[server]: Update return_all_coordinates

server/src/functions/return_all_coordinates/lambda_function.py

@@ -1,26 +1,51 @@
 import json
 import os
 import boto3
+from boto3.dynamodb.conditions import Attr
 
 os.environ.setdefault('AWS_DEFAULT_REGION', 'us-east-1')
 dynamodb = boto3.resource('dynamodb')
 
-
 def lambda_handler(event, context):
     table = dynamodb.Table(os.environ['TABLE_NAME'])
 
     try:
-        # Scan entire table and only extract latitude and longitude
+        # Step 1: Retrieve the latest timestamp
+        items = []
+        response = table.scan(
+            ProjectionExpression="#ts",
+            ExpressionAttributeNames={"#ts": "timestamp"}
+        )
+        items.extend(response.get('Items', []))
+
+        while 'LastEvaluatedKey' in response:
+            response = table.scan(
+                ProjectionExpression="#ts",
+                ExpressionAttributeNames={"#ts": "timestamp"},
+                ExclusiveStartKey=response['LastEvaluatedKey']
+            )
+            items.extend(response.get('Items', []))
+
+        if not items:
+            return {'statusCode': 200, 'body': json.dumps({'coordinates': []})}
+
+        newest_timestamp = max(int(item['timestamp']) for item in items)
+
+        # Step 2: Get only items with that latest timestamp
         coordinates = []
-        response = table.scan()
+        response = table.scan(
+            FilterExpression=Attr('timestamp').eq(newest_timestamp)
+        )
 
         for item in response.get('Items', []):
             if 'latitude' in item and 'longitude' in item:
                 coordinates.append([item['latitude'], item['longitude']])
 
-        # Handle pagination
         while 'LastEvaluatedKey' in response:
-            response = table.scan(ExclusiveStartKey=response['LastEvaluatedKey'])
+            response = table.scan(
+                FilterExpression=Attr('timestamp').eq(newest_timestamp),
+                ExclusiveStartKey=response['LastEvaluatedKey']
+            )
             for item in response.get('Items', []):
                 if 'latitude' in item and 'longitude' in item:
                     coordinates.append([item['latitude'], item['longitude']])