core/ethereum: store tokens as a decision tree

core/src/apps/ethereum/tokens.py.mako

@@ -1,21 +1,31 @@
 # generated from tokens.py.mako
 # do not edit manually!
 
+<%
+from collections import defaultdict
 
-def token_by_chain_address(chain_id, address):
-    for token in tokens:
-        if chain_id == token[0] and address == token[1]:
-            return token
-    return UNKNOWN_TOKEN
-
+def group_tokens(tokens):
+    r = defaultdict(list)
+    for t in tokens:
+        r[t.chain_id].append(t)
+    return r
+%>
 
 UNKNOWN_TOKEN = (None, None, None, None)
 
 
-# fmt: off
-tokens = [
-% for t in supported_on("trezor2", erc20):
-    (${t.chain_id}, ${black_repr(t.address_bytes)}, ${black_repr(t.symbol)}, ${t.decimals}),  # ${t.chain} / ${t.name.strip()}
+def token_by_chain_address(chain_id, address):
+    if False:
+        pass
+    # fmt: off
+% for token_chain_id, tokens in group_tokens(supported_on("trezor2", erc20)).items():
+    elif chain_id == ${token_chain_id}:
+        if False:
+            pass
+        % for t in tokens:
+        elif address == ${black_repr(t.address_bytes)}:
+            return (${t.chain_id}, ${black_repr(t.address_bytes)}, ${black_repr(t.symbol)}, ${t.decimals})  # ${t.chain} / ${t.name.strip()}
+        % endfor
 % endfor
-]
-# fmt: on
+    # fmt: on
+    return UNKNOWN_TOKEN