from __future__ import annotations

import email
import imaplib
from email.message import Message
from email.utils import parseaddr
from typing import List, Optional

from .schemas import EmailMessage
from .utils import decode_mime_words, get_logger, strip_html


log = get_logger(__name__)


def _decode_payload(part: Message) -> str:
    payload = part.get_payload(decode=True)
    if payload is None:
        return ""
    charset = part.get_content_charset() or "utf-8"
    try:
        return payload.decode(charset, errors="replace")
    except Exception:
        return payload.decode("utf-8", errors="replace")


def _get_body(msg: Message) -> str:
    """
    Extract best-effort email body.
    Prefers text/plain; falls back to text/html (stripped).
    """
    if msg.is_multipart():
        text_parts: List[str] = []
        html_parts: List[str] = []
        for part in msg.walk():
            content_type = (part.get_content_type() or "").lower()
            disposition = (part.get("Content-Disposition") or "").lower()
            if "attachment" in disposition:
                continue
            if content_type == "text/plain":
                text_parts.append(_decode_payload(part))
            elif content_type == "text/html":
                html_parts.append(_decode_payload(part))

        text = "\n".join(p.strip() for p in text_parts if p.strip()).strip()
        if text:
            return text
        html = "\n".join(p.strip() for p in html_parts if p.strip()).strip()
        return strip_html(html) if html else ""

    content_type = (msg.get_content_type() or "").lower()
    decoded = _decode_payload(msg)
    return strip_html(decoded) if content_type == "text/html" else decoded.strip()


def fetch_unread_emails(
    *,
    imap_server: str,
    imap_port: int,
    username: str,
    password: str,
    folder: str = "INBOX",
    limit: int = 20,
) -> List[EmailMessage]:
    """
    Connect via IMAP, find UNSEEN emails, fetch and parse them.
    Does not modify message flags (still unread).
    """
    emails_out: List[EmailMessage] = []
    mail: Optional[imaplib.IMAP4_SSL] = None
    try:
        mail = imaplib.IMAP4_SSL(imap_server, imap_port)
        mail.login(username, password)
        mail.select(folder)

        status, data = mail.search(None, "UNSEEN")
        if status != "OK":
            raise RuntimeError(f"IMAP search failed: {status}")
        ids = (data[0] or b"").split()
        ids = ids[-limit:]

        for eid in ids:
            fstatus, fdata = mail.fetch(eid, "(RFC822)")
            if fstatus != "OK" or not fdata or not fdata[0]:
                continue
            raw = fdata[0][1]
            msg = email.message_from_bytes(raw)

            message_id = (msg.get("Message-ID") or "").strip() or f"imap:{eid.decode(errors='ignore')}"
            subject = decode_mime_words(msg.get("Subject"))

            _, from_email = parseaddr(msg.get("From") or "")
            if not from_email:
                from_email = (msg.get("Reply-To") or "").strip()

            date = (msg.get("Date") or "").strip() or None
            body = _get_body(msg)

            emails_out.append(
                EmailMessage(
                    message_id=message_id,
                    from_email=from_email,
                    subject=subject,
                    body=body,
                    date=date,
                )
            )

        return emails_out
    except Exception as e:
        if imap_server == "imap.example.com":
            log.warning("Detected default imap.example.com, returning mock emails for demo.")
            return [
                EmailMessage(
                    message_id="mock-1",
                    from_email="vip.client@luxury.com",
                    subject="Urgent Request for Private Jet Booking",
                    body="Hello Concierge,\n\nI need a private jet from New York to London tomorrow at 10 AM. Please coordinate with the flight crew.\n\nBest,\nVIP Client",
                    date="2026-04-02T10:00:00Z"
                ),
                EmailMessage(
                    message_id="mock-2",
                    from_email="support@tech-billing.com",
                    subject="Invoice Dispute: #INV-99283",
                    body="The invoice sent yesterday was incorrect. We need it adjusted immediately to avoid system lockout.\n\nRegards,\nBilling Support",
                    date="2026-04-02T11:30:00Z"
                ),
                EmailMessage(
                    message_id="mock-3",
                    from_email="spammer@free-money.xyz",
                    subject="CONGRATULATIONS!!! YOU WON A LOTTERY",
                    body="You just won 10,000,000 USD! Click here to claim your prize now: http://malicious-link.net",
                    date="2026-04-02T12:00:00Z"
                )
            ]
        raise RuntimeError(f"IMAP error: {e}") from e
    finally:
        try:
            if mail is not None:
                mail.close()
                mail.logout()
        except Exception:
            pass