import logging
import re
from datetime import datetime, timezone

from bson import ObjectId

from app.services.handoff_evaluator import evaluate_handoff
from app.services.mail_sender import deliver_email
from app.services.message_ids import build_references_header, normalize_message_id, parse_message_id_list
from app.services.thread_service import (
    attach_message_to_thread,
    message_event_at,
    threading_fields_from_parent,
)

logger = logging.getLogger(__name__)

MESSAGE_SCOPE_EXTERNAL = "EXTERNAL"
MESSAGE_SCOPE_HANDOFF = "HANDOFF"
THREAD_TYPE_EXTERNAL = "EXTERNAL"
THREAD_TYPE_HUMAN_HANDOFF = "HUMAN_HANDOFF"

HANDOFF_STATUS_ACTIVE = "ACTIVE"
HANDOFF_STATUS_WAITING = "WAITING_FOR_HUMAN"
HANDOFF_STATUS_HUMAN_REPLIED = "HUMAN_REPLIED"
HANDOFF_STATUS_AGENT_REPLIED = "AGENT_REPLIED"

OWNER_AGENT = "AGENT"
OWNER_HUMAN = "HUMAN"

LINK_EXTERNAL_TRIGGERED = "EXTERNAL_TRIGGERED_HANDOFF"
LINK_EXTERNAL_RELAYED = "EXTERNAL_RELAYED_TO_HUMAN"
LINK_HUMAN_TRIGGERED_EXTERNAL = "HUMAN_TRIGGERED_EXTERNAL_REPLY"
LINK_EXTERNAL_UPDATE_RELAYED = "EXTERNAL_UPDATE_RELAYED_TO_HUMAN"


def _now() -> datetime:
    return datetime.now(timezone.utc)


def _snippet(text: str, limit: int = 240) -> str:
    return re.sub(r"\s+", " ", (text or "")).strip()[:limit]


def _handoff_subject(external_subject: str) -> str:
    subject = (external_subject or "(No subject)").strip()
    if subject.lower().startswith("human handoff:"):
        return subject
    return f"Human Handoff: {subject}"


def _build_handoff_body(
    *,
    external_sender: str,
    external_subject: str,
    external_body: str,
    handoff_reason: str,
    agent_email: str,
) -> str:
    return (
        "Human Handoff\n\n"
        "A conversation needs your attention.\n\n"
        f"From\n{external_sender}\n\n"
        f"Subject\n{external_subject}\n\n"
        "Latest message\n\n"
        f"\"{external_body.strip()}\"\n\n"
        "Why this was handed off\n\n"
        f"{handoff_reason}\n\n"
        "────────────────────────────────────────\n\n"
        f"Reply to this email to respond to the original sender through {agent_email}.\n\n"
        "Your reply will be sent to the customer.\n\n"
        "────────────────────────────────────────\n\n"
        "Gentic Human Handoff"
    )


async def create_empty_handoff_thread(
    database,
    *,
    account_id: str,
    subject: str,
) -> ObjectId:
    now = _now()
    document = {
        "account_id": account_id,
        "thread_type": THREAD_TYPE_HUMAN_HANDOFF,
        "normalized_subject": subject,
        "created_at": now,
        "updated_at": now,
        "last_message_at": now,
        "latest_message_id": None,
        "message_count": 0,
    }
    result = await database.email_threads.insert_one(document)
    return result.inserted_id


async def _record_message_link(
    database,
    *,
    handoff_id: ObjectId,
    external_message_id: ObjectId | None,
    handoff_message_id: ObjectId,
    relationship: str,
) -> None:
    await database.handoff_message_links.insert_one(
        {
            "handoff_id": handoff_id,
            "external_message_id": external_message_id,
            "handoff_message_id": handoff_message_id,
            "relationship": relationship,
            "created_at": _now(),
        }
    )


