implemente attachemtn download route

app/lib/actions.ts

@@ -46,13 +46,14 @@ const serializeAttachment = async (billAttachment: File | null) => {
         return null;
     }
 
-    // convert the file contents to a base64 string
+    // convert the billAttachment file contents to format that can be stored in the database
     const fileContents = await billAttachment.arrayBuffer();
     const fileContentsBase64 = Buffer.from(fileContents).toString('base64');
 
+
     // create an object to store the file in the database
     return({
-        fileName: decodeURIComponent(fileName),
+        fileName,
         fileSize,
         fileType,
         fileLastModified,

app/lib/fetchBillById.ts

@@ -0,0 +1,31 @@
+import { PlainBill, MongoLocation } from '@/app/lib/db-types';
+import clientPromise from '@/app/lib/mongodb';
+
+export const fetchBillById = async (locationID:string, billID:string) => {
+    const client = await clientPromise;
+    const db = client.db("rezije");
+
+    // find a location with the given locationID
+    const billLocation = await db.collection<MongoLocation>("lokacije").findOne({ _id: locationID })
+
+    if(!billLocation) {
+        console.log(`Location ${locationID} not found`);
+        return(null);
+    }
+
+    // find a bill with the given billID
+    const mongoBill = billLocation?.bills.find(({ _id }) => _id.toString() === billID);
+
+    if(!mongoBill) {
+        console.log('Bill not found');
+        return(null);
+    }
+
+    const { _id, ...billBase  } = mongoBill;
+
+    return({
+        id: _id.toString(),
+        ...billBase
+    } as PlainBill);
+
+}