'use strict';

// Node.js pagination middleware and view helpers.

// * Author: [@niftylettuce](https://twitter.com/#!/niftylettuce)
// * Source: <https://github.com/niftylettuce/middleware paginate>

const qs = require('qs');
const url = require('url');
const _ = require('lodash');
//const util = require('util');

const href = (req) => {

    return function (prev, params) {
        const query = _.clone(req.query);

        if (typeof prev === 'object') {
            params = prev;
            prev = false;
        } else {
            prev = (typeof prev === 'boolean') ? prev : false;
            query.page = parseInt(query.page, 10);
            query.page = prev ? query.page -= 1 : query.page += 1;
            query.page = (query.page < 1) ? 1 : query.page;
        }

        // allow overriding querystring params
        // (useful for sorting and filtering)
        // another alias for `_.assign` is `_.extend`
        if (_.isObject(params))
            query = _.assign(query, params);

        return url.parse(req.originalUrl).pathname + '?' + qs.stringify(query);
    };
};


const hasNextPages = (req) => {
    return function (pageCount) {
        if (typeof pageCount !== 'number' || pageCount < 0)
            throw new Error('middleware paginate: `pageCount` is not a number >= 0');
        return req.query.page < pageCount;
    };
};


const getArrayPages = (req) => {
    return function (limit, pageCount, currentPage) {
        const maxPage = pageCount;

        // limit default is 3
        limit = limit || 3;

        if (typeof limit !== 'number' || limit < 0)
            throw new Error('middleware paginate: `limit` is not a number >= 0');

        if (typeof pageCount !== 'number' || pageCount < 0)
            throw new Error('middleware paginate: `pageCount` is not a number >= 0');

        currentPage = parseInt(currentPage, 10);
        if (Number.isNaN(currentPage) || currentPage < 0)
            throw new Error('middleware paginate: `currentPage` is not a number >= 0');

        if (limit > 0) {
            let end = Math.min(Math.max(currentPage + Math.floor(limit / 2), limit), pageCount);
            let start = Math.max(1, (currentPage < (limit - 1)) ? 1 : (end - limit) + 1);

            let pages = [];
            for (let i = start; i <= end; i++) {
                pages.push({
                    number: i,
                    url: href(req)()
                        .replace('page=' + (currentPage + 1), 'page=' + i)
                });
            }

            return pages;
        }
    }
}


const middleware = (limit = 10, maxLimit = 50) => {

    const _limit = (typeof limit === 'number') ? parseInt(limit, 10) : 10;
    const _maxLimit = (typeof maxLimit === 'number') ? parseInt(maxLimit, 10) : 50;

    return function _middleware(req, res, next) {
        req.query.page = (typeof req.query.page === 'string') ? parseInt(req.query.page, 10) || 1 : 1;
        req.query.limit = (typeof req.query.limit === 'string') ? parseInt(req.query.limit, 10) || 0 : _limit;

        if (req.query.limit > _maxLimit)
            req.query.limit = _maxLimit;

        if (req.query.page < 1)
            req.query.page = 1;

        if (req.query.limit < 0)
            req.query.limit = 0;

        //req.skip = req.offset = (req.query.page * req.query.limit) - req.query.limit;

        res.locals.paginate = res.locals.paginate ? res.locals.paginate : {};
        res.locals.paginate.page = req.query.page;
        res.locals.paginate.limit = req.query.limit;
        res.locals.paginate.href = href(req);
        res.locals.paginate.hasPreviousPages = req.query.page > 1;
        res.locals.paginate.hasNextPages = hasNextPages(req);
        res.locals.paginate.getArrayPages = getArrayPages(req);
        
        next();
    };

};

module.exports = {
    href,
    hasNextPages,
    getArrayPages,
    middleware
}