"""Task API routes for listing, streaming, and mutating board tasks."""

from __future__ import annotations

import asyncio
import json
from collections import deque
from collections.abc import AsyncIterator, Sequence
from contextlib import suppress
from datetime import datetime, timezone
from typing import TYPE_CHECKING, cast
from uuid import UUID

from fastapi import APIRouter, Depends, HTTPException, Query, Request, status
from sqlalchemy import asc, desc, or_
from sqlmodel import col, select
from sqlmodel.sql.expression import Select
from sse_starlette.sse import EventSourceResponse

from app.api.deps import (
    ActorContext,
    get_board_for_actor_read,
    get_board_for_user_write,
    get_task_or_404,
    require_admin_auth,
    require_admin_or_agent,
)
from app.core.time import utcnow
from app.db import crud
from app.db.pagination import paginate
from app.db.session import async_session_maker, get_session
from app.integrations.openclaw_gateway import GatewayConfig as GatewayClientConfig
from app.integrations.openclaw_gateway import (
    OpenClawGatewayError,
    ensure_session,
    send_message,
)
from app.models.activity_events import ActivityEvent
from app.models.agents import Agent
from app.models.approvals import Approval
from app.models.boards import Board
from app.models.gateways import Gateway
from app.models.task_dependencies import TaskDependency
from app.models.task_fingerprints import TaskFingerprint
from app.models.tasks import Task
from app.schemas.common import OkResponse
from app.schemas.errors import BlockedTaskError
from app.schemas.pagination import DefaultLimitOffsetPage
from app.schemas.tasks import (
    TaskCommentCreate,
    TaskCommentRead,
    TaskCreate,
    TaskRead,
    TaskUpdate,
)
from app.services.activity_log import record_activity
from app.services.mentions import extract_mentions, matches_agent_mention
from app.services.organizations import require_board_access
from app.services.task_dependencies import (
    blocked_by_dependency_ids,
    dependency_ids_by_task_id,
    dependency_status_by_id,
    dependent_task_ids,
    replace_task_dependencies,
    validate_dependency_update,
)

if TYPE_CHECKING:
    from sqlmodel.ext.asyncio.session import AsyncSession

    from app.core.auth import AuthContext

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

ALLOWED_STATUSES = {"inbox", "in_progress", "review", "done"}
TASK_EVENT_TYPES = {
    "task.created",
    "task.updated",
    "task.status_changed",
    "task.comment",
}
SSE_SEEN_MAX = 2000
TASK_SNIPPET_MAX_LEN = 500
TASK_SNIPPET_TRUNCATED_LEN = 497
BOARD_READ_DEP = Depends(get_board_for_actor_read)
ACTOR_DEP = Depends(require_admin_or_agent)
SINCE_QUERY = Query(default=None)
STATUS_QUERY = Query(default=None, alias="status")
BOARD_WRITE_DEP = Depends(get_board_for_user_write)
SESSION_DEP = Depends(get_session)
ADMIN_AUTH_DEP = Depends(require_admin_auth)
TASK_DEP = Depends(get_task_or_404)


def _comment_validation_error() -> HTTPException:
    return HTTPException(
        status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
        detail="Comment is required.",
    )


def _blocked_task_error(blocked_by_task_ids: Sequence[UUID]) -> HTTPException:
    return HTTPException(
        status_code=status.HTTP_409_CONFLICT,
        detail={
            "message": "Task is blocked by incomplete dependencies.",
            "blocked_by_task_ids": [str(value) for value in blocked_by_task_ids],
        },
    )


def _truncate_snippet(value: str) -> str:
    text = value.strip()
    if len(text) <= TASK_SNIPPET_MAX_LEN:
        return text
    return f"{text[:TASK_SNIPPET_TRUNCATED_LEN]}..."


async def has_valid_recent_comment(
    session: AsyncSession,
    task: Task,
    agent_id: UUID | None,
    since: datetime | None,
) -> bool:
    """Check whether the task has a recent non-empty comment by the agent."""
    if agent_id is None or since is None:
        return False
    statement = (
        select(ActivityEvent)
        .where(col(ActivityEvent.task_id) == task.id)
        .where(col(ActivityEvent.event_type) == "task.comment")
        .where(col(ActivityEvent.agent_id) == agent_id)
        .where(col(ActivityEvent.created_at) >= since)
        .order_by(desc(col(ActivityEvent.created_at)))
    )
    event = (await session.exec(statement)).first()
    if event is None or event.message is None:
        return False
    return bool(event.message.strip())


