from __future__ import annotations

from datetime import datetime

from fastapi import APIRouter, Depends, HTTPException, BackgroundTasks
from sqlmodel import Session, select
from sqlalchemy.exc import IntegrityError

from app.api.utils import log_activity, get_actor_employee_id
from app.db.session import get_session
from app.models.org import Employee
from app.models.work import Task, TaskComment
from app.schemas.work import TaskCommentCreate, TaskCreate, TaskUpdate
from app.integrations.notify import NotifyContext, notify_openclaw

router = APIRouter(tags=["work"])

ALLOWED_STATUSES = {"backlog", "ready", "in_progress", "review", "done", "blocked"}


def _validate_task_assignee(session: Session, assignee_employee_id: int) -> None:
    """Enforce that only provisioned agents can be assigned tasks.

    Humans can be assigned regardless.
    Agents must be active, notify_enabled, and have openclaw_session_key.
    """

    emp = session.get(Employee, assignee_employee_id)
    if emp is None:
        raise HTTPException(status_code=400, detail="Assignee employee not found")

    if emp.employee_type == "agent":
        if emp.status != "active":
            raise HTTPException(status_code=400, detail="Cannot assign task to inactive agent")
        if not emp.notify_enabled:
            raise HTTPException(status_code=400, detail="Cannot assign task to agent with notifications disabled")
        if not emp.openclaw_session_key:
            raise HTTPException(status_code=400, detail="Cannot assign task to unprovisioned agent")


@router.get("/tasks", response_model=list[Task])
def list_tasks(project_id: int | None = None, session: Session = Depends(get_session)):
    stmt = select(Task).order_by(Task.id.asc())
    if project_id is not None:
        stmt = stmt.where(Task.project_id == project_id)
    return session.exec(stmt).all()


@router.post("/tasks", response_model=Task)
def create_task(payload: TaskCreate, background: BackgroundTasks, session: Session = Depends(get_session), actor_employee_id: int = Depends(get_actor_employee_id)):
    if payload.created_by_employee_id is None:
        payload = TaskCreate(**{**payload.model_dump(), "created_by_employee_id": actor_employee_id})

    if payload.assignee_employee_id is not None:
        _validate_task_assignee(session, payload.assignee_employee_id)

    # Default reviewer to the manager of the assignee (if not explicitly provided).
    if payload.reviewer_employee_id is None and payload.assignee_employee_id is not None:
        assignee = session.get(Employee, payload.assignee_employee_id)
        if assignee is not None and assignee.manager_id is not None:
            payload = TaskCreate(**{**payload.model_dump(), "reviewer_employee_id": assignee.manager_id})

    task = Task(**payload.model_dump())
    if task.status not in ALLOWED_STATUSES:
        raise HTTPException(status_code=400, detail="Invalid status")
    task.updated_at = datetime.utcnow()
    session.add(task)

    try:
        session.flush()
        log_activity(
            session,
            actor_employee_id=actor_employee_id,
            entity_type="task",
            entity_id=task.id,
            verb="created",
            payload={"project_id": task.project_id, "title": task.title},
        )
        session.commit()
    except IntegrityError:
        session.rollback()
        raise HTTPException(status_code=409, detail="Task create violates constraints")

    session.refresh(task)
    background.add_task(notify_openclaw, session, NotifyContext(event="task.created", actor_employee_id=actor_employee_id, task=task))
    # Explicitly return a serializable payload (guards against empty {} responses)
    return Task.model_validate(task)


@router.patch("/tasks/{task_id}", response_model=Task)
def update_task(task_id: int, payload: TaskUpdate, background: BackgroundTasks, session: Session = Depends(get_session), actor_employee_id: int = Depends(get_actor_employee_id)):
    task = session.get(Task, task_id)
    if not task:
        raise HTTPException(status_code=404, detail="Task not found")

    before = {"assignee_employee_id": task.assignee_employee_id, "reviewer_employee_id": task.reviewer_employee_id, "status": task.status}

    data = payload.model_dump(exclude_unset=True)
    if "assignee_employee_id" in data and data["assignee_employee_id"] is not None:
        _validate_task_assignee(session, data["assignee_employee_id"])
    if "status" in data and data["status"] not in ALLOWED_STATUSES:
        raise HTTPException(status_code=400, detail="Invalid status")

    for k, v in data.items():
        setattr(task, k, v)
    task.updated_at = datetime.utcnow()
    session.add(task)

    try:
        session.flush()
        log_activity(session, actor_employee_id=actor_employee_id, entity_type="task", entity_id=task.id, verb="updated", payload=data)
        session.commit()
    except IntegrityError:
        session.rollback()
        raise HTTPException(status_code=409, detail="Task update violates constraints")

    session.refresh(task)

    # notify based on meaningful changes
    changed = {}
    if before.get("assignee_employee_id") != task.assignee_employee_id:
        changed["assignee_employee_id"] = {"from": before.get("assignee_employee_id"), "to": task.assignee_employee_id}
        background.add_task(notify_openclaw, session, NotifyContext(event="task.assigned", actor_employee_id=actor_employee_id, task=task, changed_fields=changed))
    if before.get("status") != task.status:
        changed["status"] = {"from": before.get("status"), "to": task.status}
        background.add_task(notify_openclaw, session, NotifyContext(event="status.changed", actor_employee_id=actor_employee_id, task=task, changed_fields=changed))
    if not changed and data:
        background.add_task(notify_openclaw, session, NotifyContext(event="task.updated", actor_employee_id=actor_employee_id, task=task, changed_fields=data))

    return Task.model_validate(task)


@router.delete("/tasks/{task_id}")
def delete_task(task_id: int, session: Session = Depends(get_session), actor_employee_id: int = Depends(get_actor_employee_id)):
    task = session.get(Task, task_id)
    if not task:
        raise HTTPException(status_code=404, detail="Task not found")

    session.delete(task)
    try:
        session.flush()
        log_activity(session, actor_employee_id=actor_employee_id, entity_type="task", entity_id=task_id, verb="deleted")
        session.commit()
    except IntegrityError:
        session.rollback()
        raise HTTPException(status_code=409, detail="Task delete violates constraints")

    return {"ok": True}


@router.get("/task-comments", response_model=list[TaskComment])
def list_task_comments(task_id: int, session: Session = Depends(get_session)):
    return session.exec(select(TaskComment).where(TaskComment.task_id == task_id).order_by(TaskComment.id.asc())).all()


@router.post("/task-comments", response_model=TaskComment)
def create_task_comment(payload: TaskCommentCreate, background: BackgroundTasks, session: Session = Depends(get_session), actor_employee_id: int = Depends(get_actor_employee_id)):
    if payload.author_employee_id is None:
        payload = TaskCommentCreate(**{**payload.model_dump(), "author_employee_id": actor_employee_id})

    c = TaskComment(**payload.model_dump())
    session.add(c)

    try:
        session.flush()
        log_activity(session, actor_employee_id=actor_employee_id, entity_type="task", entity_id=c.task_id, verb="commented")
        session.commit()
    except IntegrityError:
        session.rollback()
        raise HTTPException(status_code=409, detail="Comment create violates constraints")

    session.refresh(c)
    task = session.get(Task, c.task_id)
    if task is not None:
        background.add_task(notify_openclaw, session, NotifyContext(event="comment.created", actor_employee_id=actor_employee_id, task=task, comment=c))
    return TaskComment.model_validate(c)