import axios from "axios";
import { YoutubeException } from "./Exception/YoutubeException";

// Create type data for Youtube embed
export type YoutubeEmbedData = {
    title: string;
    html: string;
};

const cacheManagement: Map<string, YoutubeEmbedData> = new Map();

const getUrlFromHtml = (html: string) => {
    const div = document.createElement("div");
    div.insertAdjacentHTML("beforeend", html);
    const iframe: HTMLIFrameElement = div.firstChild as HTMLIFrameElement;
    return iframe.src;
};

const generateUrlOembed = (url: URL) => {
    const urlToFetch = new URL("https://www.youtube.com/oembed");
    urlToFetch.searchParams.set("url", url.toString());
    urlToFetch.searchParams.set("format", "json");
    return urlToFetch.toString();
};

/**
 * Resolves the /embed/ form of a YouTube link, or undefined when YouTube has none to give:
 * oembed answers 401 for a private video and 404 for an unknown one.
 */
export const getYoutubeEmbedUrl = async (url: URL): Promise<string | undefined> => {
    if (isEmbeddableYoutubeLink(url)) return url.toString();
    const urlToFetch = generateUrlOembed(url);
    let embedData = cacheManagement.get(urlToFetch);
    if (embedData === undefined) {
        try {
            embedData = (await axios.get<YoutubeEmbedData>(urlToFetch)).data;
        } catch {
            return undefined;
        }
        cacheManagement.set(urlToFetch, embedData);
    }
    return embedData.html === undefined ? undefined : getUrlFromHtml(embedData.html);
};

const YOUTUBE_HOSTS = ["youtube.com", "www.youtube.com", "m.youtube.com", "youtu.be", "www.youtube-nocookie.com"];

// Matching on the host: a substring test on the whole URL missed youtu.be short links and
// let https://example.com/?q=youtube through to the oembed endpoint.
export const isYoutubeLink = (url: URL): boolean => {
    return YOUTUBE_HOSTS.includes(url.hostname);
};

// Create function to check if the Youtbe link in parameter is embedable or not
export const isEmbeddableYoutubeLink = (url: URL): boolean => {
    return url.pathname.startsWith("/embed/");
};

// Get title from youtube link save in cache
export const getTitleFromYoutubeUrl = (url: URL): string | undefined => {
    return cacheManagement.get(generateUrlOembed(url))?.title;
};

export const validateYoutubeLink = (url: URL) => {
    if (!isYoutubeLink(url)) throw new YoutubeException();
};