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(timezone.utc).replace(tzinfo=None)
    return parsed


async def _lead_was_mentioned(
    session: AsyncSession,
    task: Task,
    lead: Agent,
) -> bool:
    statement = (
        select(ActivityEvent.message)
        .where(col(ActivityEvent.task_id) == task.id)
        .where(col(ActivityEvent.event_type) == "task.comment")
        .order_by(desc(col(ActivityEvent.created_at)))
    )
    for message in await session.exec(statement):
        if not message:
            continue
        mentions = extract_mentions(message)
        if matches_agent_mention(lead, mentions):
            return True
    return False


def _lead_created_task(task: Task, lead: Agent) -> bool:
    if not task.auto_created or not task.auto_reason:
        return False
    return task.auto_reason == f"lead_agent:{lead.id}"


async def _reconcile_dependents_for_dependency_toggle(
    session: AsyncSession,
    *,
    board_id: UUID,
    dependency_task: Task,
    previous_status: str,
    actor_agent_id: UUID | None,
) -> None:
    done_toggled = (previous_status == "done") != (dependency_task.status == "done")
    if not done_toggled:
        return

    dependent_ids = await dependent_task_ids(
        session,
        board_id=board_id,
        dependency_task_id=dependency_task.id,
    )
    if not dependent_ids:
        return

    dependents = list(
        await session.exec(
            select(Task)
            .where(col(Task.board_id) == board_id)
            .where(col(Task.id).in_(dependent_ids)),
        ),
    )
    reopened = previous_status == "done" and dependency_task.status != "done"

    for dependent in dependents:
        if dependent.status == "done":
            continue
        if reopened:
            should_reset = (
                dependent.status != "inbox"
                or dependent.assigned_agent_id is not None
                or dependent.in_progress_at is not None
            )
            if should_reset:
                dependent.status = "inbox"
                dependent.assigned_agent_id = None
                dependent.in_progress_at = None
                dependent.updated_at = utcnow()
                session.add(dependent)
                record_activity(
                    session,
                    event_type="task.status_changed",
                    task_id=dependent.id,
                    message=(
                        "Task returned to inbox: dependency reopened "
                        f"({dependency_task.title})."
                    ),
                    agent_id=actor_agent_id,
                )
            else:
                record_activity(
                    session,
                    event_type="task.updated",
                    task_id=dependent.id,
                    message=f"Dependency completion changed: {dependency_task.title}.",
                    agent_id=actor_agent_id,
                )
        else:
            record_activity(
                session,
                event_type="task.updated",
                task_id=dependent.id,
                message=f"Dependency completion changed: {dependency_task.title}.",
                agent_id=actor_agent_id,
            )


async def _fetch_task_events(
    session: AsyncSession,
    board_id: UUID,
    since: datetime,
) -> list[tuple[ActivityEvent, Task | None]]:
    task_ids = list(
        await session.exec(select(Task.id).where(col(Task.board_id) == board_id)),
    )
    if not task_ids:
        return []
    statement = cast(
        Select[tuple[ActivityEvent, Task | None]],
        select(ActivityEvent, Task)
        .outerjoin(Task, col(ActivityEvent.task_id) == col(Task.id))
        .where(col(ActivityEvent.task_id).in_(task_ids))
        .where(col(ActivityEvent.event_type).in_(TASK_EVENT_TYPES))
        .where(col(ActivityEvent.created_at) >= since)
        .order_by(asc(col(ActivityEvent.created_at))),
    )
    return list(await session.exec(statement))


def _serialize_comment(event: ActivityEvent) -> dict[str, object]:
    return TaskCommentRead.model_validate(event).model_dump(mode="json")


async def _gateway_config(
    session: AsyncSession, board: Board,
) -> GatewayClientConfig | None:
    if not board.gateway_id:
        return None
    gateway = await Gateway.objects.by_id(board.gateway_id).first(session)
    if gateway is None or not gateway.url:
        return None
    return GatewayClientConfig(url=gateway.url, token=gateway.token)


async def _send_lead_task_message(
    *,
    session_key: str,
    config: GatewayClientConfig,
    message: str,
) -> None:
    await ensure_session(session_key, config=config, label="Lead Agent")
    await send_message(message, session_key=session_key, config=config, deliver=False)


async def _send_agent_task_message(
    *,
    session_key: str,
    config: GatewayClientConfig,
    agent_name: str,
    message: str,
) -> None:
    await ensure_session(session_key, config=config, label=agent_name)
    await send_message(message, session_key=session_key, config=config, deliver=False)


