# app/services/email_service.py
"""
Email service with multi-provider support.

Supports:
- SMTP (default)
- SendGrid
- Mailgun
- Amazon SES

Features:
- Multi-language templates from database
- Jinja2 template rendering
- Email logging and tracking
- Queue support via background tasks
"""

import json
import logging
import smtplib
from abc import ABC, abstractmethod
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from typing import Any

from jinja2 import Environment, BaseLoader
from sqlalchemy.orm import Session

from app.core.config import settings
from models.database.email import EmailLog, EmailStatus, EmailTemplate

logger = logging.getLogger(__name__)


# =============================================================================
# EMAIL PROVIDER ABSTRACTION
# =============================================================================


class EmailProvider(ABC):
    """Abstract base class for email providers."""

    @abstractmethod
    def send(
        self,
        to_email: str,
        to_name: str | None,
        subject: str,
        body_html: str,
        body_text: str | None,
        from_email: str,
        from_name: str | None,
        reply_to: str | None = None,
    ) -> tuple[bool, str | None, str | None]:
        """
        Send an email.

        Returns:
            tuple: (success, provider_message_id, error_message)
        """
        pass


class SMTPProvider(EmailProvider):
    """SMTP email provider."""

    def send(
        self,
        to_email: str,
        to_name: str | None,
        subject: str,
        body_html: str,
        body_text: str | None,
        from_email: str,
        from_name: str | None,
        reply_to: str | None = None,
    ) -> tuple[bool, str | None, str | None]:
        try:
            msg = MIMEMultipart("alternative")
            msg["Subject"] = subject
            msg["From"] = f"{from_name} <{from_email}>" if from_name else from_email
            msg["To"] = f"{to_name} <{to_email}>" if to_name else to_email

            if reply_to:
                msg["Reply-To"] = reply_to

            # Attach text and HTML parts
            if body_text:
                msg.attach(MIMEText(body_text, "plain", "utf-8"))
            msg.attach(MIMEText(body_html, "html", "utf-8"))

            # Connect and send
            if settings.smtp_use_ssl:
                server = smtplib.SMTP_SSL(settings.smtp_host, settings.smtp_port)
            else:
                server = smtplib.SMTP(settings.smtp_host, settings.smtp_port)

            try:
                if settings.smtp_use_tls and not settings.smtp_use_ssl:
                    server.starttls()

                if settings.smtp_user and settings.smtp_password:
                    server.login(settings.smtp_user, settings.smtp_password)

                server.sendmail(from_email, [to_email], msg.as_string())
                return True, None, None

            finally:
                server.quit()

        except Exception as e:
            logger.error(f"SMTP send error: {e}")
            return False, None, str(e)


class SendGridProvider(EmailProvider):
    """SendGrid email provider."""

    def send(
        self,
        to_email: str,
        to_name: str | None,
        subject: str,
        body_html: str,
        body_text: str | None,
        from_email: str,
        from_name: str | None,
        reply_to: str | None = None,
    ) -> tuple[bool, str | None, str | None]:
        try:
            from sendgrid import SendGridAPIClient
            from sendgrid.helpers.mail import Mail, Email, To, Content

            message = Mail(
                from_email=Email(from_email, from_name),
                to_emails=To(to_email, to_name),
                subject=subject,
            )

            message.add_content(Content("text/html", body_html))
            if body_text:
                message.add_content(Content("text/plain", body_text))

            if reply_to:
                message.reply_to = Email(reply_to)

            sg = SendGridAPIClient(settings.sendgrid_api_key)
            response = sg.send(message)

            if response.status_code in (200, 201, 202):
                message_id = response.headers.get("X-Message-Id")
                return True, message_id, None
            else:
                return False, None, f"SendGrid error: {response.status_code}"

        except ImportError:
            return False, None, "SendGrid library not installed. Run: pip install sendgrid"
        except Exception as e:
            logger.error(f"SendGrid send error: {e}")
            return False, None, str(e)


class MailgunProvider(EmailProvider):
    """Mailgun email provider."""

    def send(
        self,
        to_email: str,
        to_name: str | None,
        subject: str,
        body_html: str,
        body_text: str | None,
        from_email: str,
        from_name: str | None,
        reply_to: str | None = None,
    ) -> tuple[bool, str | None, str | None]:
        try:
            import requests

            from_str = f"{from_name} <{from_email}>" if from_name else from_email
            to_str = f"{to_name} <{to_email}>" if to_name else to_email

            data = {
                "from": from_str,
                "to": to_str,
                "subject": subject,
                "html": body_html,
            }

            if body_text:
                data["text"] = body_text
            if reply_to:
                data["h:Reply-To"] = reply_to

            response = requests.post(
                f"https://api.mailgun.net/v3/{settings.mailgun_domain}/messages",
                auth=("api", settings.mailgun_api_key),
                data=data,
                timeout=30,
            )

            if response.status_code == 200:
                result = response.json()
                return True, result.get("id"), None
            else:
                return False, None, f"Mailgun error: {response.status_code} - {response.text}"

        except Exception as e:
            logger.error(f"Mailgun send error: {e}")
            return False, None, str(e)


class SESProvider(EmailProvider):
    """Amazon SES email provider."""

