"""Monthly usage against plan limits, from usage_events."""

from datetime import UTC, datetime

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

from app.models import Artifact, UsageEvent, Workspace
from app.services.plans import Plan, effective_plan, plan_limit_error


def month_start(now: datetime | None = None) -> datetime:
    now = now or datetime.now(UTC)
    return now.replace(day=1, hour=0, minute=0, second=0, microsecond=0)


def month_usage(db: Session, workspace_id) -> dict:
    since = month_start()

    def total(kind: str, unit: str) -> float:
        return float(db.scalar(
            select(func.coalesce(func.sum(UsageEvent.quantity), 0)).where(
                UsageEvent.workspace_id == workspace_id, UsageEvent.kind == kind,
                UsageEvent.unit == unit, UsageEvent.created_at >= since,
            )
        ) or 0)

    kits = db.scalar(
        select(func.count()).select_from(Artifact).where(
            Artifact.workspace_id == workspace_id, Artifact.type == "launch_kit", Artifact.created_at >= since
        )
    ) or 0
    return {
        "audio_minutes": round(total("tts", "seconds") / 60, 1),
        "video_minutes": round(total("video", "seconds") / 60, 1),
        "launch_kits": kits,
        "llm_tokens": int(total("llm", "tokens")),
        "since": since.isoformat(),
    }


def usage_report(db: Session, workspace: Workspace) -> dict:
    plan = effective_plan(db, workspace)
    used = month_usage(db, workspace.id)
    return {
        "plan": plan.id,
        "used": used,
        "limits": {"audio_minutes": plan.audio_minutes, "video_minutes": plan.video_minutes,
                   "launch_kits": plan.launch_kits, "sources": plan.sources, "indexed_posts": plan.indexed_posts},
    }


def check_limit(db: Session, workspace: Workspace, kind: str, amount: float = 1) -> Plan:
    """Raise 402 plan_limit when this request would go over the monthly allowance."""
    plan = effective_plan(db, workspace)
    used = month_usage(db, workspace.id)
    limit = {"audio_minutes": plan.audio_minutes, "video_minutes": plan.video_minutes,
             "launch_kits": plan.launch_kits}[kind]
    if limit >= 0 and used[kind] + amount > limit:
        label = kind.replace("_", " ")
        raise plan_limit_error(plan, kind, f"This would go over your {limit} {label} this month.")
    return plan