async def _notify_agent_on_task_assign(
    *,
    session: AsyncSession,
    board: Board,
    task: Task,
    agent: Agent,
) -> None:
    if not agent.openclaw_session_id:
        return
    config = await _gateway_config(session, board)
    if config is None:
        return
    description = _truncate_snippet(task.description or "")
    details = [
        f"Board: {board.name}",
        f"Task: {task.title}",
        f"Task ID: {task.id}",
        f"Status: {task.status}",
    ]
    if description:
        details.append(f"Description: {description}")
    message = (
        "TASK ASSIGNED\n"
        + "\n".join(details)
        + (
            "\n\nTake action: open the task and begin work. "
            "Post updates as task comments."
        )
    )
    try:
        await _send_agent_task_message(
            session_key=agent.openclaw_session_id,
            config=config,
            agent_name=agent.name,
            message=message,
        )
        record_activity(
            session,
            event_type="task.assignee_notified",
            message=f"Agent notified for assignment: {agent.name}.",
            agent_id=agent.id,
            task_id=task.id,
        )
        await session.commit()
    except OpenClawGatewayError as exc:
        record_activity(
            session,
            event_type="task.assignee_notify_failed",
            message=f"Assignee notify failed: {exc}",
            agent_id=agent.id,
            task_id=task.id,
        )
        await session.commit()


async def _notify_lead_on_task_create(
    *,
    session: AsyncSession,
    board: Board,
    task: Task,
) -> None:
    lead = (
        await Agent.objects.filter_by(board_id=board.id)
        .filter(col(Agent.is_board_lead).is_(True))
        .first(session)
    )
    if lead is None or not lead.openclaw_session_id:
        return
    config = await _gateway_config(session, board)
    if config is None:
        return
    description = _truncate_snippet(task.description or "")
    details = [
        f"Board: {board.name}",
        f"Task: {task.title}",
        f"Task ID: {task.id}",
        f"Status: {task.status}",
    ]
    if description:
        details.append(f"Description: {description}")
    message = (
        "NEW TASK ADDED\n"
        + "\n".join(details)
        + "\n\nTake action: triage, assign, or plan next steps."
    )
    try:
        await _send_lead_task_message(
            session_key=lead.openclaw_session_id,
            config=config,
            message=message,
        )
        record_activity(
            session,
            event_type="task.lead_notified",
            message=f"Lead agent notified for task: {task.title}.",
            agent_id=lead.id,
            task_id=task.id,
        )
        await session.commit()
    except OpenClawGatewayError as exc:
        record_activity(
            session,
            event_type="task.lead_notify_failed",
            message=f"Lead notify failed: {exc}",
            agent_id=lead.id,
            task_id=task.id,
        )
        await session.commit()


async def _notify_lead_on_task_unassigned(
    *,
    session: AsyncSession,
    board: Board,
    task: Task,
) -> None:
    lead = (
        await Agent.objects.filter_by(board_id=board.id)
        .filter(col(Agent.is_board_lead).is_(True))
        .first(session)
    )
    if lead is None or not lead.openclaw_session_id:
        return
    config = await _gateway_config(session, board)
    if config is None:
        return
    description = _truncate_snippet(task.description or "")
    details = [
        f"Board: {board.name}",
        f"Task: {task.title}",
        f"Task ID: {task.id}",
        f"Status: {task.status}",
    ]
    if description:
        details.append(f"Description: {description}")
    message = (
        "TASK BACK IN INBOX\n"
        + "\n".join(details)
        + "\n\nTake action: assign a new owner or adjust the plan."
    )
    try:
        await _send_lead_task_message(
            session_key=lead.openclaw_session_id,
            config=config,
            message=message,
        )
        record_activity(
            session,
            event_type="task.lead_unassigned_notified",
            message=f"Lead notified task returned to inbox: {task.title}.",
            agent_id=lead.id,
            task_id=task.id,
        )
        await session.commit()
    except OpenClawGatewayError as exc:
        record_activity(
            session,
            event_type="task.lead_unassigned_notify_failed",
            message=f"Lead notify failed: {exc}",
            agent_id=lead.id,
            task_id=task.id,
        )
        await session.commit()


@router.get("/stream")
async def stream_tasks(  # noqa: C901
    request: Request,
    board: Board = BOARD_READ_DEP,
    _actor: ActorContext = ACTOR_DEP,
    since: str | None = SINCE_QUERY,
) -> EventSourceResponse:
    """Stream task and task-comment events as SSE payloads."""
    since_dt = _parse_since(since) or utcnow()
    seen_ids: set[UUID] = set()
    seen_queue: deque[UUID] = deque()

