import logging
from datetime import datetime, timedelta, timezone

from sqlalchemy import func, select, delete as sa_delete
from sqlalchemy.orm import selectinload

from fabledassistant.models import async_session
from fabledassistant.models.conversation import Conversation, Message
from fabledassistant.config import Config
from fabledassistant.services.llm import generate_completion
from fabledassistant.services.notes import create_note
from fabledassistant.services.settings import get_setting

logger = logging.getLogger(__name__)


async def create_conversation(
    user_id: int, title: str = "", model: str = "", conversation_type: str = "chat"
) -> Conversation:
    async with async_session() as session:
        conv = Conversation(user_id=user_id, title=title, model=model, conversation_type=conversation_type)
        session.add(conv)
        await session.commit()
        # Re-fetch with messages eagerly loaded to avoid lazy-load in async context
        result = await session.execute(
            select(Conversation)
            .options(selectinload(Conversation.messages))
            .where(Conversation.id == conv.id)
        )
        return result.scalars().first()


async def get_conversation(
    user_id: int, conversation_id: int
) -> Conversation | None:
    async with async_session() as session:
        result = await session.execute(
            select(Conversation)
            .options(selectinload(Conversation.messages))
            .where(
                Conversation.id == conversation_id,
                Conversation.user_id == user_id,
            )
        )
        return result.scalars().first()


async def list_conversations(
    user_id: int, limit: int = 50, offset: int = 0, conv_type: str = "chat"
) -> tuple[list[dict], int]:
    async with async_session() as session:
        total = await session.scalar(
            select(func.count(Conversation.id)).where(
                Conversation.user_id == user_id,
                Conversation.conversation_type == conv_type,
            )
        ) or 0

        # Subquery for message count — avoids loading all messages
        msg_count = (
            select(func.count(Message.id))
            .where(Message.conversation_id == Conversation.id)
            .correlate(Conversation)
            .scalar_subquery()
        )

        result = await session.execute(
            select(Conversation, msg_count.label("message_count"))
            .where(Conversation.user_id == user_id, Conversation.conversation_type == conv_type)
            .order_by(Conversation.updated_at.desc())
            .limit(limit)
            .offset(offset)
        )

        conversations = []
        for row in result.all():
            conv = row[0]
            d = {
                "id": conv.id,
                "title": conv.title,
                "model": conv.model,
                "conversation_type": conv.conversation_type,
                "briefing_date": conv.briefing_date.isoformat() if conv.briefing_date else None,
                "message_count": row[1],
                "created_at": conv.created_at.isoformat(),
                "updated_at": conv.updated_at.isoformat(),
            }
            conversations.append(d)

        return conversations, total


async def delete_conversation(user_id: int, conversation_id: int) -> bool:
    async with async_session() as session:
        result = await session.execute(
            select(Conversation).where(
                Conversation.id == conversation_id,
                Conversation.user_id == user_id,
            )
        )
        conv = result.scalars().first()
        if conv is None:
            return False
        await session.delete(conv)
        await session.commit()
        return True


async def bulk_delete_conversations(user_id: int, ids: list[int]) -> int:
    """Delete multiple conversations by ID for a user. Returns count deleted."""
    if not ids:
        return 0
    async with async_session() as session:
        result = await session.execute(
            sa_delete(Conversation)
            .where(Conversation.user_id == user_id, Conversation.id.in_(ids))
            .returning(Conversation.id)
        )
        await session.commit()
        return len(result.fetchall())


async def cleanup_old_conversations(user_id: int, days: int) -> int:
    """Delete conversations older than `days` days. Returns count deleted."""
    if days <= 0:
        return 0
    cutoff = datetime.now(timezone.utc) - timedelta(days=days)
    async with async_session() as session:
        result = await session.execute(
            sa_delete(Conversation)
            .where(
                Conversation.user_id == user_id,
                Conversation.updated_at < cutoff,
                Conversation.conversation_type != "mcp",  # preserve MCP audit trail
            )
            .returning(Conversation.id)
        )
        await session.commit()
        return len(result.fetchall())


