"""Business logic for the kommunikation plugin."""

from __future__ import annotations

import logging
import re
import uuid
from datetime import datetime, timezone
from typing import Any

from sqlalchemy import select, update, func, and_, or_
from sqlalchemy.ext.asyncio import AsyncSession

from app.core.event_bus import get_event_bus
from app.plugins.builtins.kommunikation.models import (
    CommConversation,
    CommConversationMute,
    CommConversationPin,
    CommMessage,
    CommMessageAttachment,
    CommMessageBlock,
    CommMessageEdit,
    CommMessageRead,
    CommMessageReaction,
    CommParticipant,
)
from app.plugins.builtins.kommunikation.participant_registry import get_participant_registry
from app.plugins.builtins.kommunikation.rbac import CommRBAC

logger = logging.getLogger(__name__)

MAX_TRIGGER_DEPTH = 3


# ─── Mention Parsing ───

MENTION_PATTERN = re.compile(r"@(\w+)")


def parse_mentions(content: str) -> list[str]:
    """Parse @mentions from message content. Returns list of mentioned types/names."""
    return MENTION_PATTERN.findall(content)


# ─── Conversation Helpers ───


def conversation_to_response(
    conv: CommConversation,
    participants: list[CommParticipant],
    unread_count: int = 0,
    is_pinned_by_user: bool = False,
) -> dict[str, Any]:
    """Convert a CommConversation to a response dict."""
    return {
        "id": str(conv.id),
        "title": conv.title,
        "is_locked": conv.is_locked,
        "locked_by": conv.locked_by,
        "is_direct": conv.is_direct,
        "is_archived": conv.is_archived,
        "is_pinned": is_pinned_by_user,
        "created_by": str(conv.created_by) if conv.created_by else None,
        "created_by_type": conv.created_by_type,
        "last_msg_at": conv.last_msg_at.isoformat() if conv.last_msg_at else None,
        "last_msg_preview": conv.last_msg_preview,
        "last_msg_sender_type": conv.last_msg_sender_type,
        "participants": [participant_to_response(p) for p in participants],
        "unread_count": unread_count,
        "metadata": conv.metadata_ or {},
    }


def participant_to_response(p: CommParticipant) -> dict[str, Any]:
    """Convert a CommParticipant to a response dict."""
    return {
        "id": str(p.id),
        "conversation_id": str(p.conversation_id),
        "participant_id": str(p.participant_id) if p.participant_id else None,
        "participant_type": p.participant_type,
        "display_name": p.display_name,
        "role": p.role,
        "joined_at": p.joined_at.isoformat() if p.joined_at else None,
    }


def message_to_response(
    msg: CommMessage,
    blocks: list[CommMessageBlock] | None = None,
    attachments: list[CommMessageAttachment] | None = None,
    reactions: list[CommMessageReaction] | None = None,
) -> dict[str, Any]:
    """Convert a CommMessage to a response dict."""
    return {
        "id": str(msg.id),
        "conversation_id": str(msg.conversation_id),
        "sender_id": str(msg.sender_id) if msg.sender_id else None,
        "sender_type": msg.sender_type,
        "content": msg.content,
        "content_format": msg.content_format,
        "metadata": msg.metadata_ or {},
        "reply_to_id": str(msg.reply_to_id) if msg.reply_to_id else None,
        "is_pinned": msg.is_pinned,
        "created_at": msg.created_at.isoformat() if msg.created_at else None,
        "edited_at": msg.edited_at.isoformat() if msg.edited_at else None,
        "blocks": [
            {
                "id": str(b.id),
                "block_type": b.block_type,
                "block_data": b.block_data,
                "sort_order": b.sort_order,
            }
            for b in (blocks or [])
        ],
        "attachments": [
            {
                "id": str(a.id),
                "file_id": str(a.file_id) if a.file_id else None,
                "file_source": a.file_source,
                "file_name": a.file_name,
                "file_type": a.file_type,
                "file_size": a.file_size,
                "thumbnail_path": a.thumbnail_path,
            }
            for a in (attachments or [])
        ],
        "reactions": [
            {
                "id": str(r.id),
                "message_id": str(r.message_id),
                "user_id": str(r.user_id),
                "emoji": r.emoji,
            }
            for r in (reactions or [])
        ],
    }