async def _latest_external_message(database, account_id: str, external_thread_id: ObjectId) -> dict | None:
    pipeline = [
        {
            "$match": {
                "account_id": account_id,
                "thread_id": external_thread_id,
                "message_scope": MESSAGE_SCOPE_EXTERNAL,
                "deletion_state": {"$in": [None, ""]},
            }
        },
        {"$sort": {"event_at": -1, "_id": -1}},
        {"$limit": 1},
        {
            "$lookup": {
                "from": "messages",
                "localField": "message_id",
                "foreignField": "_id",
                "as": "message",
            }
        },
        {"$unwind": "$message"},
    ]
    cursor = await database.mailbox_entries.aggregate(pipeline)
    rows = [row async for row in cursor]
    return rows[0]["message"] if rows else None


async def _latest_handoff_message(database, account_id: str, handoff_thread_id: ObjectId) -> dict | None:
    pipeline = [
        {
            "$match": {
                "account_id": account_id,
                "thread_id": handoff_thread_id,
                "message_scope": MESSAGE_SCOPE_HANDOFF,
            }
        },
        {"$sort": {"event_at": -1, "_id": -1}},
        {"$limit": 1},
        {
            "$lookup": {
                "from": "messages",
                "localField": "message_id",
                "foreignField": "_id",
                "as": "message",
            }
        },
        {"$unwind": "$message"},
    ]
    cursor = await database.mailbox_entries.aggregate(pipeline)
    rows = [row async for row in cursor]
    return rows[0]["message"] if rows else None


async def find_active_handoff_for_external_thread(
    database,
    account_id: str,
    external_thread_id: ObjectId,
) -> dict | None:
    return await database.human_handoffs.find_one(
        {
            "account_id": account_id,
            "external_thread_id": external_thread_id,
            "status": {"$in": [HANDOFF_STATUS_ACTIVE, HANDOFF_STATUS_WAITING, HANDOFF_STATUS_HUMAN_REPLIED, HANDOFF_STATUS_AGENT_REPLIED]},
        }
    )


async def resolve_handoff_from_inbound(
    database,
    *,
    account_id: str,
    agent_email: str,
    sender_address: str,
    in_reply_to: str | None,
    references: list[str],
) -> dict | None:
    sender = sender_address.lower()
    rules = await database.human_handoff_rules.find(
        {"account_id": account_id, "owner_email": sender, "active": True}
    ).to_list(length=10)
    if not rules:
        return None

    search_ids = [*([in_reply_to] if in_reply_to else []), *references]
    if not search_ids:
        return None

    for internet_id in reversed(parse_message_id_list(" ".join(search_ids))):
        message = await database.messages.find_one(
            {
                "message_id": internet_id,
                "message_scope": MESSAGE_SCOPE_HANDOFF,
            }
        )
        if message is None:
            continue
        entry = await database.mailbox_entries.find_one(
            {
                "account_id": account_id,
                "message_id": message["_id"],
                "message_scope": MESSAGE_SCOPE_HANDOFF,
            }
        )
        if entry is None:
            continue
        handoff = await database.human_handoffs.find_one(
            {
                "account_id": account_id,
                "handoff_thread_id": entry["thread_id"],
                "human_email": sender,
                "status": {"$ne": "CLOSED"},
            }
        )
        if handoff:
            return handoff
    return None


async def store_handoff_message(
    database,
    *,
    account_id: str,
    agent_email: str,
    handoff_thread_id: ObjectId,
    direction: str,
    sender: dict,
    recipients: list[dict],
    subject: str,
    body_text: str,
    internet_message_id: str | None = None,
    in_reply_to: str | None = None,
    references: list[str] | None = None,
    handoff_id: ObjectId | None = None,
    link_relationship: str | None = None,
    external_message_id: ObjectId | None = None,
    event_at: datetime | None = None,
) -> dict:
    now = event_at or _now()
    document = {
        "direction": direction,
        "message_scope": MESSAGE_SCOPE_HANDOFF,
        "account_id": account_id,
        "sender": sender,
        "to": recipients,
        "subject": subject,
        "snippet": _snippet(body_text),
        "body_text": body_text,
        "body_html": None,
        "attachments": [],
        "created_at": now,
        "sent_at": now if direction == "outbound" else None,
        "received_at": now if direction == "inbound" else None,
        "status": "received" if direction == "inbound" else "accepted",
        "message_id": normalize_message_id(internet_message_id),
        "in_reply_to": normalize_message_id(in_reply_to),
        "references": references or [],
    }
    result = await database.messages.insert_one(document)
    document["_id"] = result.inserted_id
    await attach_message_to_thread(
        database,
        account_id=account_id,
        thread_id=handoff_thread_id,
        message_id=result.inserted_id,
        subject=subject,
        event_at=now,
    )
    await database.mailbox_entries.insert_one(
        {
            "account_id": account_id,
            "message_id": result.inserted_id,
            "thread_id": handoff_thread_id,
            "mailbox": "handoff",
            "message_scope": MESSAGE_SCOPE_HANDOFF,
            "direction": direction,
            "sender": sender,
            "recipients": recipients,
            "subject": subject,
            "snippet": document["snippet"],
            "attachments": [],
            "status": document["status"],
            "is_read": direction == "outbound",
            "is_starred": False,
            "event_at": now,
            "created_at": now,
            "trashed_at": None,
            "deletion_state": None,
        }
    )
    if handoff_id and link_relationship:
        await _record_message_link(
            database,
            handoff_id=handoff_id,
            external_message_id=external_message_id,
            handoff_message_id=result.inserted_id,
            relationship=link_relationship,
        )
    return document