_UNSET = object()


async def update_conversation(
    user_id: int,
    conversation_id: int,
    title: str | None = None,
    model: str | None = None,
    rag_project_id: object = _UNSET,
) -> Conversation | None:
    async with async_session() as session:
        result = await session.execute(
            select(Conversation).where(
                Conversation.id == conversation_id,
                Conversation.user_id == user_id,
            )
        )
        conv = result.scalars().first()
        if conv is None:
            return None
        if title is not None:
            conv.title = title
        if model is not None:
            conv.model = model
        if rag_project_id is not _UNSET:
            conv.rag_project_id = rag_project_id  # type: ignore[assignment]
        conv.updated_at = datetime.now(timezone.utc)
        await session.commit()
        await session.refresh(conv)
        return conv


async def update_conversation_title(
    user_id: int, conversation_id: int, title: str
) -> Conversation | None:
    return await update_conversation(user_id, conversation_id, title=title)


async def add_message(
    conversation_id: int,
    role: str,
    content: str,
    context_note_id: int | None = None,
    status: str | None = None,
) -> Message:
    async with async_session() as session:
        kwargs: dict = dict(
            conversation_id=conversation_id,
            role=role,
            content=content,
            context_note_id=context_note_id,
        )
        if status is not None:
            kwargs["status"] = status
        msg = Message(**kwargs)
        session.add(msg)
        # Touch conversation updated_at
        conv = await session.get(Conversation, conversation_id)
        if conv:
            conv.updated_at = datetime.now(timezone.utc)
        await session.commit()
        await session.refresh(msg)
        return msg


async def get_message(message_id: int) -> Message | None:
    async with async_session() as session:
        return await session.get(Message, message_id)


async def save_response_as_note(user_id: int, message_id: int) -> dict:
    """Create a note from an assistant message. Returns the new note dict."""
    msg = await get_message(message_id)
    if msg is None:
        raise ValueError("Message not found")
    if msg.role != "assistant":
        raise ValueError("Can only save assistant messages as notes")

    conv = await get_conversation(user_id, msg.conversation_id)

    # Generate title via LLM using the assistant message content
    title = ""
    if conv:
        model = conv.model or await get_setting(
            user_id, "default_model", Config.OLLAMA_MODEL
        )
        try:
            prompt_messages = [
                {
                    "role": "system",
                    "content": (
                        "Generate a concise 3-8 word title for a note based on "
                        "this content. Reply with ONLY the title, no quotes or "
                        "punctuation."
                    ),
                },
                {"role": "user", "content": msg.content[:2000]},
            ]
            title = await generate_completion(prompt_messages, model)
            title = title.strip().strip('"\'').strip()[:100]
        except Exception:
            logger.warning("Failed to generate note title, using fallback", exc_info=True)

    if not title:
        lines = msg.content.strip().split("\n", 1)
        title = lines[0].strip().lstrip("# ")[:100]

    note = await create_note(user_id, title=title, body=msg.content, tags=["chat"])
    return note.to_dict()


async def summarize_conversation_as_note(
    user_id: int, conversation_id: int, model: str
) -> dict:
    """Summarize a conversation using the LLM and save as a note."""
    conv = await get_conversation(user_id, conversation_id)
    if conv is None:
        raise ValueError("Conversation not found")

    # Build the conversation text
    conv_text = []
    for msg in conv.messages:
        if msg.role == "system":
            continue
        label = "User" if msg.role == "user" else "Assistant"
        conv_text.append(f"{label}: {msg.content}")

    prompt_messages = [
        {
            "role": "system",
            "content": (
                "Summarize the following conversation into a concise note. "
                "Include key points, decisions, and any action items. "
                "Format the summary in markdown."
            ),
        },
        {"role": "user", "content": "\n\n".join(conv_text)},
    ]

    logger.info("Summarizing conversation %d with model %s", conversation_id, model)
    summary = await generate_completion(prompt_messages, model)

    title = conv.title or "Conversation Summary"
    title = f"Summary: {title}"

    note = await create_note(user_id, title=title, body=summary, tags=["chat"])
    return note.to_dict()