pip install --upgrade google-api-python-client google-auth-httplib2 google-auth-oauthlib

# quickstart.py
import os.path
from google.auth.transport.requests import Request
from google.oauth2.credentials import Credentials
from google_auth_oauthlib.flow import InstalledAppFlow

SCOPES = ['https://www.googleapis.com/auth/gmail.send']

def authenticate():
    creds = None
    if os.path.exists('token.json'):
        creds = Credentials.from_authorized_user_file('token.json', SCOPES)
    if not creds or not creds.valid:
        if creds and creds.expired and creds.refresh_token:
            creds.refresh(Request())
        else:
            flow = InstalledAppFlow.from_client_secrets_file('credentials.json', SCOPES)
            creds = flow.run_local_server(port=0)
        with open('token.json', 'w') as token:
            token.write(creds.to_json())
    return creds

if __name__ == '__main__':
    authenticate()
    print("✅ Authorization successful! token.json generated")

python3 quickstart.py

# send_email.py
import base64
import os
import sys
from google.auth.transport.requests import Request
from google.oauth2.credentials import Credentials
from googleapiclient.discovery import build
from googleapiclient.errors import HttpError
from email.mime.text import MIMEText

SCOPES = ['https://www.googleapis.com/auth/gmail.send']

def get_service():
    creds = None
    if os.path.exists('token.json'):
        creds = Credentials.from_authorized_user_file('token.json', SCOPES)
    if not creds or not creds.valid:
        if creds and creds.expired and creds.refresh_token:
            creds.refresh(Request())
        else:
            raise Exception("Token invalid, please re-authorize")
    return build('gmail', 'v1', credentials=creds)

def send_email(to, subject, body):
    service = get_service()
    message = MIMEText(body, 'plain', 'utf-8')
    message['To'] = to
    message['Subject'] = subject
    raw = base64.urlsafe_b64encode(message.as_bytes()).decode()
    
    try:
        result = service.users().messages().send(
            userId='me', body={'raw': raw}
        ).execute()
        print(f"✅ Sent! Message ID: {result['id']}")
        return True
    except HttpError as error:
        print(f"❌ Failed: {error}")
        return False

if __name__ == '__main__':
    to = sys.argv[1] if len(sys.argv) > 1 else input("To: ")
    subject = sys.argv[2] if len(sys.argv) > 2 else "Test Email"
    body = sys.argv[3] if len(sys.argv) > 3 else "This is a test email sent via Gmail API."
    send_email(to, subject, body)

python3 send_email.py "your-email@gmail.com" "Gmail API Test" "Hello from my VPS! 🎉"

#!/bin/bash
# send_email.sh — Send email via Gmail API
# Usage: ./send_email.sh "recipient" "subject" "body"

TO="$1"
SUBJECT="$2"
BODY="$3"

python3 -c "
import sys
sys.path.insert(0, '/opt/email-sender')
from send_email import send_email
send_email('$TO', '$SUBJECT', '$BODY')
"

# Check SSL certificate daily at 8 AM
0 8 * * * /opt/scripts/check_ssl.sh || /opt/email-sender/send_email.sh "admin@example.com" "⚠️ SSL Certificate Expiring Soon" "$(date): Certificate check failed, please investigate"

# Monthly VPS summary on the 1st
0 9 1 * * /opt/scripts/summary.sh && /opt/email-sender/send_email.sh "admin@example.com" "📊 Monthly VPS Report" "$(cat /tmp/monthly_report.txt)"

#!/bin/bash
# disk_alert.sh
THRESHOLD=85
USAGE=$(df -h / | awk 'NR==2 {print $5}' | sed 's/%//')

if [ "$USAGE" -ge "$THRESHOLD" ]; then
    /opt/email-sender/send_email.sh \
        "admin@example.com" \
        "🚨 Disk Space Alert: ${USAGE}% Used" \
        "Server: $(hostname)\nTime: $(date)\nDisk Usage: ${USAGE}%\n\n$(df -h)"
fi

0 * * * * /opt/scripts/disk_alert.sh

#!/bin/bash
# docker_restart_notify.sh
RESTARTED=$(docker ps -a --filter "status=exited" --format "{{.Names}} {{.Status}}" | head -5)
if [ -n "$RESTARTED" ]; then
    /opt/email-sender/send_email.sh \
        "admin@example.com" \
        "🔄 Docker Container Crashed" \
        "These containers have exited:\n\n$RESTARTED\n\nPlease investigate."
fi

#!/bin/bash
# nginx_error_monitor.sh
ERRORS=$(tail -n 50 /var/log/nginx/error.log | grep -iE "error|critical|alert" | tail -10)
if [ -n "$ERRORS" ]; then
    /opt/email-sender/send_email.sh \
        "admin@example.com" \
        "⚠️ Nginx Errors Detected" \
        "Recent Nginx error log entries:\n\n$ERRORS"
fi

import time
from googleapiclient.errors import HttpError

def send_with_retry(service, body, max_retries=3):
    for attempt in range(max_retries):
        try:
            return service.users().messages().send(
                userId='me', body=body
            ).execute()
        except HttpError as e:
            if e.resp.status == 429 and attempt < max_retries - 1:
                wait = 2 ** attempt
                print(f"⚠️ Rate limited, waiting {wait}s...")
                time.sleep(wait)
            else:
                raise
    return None

TOKENS = ['token1.json', 'token2.json', 'token3.json']
current = 0

def get_next_token():
    global current
    token = TOKENS[current % len(TOKENS)]
    current += 1
    return token