import re
from datetime import timezone
from email import policy
from email.parser import BytesParser
from email.utils import getaddresses, parsedate_to_datetime
from html import unescape

from app.services.message_ids import first_message_id, parse_message_id_list
from app.services.reply_extractor import build_reply_display


def _addresses(values: list[str]) -> list[dict[str, str]]:
    return [
        {
            "name": name.strip() or address.split("@", 1)[0],
            "address": address.lower(),
        }
        for name, address in getaddresses(values)
        if address
    ]


def _text(part) -> str:
    try:
        value = part.get_content()
    except (LookupError, UnicodeError):
        payload = part.get_payload(decode=True) or b""
        value = payload.decode("utf-8", errors="replace")
    return value if isinstance(value, str) else ""


def _header_str(value) -> str | None:
    if value is None:
        return None
    cleaned = str(value).strip()
    return cleaned or None


def _snippet(text: str, html: str | None, limit: int = 240) -> str:
    return build_reply_display(body_text=text, body_html=html, limit=limit)["snippet"]


def parse_mime(raw: bytes) -> dict:
    message = BytesParser(policy=policy.default).parsebytes(raw)
    sender = _addresses(message.get_all("from", []))
    from_value = sender[0] if sender else {"name": "Unknown sender", "address": ""}
    text_parts: list[str] = []
    html_parts: list[str] = []
    attachments: list[dict] = []

    for part in message.walk():
        if part.is_multipart():
            continue
        disposition = part.get_content_disposition()
        filename = part.get_filename()
        content_type = part.get_content_type()
        payload = part.get_payload(decode=True) or b""
        if disposition == "attachment" or filename:
            attachments.append(
                {
                    "filename": filename or "attachment",
                    "content_type": content_type,
                    "size": len(payload),
                    "content_id": (part.get("Content-ID") or "").strip("<>") or None,
                    "disposition": disposition or "attachment",
                }
            )
        elif content_type == "text/plain":
            text_parts.append(_text(part))
        elif content_type == "text/html":
            html_parts.append(_text(part))

    date = None
    if message.get("Date"):
        try:
            date = parsedate_to_datetime(message["Date"])
            if date.tzinfo is None:
                date = date.replace(tzinfo=timezone.utc)
            date = date.astimezone(timezone.utc)
        except (TypeError, ValueError, OverflowError):
            pass
    body_text = "\n".join(text_parts).strip()
    body_html = "\n".join(html_parts).strip() or None
    internet_message_id = first_message_id(message.get("Message-ID"))
    in_reply_to = first_message_id(message.get("In-Reply-To"))
    references = parse_message_id_list(message.get("References"))
    raw_headers = {
        "message_id": _header_str(message.get("Message-ID")),
        "in_reply_to": _header_str(message.get("In-Reply-To")),
        "references": _header_str(message.get("References")),
        "subject": _header_str(message.get("Subject")),
        "date": _header_str(message.get("Date")),
        "from": _header_str(message.get("From")),
        "to": _header_str(message.get("To")),
        "cc": _header_str(message.get("Cc")),
        "reply_to": _header_str(message.get("Reply-To")),
    }
    return {
        "message_id": internet_message_id,
        "in_reply_to": in_reply_to,
        "references": references,
        "raw_headers": raw_headers,
        "sender": from_value,
        "to": _addresses(message.get_all("to", [])),
        "cc": _addresses(message.get_all("cc", [])),
        "reply_to": _addresses(message.get_all("reply-to", [])),
        "subject": str(message.get("Subject") or ""),
        "sent_at": date,
        "body_text": body_text,
        "body_html": body_html,
        "snippet": _snippet(body_text, body_html),
        "attachments": attachments,
    }