"""Email 도구 — IMAP을 통한 메일 조회 (read-only, 멀티 폴더)."""

from __future__ import annotations

import email
import email.header
import email.utils
import imaplib
import logging
from datetime import datetime, timedelta, timezone

from config import settings

logger = logging.getLogger(__name__)

TOOL_NAME = "email"
MAX_RESULTS = 10
PREVIEW_LEN = 200
FOLDERS = ["INBOX", "Gmail", "Technicalkorea"]

FOLDER_LABELS = {
    "INBOX": "개인",
    "Gmail": "Gmail",
    "Technicalkorea": "회사",
}


def _make_result(ok: bool, operation: str, data=None, summary: str = "", error: str | None = None) -> dict:
    return {"ok": ok, "tool": TOOL_NAME, "operation": operation, "data": data or [], "summary": summary, "error": error}


def _decode_header(raw: str) -> str:
    parts = email.header.decode_header(raw)
    decoded = []
    for part, charset in parts:
        if isinstance(part, bytes):
            decoded.append(part.decode(charset or "utf-8", errors="replace"))
        else:
            decoded.append(part)
    return "".join(decoded)


def _parse_date(date_str: str) -> datetime:
    """메일 Date 헤더 → datetime. 실패 시 epoch."""
    try:
        return email.utils.parsedate_to_datetime(date_str)
    except Exception:
        return datetime(1970, 1, 1, tzinfo=timezone.utc)


def _get_body(msg) -> str:
    """메일 본문 추출."""
    if msg.is_multipart():
        for part in msg.walk():
            if part.get_content_type() == "text/plain":
                payload = part.get_payload(decode=True)
                if payload:
                    charset = part.get_content_charset() or "utf-8"
                    return payload.decode(charset, errors="replace")
        for part in msg.walk():
            if part.get_content_type() == "text/html":
                payload = part.get_payload(decode=True)
                if payload:
                    charset = part.get_content_charset() or "utf-8"
                    return payload.decode(charset, errors="replace")
    else:
        payload = msg.get_payload(decode=True)
        if payload:
            charset = msg.get_content_charset() or "utf-8"
            return payload.decode(charset, errors="replace")
    return ""


def _connect():
    if not settings.mailplus_host or not settings.mailplus_user:
        return None
    conn = imaplib.IMAP4_SSL(settings.mailplus_host, settings.mailplus_port)
    conn.login(settings.mailplus_user, settings.mailplus_pass)
    return conn


async def search(query: str = "", days: int = 7) -> dict:
    """전체 폴더에서 최근 메일 검색."""
    try:
        conn = _connect()
        if not conn:
            return _make_result(False, "search", error="메일 설정이 없습니다.")

        since = (datetime.now() - timedelta(days=days)).strftime("%d-%b-%Y")
        if query:
            criteria = f'(SINCE {since} SUBJECT "{query}")'
        else:
            criteria = f"(SINCE {since})"

        all_results = []
        failed_folders = []

        for folder in FOLDERS:
            try:
                conn.select(folder, readonly=True)
                _, data = conn.search(None, criteria)
                uids = data[0].split()
                uids = uids[-MAX_RESULTS:]  # 폴더당 최대

                for uid in uids:
                    try:
                        _, msg_data = conn.fetch(uid, "(RFC822.HEADER)")
                        if not msg_data or not msg_data[0]:
                            continue
                        raw = msg_data[0][1]
                        msg = email.message_from_bytes(raw)

                        subject = _decode_header(msg.get("Subject", "(제목 없음)"))
                        from_addr = _decode_header(msg.get("From", ""))
                        date_str = msg.get("Date", "")
                        dt = _parse_date(date_str)
                        label = FOLDER_LABELS.get(folder, folder)

                        all_results.append({
                            "uid": f"{folder}:{uid.decode()}",
                            "folder": label,
                            "subject": subject,
                            "from": from_addr,
                            "date": dt.strftime("%m/%d %H:%M"),
                            "_sort_key": dt.timestamp(),
                        })
                    except Exception:
                        continue

                conn.close()
            except Exception as e:
                logger.warning("Email folder %s failed: %s", folder, e)
                failed_folders.append(folder)
                continue

        conn.logout()

        # 날짜순 정렬 (최신 먼저) + 제한
        all_results.sort(key=lambda x: x.get("_sort_key", 0), reverse=True)
        all_results = all_results[:MAX_RESULTS]
        for r in all_results:
            r.pop("_sort_key", None)

        summary = f"최근 {days}일간 {len(all_results)}개의 메일이 있습니다."
        if failed_folders:
            summary += f" (일부 폴더 조회 실패: {', '.join(failed_folders)})"

        return _make_result(True, "search", data=all_results, summary=summary)

    except Exception as e:
        logger.exception("Email search failed")
        return _make_result(False, "search", error=str(e))


async def read(uid: str) -> dict:
    """특정 메일 본문 조회. uid 형식: folder:uid"""
    try:
        conn = _connect()
        if not conn:
            return _make_result(False, "read", error="메일 설정이 없습니다.")

        # folder:uid 파싱
        if ":" in uid:
            folder, imap_uid = uid.split(":", 1)
        else:
            folder, imap_uid = "INBOX", uid

        conn.select(folder, readonly=True)
        _, msg_data = conn.fetch(imap_uid.encode(), "(RFC822)")

        if not msg_data or not msg_data[0]:
            conn.close()
            conn.logout()
            return _make_result(False, "read", error=f"메일을 찾을 수 없습니다.")

        raw = msg_data[0][1]
        msg = email.message_from_bytes(raw)

        subject = _decode_header(msg.get("Subject", ""))
        from_addr = _decode_header(msg.get("From", ""))
        date_str = msg.get("Date", "")
        body = _get_body(msg)[:PREVIEW_LEN * 5]

        conn.close()
        conn.logout()

        data = {"uid": uid, "subject": subject, "from": from_addr, "date": date_str, "body": body}
        return _make_result(True, "read", data=data, summary=f"메일: {subject}")

    except Exception as e:
        logger.exception("Email read failed")
        return _make_result(False, "read", error=str(e))