import fs from 'fs';
import util from 'util';

import * as api from './api.mjs';
import {graphToDOT} from './graph.mjs';

// Fetch the output path from command line
if (process.argv.length !== 4)
{
    console.error(`Usage: ${process.argv[1]} ROOT DEST
Explore videos linked from ROOT and write the resulting graph to DEST.`);
    process.exit(1);
}

const root = process.argv[2];
const dest = process.argv[3];

// Store metadata about each visited video
const videosNodes = Object.create(null);

// List of videos linked from each video either through a card or an
// endscreen item
const nextVideos = Object.create(null);

/**
 * Recursively explore a video and the video linked from it to fill
 * the video graph.
 *
 * @param videoId Source video identifier.
 */
const exploreVideo = async videoId =>
{
    // Make sure we don’t explore the same video twice
    if (videoId in videosNodes)
    {
        return Promise.resolve();
    }

    videosNodes[videoId] = {};

    const playerConfig = await api.getPlayerConfig(videoId);
    videosNodes[videoId] = api.getVideoMeta(playerConfig);
    nextVideos[videoId] = new Set();

    // Add links between this video and the linked ones
    api.getEndScreenVideos(playerConfig)
        .forEach(nextId => nextVideos[videoId].add(nextId));
    api.getCardVideos(playerConfig)
        .forEach(nextId => nextVideos[videoId].add(nextId));

    // Recurse on linked videos
    return Promise.all(
        Array.from(nextVideos[videoId])
            .map(id => exploreVideo(id))
    );
};

console.log('Starting to explore!');
exploreVideo(root).then(() =>
{
    fs.writeFileSync(dest, graphToDOT(videosNodes, nextVideos));
    console.log(`Finished. Result in ${dest}`);
}).catch(console.error);