from __future__ import annotations

from datetime import date, datetime, time, timedelta, timezone
from decimal import Decimal
from typing import Any, Protocol
from uuid import UUID, uuid4

from sqlalchemy import Select, func, select
from sqlalchemy.ext.asyncio import AsyncSession

from core.http.errors import ApiProblemError
from models.agent_chat_message import AgentChatMessage
from models.agent_chat_session import AgentChatSession
from models.system_agents import SystemAgents
from schemas.enums import AgentChatMessageRole
from schemas.domain.chat_message import (
    AgentChatMessage as AgentChatMessageSchema,
    AgentChatMessageMetadata,
)


class ToolResultPayloadStorage(Protocol):
    async def read_json(
        self, *, bucket: str, path: str
    ) -> dict[str, object] | None: ...


class AgentRepository:
    def __init__(
        self,
        session: AsyncSession,
        *,
        tool_result_storage: ToolResultPayloadStorage | None = None,
    ) -> None:
        self._session: AsyncSession = session
        self._tool_result_storage: ToolResultPayloadStorage | None = tool_result_storage

    async def get_session_owner(self, *, session_id: str) -> str:
        try:
            session_uuid = UUID(session_id)
        except ValueError as exc:
            raise ApiProblemError(
                status_code=422,
                code="AGENT_SESSION_ID_INVALID",
                detail="Invalid session_id",
            ) from exc

        stmt = (
            select(AgentChatSession.user_id)
            .where(AgentChatSession.id == session_uuid)
            .where(AgentChatSession.deleted_at.is_(None))
        )
        owner_id = (await self._session.execute(stmt)).scalar_one_or_none()
        if owner_id is None:
            raise ApiProblemError(
                status_code=404,
                code="AGENT_SESSION_NOT_FOUND",
                detail="Session not found",
            )
        return str(owner_id)

    async def create_session_for_user(
        self, *, user_id: str, session_id: str | None = None
    ) -> str:
        try:
            user_uuid = UUID(user_id)
        except ValueError as exc:
            raise ApiProblemError(
                status_code=422,
                code="AGENT_USER_ID_INVALID",
                detail="Invalid user_id",
            ) from exc
        session_uuid = None
        if session_id is not None:
            try:
                session_uuid = UUID(session_id)
            except ValueError as exc:
                raise ApiProblemError(
                    status_code=422,
                    code="AGENT_SESSION_ID_INVALID",
                    detail="Invalid session_id",
                ) from exc

        session = AgentChatSession(
            id=session_uuid,
            user_id=user_uuid,
        )
        self._session.add(session)
        await self._session.flush()
        await self._session.refresh(session)
        return str(session.id)

    async def commit(self) -> None:
        await self._session.commit()

    async def rollback(self) -> None:
        await self._session.rollback()

    async def delete_session(self, *, session_id: str) -> None:
        try:
            session_uuid = UUID(session_id)
        except ValueError as exc:
            raise ApiProblemError(
                status_code=422,
                code="AGENT_SESSION_ID_INVALID",
                detail="Invalid session_id",
            ) from exc
        stmt = (
            select(AgentChatSession)
            .where(AgentChatSession.id == session_uuid)
            .with_for_update()
        )
        session = (await self._session.execute(stmt)).scalar_one_or_none()
        if session is None:
            return
        if session.deleted_at is not None:
            return
        session.deleted_at = datetime.now(timezone.utc)
        await self._session.flush()

    async def persist_user_message(
        self,
        *,
        session_id: str,
        content: str,
        metadata: AgentChatMessageMetadata | None,
        visibility_mask: int,
    ) -> None:
        from models.agent_chat_message import AgentChatMessage as OrmAgentChatMessage

        try:
            session_uuid = UUID(session_id)
        except ValueError as exc:
            raise ApiProblemError(
                status_code=422,
                code="AGENT_SESSION_ID_INVALID",
                detail="Invalid session_id",
            ) from exc