async def send_handoff_to_human(
    database,
    *,
    account_id: str,
    agent_email: str,
    human_email: str,
    external_message: dict,
    external_thread_id: ObjectId,
    handoff_reason: str,
    domain,
    existing_handoff: dict | None = None,
) -> dict:
    external_sender = external_message.get("sender", {})
    external_sender_text = external_sender.get("address") or "unknown sender"
    external_subject = external_message.get("subject", "")
    external_body = external_message.get("body_text") or external_message.get("snippet") or ""

    if existing_handoff:
        handoff_id = existing_handoff["_id"]
        handoff_thread_id = existing_handoff["handoff_thread_id"]
        parent = await _latest_handoff_message(database, account_id, handoff_thread_id)
        threading = threading_fields_from_parent(parent) if parent else {}
        subject = _handoff_subject(external_subject)
        body = _build_handoff_body(
            external_sender=external_sender_text,
            external_subject=external_subject,
            external_body=external_body,
            handoff_reason="New message in the linked conversation.",
            agent_email=agent_email,
        )
        relationship = LINK_EXTERNAL_UPDATE_RELAYED
    else:
        handoff_thread_id = await create_empty_handoff_thread(
            database,
            account_id=account_id,
            subject=_handoff_subject(external_subject),
        )
        threading = {}
        subject = _handoff_subject(external_subject)
        body = _build_handoff_body(
            external_sender=external_sender_text,
            external_subject=external_subject,
            external_body=external_body,
            handoff_reason=handoff_reason,
            agent_email=agent_email,
        )
        handoff_doc = {
            "account_id": account_id,
            "agent_email": agent_email.lower(),
            "human_email": human_email.lower(),
            "external_thread_id": external_thread_id,
            "handoff_thread_id": handoff_thread_id,
            "external_subject": external_subject,
            "external_sender": external_sender_text,
            "handoff_reason": handoff_reason,
            "status": HANDOFF_STATUS_WAITING,
            "current_owner": OWNER_HUMAN,
            "created_at": _now(),
            "updated_at": _now(),
            "last_external_message_at": message_event_at(external_message),
            "last_human_message_at": None,
        }
        insert = await database.human_handoffs.insert_one(handoff_doc)
        handoff_id = insert.inserted_id
        relationship = LINK_EXTERNAL_TRIGGERED

    internet_message_id = await deliver_email(
        sender=agent_email,
        recipients=[human_email],
        cc=[],
        bcc=[],
        subject=subject,
        body_text=body,
        body_html=None,
        domain=domain,
        in_reply_to=threading.get("in_reply_to"),
        references=threading.get("references"),
    )

    handoff_message = await store_handoff_message(
        database,
        account_id=account_id,
        agent_email=agent_email,
        handoff_thread_id=handoff_thread_id,
        direction="outbound",
        sender={"name": "Gentic Agent", "address": agent_email},
        recipients=[{"name": human_email.split("@")[0], "address": human_email}],
        subject=subject,
        body_text=body,
        internet_message_id=internet_message_id,
        in_reply_to=threading.get("in_reply_to"),
        references=threading.get("references"),
        handoff_id=handoff_id,
        link_relationship=relationship,
        external_message_id=external_message["_id"],
    )

