import logging
import re
from dataclasses import dataclass
from datetime import datetime, timezone

from bson import ObjectId

from app.models import MailDomain
from app.services.handoff_email_templates import external_reply_subject
from app.services.mail_sender import deliver_email, log_outbound_mime_headers
from app.services.message_ids import (
    build_references_header,
    canonical_message_id,
    folded_message_id,
    first_message_id,
    internet_message_id_of_message,
    message_id_fields,
)
from app.services.mime_parser import parse_mime
from app.services.raw_mime_storage import get_raw_mime_storage
from app.services.thread_service import threading_fields_from_parent

logger = logging.getLogger(__name__)

MESSAGE_SCOPE_EXTERNAL = "EXTERNAL"
MESSAGE_SCOPE_HANDOFF = "HANDOFF"


class ExternalReplyThreadingError(RuntimeError):
    pass


@dataclass(frozen=True)
class ExternalReplyThreading:
    in_reply_to: str | None
    references: list[str]
    parent_internal_message_id: ObjectId
    replying_to_internet_message_id: str | None


@dataclass(frozen=True)
class ExternalReplyPlan:
    subject: str
    body_text: str
    body_html: str | None
    threading: ExternalReplyThreading
    recipients: list[str]


def internet_message_id_of(message: dict) -> str | None:
    stored = canonical_message_id(
        message.get("internet_message_id") or message.get("message_id")
    )
    raw_header = (message.get("raw_headers") or {}).get("message_id")
    raw_canonical = canonical_message_id(raw_header)
    if raw_canonical and stored:
        if folded_message_id(raw_canonical) == folded_message_id(stored):
            return raw_canonical
    return stored or raw_canonical


async def resolve_external_reply_parent(
    database,
    *,
    account_id: str,
    external_thread_id: ObjectId,
    customer_address: str,
    handoff: dict | None = None,
) -> dict | None:
    """Pick the latest external inbound customer message with a real Message-ID."""
    customer = customer_address.lower()
    pipeline = [
        {
            "$match": {
                "account_id": account_id,
                "thread_id": external_thread_id,
                "message_scope": MESSAGE_SCOPE_EXTERNAL,
                "deletion_state": {"$in": [None, ""]},
            }
        },
        {"$sort": {"event_at": -1, "_id": -1}},
        {
            "$lookup": {
                "from": "messages",
                "localField": "message_id",
                "foreignField": "_id",
                "as": "message",
            }
        },
        {"$unwind": "$message"},
        {
            "$match": {
                "message.message_scope": {"$in": [MESSAGE_SCOPE_EXTERNAL, None]},
                "message.direction": "inbound",
                "$or": [
                    {"message.internet_message_id": {"$gt": ""}},
                    {"message.message_id": {"$gt": ""}},
                ],
            }
        },
        {"$limit": 1},
    ]
    cursor = await database.mailbox_entries.aggregate(pipeline)
    rows = [row async for row in cursor]
    if rows:
        return rows[0]["message"]

    if handoff and handoff.get("trigger_external_message_id"):
        trigger = await database.messages.find_one(
            {
                "_id": handoff["trigger_external_message_id"],
                "message_scope": MESSAGE_SCOPE_EXTERNAL,
            }
        )
        if trigger and internet_message_id_of(trigger):
            return trigger

    trigger_internet = handoff.get("trigger_internet_message_id") if handoff else None
    if trigger_internet:
        folded = folded_message_id(trigger_internet)
        trigger = await database.messages.find_one(
            {
                "message_scope": MESSAGE_SCOPE_EXTERNAL,
                "message_id_folded": folded,
            }
        )
        if trigger:
            return trigger

    return None


def validate_external_reply_parent(parent_external_message: dict) -> None:
    parent_id = internet_message_id_of(parent_external_message)
    if not parent_id:
        raise ExternalReplyThreadingError(
            "External reply parent is missing internet_message_id"
        )
    scope = parent_external_message.get("message_scope")
    if scope == MESSAGE_SCOPE_HANDOFF:
        raise ExternalReplyThreadingError(
            "External reply parent must not be a HANDOFF-scoped message"
        )


async def assert_in_reply_to_resolves_to_external_parent(
    database,
    in_reply_to: str | None,
) -> dict:
    """Ensure In-Reply-To points at an EXTERNAL message, never HANDOFF."""
    canonical = canonical_message_id(in_reply_to)
    folded = folded_message_id(canonical)
    if not canonical or not folded:
        raise ExternalReplyThreadingError("External reply is missing In-Reply-To")