        stmt = (
            select(AgentChatSession)
            .where(AgentChatSession.id == session_uuid)
            .with_for_update()
        )
        session_row = (await self._session.execute(stmt)).scalar_one_or_none()
        if session_row is None:
            raise ApiProblemError(
                status_code=404,
                code="AGENT_SESSION_NOT_FOUND",
                detail="Session not found",
            )

        next_seq = int(session_row.message_count or 0) + 1
        if not _has_title(session_row.title):
            session_title = _derive_session_title(content)
            if session_title is not None:
                session_row.title = session_title

        message = OrmAgentChatMessage(
            id=uuid4(),
            session_id=session_uuid,
            seq=next_seq,
            role=AgentChatMessageRole.USER,
            content=content,
            visibility_mask=max(int(visibility_mask), 0),
            metadata_json=metadata.model_dump(by_alias=True) if metadata else None,
        )
        self._session.add(message)
        session_row.message_count = next_seq
        session_row.last_activity_at = datetime.now(timezone.utc)
        await self._session.flush()

    async def get_assistant_message_count(self, *, session_id: str) -> int:
        try:
            session_uuid = UUID(session_id)
        except ValueError as exc:
            raise ApiProblemError(
                status_code=422,
                code="AGENT_SESSION_ID_INVALID",
                detail="Invalid session_id",
            ) from exc

        stmt = (
            select(func.count(AgentChatMessage.id))
            .where(AgentChatMessage.session_id == session_uuid)
            .where(AgentChatMessage.deleted_at.is_(None))
            .where(AgentChatMessage.role == AgentChatMessageRole.ASSISTANT)
        )
        count = (await self._session.execute(stmt)).scalar_one()
        return int(count)

    async def get_history_day(
        self,
        *,
        session_id: str,
        before: date | None,
        visibility_mask: int | None = None,
    ) -> dict[str, object] | None:
        try:
            session_uuid = UUID(session_id)
        except ValueError as exc:
            raise ApiProblemError(
                status_code=422,
                code="AGENT_SESSION_ID_INVALID",
                detail="Invalid session_id",
            ) from exc

        before_start = (
            datetime.combine(before, time.min, tzinfo=timezone.utc)
            if before is not None
            else None
        )

        target_created_at_stmt = (
            select(AgentChatMessage.created_at)
            .where(AgentChatMessage.session_id == session_uuid)
            .where(AgentChatMessage.deleted_at.is_(None))
            .order_by(AgentChatMessage.created_at.desc())
            .limit(1)
        )
        target_created_at_stmt = self._apply_visibility_filter(
            stmt=target_created_at_stmt,
            visibility_mask=visibility_mask,
        )
        if before_start is not None:
            target_created_at_stmt = target_created_at_stmt.where(
                AgentChatMessage.created_at < before_start
            )
        target_created_at = (
            await self._session.execute(target_created_at_stmt)
        ).scalar_one_or_none()

        if target_created_at is None:
            return None

        target_day = target_created_at.astimezone(timezone.utc).date()

        start = datetime.combine(target_day, time.min, tzinfo=timezone.utc)
        end = start + timedelta(days=1)
        message_stmt = (
            select(AgentChatMessage)
            .where(AgentChatMessage.session_id == session_uuid)
            .where(AgentChatMessage.deleted_at.is_(None))
            .where(AgentChatMessage.created_at >= start)
            .where(AgentChatMessage.created_at < end)
            .order_by(AgentChatMessage.seq.asc())
        )
        message_stmt = self._apply_visibility_filter(
            stmt=message_stmt,
            visibility_mask=visibility_mask,
        )
        messages = (await self._session.execute(message_stmt)).scalars().all()
        has_more_stmt = (
            select(AgentChatMessage.id)
            .where(AgentChatMessage.session_id == session_uuid)
            .where(AgentChatMessage.deleted_at.is_(None))
            .where(AgentChatMessage.created_at < start)
            .limit(1)
        )
        has_more_stmt = self._apply_visibility_filter(
            stmt=has_more_stmt,
            visibility_mask=visibility_mask,
        )
        has_more = (
            await self._session.execute(has_more_stmt)
        ).scalar_one_or_none() is not None
        snapshot_messages: list[dict[str, object]] = []
        for message in messages:
            snapshot_messages.append(
                (await self._to_chat_message_schema(message)).model_dump(
                    mode="json", by_alias=True, exclude_none=True
                )
            )
        return {
            "day": target_day.isoformat(),
            "hasMore": has_more,
            "messages": snapshot_messages,
        }