    await database.human_handoffs.update_one(
        {"_id": handoff_id},
        {
            "$set": {
                "status": HANDOFF_STATUS_WAITING,
                "current_owner": OWNER_HUMAN,
                "updated_at": _now(),
                "last_external_message_at": message_event_at(external_message),
                "latest_handoff_message_id": handoff_message["_id"],
            }
        },
    )
    logger.info(
        "handoff_sent handoff_id=%s external_thread=%s handoff_thread=%s",
        handoff_id,
        external_thread_id,
        handoff_thread_id,
    )
    return await database.human_handoffs.find_one({"_id": handoff_id})


async def _handoff_rule_for_human(database, account_id: str, human_email: str) -> dict | None:
    return await database.human_handoff_rules.find_one(
        {
            "account_id": account_id,
            "owner_email": human_email.lower(),
            "active": True,
        }
    )


async def process_human_reply(
    database,
    *,
    account_id: str,
    agent_email: str,
    handoff: dict,
    inbound_parsed: dict,
    inbound_body: str,
    domain,
) -> None:
    handoff_thread_id = handoff["handoff_thread_id"]
    external_thread_id = handoff["external_thread_id"]
    human_email = handoff["human_email"]
    rule = await _handoff_rule_for_human(database, account_id, human_email)
    allow_replies = rule.get("allow_replies", True) if rule else True

    human_message = await store_handoff_message(
        database,
        account_id=account_id,
        agent_email=agent_email,
        handoff_thread_id=handoff_thread_id,
        direction="inbound",
        sender={"name": human_email.split("@")[0], "address": human_email},
        recipients=[{"name": "Gentic Agent", "address": agent_email}],
        subject=inbound_parsed.get("subject", ""),
        body_text=inbound_body,
        internet_message_id=inbound_parsed.get("message_id"),
        in_reply_to=inbound_parsed.get("in_reply_to"),
        references=inbound_parsed.get("references", []),
        handoff_id=handoff["_id"],
        link_relationship=LINK_HUMAN_TRIGGERED_EXTERNAL,
    )

    now = _now()
    if not allow_replies:
        await database.human_handoffs.update_one(
            {"_id": handoff["_id"]},
            {
                "$set": {
                    "status": HANDOFF_STATUS_HUMAN_REPLIED,
                    "current_owner": OWNER_AGENT,
                    "updated_at": now,
                    "last_human_message_at": now,
                }
            },
        )
        return

    external_parent = await _latest_external_message(database, account_id, external_thread_id)
    if external_parent is None:
        logger.warning("handoff_reply_missing_external_parent handoff_id=%s", handoff["_id"])
        return

    threading = threading_fields_from_parent(external_parent)
    external_subject = handoff.get("external_subject") or external_parent.get("subject", "")
    if not re.match(r"^re:\s*", external_subject, flags=re.IGNORECASE):
        external_subject = f"Re: {external_subject}"

    external_recipient = handoff.get("external_sender") or external_parent.get("sender", {}).get("address")
    if not external_recipient:
        return

    customer_body = inbound_body.strip()
    internet_message_id = await deliver_email(
        sender=agent_email,
        recipients=[external_recipient],
        cc=[],
        bcc=[],
        subject=external_subject,
        body_text=customer_body,
        body_html=None,
        domain=domain,
        in_reply_to=threading.get("in_reply_to"),
        references=threading.get("references"),
    )