    async def event_generator() -> AsyncIterator[dict[str, str]]:  # noqa: C901
        last_seen = since_dt
        while True:
            if await request.is_disconnected():
                break
            deps_map: dict[UUID, list[UUID]] = {}
            dep_status: dict[UUID, str] = {}
            async with async_session_maker() as session:
                rows = await _fetch_task_events(session, board.id, last_seen)
                task_ids = [
                    task.id
                    for event, task in rows
                    if task is not None and event.event_type != "task.comment"
                ]
                if task_ids:
                    deps_map = await dependency_ids_by_task_id(
                        session,
                        board_id=board.id,
                        task_ids=list({*task_ids}),
                    )
                    dep_ids: list[UUID] = []
                    for value in deps_map.values():
                        dep_ids.extend(value)
                    if dep_ids:
                        dep_status = await dependency_status_by_id(
                            session,
                            board_id=board.id,
                            dependency_ids=list({*dep_ids}),
                        )
            for event, task in rows:
                if event.id in seen_ids:
                    continue
                seen_ids.add(event.id)
                seen_queue.append(event.id)
                if len(seen_queue) > SSE_SEEN_MAX:
                    oldest = seen_queue.popleft()
                    seen_ids.discard(oldest)
                last_seen = max(event.created_at, last_seen)
                payload: dict[str, object] = {"type": event.event_type}
                if event.event_type == "task.comment":
                    payload["comment"] = _serialize_comment(event)
                elif task is None:
                    payload["task"] = None
                else:
                    dep_list = deps_map.get(task.id, [])
                    blocked_by = blocked_by_dependency_ids(
                        dependency_ids=dep_list,
                        status_by_id=dep_status,
                    )
                    if task.status == "done":
                        blocked_by = []
                    payload["task"] = (
                        TaskRead.model_validate(task, from_attributes=True)
                        .model_copy(
                            update={
                                "depends_on_task_ids": dep_list,
                                "blocked_by_task_ids": blocked_by,
                                "is_blocked": bool(blocked_by),
                            },
                        )
                        .model_dump(mode="json")
                    )
                yield {"event": "task", "data": json.dumps(payload)}
            await asyncio.sleep(2)

    return EventSourceResponse(event_generator(), ping=15)


@router.get("", response_model=DefaultLimitOffsetPage[TaskRead])
async def list_tasks(  # noqa: C901
    status_filter: str | None = STATUS_QUERY,
    assigned_agent_id: UUID | None = None,
    unassigned: bool | None = None,
    board: Board = BOARD_READ_DEP,
    session: AsyncSession = SESSION_DEP,
    _actor: ActorContext = ACTOR_DEP,
) -> DefaultLimitOffsetPage[TaskRead]:
    """List board tasks with optional status and assignment filters."""
    statement = select(Task).where(Task.board_id == board.id)
    if status_filter:
        statuses = [s.strip() for s in status_filter.split(",") if s.strip()]
        if statuses:
            if any(status_value not in ALLOWED_STATUSES for status_value in statuses):
                raise HTTPException(
                    status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
                    detail="Unsupported task status filter.",
                )
            statement = statement.where(col(Task.status).in_(statuses))
    if assigned_agent_id is not None:
        statement = statement.where(col(Task.assigned_agent_id) == assigned_agent_id)
    if unassigned:
        statement = statement.where(col(Task.assigned_agent_id).is_(None))
    statement = statement.order_by(col(Task.created_at).desc())

    async def _transform(items: Sequence[object]) -> Sequence[object]:
        tasks = cast(Sequence[Task], items)
        if not tasks:
            return []
        task_ids = [task.id for task in tasks]
        deps_map = await dependency_ids_by_task_id(
            session, board_id=board.id, task_ids=task_ids,
        )
        dep_ids: list[UUID] = []
        for value in deps_map.values():
            dep_ids.extend(value)
        dep_status = await dependency_status_by_id(
            session,
            board_id=board.id,
            dependency_ids=list({*dep_ids}),
        )

        output: list[TaskRead] = []
        for task in tasks:
            dep_list = deps_map.get(task.id, [])
            blocked_by = blocked_by_dependency_ids(
                dependency_ids=dep_list, status_by_id=dep_status,
            )
            if task.status == "done":
                blocked_by = []
            output.append(
                TaskRead.model_validate(task, from_attributes=True).model_copy(
                    update={
                        "depends_on_task_ids": dep_list,
                        "blocked_by_task_ids": blocked_by,
                        "is_blocked": bool(blocked_by),
                    },
                ),
            )
        return output

    return await paginate(session, statement, transformer=_transform)


