const common = require('../../lib/common');
const {extract, hasProvider} = require('oembed-parser');
const Promise = require('bluebird');
const request = require('../../lib/request');
const cheerio = require('cheerio');

const findUrlWithProvider = (url) => {
    let provider;

    // build up a list of URL variations to test against because the oembed
    // providers list is not always up to date with scheme or www vs non-www
    let baseUrl = url.replace(/^\/\/|^https?:\/\/(?:www\.)?/, '');
    let testUrls = [
        `http://${baseUrl}`,
        `https://${baseUrl}`,
        `http://www.${baseUrl}`,
        `https://www.${baseUrl}`
    ];

    for (let testUrl of testUrls) {
        provider = hasProvider(testUrl);
        if (provider) {
            url = testUrl;
            break;
        }
    }

    return {url, provider};
};

const getOembedUrlFromHTML = (html) => {
    return cheerio('link[type="application/json+oembed"]', html).attr('href');
};

const oembed = {
    read(options) {
        let {url} = options;

        if (!url || !url.trim()) {
            return Promise.reject(new common.errors.BadRequestError({
                message: common.i18n.t('errors.api.oembed.noUrlProvided')
            }));
        }

        function unknownProvider() {
            return Promise.reject(new common.errors.ValidationError({
                message: common.i18n.t('errors.api.oembed.unknownProvider'),
                context: url
            }));
        }

        function knownProvider(url) {
            return extract(url).catch((err) => {
                return Promise.reject(new common.errors.InternalServerError({
                    message: err.message
                }));
            });
        }

        let provider;
        ({url, provider} = findUrlWithProvider(url));

        if (provider) {
            return knownProvider(url);
        }

        // see if the URL is a redirect to cater for shortened urls
        return request(url, {
            method: 'GET',
            timeout: 2 * 1000,
            followRedirect: true
        }).then((response) => {
            if (response.url !== url) {
                ({url, provider} = findUrlWithProvider(response.url));
                return provider ? knownProvider(url) : unknownProvider();
            }

            const oembedUrl = getOembedUrlFromHTML(response.body);

            if (!oembedUrl) {
                return unknownProvider();
            }

            return request(oembedUrl, {
                method: 'GET',
                json: true
            }).then((response) => {
                return response.body;
            });
        }).catch(() => {
            return unknownProvider();
        });
    }
};

module.exports = oembed;