    def send(
        self,
        to_email: str,
        to_name: str | None,
        subject: str,
        body_html: str,
        body_text: str | None,
        from_email: str,
        from_name: str | None,
        reply_to: str | None = None,
    ) -> tuple[bool, str | None, str | None]:
        try:
            import boto3

            ses = boto3.client(
                "ses",
                region_name=settings.aws_region,
                aws_access_key_id=settings.aws_access_key_id,
                aws_secret_access_key=settings.aws_secret_access_key,
            )

            from_str = f"{from_name} <{from_email}>" if from_name else from_email

            body = {"Html": {"Charset": "UTF-8", "Data": body_html}}
            if body_text:
                body["Text"] = {"Charset": "UTF-8", "Data": body_text}

            kwargs = {
                "Source": from_str,
                "Destination": {"ToAddresses": [to_email]},
                "Message": {
                    "Subject": {"Charset": "UTF-8", "Data": subject},
                    "Body": body,
                },
            }

            if reply_to:
                kwargs["ReplyToAddresses"] = [reply_to]

            response = ses.send_email(**kwargs)
            return True, response.get("MessageId"), None

        except ImportError:
            return False, None, "boto3 library not installed. Run: pip install boto3"
        except Exception as e:
            logger.error(f"SES send error: {e}")
            return False, None, str(e)


class DebugProvider(EmailProvider):
    """Debug provider - logs emails instead of sending."""

    def send(
        self,
        to_email: str,
        to_name: str | None,
        subject: str,
        body_html: str,
        body_text: str | None,
        from_email: str,
        from_name: str | None,
        reply_to: str | None = None,
    ) -> tuple[bool, str | None, str | None]:
        logger.info(
            f"\n{'='*60}\n"
            f"DEBUG EMAIL\n"
            f"{'='*60}\n"
            f"To: {to_name} <{to_email}>\n"
            f"From: {from_name} <{from_email}>\n"
            f"Reply-To: {reply_to}\n"
            f"Subject: {subject}\n"
            f"{'='*60}\n"
            f"Body (text):\n{body_text or '(none)'}\n"
            f"{'='*60}\n"
            f"Body (html):\n{body_html[:500]}...\n"
            f"{'='*60}\n"
        )
        return True, f"debug-{to_email}", None


# =============================================================================
# EMAIL SERVICE
# =============================================================================


def get_provider() -> EmailProvider:
    """Get the configured email provider."""
    if settings.email_debug:
        return DebugProvider()

    provider_map = {
        "smtp": SMTPProvider,
        "sendgrid": SendGridProvider,
        "mailgun": MailgunProvider,
        "ses": SESProvider,
    }

    provider_class = provider_map.get(settings.email_provider.lower())
    if not provider_class:
        logger.warning(f"Unknown email provider: {settings.email_provider}, using SMTP")
        return SMTPProvider()

    return provider_class()


class EmailService:
    """
    Email service for sending templated emails.

    Usage:
        email_service = EmailService(db)

        # Send using database template
        email_service.send_template(
            template_code="signup_welcome",
            language="en",
            to_email="user@example.com",
            to_name="John Doe",
            variables={"first_name": "John", "login_url": "https://..."},
            vendor_id=1,
        )

        # Send raw email
        email_service.send_raw(
            to_email="user@example.com",
            subject="Hello",
            body_html="<h1>Hello</h1>",
        )
    """

    def __init__(self, db: Session):
        self.db = db
        self.provider = get_provider()
        self.jinja_env = Environment(loader=BaseLoader())

    def get_template(
        self, template_code: str, language: str = "en"
    ) -> EmailTemplate | None:
        """Get email template from database with fallback to English."""
        template = (
            self.db.query(EmailTemplate)
            .filter(
                EmailTemplate.code == template_code,
                EmailTemplate.language == language,
                EmailTemplate.is_active == True,
            )
            .first()
        )

        # Fallback to English if not found
        if not template and language != "en":
            template = (
                self.db.query(EmailTemplate)
                .filter(
                    EmailTemplate.code == template_code,
                    EmailTemplate.language == "en",
                    EmailTemplate.is_active == True,
                )
                .first()
            )

        return template

    def render_template(self, template_string: str, variables: dict[str, Any]) -> str:
        """Render a Jinja2 template string with variables."""
        try:
            template = self.jinja_env.from_string(template_string)
            return template.render(**variables)
        except Exception as e:
            logger.error(f"Template rendering error: {e}")
            return template_string

    def send_template(
        self,
        template_code: str,
        to_email: str,
        to_name: str | None = None,
        language: str = "en",
        variables: dict[str, Any] | None = None,
        vendor_id: int | None = None,
        user_id: int | None = None,
        related_type: str | None = None,
        related_id: int | None = None,
    ) -> EmailLog:
        """
        Send an email using a database template.