# ─── Conversation CRUD ───


async def list_conversations(
    db: AsyncSession,
    tenant_id: uuid.UUID,
    user_id: uuid.UUID,
    include_archived: bool = False,
) -> list[dict[str, Any]]:
    """List all conversations for a user."""
    # Get conversations where user is a participant
    result = await db.execute(
        select(CommConversation)
        .join(CommParticipant, CommParticipant.conversation_id == CommConversation.id)
        .where(
            CommParticipant.participant_id == user_id,
            CommParticipant.participant_type == "user",
            CommParticipant.left_at.is_(None),
            CommConversation.tenant_id == tenant_id,
            CommConversation.deleted_at.is_(None),
        )
        .order_by(CommConversation.last_msg_at.desc().nullslast())
    )
    conversations = result.scalars().all()

    # Get user's pinned conversations
    pins_result = await db.execute(
        select(CommConversationPin).where(
            CommConversationPin.user_id == user_id,
            CommConversationPin.tenant_id == tenant_id,
        )
    )
    pinned_ids = {p.conversation_id for p in pins_result.scalars().all()}

    conv_list = []
    for conv in conversations:
        if conv.is_archived and not include_archived:
            continue
        # Get participants
        parts_result = await db.execute(
            select(CommParticipant).where(
                CommParticipant.conversation_id == conv.id,
                CommParticipant.left_at.is_(None),
            )
        )
        participants = list(parts_result.scalars().all())

        # Get unread count
        unread = await _get_unread_count(db, tenant_id, conv.id, user_id)

        conv_list.append(
            conversation_to_response(
                conv, participants, unread_count=unread, is_pinned_by_user=conv.id in pinned_ids
            )
        )

    # Sort: pinned first, then by last_msg_at
    conv_list.sort(key=lambda c: (not c["is_pinned"], c["last_msg_at"] or ""), reverse=False)
    # Actually: pinned first (True > False in reverse), then newest first
    conv_list.sort(key=lambda c: c["last_msg_at"] or "0000", reverse=True)
    conv_list.sort(key=lambda c: c["is_pinned"], reverse=True)

    return conv_list


async def get_conversation(
    db: AsyncSession,
    tenant_id: uuid.UUID,
    conversation_id: uuid.UUID,
    user_id: uuid.UUID,
) -> dict[str, Any] | None:
    """Get a single conversation with participants."""
    result = await db.execute(
        select(CommConversation).where(
            CommConversation.id == conversation_id,
            CommConversation.tenant_id == tenant_id,
            CommConversation.deleted_at.is_(None),
        )
    )
    conv = result.scalar_one_or_none()
    if conv is None:
        return None

    # Check user is participant
    if not await CommRBAC.is_participant(db, conversation_id, user_id):
        return None

    parts_result = await db.execute(
        select(CommParticipant).where(
            CommParticipant.conversation_id == conv.id,
            CommParticipant.left_at.is_(None),
        )
    )
    participants = list(parts_result.scalars().all())

    # Check pinned
    pin_result = await db.execute(
        select(CommConversationPin).where(
            CommConversationPin.conversation_id == conv.id,
            CommConversationPin.user_id == user_id,
        )
    )
    is_pinned = pin_result.scalar_one_or_none() is not None

    unread = await _get_unread_count(db, tenant_id, conv.id, user_id)

    return conversation_to_response(conv, participants, unread_count=unread, is_pinned_by_user=is_pinned)


async def create_conversation(
    db: AsyncSession,
    tenant_id: uuid.UUID,
    user_id: uuid.UUID,
    title: str | None = None,
    participant_ids: list[str] | None = None,
    is_direct: bool = False,
    initial_message: str | None = None,
) -> dict[str, Any]:
    """Create a new conversation."""
    conv = CommConversation(
        tenant_id=tenant_id,
        title=title,
        is_direct=is_direct,
        created_by=user_id,
        created_by_type="user",
        metadata_={},
    )
    db.add(conv)
    await db.flush()

