"""Approval listing, streaming, creation, and update endpoints."""

from __future__ import annotations

import asyncio
import json
from datetime import UTC, datetime
from typing import TYPE_CHECKING
from uuid import UUID

from fastapi import APIRouter, Depends, HTTPException, Query, Request, status
from sqlalchemy import asc, case, func, or_
from sqlmodel import col, select
from sse_starlette.sse import EventSourceResponse

from app.api.deps import (
    ActorContext,
    get_board_for_actor_read,
    get_board_for_actor_write,
    get_board_for_user_write,
    require_admin_or_agent,
)
from app.core.time import utcnow
from app.db.pagination import paginate
from app.db.session import async_session_maker, get_session
from app.models.approvals import Approval
from app.schemas.approvals import ApprovalCreate, ApprovalRead, ApprovalStatus, ApprovalUpdate
from app.schemas.pagination import DefaultLimitOffsetPage

if TYPE_CHECKING:
    from collections.abc import AsyncIterator

    from fastapi_pagination.limit_offset import LimitOffsetPage
    from sqlmodel.ext.asyncio.session import AsyncSession

    from app.models.boards import Board

router = APIRouter(prefix="/boards/{board_id}/approvals", tags=["approvals"])

TASK_ID_KEYS: tuple[str, ...] = ("task_id", "taskId", "taskID")
STREAM_POLL_SECONDS = 2
STATUS_FILTER_QUERY = Query(default=None, alias="status")
SINCE_QUERY = Query(default=None)
BOARD_READ_DEP = Depends(get_board_for_actor_read)
BOARD_WRITE_DEP = Depends(get_board_for_actor_write)
BOARD_USER_WRITE_DEP = Depends(get_board_for_user_write)
SESSION_DEP = Depends(get_session)
ACTOR_DEP = Depends(require_admin_or_agent)


def _extract_task_id(payload: dict[str, object] | None) -> UUID | None:
    if not payload:
        return None
    for key in TASK_ID_KEYS:
        value = payload.get(key)
        if isinstance(value, UUID):
            return value
        if isinstance(value, str):
            try:
                return UUID(value)
            except ValueError:
                continue
    return None


def _parse_since(value: str | None) -> datetime | None:
    if not value:
        return None
    normalized = value.strip()
    if not normalized:
        return None
    normalized = normalized.replace("Z", "+00:00")
    try:
        parsed = datetime.fromisoformat(normalized)
    except ValueError:
        return None
    if parsed.tzinfo is not None:
        return parsed.astimezone(UTC).replace(tzinfo=None)
    return parsed


def _approval_updated_at(approval: Approval) -> datetime:
    return approval.resolved_at or approval.created_at


def _serialize_approval(approval: Approval) -> dict[str, object]:
    return ApprovalRead.model_validate(
        approval,
        from_attributes=True,
    ).model_dump(mode="json")


async def _fetch_approval_events(
    session: AsyncSession,
    board_id: UUID,
    since: datetime,
) -> list[Approval]:
    statement = (
        Approval.objects.filter_by(board_id=board_id)
        .filter(
            or_(
                col(Approval.created_at) >= since,
                col(Approval.resolved_at) >= since,
            ),
        )
        .order_by(asc(col(Approval.created_at)))
    )
    return await statement.all(session)


@router.get("", response_model=DefaultLimitOffsetPage[ApprovalRead])
async def list_approvals(
    status_filter: ApprovalStatus | None = STATUS_FILTER_QUERY,
    board: Board = BOARD_READ_DEP,
    session: AsyncSession = SESSION_DEP,
    _actor: ActorContext = ACTOR_DEP,
) -> LimitOffsetPage[ApprovalRead]:
    """List approvals for a board, optionally filtering by status."""
    statement = Approval.objects.filter_by(board_id=board.id)
    if status_filter:
        statement = statement.filter(col(Approval.status) == status_filter)
    statement = statement.order_by(col(Approval.created_at).desc())
    return await paginate(session, statement.statement)


