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

const ACCESS_LEVEL_MIN = 0;
const ACCESS_LEVEL_MAX = 3;

function normalizeAccessLevel(value) {
  return Number.isInteger(value) && value >= ACCESS_LEVEL_MIN && value <= ACCESS_LEVEL_MAX
    ? value
    : ACCESS_LEVEL_MIN;
}

function getHighestDrugAccessLevels(drugs = []) {
  return drugs.reduce(
    (levels, drug) => ({
      antibioticLevel: Math.max(levels.antibioticLevel, normalizeAccessLevel(drug && drug.antibiotic_level)),
      tumorUse: Math.max(levels.tumorUse, normalizeAccessLevel(drug && drug.tumor_use)),
    }),
    { antibioticLevel: ACCESS_LEVEL_MIN, tumorUse: ACCESS_LEVEL_MIN }
  );
}

async function getRequiredDrugAccessLevels(db, drugs) {
  const drugIds = Array.isArray(drugs)
    ? [...new Set(drugs
      .map(drug => drug && drug._id)
      .filter(id => ObjectId.isValid(id))
      .map(id => String(id)))]
    : [];

  if (drugIds.length === 0) {
    return getHighestDrugAccessLevels([]);
  }

  const drugList = await db.collection("drug-info").find(
    { _id: { $in: drugIds.map(id => new ObjectId(id)) } },
    { projection: { antibiotic_level: 1, tumor_use: 1 } }
  ).toArray();

  return getHighestDrugAccessLevels(drugList);
}

function doctorMeetsDrugAccessLevels(doctor, requiredLevels) {
  return normalizeAccessLevel(doctor && doctor.antibiotic_level) >= normalizeAccessLevel(requiredLevels && requiredLevels.antibioticLevel)
    && normalizeAccessLevel(doctor && doctor.tumor_use) >= normalizeAccessLevel(requiredLevels && requiredLevels.tumorUse);
}

function getDoctorAccessLevelQuery(minimumAntibioticLevel, minimumTumorUse) {
  const query = {};
  const antibioticLevel = normalizeAccessLevel(minimumAntibioticLevel);
  const tumorUse = normalizeAccessLevel(minimumTumorUse);
  if (antibioticLevel > 0) {
    query.antibiotic_level = { $gte: antibioticLevel };
  }
  if (tumorUse > 0) {
    query.tumor_use = { $gte: tumorUse };
  }
  return query;
}

module.exports = {
  normalizeAccessLevel,
  getHighestDrugAccessLevels,
  getRequiredDrugAccessLevels,
  doctorMeetsDrugAccessLevels,
  getDoctorAccessLevelQuery,
};