Turn into an Express server

1 year ago · bc93a2788e
15 changed files with 792 additions and 149 deletions
--- a/app.mjs
+++ b/app.mjs
@ -0,0 +1,18 @@
+import express from 'express';
+import path from 'path';
+import cookieParser from 'cookie-parser';
+import logger from 'morgan';
+import { fileURLToPath } from 'url';
+
+const thisdir = path.dirname(fileURLToPath(import.meta.url));
+const app = express();
+export default app;
+
+app.use(logger('dev'));
+app.use(express.json());
+app.use(express.urlencoded({ extended: false }));
+app.use(cookieParser());
+app.use(express.static(path.join(thisdir, 'public')));
+
+import mazes from './routes/mazes.mjs';
+app.use('/mazes', mazes);
--- a/bin/www.mjs
+++ b/bin/www.mjs
@ -0,0 +1,69 @@
+import http from 'http';
+import debug from 'debug';
+
+const log = debug('youtube-maze:server');
+
+/**
+ * Normalize a port into a number, string, or false.
+ */
+const normalizePort = val =>
+{
+    const port = parseInt(val, 10);
+
+    // Named pipe
+    if (isNaN(port))
+    {
+        return val;
+    }
+
+    // Port number
+    if (port >= 0)
+    {
+        return port;
+    }
+
+    return false;
+};
+
+// Instantiate app
+import app from '../app.mjs';
+const port = normalizePort(process.env.PORT || '3000');
+app.set('port', port);
+
+// Create HTTP server
+const server = http.createServer(app);
+server.listen(port);
+server.keepAliveTimeout = 60000;
+
+server.on('error', error => {
+    if (error.syscall !== 'listen')
+    {
+        throw error;
+    }
+
+    const bind = typeof port === 'string' ? `Pipe ${port}` : `Port ${port}`;
+
+    // Handle specific listen errors with friendly messages
+    switch (error.code)
+    {
+        case 'EACCES':
+            console.error(`${bind} requires elevated privileges`);
+            process.exit(1);
+
+        case 'EADDRINUSE':
+            console.error(`${bind} is already in use`);
+            process.exit(1);
+
+        default:
+            throw error;
+    }
+});
+
+server.on('listening', () => {
+    const addr = server.address();
+    const bind = typeof addr === 'string'
+        ? `pipe ${addr}`
+        : `port ${addr.port}`;
+
+    log(`Listening on ${bind}`);
+});
--- a/explore/graph.mjs
+++ b/explore/graph.mjs
@ -1,44 +0,0 @@
-'use strict';
-
-import util from 'util';
-
-const YOUTUBE_WATCH = 'https://youtu.be/%s';
-const GRAPH_NODE = '    "%s" [label="%s", URL="%s", fontcolor=blue]';
-const GRAPH_LINK = '    "%s" -> "%s"';
-
-/**
- * Escape double quotes in a string.
- */
-const escapeQuotes = str => str.replace(/"/g, '\\"');
-
-/**
- * Convert a graph of videos to the DOT format.
- *
- * @param nodes Nodes of the graph.
- * @param next For each node, list of next neighbors.
- * @param [title=identity] Function giving the name of each node.
- * @param [url=none] Function given the URL of each node, or an empty string
- * if a node has no URL.
- * @return DOT representation of the graph.
- */
-export const graphToDOT = (nodes, next) =>
-{
-    // Convert nodes
-    const nodesStr = Object.entries(nodes).map(([id, {title}]) =>
-    {
-        const url = util.format(YOUTUBE_WATCH, id);
-        return util.format(GRAPH_NODE, id, escapeQuotes(title), url);
-    }).join('\n');
-
-    // Convert edges
-    const nextStr = Object.entries(next).map(([id, neighbors]) =>
-        Array.from(neighbors)
-            .map(neighbor => util.format(GRAPH_LINK, id, neighbor))
-            .join('\n')
-    ).join('\n');
-
-    return `digraph youtube {
-        ${nodesStr}
-        ${nextStr}
-    }`;
-};
--- a/explore/index.mjs
+++ b/explore/index.mjs
@ -1,63 +0,0 @@
-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);
--- a/explore/api.mjs
+++ b/explore/api.mjs
@ -1,77 +1,90 @@
+import debug from 'debug';
 import util from 'util';
 import fetch from 'node-fetch';

