From 88bd45b02e1e5dd9184c469107ebe9f7e2db9908 Mon Sep 17 00:00:00 2001
From: Kristaps Kaupe <kristaps@blogiem.lv>
Date: Thu, 20 Jul 2023 01:57:52 +0300
Subject: [PATCH] Parse URI params in guaranteed order, for duplicates, last
 one wins

---
 jmbitcoin/jmbitcoin/bip21.py | 13 ++++++-------
 jmbitcoin/test/test_bip21.py | 11 +++++++++++
 2 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/jmbitcoin/jmbitcoin/bip21.py b/jmbitcoin/jmbitcoin/bip21.py
index 5aea31b..e92cbaf 100644
--- a/jmbitcoin/jmbitcoin/bip21.py
+++ b/jmbitcoin/jmbitcoin/bip21.py
@@ -5,7 +5,7 @@
 
 from jmbitcoin import amount_to_sat
 from typing import Dict, List, Tuple, Union
-from urllib.parse import parse_qs, quote, unquote_plus, urlencode, urlparse
+from urllib.parse import parse_qsl, quote, unquote_plus, urlencode, urlparse
 import re
 
 
@@ -29,18 +29,17 @@ def decode_bip21_uri(uri: str) -> Dict[str, Union[str, int]]:
     result = {}
     parsed = urlparse(uri)
     result['address'] = parsed.path
-    params = parse_qs(parsed.query)
-    for key in params:
+    params = parse_qsl(parsed.query)
+    for key, value in params:
         if key.startswith('req-'):
             raise ValueError("Unknown required parameter " + key +
                 " in BIP21 URI.")
         if key == 'amount':
-            amount_str = params['amount'][0]
-            _validate_bip21_amount(amount_str)
+            _validate_bip21_amount(value)
             # Convert amount to sats, as used internally by JM
-            result['amount'] = amount_to_sat(amount_str + "btc")
+            result['amount'] = amount_to_sat(value + "btc")
         else:
-            result[key] = unquote_plus(params[key][0])
+            result[key] = unquote_plus(value)
     return result
 
 
diff --git a/jmbitcoin/test/test_bip21.py b/jmbitcoin/test/test_bip21.py
index 87027ca..b902741 100644
--- a/jmbitcoin/test/test_bip21.py
+++ b/jmbitcoin/test/test_bip21.py
@@ -75,6 +75,17 @@ def test_bip21_decode():
     assert(parsed['somethingyoudontunderstand'] == '50')
     assert(parsed['somethingelseyoudontget'] == '999')
 
+    # Test multiple amount parameters, last value should win.
+    parsed = btc.decode_bip21_uri(
+        'bitcoin:175tWpb8K1S7NmH4Zx6rewF9WQrcZv245W?amount=20.3&amount=50&label=Luke-Jr')
+    assert(parsed['address'] == '175tWpb8K1S7NmH4Zx6rewF9WQrcZv245W')
+    assert(parsed['amount'] == 5000000000)
+    assert(parsed['label'] == 'Luke-Jr')
+    # Here are two amount parameters, first valid, second not valid, so URI is not valid.
+    with pytest.raises(ValueError):
+        btc.decode_bip21_uri(
+            'bitcoin:175tWpb8K1S7NmH4Zx6rewF9WQrcZv245W?amount=20.3&amount=100,000&label=Luke-Jr')
+
 
 def test_bip21_encode():
     assert(