@router.post("", response_model=TaskRead, responses={409: {"model": BlockedTaskError}})
async def create_task(
    payload: TaskCreate,
    board: Board = BOARD_WRITE_DEP,
    session: AsyncSession = SESSION_DEP,
    auth: AuthContext = ADMIN_AUTH_DEP,
) -> TaskRead:
    """Create a task and initialize dependency rows."""
    data = payload.model_dump()
    depends_on_task_ids = cast(list[UUID], data.pop("depends_on_task_ids", []) or [])

    task = Task.model_validate(data)
    task.board_id = board.id
    if task.created_by_user_id is None and auth.user is not None:
        task.created_by_user_id = auth.user.id

    normalized_deps = await validate_dependency_update(
        session,
        board_id=board.id,
        task_id=task.id,
        depends_on_task_ids=depends_on_task_ids,
    )
    dep_status = await dependency_status_by_id(
        session,
        board_id=board.id,
        dependency_ids=normalized_deps,
    )
    blocked_by = blocked_by_dependency_ids(
        dependency_ids=normalized_deps, status_by_id=dep_status,
    )
    if blocked_by and (task.assigned_agent_id is not None or task.status != "inbox"):
        raise _blocked_task_error(blocked_by)
    session.add(task)
    # Ensure the task exists in the DB before inserting dependency rows.
    await session.flush()
    for dep_id in normalized_deps:
        session.add(
            TaskDependency(
                board_id=board.id,
                task_id=task.id,
                depends_on_task_id=dep_id,
            ),
        )
    await session.commit()
    await session.refresh(task)

    record_activity(
        session,
        event_type="task.created",
        task_id=task.id,
        message=f"Task created: {task.title}.",
    )
    await session.commit()
    await _notify_lead_on_task_create(session=session, board=board, task=task)
    if task.assigned_agent_id:
        assigned_agent = await Agent.objects.by_id(task.assigned_agent_id).first(
            session,
        )
        if assigned_agent:
            await _notify_agent_on_task_assign(
                session=session,
                board=board,
                task=task,
                agent=assigned_agent,
            )
    return TaskRead.model_validate(task, from_attributes=True).model_copy(
        update={
            "depends_on_task_ids": normalized_deps,
            "blocked_by_task_ids": blocked_by,
            "is_blocked": bool(blocked_by),
        },
    )


@router.patch(
    "/{task_id}",
    response_model=TaskRead,
    responses={409: {"model": BlockedTaskError}},
)
async def update_task(  # noqa: C901, PLR0912, PLR0915
    payload: TaskUpdate,
    task: Task = TASK_DEP,
    session: AsyncSession = SESSION_DEP,
    actor: ActorContext = ACTOR_DEP,
) -> TaskRead:
    """Update task status, assignment, comment, and dependency state."""
    if task.board_id is None:
        raise HTTPException(
            status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
            detail="Task board_id is required.",
        )
    board_id = task.board_id
    if actor.actor_type == "user" and actor.user is not None:
        board = await Board.objects.by_id(board_id).first(session)
        if board is None:
            raise HTTPException(status_code=status.HTTP_404_NOT_FOUND)
        await require_board_access(session, user=actor.user, board=board, write=True)

    previous_status = task.status
    previous_assigned = task.assigned_agent_id
    updates = payload.model_dump(exclude_unset=True)
    comment = updates.pop("comment", None)
    depends_on_task_ids = cast(
        list[UUID] | None, updates.pop("depends_on_task_ids", None),
    )

    requested_fields = set(updates)
    if comment is not None:
        requested_fields.add("comment")
    if depends_on_task_ids is not None:
        requested_fields.add("depends_on_task_ids")

    async def _current_dep_ids() -> list[UUID]:
        deps_map = await dependency_ids_by_task_id(
            session, board_id=board_id, task_ids=[task.id],
        )
        return deps_map.get(task.id, [])

    async def _blocked_by(dep_ids: Sequence[UUID]) -> list[UUID]:
        if not dep_ids:
            return []
        dep_status = await dependency_status_by_id(
            session,
            board_id=board_id,
            dependency_ids=list(dep_ids),
        )
        return blocked_by_dependency_ids(
            dependency_ids=list(dep_ids), status_by_id=dep_status,
        )

    # Lead agent: delegation only.
    # Assign/unassign, resolve review, and manage dependencies.
    if actor.actor_type == "agent" and actor.agent and actor.agent.is_board_lead:
        allowed_fields = {"assigned_agent_id", "status", "depends_on_task_ids"}
        if comment is not None or not requested_fields.issubset(allowed_fields):
            raise HTTPException(
                status_code=status.HTTP_403_FORBIDDEN,
                detail=(
                    "Board leads can only assign/unassign tasks, update "
                    "dependencies, or resolve review tasks."
                ),
            )

        normalized_deps: list[UUID] | None = None
        if depends_on_task_ids is not None:
            if task.status == "done":
                raise HTTPException(
                    status_code=status.HTTP_409_CONFLICT,
                    detail=("Cannot change task dependencies after a task is done."),
                )
            normalized_deps = await replace_task_dependencies(
                session,
                board_id=board_id,
                task_id=task.id,
                depends_on_task_ids=depends_on_task_ids,
            )

        effective_deps = (
            normalized_deps if normalized_deps is not None else await _current_dep_ids()
        )
        blocked_by = await _blocked_by(effective_deps)