-const YOUTUBE_BASE = 'https://www.youtube.com/%s';
-const WATCH_BASE = util.format(YOUTUBE_BASE, 'watch?v=%s');
-const PLAYER_CONFIG_REGEX = /ytplayer\.config = (\{.*?\});/;
+import { WATCH_BASE } from './util.mjs';
+import { TemporaryError } from './retry.mjs';

-/**
- * Make a promise that is resolved in a point in the future.
- *
- * @param Number time Time to wait before resolving the promise (ms).
- * @return null
- */
-const sleep = time => new Promise(resolve => setTimeout(resolve, time));
+const log = debug('youtube-maze:api');
+const PLAYER_RESP_REGEX = /window\["ytInitialPlayerResponse"\] = (\{.*?\});/;
+const PLAYER_CONFIG_REGEX = /ytplayer\.config = (\{.*?\});/;

 /**
 * Fetch the `ytplayer.config` object for a YouTube video.
 *
 * @async
 * @param String videoId Identifier of the video to fetch.
- * @param Number retries Allowed number of retries after fetch errors.
- * @param Number cooldown Time to wait before retrying (ms).
 * @return Object The player configuration object.
 */
-export const getPlayerConfig = async (videoId, retries = 3, cooldown = 1000) =>
+export const getPlayerConfig = async (videoId) =>
 {
-    const url = util.format(WATCH_BASE, videoId);
+    const url = util.format(WATCH_BASE, encodeURIComponent(videoId));
+    log(`Fetching ${videoId} (${url})`);
+
    const res = await fetch(url);
+    debugger;
    const body = await res.text();

+    // Look for the initial player response object to check whether the
+    // video was found
+    const responseSearch = body.match(PLAYER_RESP_REGEX);
+
+    if (responseSearch === null)
+    {
+        throw new TemporaryError(`Invalid YouTube response for video ${videoId}`);
+    }
+
+    const response = JSON.parse(responseSearch[1]);
+
+    if (response.playabilityStatus.status !== 'OK')
+    {
+        throw new Error(`Video ${videoId} is not available; \
+status: ${response.playabilityStatus.status}; \
+reason: "${response.playabilityStatus.reason}"`);
+    }
+
    // Look for the definition of ytplayer.config and unserialize it
    const configSearch = body.match(PLAYER_CONFIG_REGEX);

    if (configSearch === null)
    {
-        if (retries > 0)
-        {
-            console.info(`Error while fetching ${videoId}, retrying in ${cooldown} ms`);
-            await sleep(cooldown);
-            return getPlayerConfig(videoId, retries - 1, cooldown * 2);
-        }
-        else
-        {
-            throw new Error('Unable to find player configuration');
-        }
+        throw new TemporaryError(`Unable to find player for video ${videoId}`);
    }

    const config = JSON.parse(configSearch[1]);
    config.args.player_response = JSON.parse(config.args.player_response);
+    const actualId = config.args.player_response.videoDetails.videoId;
+
+    if (videoId !== actualId)
+    {
+        throw new Error(`Video ${videoId} has actual id ${actualId}`);
+    }
+
    return config;
 };

 /**
 * Get metadata about a YouTube video.
 *
- * @param playerConfig The `ytplayer.config` object corresponding to the source
+ * @param config The `ytplayer.config` object corresponding to the source
 * YouTube video, as obtained from `getPlayerConfig`.
 * @return Object containing the video metadata.
 */
-export const getVideoMeta = playerConfig => ({
-    videoId: playerConfig.args.player_response.videoDetails.videoId,
-    title: playerConfig.args.player_response.videoDetails.title,
+export const getVideoMeta = config => ({
+    videoId: config.args.player_response.videoDetails.videoId,
+    title: config.args.player_response.videoDetails.title,
 });

