/**
 * The audio Levels plugin.
 */
var AudioLevels = (function(my) {
    var CANVAS_EXTRA = 104;
    var CANVAS_RADIUS = 7;
    var SHADOW_COLOR = '#00ccff';
    var audioLevelCanvasCache = {};

    my.LOCAL_LEVEL = 'local';

    /**
     * Updates the audio level canvas for the given peerJid. If the canvas
     * didn't exist we create it.
     */
    my.updateAudioLevelCanvas = function (peerJid) {
        var resourceJid = null;
        var videoSpanId = null;
        if (!peerJid)
            videoSpanId = 'localVideoContainer';
        else {
            resourceJid = Strophe.getResourceFromJid(peerJid);

            videoSpanId = 'participant_' + resourceJid;
        }

        videoSpan = document.getElementById(videoSpanId);

        if (!videoSpan) {
            if (resourceJid)
                console.error("No video element for jid", resourceJid);
            else
                console.error("No video element for local video.");

            return;
        }

        var audioLevelCanvas = $('#' + videoSpanId + '>canvas');

        var videoSpaceWidth = $('#remoteVideos').width();
        var thumbnailSize
            = VideoLayout.calculateThumbnailSize(videoSpaceWidth);
        var thumbnailWidth = thumbnailSize[0];
        var thumbnailHeight = thumbnailSize[1];

        if (!audioLevelCanvas || audioLevelCanvas.length === 0) {

            audioLevelCanvas = document.createElement('canvas');
            audioLevelCanvas.className = "audiolevel";
            audioLevelCanvas.style.bottom = "-" + CANVAS_EXTRA/2 + "px";
            audioLevelCanvas.style.left = "-" + CANVAS_EXTRA/2 + "px";
            resizeAudioLevelCanvas( audioLevelCanvas,
                    thumbnailWidth,
                    thumbnailHeight);

            videoSpan.appendChild(audioLevelCanvas);
        } else {
            audioLevelCanvas = audioLevelCanvas.get(0);

            resizeAudioLevelCanvas( audioLevelCanvas,
                    thumbnailWidth,
                    thumbnailHeight);
        }
    };

    /**
     * Updates the audio level UI for the given resourceJid.
     *
     * @param resourceJid the resource jid indicating the video element for
     * which we draw the audio level
     * @param audioLevel the newAudio level to render
     */
    my.updateAudioLevel = function (resourceJid, audioLevel) {
        drawAudioLevelCanvas(resourceJid, audioLevel);

        var videoSpanId = getVideoSpanId(resourceJid);

        var audioLevelCanvas = $('#' + videoSpanId + '>canvas').get(0);

        if (!audioLevelCanvas)
            return;

        var drawContext = audioLevelCanvas.getContext('2d');

        var canvasCache = audioLevelCanvasCache[resourceJid];

        drawContext.clearRect (0, 0,
                audioLevelCanvas.width, audioLevelCanvas.height);
        drawContext.drawImage(canvasCache, 0, 0);
    };

    /**
     * Resizes the given audio level canvas to match the given thumbnail size.
     */
    function resizeAudioLevelCanvas(audioLevelCanvas,
                                    thumbnailWidth,
                                    thumbnailHeight) {
        audioLevelCanvas.width = thumbnailWidth + CANVAS_EXTRA;
        audioLevelCanvas.height = thumbnailHeight + CANVAS_EXTRA;
    };

    /**
     * Draws the audio level canvas into the cached canvas object.
     *
     * @param resourceJid the resource jid indicating the video element for
     * which we draw the audio level
     * @param audioLevel the newAudio level to render
     */
    function drawAudioLevelCanvas(resourceJid, audioLevel) {
        if (!audioLevelCanvasCache[resourceJid]) {

            var videoSpanId = getVideoSpanId(resourceJid);

            var audioLevelCanvasOrig = $('#' + videoSpanId + '>canvas').get(0);

            /*
             * FIXME Testing has shown that audioLevelCanvasOrig may not exist.
             * In such a case, the method CanvasUtil.cloneCanvas may throw an
             * error. Since audio levels are frequently updated, the errors have
             * been observed to pile into the console, strain the CPU.
             */
            if (audioLevelCanvasOrig)
            {
                audioLevelCanvasCache[resourceJid]
                    = CanvasUtil.cloneCanvas(audioLevelCanvasOrig);
            }
        }

        var canvas = audioLevelCanvasCache[resourceJid];

        if (!canvas)
            return;

        var drawContext = canvas.getContext('2d');

        drawContext.clearRect(0, 0, canvas.width, canvas.height);

        var shadowLevel = getShadowLevel(audioLevel);

        if (shadowLevel > 0)
            // drawContext, x, y, w, h, r, shadowColor, shadowLevel
            CanvasUtil.drawRoundRectGlow(   drawContext,
                                            CANVAS_EXTRA/2, CANVAS_EXTRA/2,
                                            canvas.width - CANVAS_EXTRA,
                                            canvas.height - CANVAS_EXTRA,
                                            CANVAS_RADIUS,
                                            SHADOW_COLOR,
                                            shadowLevel);
    };

    /**
     * Returns the shadow/glow level for the given audio level.
     *
     * @param audioLevel the audio level from which we determine the shadow
     * level
     */
    function getShadowLevel (audioLevel) {
        var shadowLevel = 0;

        if (audioLevel <= 0.3) {
            shadowLevel = Math.round(CANVAS_EXTRA/2*(audioLevel/0.3));
        }
        else if (audioLevel <= 0.6) {
            shadowLevel = Math.round(CANVAS_EXTRA/2*((audioLevel - 0.3) / 0.3));
        }
        else {
            shadowLevel = Math.round(CANVAS_EXTRA/2*((audioLevel - 0.6) / 0.4));
        }
        return shadowLevel;
    };

    /**
     * Returns the video span id corresponding to the given resourceJid or local
     * user.
     */
    function getVideoSpanId(resourceJid) {
        var videoSpanId = null;
        if (resourceJid === AudioLevels.LOCAL_LEVEL
                || (connection.emuc.myroomjid && resourceJid
                    === Strophe.getResourceFromJid(connection.emuc.myroomjid)))
            videoSpanId = 'localVideoContainer';
        else
            videoSpanId = 'participant_' + resourceJid;

        return videoSpanId;
    };

    /**
     * Indicates that the remote video has been resized.
     */
    $(document).bind('remotevideo.resized', function (event, width, height) {
        var resized = false;
        $('#remoteVideos>span>canvas').each(function() {
            var canvas = $(this).get(0);
            if (canvas.width !== width + CANVAS_EXTRA) {
                canvas.width = width + CANVAS_EXTRA;
                resized = true;
            }

            if (canvas.heigh !== height + CANVAS_EXTRA) {
                canvas.height = height + CANVAS_EXTRA;
                resized = true;
            }
        });

        if (resized)
            Object.keys(audioLevelCanvasCache).forEach(function (resourceJid) {
                audioLevelCanvasCache[resourceJid].width
                    = width + CANVAS_EXTRA;
                audioLevelCanvasCache[resourceJid].height
                    = height + CANVAS_EXTRA;
            });
    });

    return my;

})(AudioLevels || {});