"""
Email backends.

R2-B spike: only ConsoleEmailBackend is functional. SendGrid is a stub
intentionally left to be wired in R3-C.
"""

from __future__ import annotations

import json
import sys
from datetime import datetime, timezone
from pathlib import Path
from typing import Optional, Protocol

from sendgrid import SendGridAPIClient
from sendgrid.helpers.mail import Mail, ReplyTo

from app.config import settings


# Repository convention: backend/var/email_outbox.jsonl
# This module lives at backend/app/services/email.py — go up two levels to
# reach backend/, then var/.
_BACKEND_ROOT = Path(__file__).resolve().parent.parent.parent
OUTBOX_PATH = _BACKEND_ROOT / "var" / "email_outbox.jsonl"


class EmailBackend(Protocol):
    def send(
        self,
        to: str,
        subject: str,
        html: str,
        text: Optional[str] = None,
    ) -> None:
        ...


class ConsoleEmailBackend:
    """Dev/spike backend. Prints to stdout AND appends a JSON line to
    backend/var/email_outbox.jsonl so the round-trip can be inspected
    after the fact.
    """

    def send(
        self,
        to: str,
        subject: str,
        html: str,
        text: Optional[str] = None,
    ) -> None:
        record = {
            "ts": datetime.now(timezone.utc).isoformat(),
            "to": to,
            "subject": subject,
            "html": html,
            "text": text,
        }
        print(
            f"[ConsoleEmailBackend] -> {to} | {subject}",
            file=sys.stdout,
            flush=True,
        )
        OUTBOX_PATH.parent.mkdir(parents=True, exist_ok=True)
        with OUTBOX_PATH.open("a", encoding="utf-8") as f:
            f.write(json.dumps(record) + "\n")


class SendGridEmailBackend:
    def __init__(self) -> None:
        self._client = SendGridAPIClient(settings.SENDGRID_API_KEY)
        self._from_email = settings.SENDGRID_FROM_EMAIL
        self._reply_to = settings.SENDGRID_REPLY_TO

    def send(
        self,
        to: str,
        subject: str,
        html: str,
        text: Optional[str] = None,
    ) -> None:
        message = Mail(
            from_email=self._from_email,
            to_emails=to,
            subject=subject,
            html_content=html,
            plain_text_content=text,
        )
        message.reply_to = ReplyTo(self._reply_to)
        response = self._client.send(message)
        if response.status_code >= 400:
            raise RuntimeError(
                f"SendGrid error {response.status_code}: {response.body}"
            )


def get_email_backend() -> EmailBackend:
    backend = (settings.EMAIL_BACKEND or "console").lower()
    if backend == "sendgrid":
        return SendGridEmailBackend()
    return ConsoleEmailBackend()