scratch-vm/src/serialization/sb3.js

/**
 * @fileoverview
 * Partial implementation of a SB3 serializer and deserializer. Parses provided
 * JSON and then generates all needed scratch-vm runtime structures.
 */

const vmPackage = require('../../package.json');
const Blocks = require('../engine/blocks');
const Sprite = require('../sprites/sprite');
const Variable = require('../engine/variable');

const {loadCostume} = require('../import/load-costume.js');
const {loadSound} = require('../import/load-sound.js');
const {deserializeCostume, deserializeSound} = require('./deserialize-assets.js');

/**
 * @typedef {object} ImportedProject
 * @property {Array.<Target>} targets - the imported Scratch 3.0 target objects.
 * @property {ImportedExtensionsInfo} extensionsInfo - the ID of each extension actually used by this project.
 */

/**
 * @typedef {object} ImportedExtensionsInfo
 * @property {Set.<string>} extensionIDs - the ID of each extension actually in use by blocks in this project.
 * @property {Map.<string, string>} extensionURLs - map of ID => URL from project metadata. May not match extensionIDs.
 */

const serializeBlock = function (block) {
    const obj = Object.create(null);
    obj.id = block.id;
    obj.opcode = block.opcode;
    obj.next = block.next;
    obj.parent = block.parent;
    obj.inputs = block.inputs;
    obj.fields = block.fields;
    obj.topLevel = block.topLevel ? block.topLevel : false;
    obj.shadow = block.shadow;
    if (block.topLevel) {
        if (block.x) {
            obj.x = Math.round(block.x);
        }
        if (block.y) {
            obj.y = Math.round(block.y);
        }
    }
    if (block.mutation) {
        obj.mutation = block.mutation;
    }
    return obj;
};

const serializeBlocks = function (blocks) {
    const obj = Object.create(null);
    for (const blockID in blocks) {
        if (!blocks.hasOwnProperty(blockID)) continue;
        obj[blockID] = serializeBlock(blocks[blockID]);
    }
    return obj;
};

const serializeCostume = function (costume) {
    const obj = Object.create(null);
    obj.assetId = costume.assetId;
    obj.name = costume.name;
    obj.bitmapResolution = costume.bitmapResolution;
    // serialize this property with the name 'md5ext' because that's
    // what it's actually referring to. TODO runtime objects need to be
    // updated to actually refer to this as 'md5ext' instead of 'md5'
    // but that change should be made carefully since it is very
    // pervasive
    obj.md5ext = costume.md5;
    obj.dataFormat = costume.dataFormat;
    obj.rotationCenterX = costume.rotationCenterX;
    obj.rotationCenterY = costume.rotationCenterY;
    return obj;
};

const serializeSound = function (sound) {
    const obj = Object.create(null);
    obj.assetId = sound.assetId;
    obj.name = sound.name;
    obj.dataFormat = sound.dataFormat;
    obj.format = sound.format;
    obj.rate = sound.rate;
    obj.sampleCount = sound.sampleCount;
    // serialize this property with the name 'md5ext' because that's
    // what it's actually referring to. TODO runtime objects need to be
    // updated to actually refer to this as 'md5ext' instead of 'md5'
    // but that change should be made carefully since it is very
    // pervasive
    obj.md5ext = sound.md5;
    return obj;
};

const serializeTarget = function (target) {
    const obj = Object.create(null);
    obj.isStage = target.isStage;
    obj.name = target.name;
    obj.variables = target.variables; // This means that uids for variables will persist across saves/loads
    obj.blocks = serializeBlocks(target.blocks);
    obj.currentCostume = target.currentCostume;
    obj.costumes = target.costumes.map(serializeCostume);
    obj.sounds = target.sounds.map(serializeSound);
    if (!obj.isStage) {
        // Stage does not need the following properties
        obj.visible = target.visible;
        obj.x = target.x;
        obj.y = target.y;
        obj.size = target.size;
        obj.direction = target.direction;
        obj.draggable = target.draggable;
        obj.rotationStyle = target.rotationStyle;
    }
    return obj;
};