 /**
 * Find videos linked from the endscreen of a YouTube video.
 *
- * @param playerConfig The `ytplayer.config` object corresponding to the source
+ * @param config The `ytplayer.config` object corresponding to the source
 * YouTube video, as obtained from `getPlayerConfig`.
 * @return List of identifiers of linked videos.
 */
-export const getEndScreenVideos = playerConfig =>
+export const getEndScreenVideos = config =>
 {
-    const response = playerConfig.args.player_response;
+    const response = config.args.player_response;

    if (!('endscreen' in response))
    {
@ -87,13 +100,13 @@ export const getEndScreenVideos = playerConfig =>
 /**
 * Find videos linked from as cards from a YouTube video.
 *
- * @param playerConfig The `ytplayer.config` object corresponding to the source
+ * @param config The `ytplayer.config` object corresponding to the source
 * YouTube video, as obtained from `getPlayerConfig`.
 * @return List of identifiers of linked videos.
 */
-export const getCardVideos = playerConfig =>
+export const getCardVideos = config =>
 {
-    const response = playerConfig.args.player_response;
+    const response = config.args.player_response;

    if (!('cards' in response))
    {
--- a/lib/explore.mjs
+++ b/lib/explore.mjs
@ -0,0 +1,87 @@
+import util from 'util';
+import * as api from './api.mjs';
+import { WATCH_BASE, PromiseQueue, escapeQuotes } from './util.mjs';
+import { retryable } from '../lib/retry.mjs';
+
+const GRAPH_NODE = '    "%s" [label="%s", URL="%s", fontcolor=blue]';
+const GRAPH_LINK = '    "%s" -> "%s"';
+
+const retryPlayerConfig = retryable(api.getPlayerConfig);
+
+/**
+ * Explore the video graph starting from the given root.
+ *
+ * @async
+ * @param string videoId Source video identifier.
+ * @return Array.<Object, Object> Nodes and set of neighbors of each node.
+ */
+export const exploreVideos = async videoId =>
+{
+    // Store metadata about each visited video
+    const videosNodes = Object.create(null);
+    videosNodes[videoId] = {};
+
+    // List of videos linked from each video either through a card or an
+    // endscreen item
+    const nextVideos = Object.create(null);
+    nextVideos[videoId] = new Set();
+
+    // Pending video requests
+    const queue = new PromiseQueue();
+    queue.add(retryPlayerConfig(videoId));
+
+    while (!queue.empty())
+    {
+        const config = await queue.next();
+        const meta = api.getVideoMeta(config);
+
+        videosNodes[meta.videoId] = meta;
+
+        // Add links between this video and the linked ones
+        api.getEndScreenVideos(config)
+            .forEach(nextId => nextVideos[meta.videoId].add(nextId));
+        api.getCardVideos(config)
+            .forEach(nextId => nextVideos[meta.videoId].add(nextId));
+
+        for (let nextId of nextVideos[meta.videoId])
+        {
+            if (!(nextId in videosNodes))
+            {
+                videosNodes[nextId] = {};
+                nextVideos[nextId] = new Set();
+                queue.add(retryPlayerConfig(nextId));
+            }
+        }
+    }
+
+    return [videosNodes, nextVideos];
+};
+
+/**
+ * Convert a video graph to the DOT format.
+ *
+ * @param Object videosNodes Videos of the graph.
+ * @param Object nextVideos For each video, list of next videos.
+ * @return string DOT representation of the graph.
+ */
+export const graphToDOT = (videosNodes, nextVideos) =>
+{
+    // Convert videosNodes
+    const nodesStr = Object.entries(videosNodes).map(([id, {title}]) =>