    # Add creator as admin
    creator = CommParticipant(
        tenant_id=tenant_id,
        conversation_id=conv.id,
        participant_id=user_id,
        participant_type="user",
        role="admin",
    )
    db.add(creator)

    # Add other participants
    for pid_str in (participant_ids or []):
        try:
            pid = uuid.UUID(pid_str)
            if pid == user_id:
                continue
            p = CommParticipant(
                tenant_id=tenant_id,
                conversation_id=conv.id,
                participant_id=pid,
                participant_type="user",
                role="member",
            )
            db.add(p)
        except ValueError:
            logger.warning(f"Invalid participant UUID: {pid_str}")

    await db.flush()

    # Send initial message if provided
    if initial_message:
        await send_message(
            db, tenant_id, conv.id, user_id, "user",
            content=initial_message, content_format="text",
        )

    # Publish event
    event_bus = get_event_bus()
    await event_bus.publish("conversation.created", {
        "conversation_id": str(conv.id),
        "tenant_id": str(tenant_id),
        "created_by": str(user_id),
    })

    # Get all participants for response
    parts_result = await db.execute(
        select(CommParticipant).where(
            CommParticipant.conversation_id == conv.id,
            CommParticipant.left_at.is_(None),
        )
    )
    participants = list(parts_result.scalars().all())

    return conversation_to_response(conv, participants)


async def update_conversation(
    db: AsyncSession,
    tenant_id: uuid.UUID,
    conversation_id: uuid.UUID,
    user_id: uuid.UUID,
    title: str | None = None,
    is_archived: bool | None = None,
) -> dict[str, Any] | None:
    """Update a conversation."""
    result = await db.execute(
        select(CommConversation).where(
            CommConversation.id == conversation_id,
            CommConversation.tenant_id == tenant_id,
            CommConversation.deleted_at.is_(None),
        )
    )
    conv = result.scalar_one_or_none()
    if conv is None:
        return None

    # Check locked
    if conv.is_locked and title is not None:
        # Only the locking plugin can change title on locked conversations
        # Users cannot
        pass
    elif title is not None:
        conv.title = title
        conv.title_set_by = user_id

    if is_archived is not None:
        conv.is_archived = is_archived

    await db.flush()

    return await get_conversation(db, tenant_id, conversation_id, user_id)


async def pin_conversation(
    db: AsyncSession,
    tenant_id: uuid.UUID,
    conversation_id: uuid.UUID,
    user_id: uuid.UUID,
) -> bool:
    """Pin a conversation for a user."""
    existing = await db.execute(
        select(CommConversationPin).where(
            CommConversationPin.conversation_id == conversation_id,
            CommConversationPin.user_id == user_id,
        )
    )
    if existing.scalar_one_or_none() is None:
        pin = CommConversationPin(
            tenant_id=tenant_id,
            conversation_id=conversation_id,
            user_id=user_id,
        )
        db.add(pin)
        await db.flush()
    return True


async def unpin_conversation(
    db: AsyncSession,
    conversation_id: uuid.UUID,
    user_id: uuid.UUID,
) -> bool:
    """Unpin a conversation for a user."""
    result = await db.execute(
        select(CommConversationPin).where(
            CommConversationPin.conversation_id == conversation_id,
            CommConversationPin.user_id == user_id,
        )
    )
    pin = result.scalar_one_or_none()
    if pin:
        await db.delete(pin)
        await db.flush()
    return True


