Refactor env variable handling and improve code structure (#1348)

* Update constants.ts

Refactor environment variable handling and code structure

- Introduce generic getEnvVariable function for consistent env var retrieval
- Simplify logic and remove unnecessary IIFEs
- Improve code readability and maintainability
- Maintain existing functionality and export names for compatibility

* formated constants.ts

* improved the readability of constants.ts

* Update indexer/src/constants.ts

* Update indexer/src/constants.ts

* Update indexer/src/constants.ts

* Update indexer/src/constants.ts

* Update indexer/src/constants.ts

---------

Co-authored-by: Thomas Coratger <[email protected]>

indexer/src/constants.ts

@@ -1,52 +1,62 @@
 import { padString } from "./utils/hex.ts";
 import { hash } from "./deps.ts";
 
-// Get Sink Type or returns "console" if the value is null or undefined
-export const SINK_TYPE = (() => {
-  const addr = Deno.env.get("SINK_TYPE") ?? "console";
-  if (addr !== "console" && addr !== "mongo") {
-    throw new Error("Invalid SINK_TYPE");
+// Helper function to get environment variables with validation
+const getEnvVariable = <T>(
+  key: string,
+  defaultValue: T,
+  validator?: (value: T) => boolean,
+): T => {
+  const value = Deno.env.get(key) as T ?? defaultValue;
+  if (validator && !validator(value)) {
+    throw new Error(`Invalid ${key}`);
   }
-  return addr;
-})();
+  return value;
+};
+
+// Define the sink type (console or mongo) from environment variable
+export const SINK_TYPE = getEnvVariable(
+  "SINK_TYPE",
+  "console",
+  (value) => ["console", "mongo"].includes(value as string),
+);
 
-// Get the sink options from the sink type
+// Set sink options based on the sink type
 export const SINK_OPTIONS = SINK_TYPE === "mongo"
   ? {
-    connectionString: Deno.env.get("MONGO_CONNECTION_STRING") ??
+    connectionString: getEnvVariable(
+      "MONGO_CONNECTION_STRING",
       "mongodb://mongo:mongo@mongo:27017",
-    database: Deno.env.get("MONGO_DATABASE_NAME") ?? "kakarot-test-db",
+    ),
+    database: getEnvVariable("MONGO_DATABASE_NAME", "kakarot-test-db"),
     collectionNames: ["headers", "transactions", "receipts", "logs"],
   }
   : {};
 
 // Get the starting block or returns 0 if the value is null or undefined
-export const STARTING_BLOCK = (() => {
-  const startingBlock = Number(Deno.env.get("STARTING_BLOCK") ?? 0);
-  return Number.isSafeInteger(startingBlock) && startingBlock >= 0
-    ? startingBlock
-    : (() => {
-      throw new Error("Invalid STARTING_BLOCK");
-    })();
-})();
+export const STARTING_BLOCK = getEnvVariable(
+  "STARTING_BLOCK",
+  0,
+  (value) => Number.isSafeInteger(Number(value)) && Number(value) >= 0,
+);
 
 // Get authentication token from Apibara or returns an empty string if the value is null or undefined
-export const AUTH_TOKEN = Deno.env.get("APIBARA_AUTH_TOKEN") ?? "";
+export const AUTH_TOKEN = getEnvVariable("APIBARA_AUTH_TOKEN", "");
 
 // Get stream URL or returns "http://localhost:7171" if the value is null or undefined
-export const STREAM_URL = Deno.env.get("STREAM_URL") ?? "http://localhost:7171";
+export const STREAM_URL = getEnvVariable("STREAM_URL", "http://localhost:7171");
 
 // Creates string that starts with "0x" and is padded to a total length of 64 chars
 export const NULL_BLOCK_HASH = padString("0x", 32);
 
-// Get the hash selector from the transaction executed
+// Get the selector for "transaction_executed" event
 export const TRANSACTION_EXECUTED = hash.getSelectorFromName(
   "transaction_executed",
 );
 
-// Get the Kakarot Address 0x1
-export const KAKAROT_ADDRESS: string = (() => {
-  const kakarotAddress = Deno.env.get("KAKAROT_ADDRESS");
-  if (!kakarotAddress) throw new Error("ENV: KAKAROT_ADDRESS is not set");
-  return kakarotAddress;
-})();
+// Get the Kakarot address from environment variable (0x1)
+export const KAKAROT_ADDRESS = getEnvVariable(
+  "KAKAROT_ADDRESS",
+  "",
+  (value) => !!value,
+);