// utils/paginate.util.js
const { Sequelize } = require('sequelize');
const { modelToAttributes } = require('./modelToAttributes');
const { excludeJsonbPaths } = require('./excludeJsonbPaths');
const { buildQuery } = require('./buildQuery.util');

const PAGE_START = 1;
const PAGE_SIZE  = 10;
const MAX_LIMIT  = 100;

function safeParseJSON(value, fallback = []) {
  try {
    const parsed = JSON.parse(value);
    return Array.isArray(parsed) ? parsed : fallback;
  } catch {
    return fallback;
  }
}

/**
 * Generates audit subquery attributes for createdBy, updatedBy, deletedBy
 *
 * @param {Object} mdl_Users   - Users model
 * @param {string} parentAlias - Sequelize model alias e.g. 'User', 'UserGroup'
 * @returns {Array}            - Sequelize attribute include array
 */
function auditInclude(mdl_Users, parentAlias = 'User') {
  const tableName = mdl_Users.getTableName();

  const fullNameSubquery = (foreignKey) =>
    Sequelize.literal(`(
      SELECT (u."personal_info"->>'name')::jsonb->>'full_name'
      FROM "${tableName}" AS u
      WHERE u."user_id" = "${parentAlias}"."${foreignKey}"
      LIMIT 1
    )`);

  return {
    attributes: [
      [fullNameSubquery('createdBy'), 'createdByName'],
      [fullNameSubquery('updatedBy'), 'updatedByName'],
      [fullNameSubquery('deletedBy'), 'deletedByName'],
    ],
  };
}

/**
 * Reusable paginated findAndCountAll
 *
 * @param {Object} model          - Sequelize model
 * @param {Object} req            - Express request
 * @param {Object} options
 * @param {string[]} options.excludeAttributes  - fields to exclude
 * @param {Object}   options.jsonbSchemas        - JSONB schema map
 * @param {string}   options.jsonbColumn         - JSONB column name e.g. "personal_info"
 * @param {Object}   options.findOptions         - extra Sequelize options (include, where, etc.)
 * @param {Object}   options.auditOptions        - { mdl_Users, parentAlias } to auto-include audit subqueries
 */
async function paginate(model, req, {
  excludeAttributes = [],
  jsonbSchemas      = {},
  jsonbColumn       = null,
  findOptions       = {},
  auditOptions      = null,   // ← { mdl_Users, parentAlias }
} = {}) {
  const page   = Math.max(PAGE_START, parseInt(req.query.page,  10) || PAGE_START);
  const limit  = Math.min(parseInt(req.query.limit, 10) || PAGE_SIZE, MAX_LIMIT);
  const offset = (page - PAGE_START) * limit;

  const filters = safeParseJSON(req.query.filters);
  const sort    = safeParseJSON(req.query.sort);

  const topLevelExclude = excludeAttributes.filter((f) => !f.includes('.'));
  const jsonbExclude    = excludeAttributes.filter((f) => f.includes('.'));
  const jsonbAttr       = jsonbColumn ? excludeJsonbPaths(jsonbColumn, jsonbExclude) : null;

  const attributes    = modelToAttributes(model, { exclude: excludeAttributes, jsonbSchemas });
  const ALLOWED_FIELDS = attributes.map((a) => a.field);

  const { where, order } = buildQuery(filters, sort, ALLOWED_FIELDS);

  // Build attribute includes: jsonb + audit subqueries + any extra from findOptions
  const baseIncludes  = jsonbAttr ? [jsonbAttr] : [];
  const auditAttrs    = auditOptions
    ? auditInclude(auditOptions.mdl_Users, auditOptions.parentAlias).attributes
    : [];
  const extraIncludes = findOptions.attributes?.include ?? [];
  const mergedAttributeIncludes = [...baseIncludes, ...auditAttrs, ...extraIncludes];

  const { attributes: _attr, ...restFindOptions } = findOptions;

  const { count, rows } = await model.findAndCountAll({
    ...restFindOptions,
    where:  { ...where, ...(restFindOptions.where ?? {}) },
    order,
    limit,
    offset,
    attributes: {
      exclude: topLevelExclude,
      include: mergedAttributeIncludes,
    },
  });

  const totalPages = Math.ceil(count / limit);

  return {
    data: rows,
    pagination: {
      page,
      limit,
      totalRecords: count,
      totalPages,
      hasPrevPage: page > PAGE_START,
      hasNextPage: page < totalPages,
    },
    attributes,
  };
}

module.exports = { paginate, auditInclude, safeParseJSON };