async def mute_conversation(
    db: AsyncSession,
    tenant_id: uuid.UUID,
    conversation_id: uuid.UUID,
    user_id: uuid.UUID,
) -> bool:
    """Mute a conversation for a user."""
    existing = await db.execute(
        select(CommConversationMute).where(
            CommConversationMute.conversation_id == conversation_id,
            CommConversationMute.user_id == user_id,
        )
    )
    if existing.scalar_one_or_none() is None:
        mute = CommConversationMute(
            tenant_id=tenant_id,
            conversation_id=conversation_id,
            user_id=user_id,
        )
        db.add(mute)
        await db.flush()
    return True


async def unmute_conversation(
    db: AsyncSession,
    conversation_id: uuid.UUID,
    user_id: uuid.UUID,
) -> bool:
    """Unmute a conversation for a user."""
    result = await db.execute(
        select(CommConversationMute).where(
            CommConversationMute.conversation_id == conversation_id,
            CommConversationMute.user_id == user_id,
        )
    )
    mute = result.scalar_one_or_none()
    if mute:
        await db.delete(mute)
        await db.flush()
    return True


# ─── Participant Management ───


async def add_participant(
    db: AsyncSession,
    tenant_id: uuid.UUID,
    conversation_id: uuid.UUID,
    participant_id: str,
    participant_type: str = "user",
    role: str = "member",
    display_name: str | None = None,
) -> dict[str, Any] | None:
    """Add a participant to a conversation."""
    try:
        pid = uuid.UUID(participant_id) if participant_type == "user" else None
    except ValueError:
        return None

    existing = await db.execute(
        select(CommParticipant).where(
            CommParticipant.conversation_id == conversation_id,
            CommParticipant.participant_id == pid if pid else CommParticipant.participant_type == participant_type,
            CommParticipant.participant_type == participant_type,
            CommParticipant.left_at.is_(None),
        )
    )
    if existing.scalar_one_or_none() is not None:
        return None  # Already a participant

    p = CommParticipant(
        tenant_id=tenant_id,
        conversation_id=conversation_id,
        participant_id=pid,
        participant_type=participant_type,
        role=role,
        display_name=display_name,
    )
    db.add(p)
    await db.flush()

    # Publish event
    event_bus = get_event_bus()
    await event_bus.publish("participant.joined", {
        "conversation_id": str(conversation_id),
        "participant_id": participant_id,
        "participant_type": participant_type,
        "tenant_id": str(tenant_id),
    })

    return participant_to_response(p)


async def remove_participant(
    db: AsyncSession,
    conversation_id: uuid.UUID,
    participant_id: uuid.UUID,
) -> bool:
    """Remove a participant from a conversation (set left_at)."""
    result = await db.execute(
        select(CommParticipant).where(
            CommParticipant.conversation_id == conversation_id,
            CommParticipant.participant_id == participant_id,
            CommParticipant.participant_type == "user",
            CommParticipant.left_at.is_(None),
        )
    )
    p = result.scalar_one_or_none()
    if p is None:
        return False
    p.left_at = datetime.now(timezone.utc)
    await db.flush()

    event_bus = get_event_bus()
    await event_bus.publish("participant.left", {
        "conversation_id": str(conversation_id),
        "participant_id": str(participant_id),
    })
    return True


async def change_role(
    db: AsyncSession,
    conversation_id: uuid.UUID,
    participant_id: uuid.UUID,
    new_role: str,
) -> dict[str, Any] | None:
    """Change a participant's role."""
    result = await db.execute(
        select(CommParticipant).where(
            CommParticipant.conversation_id == conversation_id,
            CommParticipant.participant_id == participant_id,
            CommParticipant.participant_type == "user",
            CommParticipant.left_at.is_(None),
        )
    )
    p = result.scalar_one_or_none()
    if p is None:
        return None
    p.role = new_role
    await db.flush()
    return participant_to_response(p)


