window.fm = (function() {
    this.headerBackground = null;
    this.originalHeaderBackground = null;
    this.defaultCoverImage = 'https://lastfm.freetls.fastly.net/i/u/174s/2a96cbd8b46e442fc41c2b86b821562f.png';
    this.indexPlayingContainer = null;
    this.indexPlayingCover = null;
    this.indexPlayingTitle = null;
    this.indexPlayingArtist = null;

    this.selectTextInElement = function(elem) {
        // MSIE
        if(document.body.createTextRange) {
            var range = document.body.createTextRange();
            range.moveToElementText(elem);
            range.select();
            return;
        }

        // Mozilla
        if(window.getSelection) {
            var select = window.getSelection(),
                range  = document.createRange();
            range.selectNodeContents(elem);
            select.removeAllRanges();
            select.addRange(range);
            return;
        }

        console.warn('Unable to select text.');
    };

    this.copySelectedText = function() {
        if(document.execCommand) {
            document.execCommand('copy');
            return;
        }

        console.warn('Unable to copy text.');
    };

    this.getNowListening = function(callback) {
        if(!callback)
            return;
        var xhr = new XMLHttpRequest;
        xhr.onreadystatechange = function() {
            if(xhr.readyState !== 4 || xhr.status !== 200)
                return;
            callback.call(this, JSON.parse(xhr.responseText));
        }.bind(this);
        xhr.open('GET', '/now-listening.json');
        xhr.send();
    };

    this.updateIndexNowListening = function() {
        window.fm.getNowListening(function(info) {
            this.indexPlayingContainer.classList[info.now_playing ? 'remove' : 'add']('header-now-playing-hidden');
            this.indexPlayingCover.alt = this.indexPlayingCover.src = (info.cover !== this.defaultCoverImage ? info.cover : '//now.flash.moe/resources/no-cover.png');
            this.indexPlayingTitle.textContent = this.indexPlayingTitle.title = info.name;
            this.indexPlayingTitle.href = info.url;
            this.indexPlayingArtist.textContent = this.indexPlayingArtist.title = info.artist.name;
            this.indexPlayingArtist.href = info.artist.url;
            this.switchHeaderBackground(
                info.now_playing && info.cover !== this.defaultCoverImage
                    ? this.indexPlayingCover.src
                    : this.originalHeaderBackground
            );
        });
    };

    this.getCurrentHeaderBackground = function() {
        return this.headerBackground.querySelector('img').src;
    };

    this.switchHeaderBackground = function(url) {
        if(this.getCurrentHeaderBackground() === url)
            return;
        var newImg = document.createElement('img'),
            oldImg = this.headerBackground.querySelector('img');
        newImg.alt = newImg.src = url;
        newImg.style.opacity = '0';
        oldImg.style.zIndex = '-1';
        newImg.style.zIndex = '0';
        this.headerBackground.appendChild(newImg);
        newImg.onload = function() {
            setTimeout(function() {
                newImg.style.opacity = null;
                setTimeout(function() {
                    newImg.style.zIndex = null;
                    this.headerBackground.removeChild(oldImg);
                }.bind(this), 500);
            }.bind(this), 50);
        }.bind(this);
        newImg.onerror = function() {
            this.switchHeaderBackground(this.originalHeaderBackground);
        }.bind(this);
    };

    this.initIndex = function(npInterval) {
        this.headerBackground = document.querySelector('.header-background');
        this.originalHeaderBackground = this.headerBackground.querySelector('img').src;
        this.indexPlayingContainer = document.querySelector('.header-now-playing');
        this.indexPlayingCover = window.fm.indexPlayingContainer.querySelector('.header-now-playing-cover img');
        this.indexPlayingCover.onerror = function() {
            this.indexPlayingCover.src = '//now.flash.moe/resources/no-cover.png';
        }.bind(this);
        this.indexPlayingTitle = window.fm.indexPlayingContainer.querySelector('.header-now-playing-title a');
        this.indexPlayingArtist = window.fm.indexPlayingContainer.querySelector('.header-now-playing-artist a');
        this.updateIndexNowListening();
        setInterval(this.updateIndexNowListening, (npInterval || 30) * 1000);
    };

    return this;
}).call(window.fm || {});