"""Gmail IMAP sync — second email source for task ingestion.

Requirements:
- Enable IMAP in Gmail settings (Settings → See all settings → Forwarding and POP/IMAP)
- Generate an App Password at https://myaccount.google.com/apppasswords
  (requires 2FA to be enabled on your Google account)
- Set GMAIL_USERNAME and GMAIL_PASSWORD env vars
"""

import os
import imaplib
import email as email_lib
from email.header import decode_header
import traceback
from app.db.session import SessionLocal
from app.models import Task


def _get_gmail_connection():
    server = os.getenv("GMAIL_IMAP_SERVER", "imap.gmail.com")
    port = int(os.getenv("GMAIL_IMAP_PORT", "993"))
    username = os.getenv("GMAIL_USERNAME", "")
    password = os.getenv("GMAIL_PASSWORD", "")

    if not username or not password:
        return None  # Not configured, skip silently

    conn = imaplib.IMAP4_SSL(server, port)
    conn.login(username, password)
    return conn


def _decode_header_value(value) -> str:
    if value is None:
        return ""
    parts = decode_header(value)
    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 _get_body_snippet(msg, max_chars: int = 300) -> str:
    if msg.is_multipart():
        for part in msg.walk():
            if part.get_content_type() == "text/plain" and part.get("Content-Disposition") is None:
                payload = part.get_payload(decode=True)
                if payload:
                    return payload.decode(part.get_content_charset() or "utf-8", errors="replace")[:max_chars]
    else:
        payload = msg.get_payload(decode=True)
        if payload:
            return payload.decode(msg.get_content_charset() or "utf-8", errors="replace")[:max_chars]
    return ""


def sync_gmail():
    """Fetch unread emails from Gmail inbox and create tasks.

    Returns True on success (or if not configured), False on error.
    """
    try:
        conn = _get_gmail_connection()
    except imaplib.IMAP4.error as e:
        print(f"Gmail IMAP auth failed: {e}")
        print("Make sure you're using an App Password (not your regular Google password).")
        print("Generate one at: https://myaccount.google.com/apppasswords")
        return False
    except Exception as e:
        print(f"Gmail IMAP connection failed: {e}")
        traceback.print_exc()
        return False

    if conn is None:
        # Not configured — skip silently
        return True

    try:
        conn.select("INBOX")

        # Search for unread emails
        status, data = conn.uid("SEARCH", None, "UNSEEN")
        if status != "OK" or not data[0]:
            conn.logout()
            return True  # Nothing to process

        uid_list = data[0].split()
        db = SessionLocal()

        synced_count = 0
        for uid_bytes in uid_list:
            try:
                _, msg_data = conn.uid("FETCH", uid_bytes, "(RFC822)")
                if not msg_data or not msg_data[0]:
                    continue
                raw = msg_data[0][1]
                msg = email_lib.message_from_bytes(raw)

                message_id = msg.get("Message-ID", "").strip()
                if not message_id:
                    continue

                title = _decode_header_value(msg.get("Subject", "(No Subject)"))
                sender = _decode_header_value(msg.get("From", ""))
                body_snippet = _get_body_snippet(msg)

                # Parse email send date
                from email.utils import parsedate_to_datetime
                email_date = None
                try:
                    date_str = msg.get("Date")
                    if date_str:
                        email_date = parsedate_to_datetime(date_str)
                except Exception:
                    pass

                # Skip if already tracked (including dismissed)
                existing = db.query(Task).filter(Task.source_id == message_id).first()
                if existing:
                    continue