        # Blocked tasks cannot be assigned or moved out of inbox (unless already done).
        if blocked_by and task.status != "done":
            task.status = "inbox"
            task.assigned_agent_id = None
            task.in_progress_at = None
        else:
            if "assigned_agent_id" in updates:
                assigned_id = updates["assigned_agent_id"]
                if assigned_id:
                    agent = await Agent.objects.by_id(assigned_id).first(session)
                    if agent is None:
                        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND)
                    if agent.is_board_lead:
                        raise HTTPException(
                            status_code=status.HTTP_403_FORBIDDEN,
                            detail="Board leads cannot assign tasks to themselves.",
                        )
                    if (
                        agent.board_id
                        and task.board_id
                        and agent.board_id != task.board_id
                    ):
                        raise HTTPException(status_code=status.HTTP_409_CONFLICT)
                    task.assigned_agent_id = agent.id
                else:
                    task.assigned_agent_id = None

            if "status" in updates:
                if task.status != "review":
                    raise HTTPException(
                        status_code=status.HTTP_403_FORBIDDEN,
                        detail=(
                            "Board leads can only change status when a task is "
                            "in review."
                        ),
                    )
                if updates["status"] not in {"done", "inbox"}:
                    raise HTTPException(
                        status_code=status.HTTP_403_FORBIDDEN,
                        detail=(
                            "Board leads can only move review tasks to done "
                            "or inbox."
                        ),
                    )
                if updates["status"] == "inbox":
                    task.assigned_agent_id = None
                    task.in_progress_at = None
                task.status = updates["status"]

        task.updated_at = utcnow()
        session.add(task)
        if task.status != previous_status:
            event_type = "task.status_changed"
            message = f"Task moved to {task.status}: {task.title}."
        else:
            event_type = "task.updated"
            message = f"Task updated: {task.title}."
        record_activity(
            session,
            event_type=event_type,
            task_id=task.id,
            message=message,
            agent_id=actor.agent.id,
        )
        await _reconcile_dependents_for_dependency_toggle(
            session,
            board_id=board_id,
            dependency_task=task,
            previous_status=previous_status,
            actor_agent_id=actor.agent.id,
        )
        await session.commit()
        await session.refresh(task)

        if task.assigned_agent_id and task.assigned_agent_id != previous_assigned:
            assigned_agent = await Agent.objects.by_id(task.assigned_agent_id).first(
                session,
            )
            if assigned_agent:
                board = (
                    await Board.objects.by_id(task.board_id).first(session)
                    if task.board_id
                    else None
                )
                if board:
                    await _notify_agent_on_task_assign(
                        session=session,
                        board=board,
                        task=task,
                        agent=assigned_agent,
                    )

        dep_ids = await _current_dep_ids()
        blocked_ids = await _blocked_by(dep_ids)
        if task.status == "done":
            blocked_ids = []
        return TaskRead.model_validate(task, from_attributes=True).model_copy(
            update={
                "depends_on_task_ids": dep_ids,
                "blocked_by_task_ids": blocked_ids,
                "is_blocked": bool(blocked_ids),
            },
        )

    # Non-lead agent: can only change status + comment, and cannot start blocked tasks.
    if actor.actor_type == "agent":
        if (
            actor.agent
            and actor.agent.board_id
            and task.board_id
            and actor.agent.board_id != task.board_id
        ):
            raise HTTPException(status_code=status.HTTP_403_FORBIDDEN)
        allowed_fields = {"status", "comment"}
        if depends_on_task_ids is not None or not set(updates).issubset(allowed_fields):
            raise HTTPException(status_code=status.HTTP_403_FORBIDDEN)
        if "status" in updates:
            if updates["status"] != "inbox":
                dep_ids = await _current_dep_ids()
                blocked_ids = await _blocked_by(dep_ids)
                if blocked_ids:
                    raise _blocked_task_error(blocked_ids)
            if updates["status"] == "inbox":
                task.assigned_agent_id = None
                task.in_progress_at = None
            else:
                task.assigned_agent_id = actor.agent.id if actor.agent else None
                if updates["status"] == "in_progress":
                    task.in_progress_at = utcnow()
    else:
        # Admin user: dependencies can be edited until the task is done.
        admin_normalized_deps: list[UUID] | None = None
        if depends_on_task_ids is not None:
            if task.status == "done":
                raise HTTPException(
                    status_code=status.HTTP_409_CONFLICT,
                    detail=("Cannot change task dependencies after a task is done."),
                )
            admin_normalized_deps = await replace_task_dependencies(
                session,
                board_id=board_id,
                task_id=task.id,
                depends_on_task_ids=depends_on_task_ids,
            )

