function PostInfo(id, media) {
    this.id = id;
    this.media = media;
}

// Loads JSON of current page and makes an id-md5 list of posts.
function getPosts() {
    var jsonUrl = document.URL.replace("html", "json");
    var json = JSON.parse(httpGet(jsonUrl));

    var posts = json.threads[0].posts;
    return posts.map(function(post) {
        return getInfo(post);
    });
}

// Makes a GET request to a given URL and returns response text.
function httpGet(url) {
    var xmlHttp = new XMLHttpRequest();

    xmlHttp.open("GET", url, false);
    xmlHttp.send(null);

    return xmlHttp.responseText;
}

function getInfo(post) {
    var media = post.files.map(function(file) {
        return file.md5;
    });

    return new PostInfo(post.number, media);
}