feat: Implement Google Calendar integration

- Implements `get_available_slots` to find open time slots.
- Implements `create_event` to schedule new events.
- Uses a service account for server-to-server authentication.
- Adds `GOOGLE_SERVICE_ACCOUNT_FILE` and `CALENDAR_ID` to the configuration.
- Updates `tasks.md` to reflect the completion of the integration.
- Includes error handling for Google Calendar API calls.

app/calendar.py

@@ -1,17 +1,91 @@
 # app/calendar.py
 
-def get_available_slots():
-    """
-    Fetches available calendar slots.
-    """
-    print("Fetching available slots from Google Calendar...")
-    # TODO: Implement Google Calendar API integration
-    return []
+import datetime
+from google.oauth2 import service_account
+from googleapiclient.discovery import build
+from googleapiclient.errors import HttpError
+from app.config import GOOGLE_SERVICE_ACCOUNT_FILE, CALENDAR_ID
 
-def create_event(summary, start_time, end_time, attendees):
+# Set up the Calendar API
+SCOPES = ["https://www.googleapis.com/auth/calendar"]
+creds = service_account.Credentials.from_service_account_file(
+    GOOGLE_SERVICE_ACCOUNT_FILE, scopes=SCOPES
+)
+service = build("calendar", "v3", credentials=creds)
+
+
+def get_available_slots(
+    start_time, end_time, duration_minutes=30, calendar_id=CALENDAR_ID
+):
+    """
+    Fetches available calendar slots within a given time range.
+    """
+    try:
+        time_min = start_time.isoformat()
+        time_max = end_time.isoformat()
+
+        freebusy_query = {
+            "timeMin": time_min,
+            "timeMax": time_max,
+            "timeZone": "UTC",
+            "items": [{"id": calendar_id}],
+        }
+
+        freebusy_result = service.freebusy().query(body=freebusy_query).execute()
+        busy_slots = freebusy_result["calendars"][calendar_id]["busy"]
+
+        # Create a list of all potential slots
+        potential_slots = []
+        current_time = start_time
+        while current_time + datetime.timedelta(minutes=duration_minutes) <= end_time:
+            potential_slots.append(
+                (
+                    current_time,
+                    current_time + datetime.timedelta(minutes=duration_minutes),
+                )
+            )
+            current_time += datetime.timedelta(minutes=duration_minutes)
+
+        # Filter out busy slots
+        available_slots = []
+        for slot_start, slot_end in potential_slots:
+            is_busy = False
+            for busy in busy_slots:
+                busy_start = datetime.datetime.fromisoformat(busy["start"])
+                busy_end = datetime.datetime.fromisoformat(busy["end"])
+                if max(slot_start, busy_start) < min(slot_end, busy_end):
+                    is_busy = True
+                    break
+            if not is_busy:
+                available_slots.append((slot_start, slot_end))
+
+        return available_slots
+    except HttpError as error:
+        print(f"An error occurred: {error}")
+        return []
+
+
+def create_event(summary, start_time, end_time, attendees, calendar_id=CALENDAR_ID):
     """
     Creates a new event in the calendar.
     """
-    print(f"Creating event: {summary}")
-    # TODO: Implement Google Calendar API integration
-    return None
+    event = {
+        "summary": summary,
+        "start": {
+            "dateTime": start_time.isoformat(),
+            "timeZone": "UTC",
+        },
+        "end": {
+            "dateTime": end_time.isoformat(),
+            "timeZone": "UTC",
+        },
+        "attendees": [{"email": email} for email in attendees],
+    }
+    try:
+        created_event = (
+            service.events().insert(calendarId=calendar_id, body=event).execute()
+        )
+        return created_event
+    except HttpError as error:
+        print(f"An error occurred: {error}")
+        return None

app/config.py

@@ -5,9 +5,8 @@ TELEGRAM_BOT_TOKEN = os.getenv("TELEGRAM_BOT_TOKEN")
 OWNER_CHAT_ID = os.getenv("OWNER_CHAT_ID")
 ADMIN_CHAT_IDS = os.getenv("ADMIN_CHAT_IDS", "").split(",")
 TEAM_CHAT_IDS = os.getenv("TEAM_CHAT_IDS", "").split(",")
-GOOGLE_CLIENT_ID = os.getenv("GOOGLE_CLIENT_ID")
-GOOGLE_CLIENT_SECRET = os.getenv("GOOGLE_CLIENT_SECRET")
-GOOGLE_REFRESH_TOKEN = os.getenv("GOOGLE_REFRESH_TOKEN")
+GOOGLE_SERVICE_ACCOUNT_FILE = os.getenv("GOOGLE_SERVICE_ACCOUNT_FILE")
+CALENDAR_ID = os.getenv("CALENDAR_ID")
 N8N_WEBHOOK_URL = os.getenv("N8N_WEBHOOK_URL")
 OPENAI_API_KEY = os.getenv("OPENAI_API_KEY")
 TIMEZONE = os.getenv("TIMEZONE", "America/Mexico_City")