!r} BTC")
+            out['amount'] = int(amount)
+        except Exception as e:
+            raise InvalidBitcoinURI(f"failed to parse 'amount' field: {repr(e)}") from e
+    if 'message' in out:
+        out['message'] = out['message']
+        out['memo'] = out['message']
+    if 'time' in out:
+        try:
+            out['time'] = int(out['time'])
+        except Exception as e:
+            raise InvalidBitcoinURI(f"failed to parse 'time' field: {repr(e)}") from e
+    if 'exp' in out:
+        try:
+            out['exp'] = int(out['exp'])
+        except Exception as e:
+            raise InvalidBitcoinURI(f"failed to parse 'exp' field: {repr(e)}") from e
+    if 'sig' in out:
+        try:
+            out['sig'] = bitcoin.base_decode(out['sig'], base=58).hex()
+        except Exception as e:
+            raise InvalidBitcoinURI(f"failed to parse 'sig' field: {repr(e)}") from e
+    if 'lightning' in out:
+        try:
+            lnaddr = lndecode(out['lightning'])
+        except LnDecodeException as e:
+            raise InvalidBitcoinURI(f"Failed to decode 'lightning' field: {e!r}") from e
+        amount_sat = out.get('amount')
+        if amount_sat:
+            # allow small leeway due to msat precision
+            if abs(amount_sat - int(lnaddr.get_amount_sat())) > 1:
+                raise InvalidBitcoinURI("Inconsistent lightning field in bip21: amount")
+        address = out.get('address')
+        ln_fallback_addr = lnaddr.get_fallback_address()
+        if address and ln_fallback_addr:
+            if ln_fallback_addr != address:
+                raise InvalidBitcoinURI("Inconsistent lightning field in bip21: address")
+
+    return out
+
+
+def create_bip21_uri(addr, amount_sat: Optional[int], message: Optional[str],
+                     *, extra_query_params: Optional[dict] = None) -> str:
+    if not bitcoin.is_address(addr):
+        return ""
+    if extra_query_params is None:
+        extra_query_params = {}
+    query = []
+    if amount_sat:
+        query.append('amount=%s' % format_satoshis_plain(amount_sat))
+    if message:
+        query.append('message=%s' % urllib.parse.quote(message))
+    for k, v in extra_query_params.items():
+        if not isinstance(k, str) or k != urllib.parse.quote(k):
+            raise Exception(f"illegal key for URI: {repr(k)}")
+        v = urllib.parse.quote(v)
+        query.append(f"{k}={v}")
+    p = urllib.parse.ParseResult(
+        scheme=BITCOIN_BIP21_URI_SCHEME,
+        netloc='',
+        path=addr,
+        params='',
+        query='&'.join(query),
+        fragment=''
+    )
+    return str(urllib.parse.urlunparse(p))