"""Task queue for intelligent evaluations (任务队列).

Platform scans executing evals every minute and enqueues tasks for
OpenClaw workers to pick up. Tasks are prioritized by:
1. Time slot due (时段到期)
2. Session deficit (欠账多)
3. Wait time (等待时间长)
"""

from datetime import timedelta
from typing import Optional

from sqlmodel import Session, select, update

from agenteval.intelligent_eval.models import IntelligentEvalStatus
from agenteval.storage.db import (
    IntelligentEvalDB,
    IntelligentEvalTaskQueueDB,
    utc_now,
)


def _is_slot_due(slot: dict, current_offset: timedelta) -> bool:
    """Thin wrapper delegating to :func:`agenteval.intelligent_eval.domain.is_slot_due`."""
    from agenteval.intelligent_eval.domain import is_slot_due as _impl
    return _impl(slot, current_offset)


def _calculate_session_deficit(eval_db: IntelligentEvalDB, session: Session) -> int:
    """Thin wrapper delegating to :func:`agenteval.intelligent_eval.domain.calculate_session_deficit`."""
    from agenteval.intelligent_eval.domain import calculate_session_deficit as _impl
    return _impl(eval_db, session)


def _calculate_priority(eval_db: IntelligentEvalDB, session: Session) -> int:
    """Thin wrapper delegating to :func:`agenteval.intelligent_eval.domain.calculate_priority`."""
    from agenteval.intelligent_eval.domain import calculate_priority as _impl
    return _impl(eval_db, session)


def _get_attention_reason(eval_db: IntelligentEvalDB, session: Session) -> Optional[str]:
    """Thin wrapper delegating to :func:`agenteval.intelligent_eval.domain.get_attention_reason`."""
    from agenteval.intelligent_eval.domain import get_attention_reason as _impl
    return _impl(eval_db, session)


def _has_pending_task(eval_id: str, session: Session) -> bool:
    """Check if eval already has a pending task (去重)."""
    existing = session.exec(
        select(IntelligentEvalTaskQueueDB).where(
            IntelligentEvalTaskQueueDB.eval_id == eval_id,
            IntelligentEvalTaskQueueDB.status == "pending",
        )
    ).first()
    return existing is not None


def scan_and_enqueue_tasks(session: Session) -> int:
    """Scan all executing evals and enqueue tasks.

    Returns:
        Number of tasks enqueued
    """
    # Get all executing evals
    evals = session.exec(
        select(IntelligentEvalDB).where(IntelligentEvalDB.status == IntelligentEvalStatus.EXECUTING.value)
    ).all()

    enqueued = 0

    for eval_db in evals:
        # Check if eval needs attention
        reason = _get_attention_reason(eval_db, session)
        if reason is None:
            continue

        # Check if already has pending task (去重)
        if _has_pending_task(eval_db.id, session):
            continue

        # Calculate priority
        priority = _calculate_priority(eval_db, session)

        # Create task
        task = IntelligentEvalTaskQueueDB(
            eval_id=eval_db.id,
            status="pending",
            priority=priority,
            reason=reason,
            created_at=utc_now(),
            updated_at=utc_now(),
        )
        session.add(task)
        enqueued += 1

    session.commit()
    return enqueued


def get_next_task(session: Session) -> Optional[IntelligentEvalTaskQueueDB]:
    """Get next pending task (highest priority).

    Returns:
        Task with lowest priority value (highest priority), or None
    """
    task = session.exec(
        select(IntelligentEvalTaskQueueDB)
        .where(IntelligentEvalTaskQueueDB.status == "pending")
        .order_by(IntelligentEvalTaskQueueDB.priority, IntelligentEvalTaskQueueDB.created_at)
        .limit(1)
    ).first()
    return task


def assign_task(task_id: str, cron_id: str, session: Session) -> bool:
    """Atomically assign a pending task to a cron (CAS on status).

    P1 真问题修复（§6.1）: use ``UPDATE ... WHERE status='pending'`` and decide
    on ``rowcount`` so two concurrent workers cannot both claim the same task.
    The previous read-check-write left a race because SQLite + two sessions
    could each read ``status=pending`` and each commit.
    """
    stmt = (
        update(IntelligentEvalTaskQueueDB)
        .where(IntelligentEvalTaskQueueDB.id == task_id)
        .where(IntelligentEvalTaskQueueDB.status == "pending")
        .values(
            status="assigned",
            assigned_cron_id=cron_id,
            assigned_at=utc_now(),
            updated_at=utc_now(),
        )
    )
    result = session.exec(stmt)
    session.commit()
    return result.rowcount > 0


def complete_task(task_id: str, success: bool, error: Optional[str], session: Session) -> bool:
    """Atomically mark a task as completed/failed (CAS on status).

    P1 真问题修复（§6.1 审计）: guard with ``status='assigned'`` so a
    double-complete from worker + stuck-handler leaves the DB in one state.
    """
    terminal = "completed" if success else "failed"
    stmt = (
        update(IntelligentEvalTaskQueueDB)
        .where(IntelligentEvalTaskQueueDB.id == task_id)
        .where(IntelligentEvalTaskQueueDB.status == "assigned")
        .values(
            status=terminal,
            completed_at=utc_now(),
            error=error,
            updated_at=utc_now(),
        )
    )
    result = session.exec(stmt)
    session.commit()
    return result.rowcount > 0

def requeue_stuck_task(eval_id: str, cron_id: str, session: Session) -> bool:
    """Mark the cron-stuck task as failed and enqueue a retry task.

    P1 deepening (S4): the stuck-task settlement logic that previously lived
    inside ``cron_pool.handle_stuck_cron`` (with a runtime import) now lives
    here as a first-class operation. ``cron_pool`` only calls this.

    Returns:
        True if a stuck task was found and requeued, False otherwise.
    """
    from agenteval.storage.db import IntelligentEvalTaskQueueDB

    task = session.exec(
        select(IntelligentEvalTaskQueueDB).where(
            IntelligentEvalTaskQueueDB.eval_id == eval_id,
            IntelligentEvalTaskQueueDB.status == "assigned",
            IntelligentEvalTaskQueueDB.assigned_cron_id == cron_id,
        )
    ).first()
    if task is None:
        return False

    complete_task(task.id, False, "Cron stuck", session)

    new_task = IntelligentEvalTaskQueueDB(
        eval_id=eval_id,
        status="pending",
        priority=1,
        reason="cron_stuck_retry",
    )
    session.add(new_task)
    return True


# ---------------------------------------------------------------------------
# P3 deepening (S2) — get_next_task with embedded eval info
# ---------------------------------------------------------------------------


def get_next_task_with_eval(session: Session) -> Optional[dict]:
    """Return the next pending task with its eval details, or None.

    P3 deepening (S2): the eval-loading + dict-building that previously lived in
    ``web/routers/intelligent_evals.py::get_next_task`` now lives here.
    """
    task = get_next_task(session)
    if task is None:
        return None

    eval_db = session.get(IntelligentEvalDB, task.eval_id)
    if eval_db is None:
        return None

    return {
        "task": {
            "id": task.id,
            "eval_id": task.eval_id,
            "priority": task.priority,
            "reason": task.reason,
            "eval": {
                "id": eval_db.id,
                "name": eval_db.name,
                "status": eval_db.status,
                "plan": eval_db.get_plan(),
                "started_at": eval_db.started_at.isoformat() if eval_db.started_at else None,
            },
        },
    }