@router.get("/stream")
async def stream_approvals(
    request: Request,
    board: Board = BOARD_READ_DEP,
    _actor: ActorContext = ACTOR_DEP,
    since: str | None = SINCE_QUERY,
) -> EventSourceResponse:
    """Stream approval updates for a board using server-sent events."""
    since_dt = _parse_since(since) or utcnow()
    last_seen = since_dt

    async def event_generator() -> AsyncIterator[dict[str, str]]:
        nonlocal last_seen
        while True:
            if await request.is_disconnected():
                break
            async with async_session_maker() as session:
                approvals = await _fetch_approval_events(session, board.id, last_seen)
                pending_approvals_count = int(
                    (
                        await session.exec(
                            select(func.count(col(Approval.id)))
                            .where(col(Approval.board_id) == board.id)
                            .where(col(Approval.status) == "pending"),
                        )
                    ).one(),
                )
                task_ids = {
                    approval.task_id for approval in approvals if approval.task_id is not None
                }
                counts_by_task_id: dict[UUID, tuple[int, int]] = {}
                if task_ids:
                    rows = list(
                        await session.exec(
                            select(
                                col(Approval.task_id),
                                func.count(col(Approval.id)).label("total"),
                                func.sum(
                                    case(
                                        (col(Approval.status) == "pending", 1),
                                        else_=0,
                                    ),
                                ).label("pending"),
                            )
                            .where(col(Approval.board_id) == board.id)
                            .where(col(Approval.task_id).in_(task_ids))
                            .group_by(col(Approval.task_id)),
                        ),
                    )
                    for task_id, total, pending in rows:
                        if task_id is None:
                            continue
                        counts_by_task_id[task_id] = (
                            int(total or 0),
                            int(pending or 0),
                        )
            for approval in approvals:
                updated_at = _approval_updated_at(approval)
                last_seen = max(updated_at, last_seen)
                payload: dict[str, object] = {
                    "approval": _serialize_approval(approval),
                    "pending_approvals_count": pending_approvals_count,
                }
                if approval.task_id is not None:
                    counts = counts_by_task_id.get(approval.task_id)
                    if counts is not None:
                        total, pending = counts
                        payload["task_counts"] = {
                            "task_id": str(approval.task_id),
                            "approvals_count": total,
                            "approvals_pending_count": pending,
                        }
                yield {"event": "approval", "data": json.dumps(payload)}
            await asyncio.sleep(STREAM_POLL_SECONDS)

    return EventSourceResponse(event_generator(), ping=15)


@router.post("", response_model=ApprovalRead)
async def create_approval(
    payload: ApprovalCreate,
    board: Board = BOARD_WRITE_DEP,
    session: AsyncSession = SESSION_DEP,
    _actor: ActorContext = ACTOR_DEP,
) -> Approval:
    """Create an approval for a board."""
    task_id = payload.task_id or _extract_task_id(payload.payload)
    approval = Approval(
        board_id=board.id,
        task_id=task_id,
        agent_id=payload.agent_id,
        action_type=payload.action_type,
        payload=payload.payload,
        confidence=payload.confidence,
        rubric_scores=payload.rubric_scores,
        status=payload.status,
    )
    session.add(approval)
    await session.commit()
    await session.refresh(approval)
    return approval


@router.patch("/{approval_id}", response_model=ApprovalRead)
async def update_approval(
    approval_id: str,
    payload: ApprovalUpdate,
    board: Board = BOARD_USER_WRITE_DEP,
    session: AsyncSession = SESSION_DEP,
) -> Approval:
    """Update an approval's status and resolution timestamp."""
    approval = await Approval.objects.by_id(approval_id).first(session)
    if approval is None or approval.board_id != board.id:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND)
    updates = payload.model_dump(exclude_unset=True)
    if "status" in updates:
        approval.status = updates["status"]
        if approval.status != "pending":
            approval.resolved_at = utcnow()
    session.add(approval)
    await session.commit()
    await session.refresh(approval)
    return approval