    parent = await database.messages.find_one(
        {
            "$or": [
                {"message_id_folded": folded},
                {"message_id": canonical},
                {"internet_message_id": canonical},
            ],
        }
    )
    if parent is None:
        raise ExternalReplyThreadingError(
            f"In-Reply-To {canonical} does not resolve to a known message"
        )
    scope = parent.get("message_scope")
    if scope == MESSAGE_SCOPE_HANDOFF:
        raise ExternalReplyThreadingError(
            f"In-Reply-To {canonical} resolves to HANDOFF-scoped message"
        )
    if scope not in (MESSAGE_SCOPE_EXTERNAL, None):
        raise ExternalReplyThreadingError(
            f"In-Reply-To {canonical} resolves to non-external message scope={scope}"
        )
    return parent


async def assert_external_threading_chain(
    database,
    *,
    in_reply_to: str | None,
    references: list[str] | None,
) -> None:
    """Ensure outbound headers only reference EXTERNAL messages."""
    await assert_in_reply_to_resolves_to_external_parent(database, in_reply_to)

    folded_targets = {
        folded_message_id(value)
        for value in [*(references or [])]
        if folded_message_id(value)
    }
    in_reply_folded = folded_message_id(in_reply_to)
    if in_reply_folded:
        folded_targets.discard(in_reply_folded)

    for folded in folded_targets:
        handoff_hit = await database.messages.find_one(
            {
                "$or": [
                    {"message_id_folded": folded},
                    {"message_id": folded},
                ],
                "message_scope": MESSAGE_SCOPE_HANDOFF,
            },
            {"_id": 1},
        )
        if handoff_hit:
            raise ExternalReplyThreadingError(
                "External reply threading references a HANDOFF message"
            )


def build_external_reply_plan(
    *,
    parent_external_message: dict,
    body_text: str,
    body_html: str | None = None,
    subject_override: str | None = None,
    recipients: list[str],
    parent_internet_id_override: str | None = None,
) -> ExternalReplyPlan:
    parent_internet_id = canonical_message_id(
        parent_internet_id_override
    ) or internet_message_id_of(parent_external_message)
    if not parent_internet_id:
        raise ExternalReplyThreadingError(
            "External reply parent is missing internet_message_id"
        )
    scope = parent_external_message.get("message_scope")
    if scope == MESSAGE_SCOPE_HANDOFF:
        raise ExternalReplyThreadingError(
            "External reply parent must not be a HANDOFF-scoped message"
        )
    threading_fields = threading_fields_from_parent(parent_external_message)
    in_reply_to = parent_internet_id or threading_fields.get("in_reply_to")
    references = threading_fields.get("references", [])
    if parent_internet_id:
        references = build_references_header(
            [ref for ref in references if folded_message_id(ref) != folded_message_id(parent_internet_id)],
            parent_internet_id,
        ).split()
    elif not references and in_reply_to:
        references = [in_reply_to]

    if subject_override:
        subject = subject_override
    else:
        parent_subject = parent_external_message.get("subject", "")
        subject = (
            parent_subject
            if re.match(r"^re:\s*", parent_subject, flags=re.IGNORECASE)
            else external_reply_subject(parent_subject)
        )
    return ExternalReplyPlan(
        subject=subject,
        body_text=body_text,
        body_html=body_html,
        threading=ExternalReplyThreading(
            in_reply_to=in_reply_to,
            references=references,
            parent_internal_message_id=parent_external_message["_id"],
            replying_to_internet_message_id=parent_internet_id,
        ),
        recipients=recipients,
    )


def log_original_external_message(
    *,
    internal_id: ObjectId | str,
    thread_id: ObjectId | str | None,
    internet_message_id: str | None,
    sender: str | None,
    recipient: str | None,
    subject: str | None,
    in_reply_to: str | None,
    references: list[str] | None,
    raw_message_available: bool,
) -> None:
    logger.info(
        "original_external_message internal_id=%s thread_id=%s internet_message_id=%s "
        "from=%s to=%s subject=%s in_reply_to=%s references=%s raw_message_available=%s",
        internal_id,
        thread_id,
        internet_message_id,
        sender,
        recipient,
        subject,
        in_reply_to,
        references,
        raw_message_available,
    )


def log_smtp_message_sending(
    *,
    generated_message_id: str | None,
    in_reply_to: str | None,
    references: list[str] | None,
    sender: str,
    recipients: list[str],
    subject: str,
    external_thread_id: ObjectId | str | None = None,
    replying_to_internal_message_id: ObjectId | str | None = None,
    replying_to_internet_message_id: str | None = None,
) -> None:
    logger.info(
        "smtp_message_sending generated_message_id=%s in_reply_to=%s references=%s "
        "from=%s to=%s subject=%s external_thread_id=%s "
        "replying_to_internal_message_id=%s replying_to_internet_message_id=%s",
        generated_message_id,
        in_reply_to,
        " ".join(references or []),
        sender,
        ",".join(recipients),
        subject,
        external_thread_id,
        replying_to_internal_message_id,
        replying_to_internet_message_id,
    )


