/**
 * Helper functions related the site properties.
 *
 * @example
*     <%- is_same_link(url_a, url_b) %>
*     <%- get_domain(url) %>
*     <%- post_count() %>
*     <%- category_count() %>
*     <%- tag_count() %>
*     <%- duration() %>
*     <%- word_count(content) %>
*     <%- md5(data) %>
*     <%- meta() %>
*     <%- hexo_version() %>
 */
const URL = require('url').URL;
const moment = require('moment');
const crypto = require('crypto');

module.exports = function (hexo) {
    hexo.extend.helper.register('is_same_link', function (a, b) {
        function santize(url) {
            let paths = url.replace(/(^\w+:|^)\/\//, '').split('#')[0].split('/').filter(p => p.trim() !== '');
            if (paths.length > 0 && paths[paths.length - 1].trim() === 'index.html') {
                paths = paths.slice(0, paths.length - 1)
            }
            return paths.join('/');
        }
        return santize(this.url_for(a)) == santize(this.url_for(b));
    });

    hexo.extend.helper.register('get_domain', function (link) {
        const url = new URL(link);
        return url.hostname;
    });

    hexo.extend.helper.register('post_count', function () {
        return this.site.posts.length;
    });

    hexo.extend.helper.register('category_count', function () {
        return this.site.categories.filter(category => category.length).length;
    });

    hexo.extend.helper.register('tag_count', function () {
        return this.site.tags.filter(tag => tag.length).length;
    });

    /**
     * Export moment.duration
     */
    hexo.extend.helper.register('duration', function () {
        return moment.duration.apply(moment, arguments);
    });

    /**
     * Get the word count of a paragraph.
     */
    hexo.extend.helper.register('word_count', function (content) {
	if (typeof(content) == "undefined") {
            return 0
        }
        content = content.replace(/<\/?[a-z][^>]*>/gi, '');
        content = content.trim();
        return content ? (content.match(/[\u00ff-\uffff]|[a-zA-Z]+/g) || []).length : 0;
    });

    hexo.extend.helper.register('md5', function (data) {
        return crypto.createHash('md5').update(data).digest("hex");
    });

    hexo.extend.helper.register('meta', function () {
        function trim(str) {
            return str.trim().replace(/^"(.*)"$/, '$1').replace(/^'(.*)'$/, '$1');
        }
    
        function split(str, sep) {
            const result = [];
            let matched = null;
            while (matched = sep.exec(str)) {
                result.push(matched[0]);
            }
            return result;
        }

        const getConfig = hexo.extend.helper.get('get_config').bind(this);
        const metas = getConfig('meta', []);
        const metaDOMArray = metas.map(function (meta) {
            const entities = split(meta, /(?:[^\\;]+|\\.)+/g);
            const entityArray = entities.map(function (entity) {
                const keyValue = split(entity, /(?:[^\\=]+|\\.)+/g);
                if (keyValue.length < 2) {
                    return null;
                }
                const key = trim(keyValue[0]);
                const value = trim(keyValue[1]);
                return key + '="' + value + '"';
            }).filter(function (entity) {
                return entity;
            });
            return '<meta ' + entityArray.join(' ') + ' />';
        });
        return metaDOMArray.join('\n');
    });

    hexo.extend.helper.register('hexo_version', function (data) {
        return hexo.version;
    });
}