import smtplib
import ssl
import os

def send_secure_email(sender_email, receiver_email, password, subject, body):
    """Establishes a secure SMTP connection and sends an email."""
    smtp_server = os.environ.get("SMTP_SERVER", "smtp.gmail.com") # Use environment variable or default
    port = int(os.environ.get("SMTP_PORT", 587)) # For starttls

    # Create a secure SSL context
    context = ssl.create_default_context()

    try:
        # Connect to the SMTP server using STARTTLS
        with smtplib.SMTP(smtp_server, port) as server:
            server.starttls(context=context)  # Secure the connection
            server.login(sender_email, password) # Authenticate with server
            message = f"Subject: {subject}\n\n{body}"
            server.sendmail(sender_email, receiver_email, message)
        print("Email sent successfully!")
    except smtplib.SMTPAuthenticationError:
        print("Authentication failed. Check your email and password/App Password.")
    except smtplib.SMTPConnectError as e:
        print(f"Connection error: {e}. Check SMTP server and port.")
    except Exception as e:
        print(f"An unexpected error occurred: {e}")

# Example usage (ensure to set environment variables or replace placeholders)
# sender = os.getenv("EMAIL_USER")
# app_password = os.getenv("EMAIL_APP_PASSWORD")
# receiver = "recipient@example.com"
# if sender and app_password:
#     send_secure_email(sender, receiver, app_password, "Secure Test", "This is a secure automated email.")
# else:
#     print("Please set EMAIL_USER and EMAIL_APP_PASSWORD environment variables.")

from email.mime.text import MIMEText
from email.mime.multipart import MIMEMultipart
import smtplib
import os

def create_mime_email(sender_email, receiver_email, subject, body, html_body=None):
    """Creates a MIME message with proper headers for better deliverability."""
    msg = MIMEMultipart('alternative')
    msg['From'] = sender_email
    msg['To'] = receiver_email
    msg['Subject'] = subject
    msg['Date'] = smtplib.utils.formatdate(localtime=True)

    # Add text part
    msg.attach(MIMEText(body, 'plain'))

    # Add HTML part if provided
    if html_body:
        msg.attach(MIMEText(html_body, 'html'))
    
    return msg

# Example of sending with the created MIME message (requires secure_send_email function from previous step)
# sender = os.getenv("EMAIL_USER")
# app_password = os.getenv("EMAIL_APP_PASSWORD")
# receiver = "recipient@example.com"
# if sender and app_password:
#     subject = "Your Order Confirmation [Ref: #12345]"
#     plain_content = "Thank you for your order! Your reference is #12345. Details at example.com/order."
#     html_content = """\n    &lt;html&gt;<br/>\n        &lt;body&gt;<br/>\n            &lt;p&gt;Thank you for your order!&lt;/p&gt;<br/>\n            &lt;p&gt;Your reference is &lt;strong&gt;#12345&lt;/strong&gt;.&lt;/p&gt;<br/>\n            &lt;p&gt;View details &lt;a href="http://example.com/order"&gt;here&lt;/a&gt;.&lt;/p&gt;<br/>\n        &lt;/body&gt;<br/>\n    &lt;/html&gt;<br/>\n    """
#     mime_message = create_mime_email(sender, receiver, subject, plain_content, html_content)
#     # Assume send_secure_email is adapted to accept msg.as_string() as body
#     # e.g., send_secure_email(sender, receiver, app_password, subject, mime_message.as_string())
#     print(mime_message.as_string()) # Print for inspection
# else:
#     print("Please set EMAIL_USER and EMAIL_APP_PASSWORD environment variables.")

import time
import random

def implement_backoff(retries=5, delay_initial_seconds=2):
    """Implements an exponential backoff strategy with jitter."""
    for i in range(retries):
        yield i
        # Exponential backoff with jitter to prevent stampeding herd problem
        sleep_time = delay_initial_seconds * (2 ** i) + random.uniform(0, 1) # Add random jitter
        print(f"Retrying in {sleep_time:.2f} seconds...")
        time.sleep(sleep_time)

def send_email_with_retries(send_function, *args, **kwargs):
    """Wraps an email sending function with retry logic and backoff."""
    for attempt in implement_backoff():
        try:
            send_function(*args, **kwargs) # Assume send_function is your email sending logic
            print("Email successfully sent on retry.")
            return True
        except Exception as e:
            print(f"Attempt {attempt + 1} failed: {e}")
            if attempt == 4: # Last attempt
                print("All retry attempts failed.")
                return False
    return False

# Example usage:
# def mock_send_email_failing_initially(sender, receiver, msg_body):
#     # Simulate transient network errors or rate limits
#     if not hasattr(mock_send_email_failing_initially, 'attempt_count'):
#         mock_send_email_failing_initially.attempt_count = 0
#     mock_send_email_failing_initially.attempt_count += 1
#     if mock_send_email_failing_initially.attempt_count < 3:
#         raise smtplib.SMTPConnectError(500, "Transient Error")
#     print(f"Mock send success on attempt {mock_send_email_failing_initially.attempt_count}")

# send_email_with_retries(mock_send_email_failing_initially, "sender@example.com", "receiver@example.com", "Hello")

import os
from dotenv import load_dotenv

# Load environment variables from a .env file (if present)
# Ensure .env is NOT committed to version control!
load_dotenv()

def get_secure_credential(key_name):
    """Retrieves a sensitive credential from environment variables."""
    credential = os.getenv(key_name)
    if not credential:
        raise ValueError(f"Environment variable '{key_name}' not set. Secure credentials are required.")
    return credential

# Example usage:
# try:
#     email_user = get_secure_credential("EMAIL_USER")
#     app_password = get_secure_credential("EMAIL_APP_PASSWORD")
#     print(f"Email User: {email_user}")
#     # print(f"App Password: {app_password}") # Avoid printing sensitive info
# except ValueError as e:
#     print(e)

# For production, consider HashiCorp Vault, AWS Secrets Manager, Google Secret Manager for dynamic secret management.
# Example .env content (for local development only, NOT production):
# EMAIL_USER=your_email@example.com
# EMAIL_APP_PASSWORD=your_generated_app_password