Add support for cron expressions for scheduling timer functions

worker.py

@@ -8,6 +8,7 @@ if os.environ.get('FLASK_ENV') != 'production':
 import asyncio
 import aiohttp
 import json
+from datetime import datetime, timezone, timedelta
 from flask import Flask
 from extensions import db, init_app
 from flask_apscheduler import APScheduler
@@ -54,17 +55,26 @@ async def execute_timer_function_async(timer_function):
                 response_data = await response.json()
 
         # Update environment and record invocation
+        # Calculate next run time based on trigger type
+        next_run = None
+        if timer_function.get('trigger_type') == 'interval' and timer_function.get('frequency_minutes'):
+            next_run = datetime.now(timezone.utc) + timedelta(minutes=timer_function['frequency_minutes'])
+        elif timer_function.get('trigger_type') == 'cron' and timer_function.get('cron_expression'):
+            from croniter import croniter
+            try:
+                next_run = croniter(timer_function['cron_expression'], datetime.now(timezone.utc)).get_next(datetime)
+            except Exception as e:
+                print(f"Error calculating next cron run for timer {timer_function['id']}: {str(e)}")
+                next_run = None
+        # For 'date' trigger type, next_run should be NULL (one-time execution)
+        
         db.execute("""
             UPDATE timer_functions 
             SET environment = %s::jsonb,
                 last_run = NOW(),
-                next_run = CASE 
-                    WHEN trigger_type = 'interval' 
-                    THEN NOW() + (frequency_minutes || ' minutes')::interval
-                    ELSE NULL
-                END
+                next_run = %s
             WHERE id = %s
-        """, [json.dumps(response_data['environment']), timer_function['id']], commit=True)
+        """, [json.dumps(response_data['environment']), next_run, timer_function['id']], commit=True)
 
         # Record the invocation
         db.execute("""
@@ -105,7 +115,7 @@ def check_and_execute_timer_functions():
             timer_functions = db.execute("""
                 SELECT 
                     id, name, code, environment, version_number,
-                    trigger_type, frequency_minutes, run_date,
+                    trigger_type, frequency_minutes, run_date, cron_expression,
                     next_run, enabled, runtime,
                     EXTRACT(EPOCH FROM (NOW() - next_run)) as seconds_since_next_run
                 FROM timer_functions