+    {
+        const url = util.format(WATCH_BASE, id);
+        return util.format(GRAPH_NODE, id, escapeQuotes(title), url);
+    }).join('\n');
+
+    // Convert edges
+    const nextStr = Object.entries(nextVideos).map(([id, neighbors]) =>
+        Array.from(neighbors)
+            .map(neighbor => util.format(GRAPH_LINK, id, neighbor))
+            .join('\n')
+    ).join('\n');
+
+    return `digraph maze {
+${nodesStr}
+
+${nextStr}}`;
+};
--- a/lib/retry.mjs
+++ b/lib/retry.mjs
@ -0,0 +1,64 @@
+import debug from 'debug';
+import { sleep } from './util.mjs';
+
+const log = debug('youtube-maze:retry');
+
+/**
+ * An error that is expected to be temporary such that the initial action
+ * may be retried.
+ */
+export class TemporaryError extends Error
+{
+    constructor(message)
+    {
+        super(message);
+        this.name = this.constructor.name;
+        Error.captureStackTrace(this, this.constructor);
+    }
+}
+
+/**
+ * Make an async function retry-able.
+ *
+ * When the underlying function throws a TemporaryError, the initial
+ * call will be repeated, under the limits set below.
+ *
+ * @param function func Async function to call.
+ * @param number retries Allowed number of retries before failing.
+ * @param number cooldown Time to wait before retrying (ms).
+ * @return function New function that is retryable.
+ */
+export const retryable = (func, retries = 3, cooldown = 1000) =>
+{
+    return async (...args) =>
+    {
+        while (true)
+        {
+            let remRetries = retries;
+            let curCooldown = cooldown;
+
+            try
+            {
+                const result = await func(...args);
+                return result;
+            }
+            catch (err)
+            {
+                if (err instanceof TemporaryError && remRetries > 0)
+                {
+                    log(`\
+${func.name}(${args}) failed with error "${err.message}"
+Retrying in ${curCooldown} ms (${remRetries} retries remaining)`);
+
+                    await sleep(curCooldown);
+                    remRetries -= 1;
+                    curCooldown *= 2;
+                }
+                else
+                {
+                    throw err;
+                }
+            }
+        }
+    };
+};
--- a/lib/util.mjs
+++ b/lib/util.mjs
@ -0,0 +1,63 @@
+import util from 'util';
+
+export const YOUTUBE_BASE = 'https://www.youtube.com/%s';
+export const WATCH_BASE = util.format(YOUTUBE_BASE, 'watch?v=%s');
+
+/**
+ * Hold a queue of promises from which results can be extracted.
+ */
+export class PromiseQueue
+{
+    constructor()
+    {
+        this.pending = new Set();
+    }
+
+    /**
+     * Add a new promise to the queue.
+     *
+     * @param Promise promise Promise to be added.
+     */
+    add(promise)
+    {
+        const wrapped = promise.then(res => {
+            this.pending.delete(wrapped);
+            return res;
+        });
+
+        this.pending.add(wrapped);
+    }
+
+    /**
+     * Check whether there is no promise pending in the queue.
+     *
+     * @return boolean
+     */
+    empty()
+    {
+        return this.pending.size === 0;
+    }
+
+    /**
+     * Extract the next available result from the promise queue.
+     *
+     * @return any Next result.
+     */
+    next()
+    {
+        return Promise.race(this.pending);
+    }
+}
+
+/**
+ * Escape double quotes in a string.
+ */
+export const escapeQuotes = str => str.replace(/"/g, '\\"');
+
+/**