# ─── Messages ───


async def get_messages(
    db: AsyncSession,
    tenant_id: uuid.UUID,
    conversation_id: uuid.UUID,
    page: int = 1,
    page_size: int = 50,
    before_id: uuid.UUID | None = None,
) -> dict[str, Any]:
    """Get paginated messages for a conversation."""
    query = select(CommMessage).where(
        CommMessage.conversation_id == conversation_id,
        CommMessage.tenant_id == tenant_id,
        CommMessage.deleted_at.is_(None),
    ).order_by(CommMessage.created_at.desc())

    if before_id:
        before_msg = await db.execute(
            select(CommMessage).where(CommMessage.id == before_id)
        )
        before = before_msg.scalar_one_or_none()
        if before:
            query = query.where(CommMessage.created_at < before.created_at)

    query = query.offset((page - 1) * page_size).limit(page_size)
    result = await db.execute(query)
    messages = list(result.scalars().all())

    # Get blocks, attachments, reactions for each message
    msg_ids = [m.id for m in messages]
    blocks_map: dict[uuid.UUID, list] = {}
    attachments_map: dict[uuid.UUID, list] = {}
    reactions_map: dict[uuid.UUID, list] = {}

    if msg_ids:
        blocks_result = await db.execute(
            select(CommMessageBlock).where(
                CommMessageBlock.message_id.in_(msg_ids),
                CommMessageBlock.deleted_at.is_(None),
            ).order_by(CommMessageBlock.sort_order)
        )
        for b in blocks_result.scalars().all():
            blocks_map.setdefault(b.message_id, []).append(b)

        atts_result = await db.execute(
            select(CommMessageAttachment).where(
                CommMessageAttachment.message_id.in_(msg_ids),
                CommMessageAttachment.deleted_at.is_(None),
            )
        )
        for a in atts_result.scalars().all():
            attachments_map.setdefault(a.message_id, []).append(a)

        reactions_result = await db.execute(
            select(CommMessageReaction).where(
                CommMessageReaction.message_id.in_(msg_ids),
            )
        )
        for r in reactions_result.scalars().all():
            reactions_map.setdefault(r.message_id, []).append(r)

    items = []
    for msg in reversed(messages):  # chronological order
        items.append(
            message_to_response(
                msg,
                blocks=blocks_map.get(msg.id, []),
                attachments=attachments_map.get(msg.id, []),
                reactions=reactions_map.get(msg.id, []),
            )
        )

    # Total count
    count_result = await db.execute(
        select(func.count()).select_from(CommMessage).where(
            CommMessage.conversation_id == conversation_id,
            CommMessage.tenant_id == tenant_id,
            CommMessage.deleted_at.is_(None),
        )
    )
    total = count_result.scalar() or 0

    has_more = (page * page_size) < total

    return {"items": items, "total": total, "page": page, "has_more": has_more}


async def send_message(
    db: AsyncSession,
    tenant_id: uuid.UUID,
    conversation_id: uuid.UUID,
    sender_id: uuid.UUID | None,
    sender_type: str,
    content: str = "",
    content_format: str = "text",
    blocks: list[dict[str, Any]] | None = None,
    reply_to_id: str | None = None,
    attachments: list[dict[str, Any]] | None = None,
    metadata: dict[str, Any] | None = None,
    trigger_depth: int = 0,
) -> dict[str, Any]:
    """Send a message to a conversation and trigger participant handlers."""
    # Create message
    msg = CommMessage(
        tenant_id=tenant_id,
        conversation_id=conversation_id,
        sender_id=sender_id,
        sender_type=sender_type,
        content=content,
        content_format=content_format,
        metadata_=metadata or {},
    )
    if reply_to_id:
        try:
            msg.reply_to_id = uuid.UUID(reply_to_id)
        except ValueError:
            pass

    db.add(msg)
    await db.flush()

    # Create blocks
    if blocks:
        for i, block in enumerate(blocks):
            b = CommMessageBlock(
                tenant_id=tenant_id,
                message_id=msg.id,
                block_type=block["block_type"],
                block_data=block["block_data"],
                sort_order=i,
            )
            db.add(b)