        Args:
            template_code: Template code (e.g., "signup_welcome")
            to_email: Recipient email address
            to_name: Recipient name (optional)
            language: Language code (default: "en")
            variables: Template variables dict
            vendor_id: Related vendor ID for logging
            user_id: Related user ID for logging
            related_type: Related entity type (e.g., "order")
            related_id: Related entity ID

        Returns:
            EmailLog record
        """
        variables = variables or {}

        # Get template
        template = self.get_template(template_code, language)
        if not template:
            logger.error(f"Email template not found: {template_code} ({language})")
            # Create failed log entry
            log = EmailLog(
                template_code=template_code,
                recipient_email=to_email,
                recipient_name=to_name,
                subject=f"[Template not found: {template_code}]",
                from_email=settings.email_from_address,
                from_name=settings.email_from_name,
                status=EmailStatus.FAILED.value,
                error_message=f"Template not found: {template_code} ({language})",
                provider=settings.email_provider,
                vendor_id=vendor_id,
                user_id=user_id,
                related_type=related_type,
                related_id=related_id,
            )
            self.db.add(log)
            self.db.commit()  # noqa: SVC-006 - Email logs are side effects, commit immediately
            return log

        # Render template
        subject = self.render_template(template.subject, variables)
        body_html = self.render_template(template.body_html, variables)
        body_text = (
            self.render_template(template.body_text, variables)
            if template.body_text
            else None
        )

        return self.send_raw(
            to_email=to_email,
            to_name=to_name,
            subject=subject,
            body_html=body_html,
            body_text=body_text,
            template_code=template_code,
            template_id=template.id,
            vendor_id=vendor_id,
            user_id=user_id,
            related_type=related_type,
            related_id=related_id,
            extra_data=json.dumps(variables) if variables else None,
        )

    def send_raw(
        self,
        to_email: str,
        subject: str,
        body_html: str,
        to_name: str | None = None,
        body_text: str | None = None,
        from_email: str | None = None,
        from_name: str | None = None,
        reply_to: str | None = None,
        template_code: str | None = None,
        template_id: int | None = None,
        vendor_id: int | None = None,
        user_id: int | None = None,
        related_type: str | None = None,
        related_id: int | None = None,
        extra_data: str | None = None,
    ) -> EmailLog:
        """
        Send a raw email without using a template.

        Returns:
            EmailLog record
        """
        from_email = from_email or settings.email_from_address
        from_name = from_name or settings.email_from_name
        reply_to = reply_to or settings.email_reply_to or None

        # Create log entry
        log = EmailLog(
            template_code=template_code,
            template_id=template_id,
            recipient_email=to_email,
            recipient_name=to_name,
            subject=subject,
            body_html=body_html,
            body_text=body_text,
            from_email=from_email,
            from_name=from_name,
            reply_to=reply_to,
            status=EmailStatus.PENDING.value,
            provider=settings.email_provider,
            vendor_id=vendor_id,
            user_id=user_id,
            related_type=related_type,
            related_id=related_id,
            extra_data=extra_data,
        )
        self.db.add(log)
        self.db.flush()

        # Check if emails are disabled
        if not settings.email_enabled:
            log.status = EmailStatus.FAILED.value
            log.error_message = "Email sending is disabled"
            self.db.commit()  # noqa: SVC-006 - Email logs are side effects, commit immediately
            logger.info(f"Email sending disabled, skipping: {to_email}")
            return log

        # Send email
        success, message_id, error = self.provider.send(
            to_email=to_email,
            to_name=to_name,
            subject=subject,
            body_html=body_html,
            body_text=body_text,
            from_email=from_email,
            from_name=from_name,
            reply_to=reply_to,
        )

        if success:
            log.mark_sent(message_id)
            logger.info(f"Email sent to {to_email}: {subject}")
        else:
            log.mark_failed(error or "Unknown error")
            logger.error(f"Email failed to {to_email}: {error}")

        self.db.commit()  # noqa: SVC-006 - Email logs are side effects, commit immediately
        return log


# =============================================================================
# CONVENIENCE FUNCTIONS
# =============================================================================


def send_email(
    db: Session,
    template_code: str,
    to_email: str,
    to_name: str | None = None,
    language: str = "en",
    variables: dict[str, Any] | None = None,
    **kwargs,
) -> EmailLog:
    """Convenience function to send a templated email."""
    service = EmailService(db)
    return service.send_template(
        template_code=template_code,
        to_email=to_email,
        to_name=to_name,
        language=language,
        variables=variables,
        **kwargs,
    )