#!/usr/bin/env python3
"""
List unread emails via IMAP (e.g. Proton Mail Bridge). Read-only; does not mark as read.
Only lists messages sent to the configured alias (MAIL_FILTER_TO, default ai.support.lecoffreio@4nkweb.com).
Output is for the agent: each mail with UID, Message-ID, From, To, Subject, Date, body.
Usage: ./gitea-issues/mail-list-unread.sh
"""

from __future__ import annotations

import email
import imaplib
import sys
from email.header import decode_header
from pathlib import Path

# Add gitea-issues to path for mail_common
sys.path.insert(0, str(Path(__file__).resolve().parent))
from mail_common import load_imap_config, repo_root, imap_ssl_context


def decode_header_value(header: str | None) -> str:
    if not header:
        return ""
    from email.header import decode_header as dh
    parts = dh(header)
    result = []
    for part, charset in parts:
        if isinstance(part, bytes):
            result.append(part.decode(charset or "utf-8", errors="replace"))
        else:
            result.append(part)
    return "".join(result)


def get_text_body(msg: email.message.Message) -> str:
    if msg.is_multipart():
        for part in msg.walk():
            if part.get_content_type() == "text/plain":
                payload = part.get_payload(decode=True)
                if payload:
                    return payload.decode(part.get_content_charset() or "utf-8", errors="replace")
        return ""
    payload = msg.get_payload(decode=True)
    if not payload:
        return ""
    return payload.decode(msg.get_content_charset() or "utf-8", errors="replace")


def is_sent_to_alias(msg: email.message.Message, filter_to: str) -> bool:
    """True if any To/Delivered-To/X-Original-To/Cc header contains the filter address."""
    if not filter_to:
        return True
    headers_to_check = ("To", "Delivered-To", "X-Original-To", "Cc", "Envelope-To")
    for name in headers_to_check:
        value = msg.get(name)
        if value:
            decoded = decode_header_value(value).lower()
            if filter_to in decoded:
                return True
    return False


def main() -> None:
    cfg = load_imap_config()
    if not cfg["user"] or not cfg["password"]:
        root = repo_root()
        env_path = root / ".secrets" / "gitea-issues" / "imap-bridge.env"
        print("[gitea-issues] ERROR: IMAP_USER and IMAP_PASSWORD required.", file=sys.stderr)
        print(f"[gitea-issues] Set env or create {env_path}", file=sys.stderr)
        sys.exit(1)

    mail = imaplib.IMAP4(cfg["host"], int(cfg["port"]))
    if cfg["use_starttls"]:
        mail.starttls(imap_ssl_context(cfg.get("ssl_verify", True)))
    mail.login(cfg["user"], cfg["password"])
    mail.select("INBOX")
    _, nums = mail.search(None, "UNSEEN")
    ids = nums[0].split()
    if not ids:
        print("[gitea-issues] No unread messages.")
        mail.logout()
        return

    shown = 0
    for uid in ids:
        uid_s = uid.decode("ascii")
        _, data = mail.fetch(uid, "(RFC822)")
        if not data or not data[0]:
            continue
        msg = email.message_from_bytes(data[0][1])
        if not is_sent_to_alias(msg, cfg.get("filter_to", "")):
            continue
        mid = msg.get("Message-ID", "").strip()
        from_ = decode_header_value(msg.get("From"))
        to_ = decode_header_value(msg.get("To"))
        subj = decode_header_value(msg.get("Subject"))
        date_h = decode_header_value(msg.get("Date"))
        body = get_text_body(msg)
        print("--- MAIL", f"UID={uid_s}", "---")
        print("Message-ID:", mid or "(none)")
        print("From:", from_)
        print("To:", to_ or "")
        print("Subject:", subj)
        print("Date:", date_h or "")
        print("Body:")
        print(body or "(empty)")
        print("--- END MAIL ---")
        shown += 1

    if shown == 0:
        print("[gitea-issues] No unread messages sent to the configured alias (MAIL_FILTER_TO).")
    mail.logout()


if __name__ == "__main__":
    main()