    # Create attachments
    if attachments:
        for att in attachments:
            a = CommMessageAttachment(
                tenant_id=tenant_id,
                message_id=msg.id,
                file_id=uuid.UUID(att["file_id"]) if att.get("file_id") else None,
                file_source=att.get("file_source", "comm"),
                file_name=att.get("file_name", ""),
                file_type=att.get("file_type", "application/octet-stream"),
                file_size=att.get("file_size"),
            )
            db.add(a)

    await db.flush()

    # Update conversation last_msg
    await db.execute(
        update(CommConversation)
        .where(CommConversation.id == conversation_id)
        .values(
            last_msg_at=datetime.now(timezone.utc),
            last_msg_preview=content[:200] if content else "",
            last_msg_sender_type=sender_type,
        )
    )

    # Publish event
    event_bus = get_event_bus()
    await event_bus.publish("message.received", {
        "conversation_id": str(conversation_id),
        "message_id": str(msg.id),
        "sender_type": sender_type,
        "tenant_id": str(tenant_id),
        "content": content,
        "trigger_depth": trigger_depth,
    })

    # Trigger participant handlers (if not at max depth)
    if trigger_depth < MAX_TRIGGER_DEPTH:
        await _trigger_participants(
            db, tenant_id, conversation_id, msg, trigger_depth
        )

    # Load blocks/attachments/reactions for response
    blocks_result = await db.execute(
        select(CommMessageBlock).where(
            CommMessageBlock.message_id == msg.id,
            CommMessageBlock.deleted_at.is_(None),
        ).order_by(CommMessageBlock.sort_order)
    )
    msg_blocks = list(blocks_result.scalars().all())

    atts_result = await db.execute(
        select(CommMessageAttachment).where(
            CommMessageAttachment.message_id == msg.id,
            CommMessageAttachment.deleted_at.is_(None),
        )
    )
    msg_atts = list(atts_result.scalars().all())

    return message_to_response(msg, blocks=msg_blocks, attachments=msg_atts)


async def _trigger_participants(
    db: AsyncSession,
    tenant_id: uuid.UUID,
    conversation_id: uuid.UUID,
    message: CommMessage,
    trigger_depth: int,
) -> None:
    """Trigger participant handlers for non-user participants."""
    # Get conversation participants
    result = await db.execute(
        select(CommParticipant).where(
            CommParticipant.conversation_id == conversation_id,
            CommParticipant.left_at.is_(None),
            CommParticipant.participant_type != "user",
        )
    )
    non_user_participants = list(result.scalars().all())

    if not non_user_participants:
        return

    # Get conversation info
    conv_result = await db.execute(
        select(CommConversation).where(CommConversation.id == conversation_id)
    )
    conv = conv_result.scalar_one_or_none()
    if conv is None:
        return

    # Parse mentions
    mentions = parse_mentions(message.content)

    # Build conversation dict
    all_parts_result = await db.execute(
        select(CommParticipant).where(
            CommParticipant.conversation_id == conversation_id,
            CommParticipant.left_at.is_(None),
        )
    )
    all_parts = [participant_to_response(p) for p in all_parts_result.scalars().all()]
    conv_dict = conversation_to_response(conv, [])
    conv_dict["participants"] = all_parts

    msg_dict = message_to_response(message)
    context = {"tenant_id": str(tenant_id), "trigger_depth": trigger_depth}

    registry = get_participant_registry()

    for p in non_user_participants:
        handler = registry.get_handler(p.participant_type)
        if handler is None:
            continue

        try:
            responses = await handler.on_message_received(
                conversation_id=conversation_id,
                message=msg_dict,
                conversation=conv_dict,
                mentions=mentions,
                context=context,
            )

            if responses:
                for resp in responses:
                    await send_message(
                        db,
                        tenant_id,
                        conversation_id,
                        sender_id=None,
                        sender_type=p.participant_type,
                        content=resp.get("content", ""),
                        content_format=resp.get("content_format", "text"),
                        blocks=resp.get("blocks"),
                        metadata={
                            **(resp.get("metadata") or {}),
                            "triggered_by": str(message.id),
                            "trigger_depth": trigger_depth + 1,
                        },
                        trigger_depth=trigger_depth + 1,
                    )
        except Exception:
            logger.exception(
                f"Participant handler error for type {p.participant_type}"
            )


