fix #1959 - LCS (#2129)

* fix #1959 - LCS

* newlines at end of files

packages/client/lib/commands/LCS_IDX.ts

@@ -0,0 +1,42 @@
+import { RedisCommandArgument, RedisCommandArguments } from '.';
+import { RangeReply, RawRangeReply, transformRangeReply } from './generic-transformers';
+import { transformArguments as transformLcsArguments } from './LCS';
+
+export { FIRST_KEY_INDEX, IS_READ_ONLY } from './LCS';
+
+export function transformArguments(
+    key1: RedisCommandArgument,
+    key2: RedisCommandArgument
+): RedisCommandArguments {
+    const args = transformLcsArguments(key1, key2);
+    args.push('IDX');
+    return args;
+}
+
+type RawReply = [
+    'matches',
+    Array<[
+        key1: RawRangeReply,
+        key2: RawRangeReply
+    ]>,
+    'len',
+    number
+];
+
+interface Reply {
+    matches: Array<{
+        key1: RangeReply;
+        key2: RangeReply;
+    }>;
+    length: number;
+}
+
+export function transformReply(reply: RawReply): Reply {
+    return {
+        matches: reply[1].map(([key1, key2]) => ({
+            key1: transformRangeReply(key1),
+            key2: transformRangeReply(key2)
+        })),
+        length: reply[3]
+    };
+}