    async def get_session_messages(
        self,
        *,
        session_id: str,
        visibility_mask: int | None = None,
    ) -> list[AgentChatMessageSchema]:
        try:
            session_uuid = UUID(session_id)
        except ValueError as exc:
            raise ApiProblemError(
                status_code=422,
                code="AGENT_SESSION_ID_INVALID",
                detail="Invalid session_id",
            ) from exc

        message_stmt = (
            select(AgentChatMessage)
            .where(AgentChatMessage.session_id == session_uuid)
            .where(AgentChatMessage.deleted_at.is_(None))
            .order_by(AgentChatMessage.seq.asc())
        )
        message_stmt = self._apply_visibility_filter(
            stmt=message_stmt,
            visibility_mask=visibility_mask,
        )
        messages = (await self._session.execute(message_stmt)).scalars().all()
        snapshot_messages: list[AgentChatMessageSchema] = []
        for message in messages:
            snapshot_messages.append(await self._to_chat_message_schema(message))
        return snapshot_messages

    async def get_recent_messages_by_user_window(
        self,
        *,
        session_id: str,
        user_message_limit: int,
        visibility_mask: int | None = None,
    ) -> list[dict[str, object]]:
        try:
            session_uuid = UUID(session_id)
        except ValueError as exc:
            raise ApiProblemError(
                status_code=422,
                code="AGENT_SESSION_ID_INVALID",
                detail="Invalid session_id",
            ) from exc

        safe_user_limit = max(int(user_message_limit), 1)
        message_stmt = (
            select(AgentChatMessage)
            .where(AgentChatMessage.session_id == session_uuid)
            .where(AgentChatMessage.deleted_at.is_(None))
            .order_by(AgentChatMessage.seq.desc())
        )
        message_stmt = self._apply_visibility_filter(
            stmt=message_stmt,
            visibility_mask=visibility_mask,
        )
        messages_desc = (await self._session.execute(message_stmt)).scalars().all()
        if not messages_desc:
            return []

        selected_desc: list[AgentChatMessage] = []
        user_count = 0
        for message in messages_desc:
            selected_desc.append(message)
            role = (
                message.role.value
                if isinstance(message.role, AgentChatMessageRole)
                else str(message.role)
            )
            if role == AgentChatMessageRole.USER.value:
                user_count += 1
            if user_count >= safe_user_limit:
                break

        selected = list(reversed(selected_desc))
        snapshot_messages: list[dict[str, object]] = []
        for message in selected:
            snapshot_messages.append(
                (await self._to_chat_message_schema(message)).model_dump(
                    mode="json", by_alias=True, exclude_none=True
                )
            )
        return snapshot_messages

    async def get_latest_session_id_for_user(self, *, user_id: str) -> str | None:
        try:
            user_uuid = UUID(user_id)
        except ValueError as exc:
            raise ApiProblemError(
                status_code=422,
                code="AGENT_USER_ID_INVALID",
                detail="Invalid user_id",
            ) from exc
        stmt = (
            select(AgentChatSession.id)
            .where(AgentChatSession.user_id == user_uuid)
            .where(AgentChatSession.deleted_at.is_(None))
            .order_by(AgentChatSession.last_activity_at.desc())
            .limit(1)
        )
        latest_id = (await self._session.execute(stmt)).scalar_one_or_none()
        if latest_id is None:
            return None
        return str(latest_id)

    async def get_latest_assistant_messages_by_user_sessions(
        self,
        *,
        user_id: str,
        visibility_mask: int | None = None,
        session_limit: int = 50,
    ) -> list[AgentChatMessageSchema]:
        try:
            user_uuid = UUID(user_id)
        except ValueError as exc:
            raise ApiProblemError(
                status_code=422,
                code="AGENT_USER_ID_INVALID",
                detail="Invalid user_id",
            ) from exc

