// 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"],
};

// createdBy/updatedBy/deletedBy filter options come from getFieldValues()
// as { value: user_id, label: full_name } — the filter sheet selects by id,
// so these need an exact match against the bigint column, never the
// substring-on-text-cast path used for everything else (that path compares
// against the raw id and can never match a name-looking value).
const AUDIT_ID_FIELDS = new Set(["createdBy", "updatedBy", "deletedBy"]);

/**
 * Builds a Sequelize `where` clause from an array of filters.
 *
 * @param {Array<{ id: string, value: any }>} filters
 * @param {Set<string>} allowedFields
 * @param {string} [parentAlias] - main model's table alias (e.g. "User"). Needed
 *   to qualify Sequelize.col() references — unqualified col() refs throw
 *   "column reference is ambiguous" as soon as a query joins another table
 *   that happens to share a column name (e.g. Users + UserGroups both have
 *   is_active/createdAt/updatedAt/deletedAt).
 * @param {Set<string>} [dateFields] - fields whose picklist values are
 *   calendar days (see below) — matched by range, not substring.
 * @returns {Object} Sequelize where clause
 */
function buildWhere(filters = [], allowedFields = new Set(), parentAlias = null, dateFields = 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];

    if (AUDIT_ID_FIELDS.has(id)) {
      where.push({ [id]: { [Op.in]: values } });
      continue;
    }

    const qualifiedCol = parentAlias ? `${parentAlias}.${id}` : id;

    // Date/timestamp columns (createdAt, updatedAt, ...) — the filter sheet's
    // picklist values are whole calendar days (e.g. "2026-07-16"), but the
    // column itself is a full timestamp. Casting the timestamp to TEXT and
    // doing a substring iLike match against just the date portion is a loose
    // match: it also picks up every OTHER row whose time-of-day component
    // happens to render into digits that appear elsewhere in the cast string,
    // so a single selected day can silently pull in unrelated rows. Match by
    // an explicit [dayStart, nextDayStart) range on the real column instead —
    // exact, and immune to how the DB happens to stringify the timestamp.
    if (dateFields.has(id) && !id.startsWith("personal_info.")) {
      const conditions = values.map((v) => {
        const datePart = String(v).slice(0, 10);
        const dayStart = new Date(`${datePart}T00:00:00.000Z`);
        const dayEnd = new Date(dayStart.getTime() + 24 * 60 * 60 * 1000);

        return Sequelize.where(Sequelize.col(qualifiedCol), {
          [Op.gte]: dayStart,
          [Op.lt]: dayEnd,
        });
      });

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

    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(qualifiedCol), "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(), parentAlias = null) {
  const order = [];
  const qualifiedId = (id) => (parentAlias ? `"${parentAlias}"."${id}"` : `"${id}"`);

  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 ${qualifiedId(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
 * @param {Array} [dateFields] - fields to match by day-range instead of substring
 * @returns {{ where: Object, order: Array }}
 */
function buildQuery(filters = [], sort = [], allowedFields = [], computedFields = [], parentAlias = null, dateFields = []) {
  const fieldSet = new Set(allowedFields);
  const computedSet = new Set(computedFields);
  const orderFieldSet = new Set([...allowedFields, ...computedFields]);
  const dateFieldSet = new Set(dateFields);

  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, parentAlias, dateFieldSet),
    order: buildOrder(sort, orderFieldSet, computedSet, parentAlias),
  };
}

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