async def send_external_reply(
    database,
    *,
    account_id: str,
    sender: str,
    sender_name: str,
    external_thread_id: ObjectId,
    plan: ExternalReplyPlan,
    domain: MailDomain,
    resolution_method: str = "in_reply_to",
    generated_by: str | None = None,
    generated_from_handoff_message_id: ObjectId | None = None,
    message_origin: str | None = None,
) -> dict:
    if generated_from_handoff_message_id:
        existing = await database.messages.find_one(
            {
                "generated_from_handoff_message_id": generated_from_handoff_message_id,
                "message_scope": MESSAGE_SCOPE_EXTERNAL,
            }
        )
        if existing:
            logger.info(
                "external_reply_idempotent_skip handoff_message=%s external=%s",
                generated_from_handoff_message_id,
                existing["_id"],
            )
            return existing

    await assert_external_threading_chain(
        database,
        in_reply_to=plan.threading.in_reply_to,
        references=plan.threading.references,
    )
    log_smtp_message_sending(
        generated_message_id=None,
        in_reply_to=plan.threading.in_reply_to,
        references=plan.threading.references,
        sender=sender,
        recipients=plan.recipients,
        subject=plan.subject,
        external_thread_id=external_thread_id,
        replying_to_internal_message_id=plan.threading.parent_internal_message_id,
        replying_to_internet_message_id=plan.threading.replying_to_internet_message_id,
    )

    internet_message_id = await deliver_email(
        sender=sender,
        recipients=plan.recipients,
        cc=[],
        bcc=[],
        subject=plan.subject,
        body_text=plan.body_text,
        body_html=plan.body_html,
        domain=domain,
        in_reply_to=plan.threading.in_reply_to,
        references=plan.threading.references,
    )
    normalized_id = canonical_message_id(internet_message_id)
    id_fields = message_id_fields(normalized_id)
    log_smtp_message_sending(
        generated_message_id=normalized_id,
        in_reply_to=plan.threading.in_reply_to,
        references=plan.threading.references,
        sender=sender,
        recipients=plan.recipients,
        subject=plan.subject,
        external_thread_id=external_thread_id,
        replying_to_internal_message_id=plan.threading.parent_internal_message_id,
        replying_to_internet_message_id=plan.threading.replying_to_internet_message_id,
    )

    now = datetime.now(timezone.utc)
    document = {
        "direction": "outbound",
        "message_scope": MESSAGE_SCOPE_EXTERNAL,
        "account_id": account_id,
        "sender": {"name": sender_name, "address": sender},
        "to": [{"name": value.split("@")[0], "address": value} for value in plan.recipients],
        "subject": plan.subject,
        "snippet": re.sub(r"\s+", " ", plan.body_text).strip()[:240],
        "body_text": plan.body_text,
        "body_html": plan.body_html,
        "attachments": [],
        "created_at": now,
        "sent_at": now,
        "status": "accepted",
        **id_fields,
        "in_reply_to": plan.threading.in_reply_to,
        "references": plan.threading.references,
        "parent_message_id": plan.threading.parent_internal_message_id,
        "thread_relation": "reply",
        "thread_resolution_method": resolution_method,
    }
    if generated_by:
        document["generated_by"] = generated_by
    if generated_from_handoff_message_id:
        document["generated_from_handoff_message_id"] = generated_from_handoff_message_id
    if message_origin:
        document["message_origin"] = message_origin
    result = await database.messages.insert_one(document)
    document["_id"] = result.inserted_id
    from app.services.thread_service import attach_message_to_thread

    await attach_message_to_thread(
        database,
        account_id=account_id,
        thread_id=external_thread_id,
        message_id=result.inserted_id,
        subject=plan.subject,
        event_at=now,
    )
    await database.mailbox_entries.insert_one(
        {
            "account_id": account_id,
            "message_id": result.inserted_id,
            "thread_id": external_thread_id,
            "mailbox": "sent",
            "message_scope": MESSAGE_SCOPE_EXTERNAL,
            "direction": "outbound",
            "sender": document["sender"],
            "recipients": document["to"],
            "subject": plan.subject,
            "snippet": document["snippet"],
            "attachments": [],
            "status": "accepted",
            "is_read": True,
            "is_starred": False,
            "event_at": now,
            "created_at": now,
            "trashed_at": None,
            "deletion_state": None,
        }
    )
    return document