// utils/queryBuilder.js
const { Sequelize, Op } = require("sequelize");

// ─── Custom sort order for ENUM fields ────────────────────────────────────────
const ENUM_SORT_ORDER = {
  acc_type: ["admin", "staff", "user"],
  reg_type: ["system", "google"],
};

/**
 * Builds a Sequelize `where` clause from an array of filters.
 *
 * @param {Array<{ id: string, value: any }>} filters
 * @returns {Object} Sequelize where clause
 */
function buildWhere(filters = [], allowedFields = new Set()) {
  const where = [];

  for (const { id, value } of filters) {
    if (!id || value === undefined || value === null || value === "") continue;
    if (allowedFields.size && !allowedFields.has(id)) continue;

    const values = Array.isArray(value) ? value : [value];

    const conditions = values.map((v) =>
      id.startsWith("personal_info.")
        ? Sequelize.where(
            Sequelize.json(`personal_info.${id.replace("personal_info.", "")}`),
            { [Op.iLike]: `%${v}%` }
          )
        : Sequelize.where(
            Sequelize.cast(Sequelize.col(id), "TEXT"),
            { [Op.iLike]: `%${v}%` }
          )
    );

    where.push({ [Op.or]: conditions });
  }

  return where.length ? { [Op.and]: where } : {};
}

/**
 * Builds a Sequelize `order` clause from an array of sort descriptors.
 * Falls back to [["createdAt", "DESC"]] if no valid sort entries.
 *
 * @param {Array<{ id: string, desc: boolean }>} sort
 * @returns {Array} Sequelize order clause
 */
function buildOrder(sort = [], allowedFields = new Set(), computedFields = new Set()) {
  const order = [];

  for (const { id, desc } of sort) {
    if (!id) continue;
    if (allowedFields.size && !allowedFields.has(id)) continue;

    // ─── Computed (subquery/literal) columns — order by the unqualified
    //     SELECT alias, since they aren't real columns on the model's table ──
    if (computedFields.has(id)) {
      order.push([Sequelize.literal(`"${id}"`), desc ? "DESC" : "ASC"]);
      continue;
    }

    // ─── ENUM fields — use CASE for custom sort order ─────────────────────
    if (ENUM_SORT_ORDER[id]) {
      const sequence = desc
        ? [...ENUM_SORT_ORDER[id]].reverse()
        :   ENUM_SORT_ORDER[id];

      const caseExpr = sequence
        .map((val, i) => `WHEN '${val}' THEN ${i}`)
        .join(" ");

      order.push([Sequelize.literal(`CASE "${id}" ${caseExpr} END`)]);
      continue;
    }

    // ─── JSONB dot-notation fields ─────────────────────────────────────────
    if (id.startsWith("personal_info.")) {
      order.push([Sequelize.json(id), desc ? "DESC" : "ASC"]);
      continue;
    }

    // ─── Regular fields ───────────────────────────────────────────────────
    order.push([id, desc ? "DESC" : "ASC"]);
  }

  return order.length ? order : [["createdAt", "DESC"]];
}

/**
 * Convenience wrapper — returns both where and order in one call.
 *
 * @param {Array} filters
 * @param {Array} sort
 * @returns {{ where: Object, order: Array }}
 */
function buildQuery(filters = [], sort = [], allowedFields = [], computedFields = []) {
  const fieldSet = new Set(allowedFields);
  const computedSet = new Set(computedFields);
  const orderFieldSet = new Set([...allowedFields, ...computedFields]);

  return {
    // Computed (subquery/literal) columns aren't real table columns — filtering
    // via Sequelize.col() would error, so only allow them in ORDER BY, not WHERE.
    where: buildWhere(filters, fieldSet),
    order: buildOrder(sort, orderFieldSet, computedSet),
  };
}

module.exports = { buildWhere, buildOrder, buildQuery };