        effective_deps = (
            admin_normalized_deps
            if admin_normalized_deps is not None
            else await _current_dep_ids()
        )
        blocked_ids = await _blocked_by(effective_deps)

        target_status = cast(str, updates.get("status", task.status))
        if blocked_ids and not (task.status == "done" and target_status == "done"):
            # Blocked tasks cannot be assigned or moved out of inbox.
            # If the task is already in flight, force it back to inbox and unassign it.
            task.status = "inbox"
            task.assigned_agent_id = None
            task.in_progress_at = None
            updates["status"] = "inbox"
            updates["assigned_agent_id"] = None

        if "status" in updates:
            if updates["status"] == "inbox":
                task.assigned_agent_id = None
                task.in_progress_at = None
            elif updates["status"] == "in_progress":
                task.in_progress_at = utcnow()

        assigned_agent_id = updates.get("assigned_agent_id")
        if assigned_agent_id:
            agent = await Agent.objects.by_id(assigned_agent_id).first(session)
            if agent is None:
                raise HTTPException(status_code=status.HTTP_404_NOT_FOUND)
            if agent.board_id and task.board_id and agent.board_id != task.board_id:
                raise HTTPException(status_code=status.HTTP_409_CONFLICT)

    for key, value in updates.items():
        setattr(task, key, value)
    task.updated_at = utcnow()

    if "status" in updates and updates["status"] == "review":
        comment_text = (comment or "").strip()
        if not comment_text and not await has_valid_recent_comment(
            session,
            task,
            task.assigned_agent_id,
            task.in_progress_at,
        ):
            raise _comment_validation_error()

    session.add(task)
    await session.commit()
    await session.refresh(task)

    if comment is not None and comment.strip():
        event = ActivityEvent(
            event_type="task.comment",
            message=comment,
            task_id=task.id,
            agent_id=actor.agent.id
            if actor.actor_type == "agent" and actor.agent
            else None,
        )
        session.add(event)
        await session.commit()

    if "status" in updates and task.status != previous_status:
        event_type = "task.status_changed"
        message = f"Task moved to {task.status}: {task.title}."
    else:
        event_type = "task.updated"
        message = f"Task updated: {task.title}."
    actor_agent_id = (
        actor.agent.id if actor.actor_type == "agent" and actor.agent else None
    )
    record_activity(
        session,
        event_type=event_type,
        task_id=task.id,
        message=message,
        agent_id=actor_agent_id,
    )
    await _reconcile_dependents_for_dependency_toggle(
        session,
        board_id=board_id,
        dependency_task=task,
        previous_status=previous_status,
        actor_agent_id=actor_agent_id,
    )
    await session.commit()

    if (
        task.status == "inbox"
        and task.assigned_agent_id is None
        and (previous_status != "inbox" or previous_assigned is not None)
    ):
        board = (
            await Board.objects.by_id(task.board_id).first(session)
            if task.board_id
            else None
        )
        if board:
            await _notify_lead_on_task_unassigned(
                session=session,
                board=board,
                task=task,
            )
    if task.assigned_agent_id and task.assigned_agent_id != previous_assigned:
        if (
            actor.actor_type == "agent"
            and actor.agent
            and task.assigned_agent_id == actor.agent.id
        ):
            # Don't notify the actor about their own assignment.
            pass
        else:
            assigned_agent = await Agent.objects.by_id(task.assigned_agent_id).first(
                session,
            )
            if assigned_agent:
                board = (
                    await Board.objects.by_id(task.board_id).first(session)
                    if task.board_id
                    else None
                )
                if board:
                    await _notify_agent_on_task_assign(
                        session=session,
                        board=board,
                        task=task,
                        agent=assigned_agent,
                    )

    dep_ids = await _current_dep_ids()
    blocked_ids = await _blocked_by(dep_ids)
    if task.status == "done":
        blocked_ids = []
    return TaskRead.model_validate(task, from_attributes=True).model_copy(
        update={
            "depends_on_task_ids": dep_ids,
            "blocked_by_task_ids": blocked_ids,
            "is_blocked": bool(blocked_ids),
        },
    )


