From e142a718732019c59191480d164e4c654bc781d9 Mon Sep 17 00:00:00 2001
From: Adam Moussa <166072409+amoussa1229@users.noreply.github.com>
Date: Fri, 3 Apr 2026 18:30:33 -0400
Subject: [PATCH] Add DynamoDB integration for Slack shift manager overrides

The scheduler now checks the afterhours-shifts DynamoDB table before
falling back to the YAML config. This enables the Slack shift manager
bot to drive schedule changes that take effect at the next 8am run.
Same-day changes are handled by direct Lambda invocation from the bot.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 src/handler.py | 60 ++++++++++++++++++++++++++++++++++++++++++++++----
 template.yaml  | 10 +++++++++
 2 files changed, 66 insertions(+), 4 deletions(-)

diff --git a/src/handler.py b/src/handler.py
index 053a163..9bf590a 100644
--- a/src/handler.py
+++ b/src/handler.py
@@ -41,21 +41,73 @@ def get_3cx_credentials() -> dict:
     return creds
 
 
+def check_dynamodb_override(date_str: str, day_name: str) -> str | None:
+    """Check the afterhours-shifts DynamoDB table for a Slack-driven override.
+
+    Returns the extension if an override exists, None otherwise.
+    Only active when SHIFT_TABLE env var is set.
+    """
+    table_name = os.environ.get("SHIFT_TABLE")
+    if not table_name:
+        return None
+
+    dynamodb = boto3.resource("dynamodb")
+    table = dynamodb.Table(table_name)
+
+    # Check date-specific override first
+    resp = table.get_item(Key={"PK": "OVERRIDE", "SK": date_str})
+    item = resp.get("Item")
+    if item:
+        ext = item["extension"]
+        if ext == "OPEN":
+            # Open shift with no pickup — use fallback from DynamoDB config or default 100
+            config_resp = table.get_item(Key={"PK": "CONFIG", "SK": "CONFIG"})
+            fallback = config_resp.get("Item", {}).get("fallback_extension", "100")
+            logger.info("DynamoDB override for %s: OPEN — using fallback Ext %s", date_str, fallback)
+            return fallback
+        logger.info("DynamoDB override for %s: Ext %s", date_str, ext)
+        return ext
+
+    # Check DynamoDB weekly schedule (takes precedence over YAML when SHIFT_TABLE is set)
+    resp = table.get_item(Key={"PK": "WEEKLY", "SK": day_name})
+    item = resp.get("Item")
+    if item:
+        ext = item["extension"]
+        logger.info("DynamoDB weekly schedule for %s (%s): Ext %s", date_str, day_name, ext)
+        return ext
+
+    return None
+
+
 def resolve_extension(schedule: dict, now: datetime) -> str:
-    """Determine which extension should handle after-hours calls today."""
+    """Determine which extension should handle after-hours calls today.
+
+    Resolution order:
+    1. DynamoDB date override (Slack-driven pickup/drop)
+    2. DynamoDB weekly schedule (if SHIFT_TABLE is set)
+    3. YAML exception overrides
+    4. YAML weekly schedule
+    """
     date_str = now.strftime("%Y-%m-%d")
+    day_name = now.strftime("%A")
+
+    # Check DynamoDB first (Slack shift manager)
+    dynamo_ext = check_dynamodb_override(date_str, day_name)
+    if dynamo_ext is not None:
+        return dynamo_ext
+
+    # Fall back to YAML config
     exceptions = schedule.get("exceptions") or {}
     if date_str in exceptions:
         ext = str(exceptions[date_str])
-        logger.info("Using exception override for %s: Ext %s", date_str, ext)
+        logger.info("Using YAML exception override for %s: Ext %s", date_str, ext)
         return ext
 
-    day_name = now.strftime("%A")
     weekly = schedule["weekly_schedule"]
     if day_name not in weekly:
         raise ValueError(f"No schedule entry for {day_name}")
     ext = str(weekly[day_name])
-    logger.info("Using weekly schedule for %s (%s): Ext %s", date_str, day_name, ext)
+    logger.info("Using YAML weekly schedule for %s (%s): Ext %s", date_str, day_name, ext)
     return ext
 
 
diff --git a/template.yaml b/template.yaml
index ec1829a..d1278fd 100644
--- a/template.yaml
+++ b/template.yaml
@@ -6,6 +6,10 @@ Parameters:
   Timezone:
     Type: String
     Default: "America/New_York"
+  ShiftTableName:
+    Type: String
+    Default: "afterhours-shifts"
+    Description: DynamoDB table for Slack shift manager overrides
 
 Globals:
   Function:
@@ -24,6 +28,7 @@ Resources:
         Variables:
           SSM_PREFIX: /3cx-scheduler
           TZ: !Ref Timezone
+          SHIFT_TABLE: !Ref ShiftTableName
       Policies:
         - Statement:
             - Effect: Allow
@@ -41,6 +46,11 @@ Resources:
               Condition:
                 StringEquals:
                   "kms:ViaService": !Sub "ssm.${AWS::Region}.amazonaws.com"
+            - Effect: Allow
+              Action:
+                - dynamodb:GetItem
+              Resource:
+                - !Sub "arn:aws:dynamodb:${AWS::Region}:${AWS::AccountId}:table/${ShiftTableName}"
       Events:
         # EST: 8am ET = 13:00 UTC (Nov-Mar)
         DailyScheduleEST: