p.js

const DEFAULT_PER_PAGE = 25;
const DEFAULT_PAGE = 1;

class Paginator {

    static describeParams(defaultPerPage = DEFAULT_PER_PAGE) {

        return {
            page: {
                type: 'number',
                // TODO: see if I can have sails validate a range on this number
                defaultsTo: DEFAULT_PAGE,
                description: '1-based, meaning lowest this can be is 1.'
            },

            perPage: {
                type: 'number',
                defaultsTo: defaultPerPage
                // TODO: see if i can have sails validate a range on this number, maybe make it enum [25, 100, 250]
            }
        };

    }

    /**
     * @param {Object} pagination
     * @param {number} pagination.page
     * @param {number} pagination.perPage
     */
    static setParams({ page=DEFAULT_PAGE, perPage=DEFAULT_PER_PAGE }) {
        const limit = perPage;
        const skip = (page - 1) * perPage;

        Paginator.NEXT_PARAMS.push({ limit, skip });
    }

    static getParams() {
        return Paginator.NEXT_PARAMS.shift() || {};
    }

    static saveParams() {
        const params = Paginator.getParams();
        const restoreParams = () => Paginator.setParams(params);

        return restoreParams;
    }

    /**
     *
     * @param {*} model
     * @param {*} [criteriaOrWhere] - must NOT include "limit" or "skip"
     * @param {Array} [populates] - array of populations to run.
     *      ie: `['masjids']` will run `await Model.find(...).populate('masjids')`.
     *      ie: `[['masjids', { sort: 'createdAt' }]]` will run `await Model.find(...).populate('masjids', { sort: 'createdAt' })`.
     *      ie: `['masjids', 'affairs']` will run two populates.
     *
     * @returns {Object} paginated
     * @returns {Object} paginated.results
     * @returns {Object} paginated.totalCount
     */
    static async find(model, criteriaOrWhere={}, populates=[]) {

        const criteria = criteriaOrWhere.hasOwnProperty('where') || criteriaOrWhere.hasOwnProperty('sort')
            ? {
                ...criteriaOrWhere,
                ...Paginator.getParams()
            } : {
                ...Paginator.getParams()
            };

        let find = model.find(criteria);
        for (const populate of populates) {
            find = find.populate(...(Array.isArray(populate) ? populate : [populate]));
        }
        const results = await find;

        return {
            results,
            totalCount: await model.count(criteria.where)
        };
    }

}

Paginator.NEXT_PARAMS = [];

module.exports = Paginator;