from fastapi import APIRouter, Depends, HTTPException, Query
from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from ..cursors import decode, encode
from ..db import get_session
from ..models import Agent as AgentModel
from ..schemas import Agent, AgentsPage

router = APIRouter()


def _to_schema(a: AgentModel) -> Agent:
    return Agent(
        agent_id=a.agent_id,
        hostname=a.hostname,
        status=a.status,
        last_seen_at=a.last_seen_at,
        features=a.features or {"push": False, "metrics": False},
        labels=a.labels or {},
    )


@router.get("/agents", response_model=AgentsPage)
async def list_agents(
    cursor: str | None = Query(default=None, max_length=512),
    limit: int = Query(default=100, ge=1, le=500),
    session: AsyncSession = Depends(get_session),
) -> AgentsPage:
    stmt = select(AgentModel).order_by(AgentModel.agent_id)
    if cursor is not None:
        (last_id,) = decode(cursor, 1)
        stmt = stmt.where(AgentModel.agent_id > last_id)
    rows = (await session.execute(stmt.limit(limit + 1))).scalars().all()
    next_cursor = None
    if len(rows) > limit:
        rows = rows[:limit]
        next_cursor = encode(rows[-1].agent_id)
    return AgentsPage(items=[_to_schema(a) for a in rows], next_cursor=next_cursor)


@router.get("/agents/{agent_id}", response_model=Agent)
async def get_agent(agent_id: str, session: AsyncSession = Depends(get_session)) -> Agent:
    res = await session.execute(select(AgentModel).where(AgentModel.agent_id == agent_id))
    a = res.scalar_one_or_none()
    if a is None:
        raise HTTPException(status_code=404, detail="agent not found")
    return _to_schema(a)