                # Limit title length
                title = title[:200] if title else "(No Subject)"
                description = f"From: {sender}\n\n{body_snippet}" if sender else body_snippet

                max_pos = db.query(Task).filter(Task.status == "open").count()
                db.add(Task(
                    title=title,
                    description=description[:2000],  # Limit description length
                    priority=4,
                    position=max_pos,
                    status="open",
                    origin="gmail",
                    source_id=message_id,
                    source_url="https://mail.google.com/mail/",
                    created_at=email_date,
                ))
                synced_count += 1

            except Exception as e:
                print(f"Error processing Gmail UID {uid_bytes}: {e}")

        db.commit()
        db.close()
        print(f"Gmail sync: {synced_count} new tasks from {len(uid_list)} unread emails")

    except Exception as e:
        print(f"Gmail sync error: {e}")
        traceback.print_exc()
        return False
    finally:
        try:
            conn.logout()
        except Exception:
            pass

    return True


def gmail_archive_email(source_id: str) -> bool:
    """Archive a Gmail email (remove from Inbox, keep in All Mail)."""
    try:
        conn = _get_gmail_connection()
    except Exception as e:
        print(f"Gmail connection failed: {e}")
        return False
    if conn is None:
        return False

    try:
        conn.select("INBOX")
        
        # Find the email
        uid_bytes = _find_gmail_email(conn, source_id)
        if not uid_bytes:
            print(f"  Gmail: email not found: {source_id[:40]}")
            return False

        # Gmail archive = move to All Mail (remove INBOX label)
        # In IMAP terms: COPY to [Gmail]/All Mail, then delete from INBOX
        try:
            conn.uid("COPY", uid_bytes, "[Gmail]/All Mail")
        except Exception:
            pass  # Might already be in All Mail
        conn.uid("STORE", uid_bytes, "+FLAGS", r"(\Deleted)")
        conn.expunge()
        print(f"  Gmail: archived email")
        return True

    except Exception as e:
        print(f"Gmail archive error: {e}")
        return False
    finally:
        try:
            conn.logout()
        except Exception:
            pass


def gmail_delete_email(source_id: str) -> bool:
    """Delete a Gmail email (move to Trash)."""
    try:
        conn = _get_gmail_connection()
    except Exception as e:
        print(f"Gmail connection failed: {e}")
        return False
    if conn is None:
        return False

    try:
        conn.select("INBOX")
        
        uid_bytes = _find_gmail_email(conn, source_id)
        if not uid_bytes:
            print(f"  Gmail: email not found for delete: {source_id[:40]}")
            return False

        # Move to Gmail Trash
        conn.uid("COPY", uid_bytes, "[Gmail]/Trash")
        conn.uid("STORE", uid_bytes, "+FLAGS", r"(\Deleted)")
        conn.expunge()
        print(f"  Gmail: deleted email")
        return True

    except Exception as e:
        print(f"Gmail delete error: {e}")
        return False
    finally:
        try:
            conn.logout()
        except Exception:
            pass


def _find_gmail_email(conn, source_id: str):
    """Find a Gmail email by Message-ID. Returns UID bytes or None."""
    # Try HEADER search
    status, data = conn.uid("SEARCH", None, f'HEADER Message-ID "{source_id}"')
    if status == "OK" and data[0]:
        return data[0].split()[0]
    # Try without quotes
    status, data = conn.uid("SEARCH", None, f'HEADER Message-ID {source_id}')
    if status == "OK" and data[0]:
        return data[0].split()[0]
    return None


def gmail_cleanup_dismissed(db_session=None):
    """Check if Gmail tasks are still in INBOX, dismiss if not."""
    try:
        conn = _get_gmail_connection()
    except Exception:
        return
    if conn is None:
        return

    try:
        conn.select("INBOX")
        db = db_session or SessionLocal()
        
        open_gmail_tasks = db.query(Task).filter(
            Task.origin == "gmail",
            Task.status == "open",
            Task.source_id != None
        ).all()

        dismissed = 0
        for task in open_gmail_tasks:
            uid = _find_gmail_email(conn, task.source_id)
            if not uid:
                task.status = "dismissed"
                dismissed += 1

        if dismissed:
            db.commit()
            print(f"  Gmail: auto-dismissed {dismissed} tasks")
        
        if not db_session:
            db.close()

    except Exception as e:
        print(f"Gmail cleanup error: {e}")
    finally:
        try:
            conn.logout()
        except Exception:
            pass