async def edit_message(
    db: AsyncSession,
    tenant_id: uuid.UUID,
    message_id: uuid.UUID,
    user_id: uuid.UUID,
    new_content: str,
) -> dict[str, Any] | None:
    """Edit a message, storing the old version in history."""
    result = await db.execute(
        select(CommMessage).where(
            CommMessage.id == message_id,
            CommMessage.tenant_id == tenant_id,
            CommMessage.deleted_at.is_(None),
        )
    )
    msg = result.scalar_one_or_none()
    if msg is None:
        return None

    # Get old blocks
    blocks_result = await db.execute(
        select(CommMessageBlock).where(
            CommMessageBlock.message_id == message_id,
            CommMessageBlock.deleted_at.is_(None),
        )
    )
    old_blocks = [b.block_data for b in blocks_result.scalars().all()]

    # Save edit history
    edit = CommMessageEdit(
        tenant_id=tenant_id,
        message_id=message_id,
        old_content=msg.content,
        old_blocks=old_blocks,
        edited_by=user_id,
    )
    db.add(edit)

    # Update message
    msg.content = new_content
    msg.edited_at = datetime.now(timezone.utc)
    await db.flush()

    return message_to_response(msg)


async def delete_message(
    db: AsyncSession,
    message_id: uuid.UUID,
) -> bool:
    """Soft-delete a message."""
    result = await db.execute(
        select(CommMessage).where(CommMessage.id == message_id)
    )
    msg = result.scalar_one_or_none()
    if msg is None:
        return False
    msg.deleted_at = datetime.now(timezone.utc)
    await db.flush()
    return True


# ─── Reactions ───


async def add_reaction(
    db: AsyncSession,
    tenant_id: uuid.UUID,
    message_id: uuid.UUID,
    user_id: uuid.UUID,
    emoji: str,
) -> dict[str, Any] | None:
    """Add an emoji reaction to a message."""
    existing = await db.execute(
        select(CommMessageReaction).where(
            CommMessageReaction.message_id == message_id,
            CommMessageReaction.user_id == user_id,
            CommMessageReaction.emoji == emoji,
        )
    )
    if existing.scalar_one_or_none() is not None:
        return None  # Already reacted

    r = CommMessageReaction(
        tenant_id=tenant_id,
        message_id=message_id,
        user_id=user_id,
        emoji=emoji,
    )
    db.add(r)
    await db.flush()

    event_bus = get_event_bus()
    await event_bus.publish("reaction.added", {
        "message_id": str(message_id),
        "emoji": emoji,
        "user_id": str(user_id),
    })

    return {
        "id": str(r.id),
        "message_id": str(r.message_id),
        "user_id": str(r.user_id),
        "emoji": r.emoji,
    }


async def remove_reaction(
    db: AsyncSession,
    message_id: uuid.UUID,
    user_id: uuid.UUID,
    emoji: str,
) -> bool:
    """Remove an emoji reaction."""
    result = await db.execute(
        select(CommMessageReaction).where(
            CommMessageReaction.message_id == message_id,
            CommMessageReaction.user_id == user_id,
            CommMessageReaction.emoji == emoji,
        )
    )
    r = result.scalar_one_or_none()
    if r is None:
        return False
    await db.delete(r)
    await db.flush()
    return True