+ * Make a promise that is resolved in a point in the future.
+ *
+ * @param number time Time to wait before resolving the promise (ms).
+ * @return null
+ */
+export const sleep = time => new Promise(resolve => setTimeout(resolve, time));
--- a/package-lock.json
+++ b/package-lock.json
@ -1,13 +1,404 @@
 {
-  "name": "epenser-maze",
-  "version": "0.2.0",
+  "name": "server",
+  "version": "0.0.0",
  "lockfileVersion": 1,
  "requires": true,
  "dependencies": {
+    "accepts": {
+      "version": "1.3.7",
+      "resolved": "https://registry.npmjs.org/accepts/-/accepts-1.3.7.tgz",
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+      "requires": {
+        "mime-types": "~2.1.24",
+        "negotiator": "0.6.2"
+      }
+    },
+    "array-flatten": {
+      "version": "1.1.1",
+      "resolved": "https://registry.npmjs.org/array-flatten/-/array-flatten-1.1.1.tgz",
+      "integrity": "sha1-ml9pkFGx5wczKPKgCJaLZOopVdI="
+    },
+    "basic-auth": {
+      "version": "2.0.1",
+      "resolved": "https://registry.npmjs.org/basic-auth/-/basic-auth-2.0.1.tgz",
+      "integrity": "sha512-NF+epuEdnUYVlGuhaxbbq+dvJttwLnGY+YixlXlME5KpQ5W3CnXA5cVTneY3SPbPDRkcjMbifrwmFYcClgOZeg==",
+      "requires": {
+        "safe-buffer": "5.1.2"
+      }
+    },
+    "body-parser": {
+      "version": "1.18.3",
+      "resolved": "https://registry.npmjs.org/body-parser/-/body-parser-1.18.3.tgz",
+      "integrity": "sha1-WykhmP/dVTs6DyDe0FkrlWlVyLQ=",
+      "requires": {
+        "bytes": "3.0.0",
+        "content-type": "~1.0.4",
+        "debug": "2.6.9",
+        "depd": "~1.1.2",
+        "http-errors": "~1.6.3",
+        "iconv-lite": "0.4.23",
+        "on-finished": "~2.3.0",
+        "qs": "6.5.2",
+        "raw-body": "2.3.3",
+        "type-is": "~1.6.16"
+      }
+    },
+    "bytes": {
+      "version": "3.0.0",
+      "resolved": "https://registry.npmjs.org/bytes/-/bytes-3.0.0.tgz",
+      "integrity": "sha1-0ygVQE1olpn4Wk6k+odV3ROpYEg="
+    },
+    "content-disposition": {
+      "version": "0.5.2",
+      "resolved": "https://registry.npmjs.org/content-disposition/-/content-disposition-0.5.2.tgz",
+      "integrity": "sha1-DPaLud318r55YcOoUXjLhdunjLQ="
+    },
+    "content-type": {
+      "version": "1.0.4",
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+    },
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+    },
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+      "requires": {
+        "cookie": "0.4.0",
+        "cookie-signature": "1.0.6"
+      }
+    },
+    "cookie-signature": {
+      "version": "1.0.6",
+      "resolved": "https://registry.npmjs.org/cookie-signature/-/cookie-signature-1.0.6.tgz",
+      "integrity": "sha1-4wOogrNCzD7oylE6eZmXNNqzriw="
+    },
+    "debug": {
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+      "resolved": "https://registry.npmjs.org/debug/-/debug-2.6.9.tgz",
+      "integrity": "sha512-bC7ElrdJaJnPbAP+1EotYvqZsb3ecl5wi6Bfi6BJTUcNowp6cvspg0jXznRTKDjm/E7AdgFBVeAPVMNcKGsHMA==",
+      "requires": {
+        "ms": "2.0.0"
+      }
+    },
+    "depd": {
+      "version": "1.1.2",
+      "resolved": "https://registry.npmjs.org/depd/-/depd-1.1.2.tgz",
+      "integrity": "sha1-m81S4UwJd2PnSbJ0xDRu0uVgtak="
+    },
+    "destroy": {
+      "version": "1.0.4",
+      "resolved": "https://registry.npmjs.org/destroy/-/destroy-1.0.4.tgz",
+      "integrity": "sha1-l4hXRCxEdJ5CBmE+N5RiBYJqvYA="
+    },
+    "ee-first": {
+      "version": "1.1.1",
+      "resolved": "https://registry.npmjs.org/ee-first/-/ee-first-1.1.1.tgz",
