const { ObjectId } = require("mongodb");

let ensureIndexesPromise = null;

async function ensureApplicableDiagnosisIndexes(db) {
  if (!ensureIndexesPromise) {
    ensureIndexesPromise = Promise.all([
      db.collection("drug-info").createIndex({ applicableDiagnosisIds: 1 }),
      db.collection("online-drug-info").createIndex({ applicableDiagnosisIds: 1 }),
    ]).catch((error) => {
      ensureIndexesPromise = null;
      throw error;
    });
  }
  await ensureIndexesPromise;
}

async function validateApplicableDiagnosisIds(params, db) {
  if (!Object.prototype.hasOwnProperty.call(params, "applicableDiagnosisIds")) {
    return { present: false, value: [] };
  }

  const rawIds = params.applicableDiagnosisIds;
  if (!Array.isArray(rawIds)) {
    throw new Error("适应诊断格式错误");
  }

  const uniqueIds = [];
  const seen = new Set();
  for (const rawId of rawIds) {
    if (typeof rawId !== "string" || !ObjectId.isValid(rawId.trim())) {
      throw new Error("适应诊断包含无效ID");
    }
    const id = rawId.trim();
    if (!seen.has(id)) {
      seen.add(id);
      uniqueIds.push(new ObjectId(id));
    }
  }

  if (uniqueIds.length) {
    const diagnosisCount = await db.collection("hlw-diagnosis").countDocuments({
      _id: { $in: uniqueIds },
    });
    if (diagnosisCount !== uniqueIds.length) {
      throw new Error("部分适应诊断不存在，请重新选择");
    }
  }

  await ensureApplicableDiagnosisIndexes(db);
  return { present: true, value: uniqueIds };
}

module.exports = {
  ensureApplicableDiagnosisIndexes,
  validateApplicableDiagnosisIds,
};