from __future__ import annotations

from typing import Literal

from sqlalchemy import func, select
from sqlalchemy.orm import Session

from app.core.config import get_settings
from app.models.outbox import OutboxEvent
from app.schemas import N8nIntegrationStatus

settings = get_settings()


def derive_n8n_status(db: Session) -> N8nIntegrationStatus:
    counts: dict[str, int] = dict(
        db.execute(
            select(OutboxEvent.delivery_status, func.count()).group_by(OutboxEvent.delivery_status)
        ).all()  # type: ignore[arg-type]
    )
    pending = counts.get("pending", 0)
    delivering = counts.get("delivering", 0)
    failed = counts.get("failed", 0)
    succeeded = counts.get("succeeded", 0)

    latest_success_at = db.scalar(
        select(func.max(OutboxEvent.updated_at)).where(OutboxEvent.delivery_status == "succeeded")
    )
    latest_failure_at = db.scalar(
        select(func.max(OutboxEvent.updated_at)).where(OutboxEvent.delivery_status == "failed")
    )

    state: Literal["disabled", "unavailable", "degraded", "operational", "no_evidence"]
    if not settings.n8n_dispatch_enabled:
        state = "disabled"
    elif failed > 0 and succeeded == 0:
        state = "unavailable"
    elif failed > 0:
        state = "degraded"
    elif succeeded > 0 or pending > 0 or delivering > 0:
        state = "operational"
    else:
        state = "no_evidence"

    return N8nIntegrationStatus(
        configured=bool(settings.n8n_webhook_url),
        dispatch_enabled=settings.n8n_dispatch_enabled,
        state=state,
        pending=pending,
        delivering=delivering,
        failed=failed,
        succeeded=succeeded,
        latest_success_at=latest_success_at,
        latest_failure_at=latest_failure_at,
    )