+      "integrity": "sha1-WQxhFWsK4vTwJVcyoViyZrxWsh0="
+    },
+    "encodeurl": {
+      "version": "1.0.2",
+      "resolved": "https://registry.npmjs.org/encodeurl/-/encodeurl-1.0.2.tgz",
+      "integrity": "sha1-rT/0yG7C0CkyL1oCw6mmBslbP1k="
+    },
+    "escape-html": {
+      "version": "1.0.3",
+      "resolved": "https://registry.npmjs.org/escape-html/-/escape-html-1.0.3.tgz",
+      "integrity": "sha1-Aljq5NPQwJdN4cFpGI7wBR0dGYg="
+    },
+    "etag": {
+      "version": "1.8.1",
+      "resolved": "https://registry.npmjs.org/etag/-/etag-1.8.1.tgz",
+      "integrity": "sha1-Qa4u62XvpiJorr/qg6x9eSmbCIc="
+    },
+    "express": {
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+    },
+    "utils-merge": {
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+      "integrity": "sha1-n5VxD1CiZ5R7LMwSR0HBAoQn5xM="
+    },
+    "vary": {
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+      "resolved": "https://registry.npmjs.org/vary/-/vary-1.1.2.tgz",
+      "integrity": "sha1-IpnwLG3tMNSllhsLn3RSShj2NPw="
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  }
 }
--- a/package.json
+++ b/package.json
@ -1,14 +1,15 @@
 {
  "name": "youtube-maze",
-  "private": true,
  "version": "0.3.0",
-  "main": "src/index.js",
-  "license": "CC0",
+  "private": true,
  "scripts": {
-    "epenser": "mkdir -p build && node explore/index.mjs EZGra6O8ClQ build/epenser.dot && dot -Tsvg build/epenser.dot -o build/epenser.svg",
-    "defakator": "mkdir -p build && node explore/index.mjs XM1ssJ8yxdg build/defakator.dot && dot -Tsvg build/defakator.dot -o build/defakator.svg"
+    "start": "node ./bin/www.mjs"
  },
  "dependencies": {
+    "cookie-parser": "~1.4.4",
+    "debug": "~2.6.9",
+    "express": "~4.16.1",
+    "morgan": "~1.9.1",
    "node-fetch": "^2.6.1"
  }
 }
--- a/public/index.html
+++ b/public/index.html
@ -0,0 +1,14 @@
+<!doctype html>
+<html lang="en">
+    <head>
+        <meta charset="utf-8">
+        <title>YouTube Maze</title>
+        <link rel="stylesheet" href="/style.css">
+    </head>
+    <body>
+        <h1>YouTube Maze</h1>
+
+        <p><a href="/mazes/EZGra6O8ClQ">e-penser</a></p>
+        <p><a href="/mazes/XM1ssJ8yxdg">Defakator</a></p>
+    </body>
+</html>
--- a/public/index2.html
+++ b/public/index2.html
@ -3,7 +3,7 @@
    <head>
        <meta charset="utf-8">
        <title>Exploration du labyrinthe du 1er avril d’e-penser</title>
-        <link href="style.css" rel="stylesheet" />
+        <link href="/style2.css" rel="stylesheet" />
    </head>
    <body>
        <h1>Exploration du labyrinthe du 1<sup>er</sup> avril d’e-penser</h1>
--- a/public/style.css
+++ b/public/style.css
@ -0,0 +1,8 @@
+body {
+  padding: 50px;
+  font: 14px "Lucida Grande", Helvetica, Arial, sans-serif;
+}
+
+a {
+  color: #00B7FF;
+}
--- a/public/style2.css
+++ b/public/style2.css
--- a/routes/mazes.mjs
+++ b/routes/mazes.mjs
@ -0,0 +1,22 @@
+import express from 'express';
+import { exploreVideos, graphToDOT } from '../lib/explore.mjs';
+import { retryable } from '../lib/retry.mjs';
+
+const router = express.Router();
+export default router;
+
+const retryExploreVideos = retryable(exploreVideos);
+
+router.get('/:videoId', async (req, res) => {
+    try
+    {
+        const graph = await retryExploreVideos(req.params.videoId);
+        const dot = graphToDOT(...graph);
+        res.send(dot);
+    }
+    catch (err)
+    {
+        console.error(err);
+        res.status(500).send('Error');
+    }
+});