    external_doc = {
        "direction": "outbound",
        "message_scope": MESSAGE_SCOPE_EXTERNAL,
        "account_id": account_id,
        "sender": {"name": "Gentic Agent", "address": agent_email},
        "to": [{"name": external_recipient.split("@")[0], "address": external_recipient}],
        "subject": external_subject,
        "snippet": _snippet(customer_body),
        "body_text": customer_body,
        "body_html": None,
        "attachments": [],
        "created_at": now,
        "sent_at": now,
        "status": "accepted",
        "message_id": normalize_message_id(internet_message_id),
        "in_reply_to": threading.get("in_reply_to"),
        "references": threading.get("references", []),
        "parent_message_id": external_parent["_id"],
        "thread_relation": "reply",
        "thread_resolution_method": "human_handoff_bridge",
    }
    ext_result = await database.messages.insert_one(external_doc)
    external_doc["_id"] = ext_result.inserted_id
    await attach_message_to_thread(
        database,
        account_id=account_id,
        thread_id=external_thread_id,
        message_id=ext_result.inserted_id,
        subject=external_subject,
        event_at=now,
    )
    await database.mailbox_entries.insert_one(
        {
            "account_id": account_id,
            "message_id": ext_result.inserted_id,
            "thread_id": external_thread_id,
            "mailbox": "sent",
            "message_scope": MESSAGE_SCOPE_EXTERNAL,
            "direction": "outbound",
            "sender": external_doc["sender"],
            "recipients": external_doc["to"],
            "subject": external_subject,
            "snippet": external_doc["snippet"],
            "attachments": [],
            "status": "accepted",
            "is_read": True,
            "is_starred": False,
            "event_at": now,
            "created_at": now,
            "trashed_at": None,
            "deletion_state": None,
        }
    )

    relay_body = f"Sent to customer:\n\n\"{customer_body}\""
    relay_subject = f"Re: {_handoff_subject(handoff.get('external_subject', ''))}"
    relay_threading = threading_fields_from_parent(human_message)
    relay_internet_id = await deliver_email(
        sender=agent_email,
        recipients=[human_email],
        cc=[],
        bcc=[],
        subject=relay_subject,
        body_text=relay_body,
        body_html=None,
        domain=domain,
        in_reply_to=relay_threading.get("in_reply_to"),
        references=relay_threading.get("references"),
    )
    await store_handoff_message(
        database,
        account_id=account_id,
        agent_email=agent_email,
        handoff_thread_id=handoff_thread_id,
        direction="outbound",
        sender={"name": "Gentic Agent", "address": agent_email},
        recipients=[{"name": human_email.split("@")[0], "address": human_email}],
        subject=relay_subject,
        body_text=relay_body,
        internet_message_id=relay_internet_id,
        in_reply_to=relay_threading.get("in_reply_to"),
        references=relay_threading.get("references"),
        handoff_id=handoff["_id"],
        link_relationship=LINK_EXTERNAL_RELAYED,
        external_message_id=ext_result.inserted_id,
    )

    await database.human_handoffs.update_one(
        {"_id": handoff["_id"]},
        {
            "$set": {
                "status": HANDOFF_STATUS_AGENT_REPLIED,
                "current_owner": OWNER_AGENT,
                "updated_at": now,
                "last_human_message_at": now,
            }
        },
    )


async def maybe_trigger_handoff(
    database,
    *,
    account_id: str,
    agent_email: str,
    external_message: dict,
    external_thread_id: ObjectId,
    domain,
) -> None:
    rules = await database.human_handoff_rules.find(
        {"account_id": account_id, "active": True}
    ).to_list(length=20)
    if not rules:
        return

    body_text = external_message.get("body_text") or external_message.get("snippet") or ""
    email_payload = {
        "subject": external_message.get("subject", ""),
        "snippet": external_message.get("snippet", ""),
        "body_text": body_text,
        "is_starred": False,
    }

    for rule in rules:
        evaluation = evaluate_handoff(
            email=email_payload,
            labels=rule.get("labels", []),
            email_types=rule.get("email_types", []),
            instructions=rule.get("instructions", ""),
        )
        if not evaluation["would_handoff"]:
            continue
        if not rule.get("allow_replies", True):
            continue

        existing = await find_active_handoff_for_external_thread(
            database, account_id, external_thread_id
        )
        reason = evaluation.get("instruction_reason") or rule.get("instructions") or "Matched handoff rules."
        await send_handoff_to_human(
            database,
            account_id=account_id,
            agent_email=agent_email,
            human_email=rule["owner_email"],
            external_message=external_message,
            external_thread_id=external_thread_id,
            handoff_reason=reason,
            domain=domain,
            existing_handoff=existing,
        )
        return