function json(data, status = 200) {
  return new Response(JSON.stringify(data), {
    status,
    headers: { "content-type": "application/json; charset=UTF-8" },
  });
}

function ratio(correct, total) {
  if (!total) return 0;
  return Math.round((correct / total) * 10000) / 100;
}

export async function onRequestGet(context) {
  const db = context.env.DB;
  if (!db) {
    return json({ success: false, error: "缺少 D1 绑定 DB" }, 500);
  }

  try {
    const url = new URL(context.request.url);
    const month = (url.searchParams.get("month") || new Date().toISOString().slice(0, 7)).trim();

    const sql = `
      SELECT
        SUM(CASE WHEN actual_result IS NOT NULL AND ensemble_prediction IS NOT NULL THEN 1 ELSE 0 END) AS ens_total,
        SUM(CASE WHEN ensemble_correct = 1 THEN 1 ELSE 0 END) AS ens_correct,

        SUM(CASE WHEN actual_result IS NOT NULL AND dlinear_prediction IS NOT NULL THEN 1 ELSE 0 END) AS dl_total,
        SUM(CASE WHEN dlinear_correct = 1 THEN 1 ELSE 0 END) AS dl_correct,

        SUM(CASE WHEN actual_result IS NOT NULL AND nbeats_prediction IS NOT NULL THEN 1 ELSE 0 END) AS nb_total,
        SUM(CASE WHEN nbeats_correct = 1 THEN 1 ELSE 0 END) AS nb_correct,

        SUM(CASE WHEN actual_result IS NOT NULL AND ttm_prediction IS NOT NULL THEN 1 ELSE 0 END) AS ttm_total,
        SUM(CASE WHEN ttm_correct = 1 THEN 1 ELSE 0 END) AS ttm_correct
      FROM backup_hourly_model_predictions
      WHERE date LIKE ?
    `;

    const row = await db.prepare(sql).bind(`${month}%`).first();

    const ensTotal = Number(row?.ens_total || 0);
    const ensCorrect = Number(row?.ens_correct || 0);

    const dlTotal = Number(row?.dl_total || 0);
    const dlCorrect = Number(row?.dl_correct || 0);

    const nbTotal = Number(row?.nb_total || 0);
    const nbCorrect = Number(row?.nb_correct || 0);

    const ttmTotal = Number(row?.ttm_total || 0);
    const ttmCorrect = Number(row?.ttm_correct || 0);

    return json({
      success: true,
      month,
      data: {
        Ensemble: {
          total: ensTotal,
          correct: ensCorrect,
          incorrect: Math.max(0, ensTotal - ensCorrect),
          accuracy: ratio(ensCorrect, ensTotal),
        },
        DLinear: {
          total: dlTotal,
          correct: dlCorrect,
          incorrect: Math.max(0, dlTotal - dlCorrect),
          accuracy: ratio(dlCorrect, dlTotal),
        },
        "N-BEATS": {
          total: nbTotal,
          correct: nbCorrect,
          incorrect: Math.max(0, nbTotal - nbCorrect),
          accuracy: ratio(nbCorrect, nbTotal),
        },
        "TTM-R2": {
          total: ttmTotal,
          correct: ttmCorrect,
          incorrect: Math.max(0, ttmTotal - ttmCorrect),
          accuracy: ratio(ttmCorrect, ttmTotal),
        },
      },
    });
  } catch (error) {
    return json({ success: false, error: String(error) }, 500);
  }
}