swaps: cache pairs to file

electrum/submarine_swaps.py

@@ -148,8 +148,8 @@ class SwapManager(Logger):
         self.normal_fee = 0
         self.lockup_fee = 0
         self.percentage = 0
-        self.min_amount = 0
-        self._max_amount = 0
+        self._min_amount = None
+        self._max_amount = None
         self.wallet = wallet
         self.lnworker = lnworker
 
@@ -170,6 +170,8 @@ class SwapManager(Logger):
             self.api_url = API_URL_TESTNET
         else:
             self.api_url = API_URL_REGTEST
+        # init default min & max
+        self.init_min_max_values()
 
     def start_network(self, *, network: 'Network', lnwatcher: 'LNWalletWatcher'):
         assert network
@@ -491,19 +493,40 @@ class SwapManager(Logger):
             raise SwapServerError() from e
         # we assume server response is well-formed; otherwise let an exception propagate to the crash reporter
         pairs = json.loads(response)
+        # cache data to disk
+        with open(self.pairs_filename(), 'w', encoding='utf-8') as f:
+            f.write(json.dumps(pairs))
         fees = pairs['pairs']['BTC/BTC']['fees']
         self.percentage = fees['percentage']
         self.normal_fee = fees['minerFees']['baseAsset']['normal']
         self.lockup_fee = fees['minerFees']['baseAsset']['reverse']['lockup']
         limits = pairs['pairs']['BTC/BTC']['limits']
-        self.min_amount = limits['minimal']
+        self._min_amount = limits['minimal']
         self._max_amount = limits['maximal']
 
+    def pairs_filename(self):
+        return os.path.join(self.wallet.config.path, 'swap_pairs')
+
+    def init_min_max_values(self):
+        # use default values if we never requested pairs
+        try:
+            with open(self.pairs_filename(), 'r', encoding='utf-8') as f:
+                pairs = json.loads(f.read())
+            limits = pairs['pairs']['BTC/BTC']['limits']
+            self._min_amount = limits['minimal']
+            self._max_amount = limits['maximal']
+        except:
+            self._min_amount = 10000
+            self._max_amount = 10000000
+
     def get_max_amount(self):
         return self._max_amount
 
+    def get_min_amount(self):
+        return self._min_amount
+
     def check_invoice_amount(self, x):
-        return x >= self.min_amount and x <= self._max_amount
+        return x >= self.get_min_amount() and x <= self.get_max_amount()
 
     def _get_recv_amount(self, send_amount: Optional[int], *, is_reverse: bool) -> Optional[int]:
         """For a given swap direction and amount we send, returns how much we will receive.
@@ -646,5 +669,5 @@ class SwapManager(Logger):
         max_recv_amt_ln = int(self.num_sats_can_receive())
         max_amt_ln = int(min(max_swap_amt_ln, max_recv_amt_ln))
         max_amt_oc = self.get_send_amount(max_amt_ln, is_reverse=False) or 0
-        min_amt_oc = self.get_send_amount(self.min_amount, is_reverse=False) or 0
+        min_amt_oc = self.get_send_amount(self.get_min_amount(), is_reverse=False) or 0
         return max_amt_oc if max_amt_oc >= min_amt_oc else None