Refactoring: add function for making code readable

src/currentCustomerAccountBalance.c

@@ -13,20 +13,12 @@ float fetchBalanceFromBalanceString(char balance_String[MAX_LENGTH]) {
     return balance;
 }
 
-float getAvailableAccountBalance(int user_id) {
+float readFileAndGetAvailableBalance(FILE *file, char stringID[MAX_LENGTH]) {
+    float balance = 0;
     bool keep_reading = true;
-    float availableBalance = 0;
-
     char buffer[MAX_LENGTH];
-    char stringID[MAX_LENGTH] = "ID=";
-    char user_id_as_string[MAX_LENGTH];
     char balance_String[MAX_LENGTH];
 
-    sprintf(user_id_as_string, "%d", user_id); // converts user_id to string
-    strcat(stringID, user_id_as_string);
-
-    FILE *file = fopen("CustomerData.txt", "r"); 
-
     while(keep_reading) {
         fgets(buffer, MAX_LENGTH, file);
         if (feof(file)) {
@@ -38,11 +30,33 @@ float getAvailableAccountBalance(int user_id) {
             fgets(buffer, MAX_LENGTH, file);
             fgets(buffer, MAX_LENGTH, file);
             strcpy(balance_String, buffer);
-            availableBalance = fetchBalanceFromBalanceString(balance_String);
+            balance = fetchBalanceFromBalanceString(balance_String);
             keep_reading = false;
         }
 
     }
+    return balance;
+}
+
+float getAvailableAccountBalance(int user_id) {
+    float availableBalance = 0;
+    char stringID[MAX_LENGTH] = "ID=";
+    char user_id_as_string[MAX_LENGTH];
+
+    sprintf(user_id_as_string, "%d", user_id); // converts user_id to string
+    strcat(stringID, user_id_as_string);
+    // Now stringID is "ID=user_id"
+
+    FILE *file = fopen("CustomerData.txt", "r"); 
+    if(file == 0) {
+        printf("Erro: file cannot be opened!");
+        return 0;
+    }
+    else {
+        availableBalance = readFileAndGetAvailableBalance(file, stringID);
+    }
+
+    
     fclose(file);
     
     return availableBalance;