# ─── Read State ───


async def mark_read(
    db: AsyncSession,
    tenant_id: uuid.UUID,
    conversation_id: uuid.UUID,
    user_id: uuid.UUID,
    last_read_msg_id: str | None = None,
) -> bool:
    """Mark conversation as read up to a message."""
    result = await db.execute(
        select(CommMessageRead).where(
            CommMessageRead.conversation_id == conversation_id,
            CommMessageRead.user_id == user_id,
        )
    )
    read = result.scalar_one_or_none()

    msg_id = uuid.UUID(last_read_msg_id) if last_read_msg_id else None

    if read is None:
        read = CommMessageRead(
            tenant_id=tenant_id,
            conversation_id=conversation_id,
            user_id=user_id,
            last_read_msg_id=msg_id,
        )
        db.add(read)
    else:
        read.last_read_msg_id = msg_id
        read.last_read_at = datetime.now(timezone.utc)

    await db.flush()
    return True


async def _get_unread_count(
    db: AsyncSession,
    tenant_id: uuid.UUID,
    conversation_id: uuid.UUID,
    user_id: uuid.UUID,
) -> int:
    """Get unread message count for a user in a conversation."""
    # Get last read message
    read_result = await db.execute(
        select(CommMessageRead).where(
            CommMessageRead.conversation_id == conversation_id,
            CommMessageRead.user_id == user_id,
        )
    )
    read = read_result.scalar_one_or_none()

    query = select(func.count()).select_from(CommMessage).where(
        CommMessage.conversation_id == conversation_id,
        CommMessage.tenant_id == tenant_id,
        CommMessage.deleted_at.is_(None),
        CommMessage.sender_type != "system",  # Don't count system messages? Or count all?
    )

    if read and read.last_read_at:
        query = query.where(CommMessage.created_at > read.last_read_at)

    result = await db.execute(query)
    return result.scalar() or 0


# ─── Plugin Room Creation ───


async def create_plugin_room(
    db: AsyncSession,
    tenant_id: uuid.UUID,
    user_id: uuid.UUID,
    plugin_name: str,
    title: str,
    participant_type: str,
    user_role: str = "member",
) -> dict[str, Any]:
    """Create a locked, pinned room for a plugin (System, Live KI, Assistent).

    The room is locked (users can't change title/participants) and pinned for the user.
    """
    # Check if room already exists for this user + plugin
    result = await db.execute(
        select(CommConversation).where(
            CommConversation.tenant_id == tenant_id,
            CommConversation.title == title,
            CommConversation.is_locked == True,
            CommConversation.locked_by == plugin_name,
            CommConversation.deleted_at.is_(None),
        ).join(CommParticipant, CommParticipant.conversation_id == CommConversation.id).where(
            CommParticipant.participant_id == user_id,
            CommParticipant.participant_type == "user",
            CommParticipant.left_at.is_(None),
        )
    )
    existing = result.scalar_one_or_none()
    if existing:
        # Already exists — return it
        return await get_conversation(db, tenant_id, existing.id, user_id) or {}

    # Create conversation
    conv = CommConversation(
        tenant_id=tenant_id,
        title=title,
        is_locked=True,
        locked_by=plugin_name,
        is_direct=False,
        created_by=None,
        created_by_type="plugin",
        metadata_={"plugin": plugin_name},
    )
    db.add(conv)
    await db.flush()

    # Add plugin as participant
    plugin_p = CommParticipant(
        tenant_id=tenant_id,
        conversation_id=conv.id,
        participant_id=None,
        participant_type=participant_type,
        role="admin",
        display_name=title,
    )
    db.add(plugin_p)

    # Add user as participant
    user_p = CommParticipant(
        tenant_id=tenant_id,
        conversation_id=conv.id,
        participant_id=user_id,
        participant_type="user",
        role=user_role,
    )
    db.add(user_p)

    # Pin for user
    pin = CommConversationPin(
        tenant_id=tenant_id,
        conversation_id=conv.id,
        user_id=user_id,
    )
    db.add(pin)

    await db.flush()

    # Publish event
    event_bus = get_event_bus()
    await event_bus.publish("conversation.created", {
        "conversation_id": str(conv.id),
        "tenant_id": str(tenant_id),
        "created_by_type": "plugin",
        "plugin_name": plugin_name,
    })

    parts = [plugin_p, user_p]
    return conversation_to_response(conv, parts, is_pinned_by_user=True)