@router.delete("/{task_id}", response_model=OkResponse)
async def delete_task(
    session: AsyncSession = SESSION_DEP,
    task: Task = TASK_DEP,
    auth: AuthContext = ADMIN_AUTH_DEP,
) -> OkResponse:
    """Delete a task and related records."""
    if task.board_id is None:
        raise HTTPException(status_code=status.HTTP_422_UNPROCESSABLE_ENTITY)
    board = await Board.objects.by_id(task.board_id).first(session)
    if board is None:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND)
    if auth.user is None:
        raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED)
    await require_board_access(session, user=auth.user, board=board, write=True)
    await crud.delete_where(
        session, ActivityEvent, col(ActivityEvent.task_id) == task.id, commit=False,
    )
    await crud.delete_where(
        session, TaskFingerprint, col(TaskFingerprint.task_id) == task.id, commit=False,
    )
    await crud.delete_where(
        session, Approval, col(Approval.task_id) == task.id, commit=False,
    )
    await crud.delete_where(
        session,
        TaskDependency,
        or_(
            col(TaskDependency.task_id) == task.id,
            col(TaskDependency.depends_on_task_id) == task.id,
        ),
        commit=False,
    )
    await session.delete(task)
    await session.commit()
    return OkResponse()


@router.get(
    "/{task_id}/comments", response_model=DefaultLimitOffsetPage[TaskCommentRead],
)
async def list_task_comments(
    task: Task = TASK_DEP,
    session: AsyncSession = SESSION_DEP,
) -> DefaultLimitOffsetPage[TaskCommentRead]:
    """List comments for a task in chronological order."""
    statement = (
        select(ActivityEvent)
        .where(col(ActivityEvent.task_id) == task.id)
        .where(col(ActivityEvent.event_type) == "task.comment")
        .order_by(asc(col(ActivityEvent.created_at)))
    )
    return await paginate(session, statement)


@router.post("/{task_id}/comments", response_model=TaskCommentRead)
async def create_task_comment(  # noqa: C901, PLR0912
    payload: TaskCommentCreate,
    task: Task = TASK_DEP,
    session: AsyncSession = SESSION_DEP,
    actor: ActorContext = ACTOR_DEP,
) -> ActivityEvent:
    """Create a task comment and notify relevant agents."""
    if task.board_id is None:
        raise HTTPException(status_code=status.HTTP_422_UNPROCESSABLE_ENTITY)
    if actor.actor_type == "user" and actor.user is not None:
        board = await Board.objects.by_id(task.board_id).first(session)
        if board is None:
            raise HTTPException(status_code=status.HTTP_404_NOT_FOUND)
        await require_board_access(session, user=actor.user, board=board, write=True)
    if (
        actor.actor_type == "agent"
        and actor.agent
        and actor.agent.is_board_lead
        and task.status != "review"
        and not await _lead_was_mentioned(session, task, actor.agent)
        and not _lead_created_task(task, actor.agent)
    ):
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail=(
                "Board leads can only comment during review, when mentioned, "
                "or on tasks they created."
            ),
        )
    event = ActivityEvent(
        event_type="task.comment",
        message=payload.message,
        task_id=task.id,
        agent_id=actor.agent.id
        if actor.actor_type == "agent" and actor.agent
        else None,
    )
    session.add(event)
    await session.commit()
    await session.refresh(event)
    mention_names = extract_mentions(payload.message)
    targets: dict[UUID, Agent] = {}
    if mention_names and task.board_id:
        for agent in await Agent.objects.filter_by(board_id=task.board_id).all(session):
            if matches_agent_mention(agent, mention_names):
                targets[agent.id] = agent
    if not mention_names and task.assigned_agent_id:
        assigned_agent = await Agent.objects.by_id(task.assigned_agent_id).first(
            session,
        )
        if assigned_agent:
            targets[assigned_agent.id] = assigned_agent
    if actor.actor_type == "agent" and actor.agent:
        targets.pop(actor.agent.id, None)
    if targets:
        board = (
            await Board.objects.by_id(task.board_id).first(session)
            if task.board_id
            else None
        )
        config = await _gateway_config(session, board) if board else None
        if board and config:
            snippet = _truncate_snippet(payload.message)
            actor_name = (
                actor.agent.name
                if actor.actor_type == "agent" and actor.agent
                else "User"
            )
            for agent in targets.values():
                if not agent.openclaw_session_id:
                    continue
                mentioned = matches_agent_mention(agent, mention_names)
                header = "TASK MENTION" if mentioned else "NEW TASK COMMENT"
                action_line = (
                    "You were mentioned in this comment."
                    if mentioned
                    else "A new comment was posted on your task."
                )
                message = (
                    f"{header}\n"
                    f"Board: {board.name}\n"
                    f"Task: {task.title}\n"
                    f"Task ID: {task.id}\n"
                    f"From: {actor_name}\n\n"
                    f"{action_line}\n\n"
                    f"Comment:\n{snippet}\n\n"
                    "If you are mentioned but not assigned, reply in the task "
                    "thread but do not change task status."
                )
                with suppress(OpenClawGatewayError):
                    await _send_agent_task_message(
                        session_key=agent.openclaw_session_id,
                        config=config,
                        agent_name=agent.name,
                        message=message,
                    )
    return event