Greatly improve id conversion performance

packages/backend/src/misc/convert-id.ts

@@ -9,27 +9,19 @@ const chars = '0123456789abcdefghijklmnopqrstuvwxyz';
 //FIXME: Make this idempotent
 export function convertId(id: string, target: IdType): string {
     if (target == IdType.IceshrimpId) {
-        let input = BigInt(id);
+        return BigInt(id).toString(36);
-        let result = '';
-
-        while (input !== 0n) {
-            result = chars.at(Number(input % 36n)) + result;
-            input /= 36n;
-        }
-
-        return result;
     }
     else if (target == IdType.MastodonId) {
         let result = 0n;
-        const iter = id.toLowerCase().split('').reverse();
+        const iter = id.toLowerCase();
 
         for (let i = 0; i < iter.length; i++){
             const char = iter[i];
             if (!chars.includes(char)) throw new Error('Invalid ID');
-            result += BigInt(chars.indexOf(char)) * BigInt(36 ** i);
+            result = result * 36n + BigInt(chars.indexOf(char));
         }
 
         return result.toString();
     }
-    throw new Error('Unknown ID type');
+		throw new Error('Unknown ID type');
 }