        safe_limit = max(int(session_limit), 1)
        session_stmt = (
            select(AgentChatSession.id)
            .where(AgentChatSession.user_id == user_uuid)
            .where(AgentChatSession.deleted_at.is_(None))
            .order_by(AgentChatSession.last_activity_at.desc())
            .limit(safe_limit)
        )
        session_ids = (await self._session.execute(session_stmt)).scalars().all()
        if not session_ids:
            return []

        snapshots: list[AgentChatMessageSchema] = []
        for session_id in session_ids:
            message_stmt = (
                select(AgentChatMessage)
                .where(AgentChatMessage.session_id == session_id)
                .where(AgentChatMessage.deleted_at.is_(None))
                .where(AgentChatMessage.role == AgentChatMessageRole.ASSISTANT)
                .order_by(AgentChatMessage.created_at.desc())
                .limit(20)
            )
            message_stmt = self._apply_visibility_filter(
                stmt=message_stmt,
                visibility_mask=visibility_mask,
            )
            candidate_messages = (
                (await self._session.execute(message_stmt)).scalars().all()
            )
            if not candidate_messages:
                continue
            selected_snapshot: AgentChatMessageSchema | None = None
            for message in candidate_messages:
                snapshot = await self._to_chat_message_schema(message)
                metadata = (
                    snapshot.metadata.model_dump(mode="json", exclude_none=True)
                    if snapshot.metadata is not None
                    else None
                )
                if not isinstance(metadata, dict):
                    continue
                agent_output = metadata.get("agent_output")
                if not isinstance(agent_output, dict):
                    continue
                derived = agent_output.get("divination_derived")
                if isinstance(derived, dict) and derived:
                    selected_snapshot = snapshot
                    break
            if selected_snapshot is not None:
                snapshots.append(selected_snapshot)

        snapshots.sort(
            key=lambda item: str(item.timestamp),
            reverse=True,
        )
        return snapshots

    async def get_system_agent_config(
        self, *, agent_type: str
    ) -> dict[str, object] | None:
        normalized_type = agent_type.strip().lower()
        if not normalized_type:
            return None
        stmt = select(SystemAgents).where(SystemAgents.agent_type == normalized_type)
        row = (await self._session.execute(stmt)).scalar_one_or_none()
        if row is None:
            return None
        config_payload = row.config if isinstance(row.config, dict) else {}
        return {
            "agent_type": normalized_type,
            "status": str(row.status),
            "config": config_payload,
        }

    async def _to_chat_message_schema(
        self, message: AgentChatMessage
    ) -> AgentChatMessageSchema:
        role = (
            message.role.value
            if isinstance(message.role, AgentChatMessageRole)
            else str(message.role)
        )
        payload_model = AgentChatMessageSchema.model_validate(
            {
                "id": str(message.id),
                "session_id": str(message.session_id),
                "seq": int(message.seq),
                "role": role,
                "content": message.content,
                "model_code": message.model_code,
                "tool_name": message.tool_name,
                "input_tokens": int(message.input_tokens or 0),
                "output_tokens": int(message.output_tokens or 0),
                "cost": str(message.cost if message.cost is not None else Decimal("0")),
                "latency_ms": message.latency_ms,
                "metadata": message.metadata_json,
                "timestamp": message.created_at.astimezone(timezone.utc).isoformat(),
            }
        )
        return payload_model

    def _apply_visibility_filter(
        self,
        *,
        stmt: Select[Any],
        visibility_mask: int | None,
    ) -> Select[Any]:
        if visibility_mask is None:
            return stmt
        required_mask = max(int(visibility_mask), 0)
        if required_mask == 0:
            return stmt
        return stmt.where(
            (AgentChatMessage.visibility_mask.op("&")(required_mask)) != 0
        )


def _has_title(title: object) -> bool:
    return isinstance(title, str) and bool(title.strip())


def _derive_session_title(content_text: str) -> str | None:
    normalized = " ".join(content_text.split())
    if not normalized:
        return None
    return normalized[:80]