/**
 * Serializes the specified VM runtime.
 * @param  {!Runtime} runtime VM runtime instance to be serialized.
 * @return {object}    Serialized runtime instance.
 */
const serialize = function (runtime) {
    // Fetch targets
    const obj = Object.create(null);
    const flattenedOriginalTargets = JSON.parse(JSON.stringify(
        runtime.targets.filter(target => target.isOriginal)));
    obj.targets = flattenedOriginalTargets.map(t => serializeTarget(t, runtime));

    // TODO Serialize monitors

    // Assemble metadata
    const meta = Object.create(null);
    meta.semver = '3.0.0';
    meta.vm = vmPackage.version;

    // Attach full user agent string to metadata if available
    meta.agent = null;
    if (typeof navigator !== 'undefined') meta.agent = navigator.userAgent;

    // Assemble payload and return
    obj.meta = meta;
    return obj;
};

/**
 * Parse a single "Scratch object" and create all its in-memory VM objects.
 * @param {!object} object From-JSON "Scratch object:" sprite, stage, watcher.
 * @param {!Runtime} runtime Runtime object to load all structures into.
 * @param {ImportedExtensionsInfo} extensions - (in/out) parsed extension information will be stored here.
 * @param {JSZip} zip Sb3 file describing this project (to load assets from)
 * @return {!Promise.<Target>} Promise for the target created (stage or sprite), or null for unsupported objects.
 */
const parseScratchObject = function (object, runtime, extensions, zip) {
    if (!object.hasOwnProperty('name')) {
        // Watcher/monitor - skip this object until those are implemented in VM.
        // @todo
        return Promise.resolve(null);
    }
    // Blocks container for this object.
    const blocks = new Blocks();

    // @todo: For now, load all Scratch objects (stage/sprites) as a Sprite.
    const sprite = new Sprite(blocks, runtime);

    // Sprite/stage name from JSON.
    if (object.hasOwnProperty('name')) {
        sprite.name = object.name;
    }
    if (object.hasOwnProperty('blocks')) {
        for (const blockId in object.blocks) {
            if (!object.blocks.hasOwnProperty(blockId)) continue;
            const blockJSON = object.blocks[blockId];
            blocks.createBlock(blockJSON);

            const dotIndex = blockJSON.opcode.indexOf('.');
            if (dotIndex >= 0) {
                const extensionId = blockJSON.opcode.substring(0, dotIndex);
                extensions.extensionIDs.add(extensionId);
            }
        }
        // console.log(blocks);
    }
    // Costumes from JSON.
    const costumePromises = (object.costumes || []).map(costumeSource => {
        // @todo: Make sure all the relevant metadata is being pulled out.
        const costume = {
            assetId: costumeSource.assetId,
            skinId: null,
            name: costumeSource.name,
            bitmapResolution: costumeSource.bitmapResolution,
            rotationCenterX: costumeSource.rotationCenterX,
            rotationCenterY: costumeSource.rotationCenterY
        };
        const dataFormat =
            costumeSource.dataFormat ||
            (costumeSource.assetType && costumeSource.assetType.runtimeFormat) || // older format
            'png'; // if all else fails, guess that it might be a PNG
        const costumeMd5Ext = costumeSource.hasOwnProperty('md5ext') ?
            costumeSource.md5ext : `${costumeSource.assetId}.${dataFormat}`;
        costume.md5 = costumeMd5Ext;
        costume.dataFormat = dataFormat;
        // deserializeCostume should be called on the costume object we're
        // creating above instead of the source costume object, because this way
        // we're always loading the 'sb3' representation of the costume
        // any translation that needs to happen will happen in the process
        // of building up the costume object into an sb3 format
        return deserializeCostume(costume, runtime, zip)
            .then(() => loadCostume(costumeMd5Ext, costume, runtime));
        // Only attempt to load the costume after the deserialization
        // process has been completed
    });
    // Sounds from JSON
    const soundPromises = (object.sounds || []).map(soundSource => {
        const sound = {
            assetId: soundSource.assetId,
            format: soundSource.format,
            rate: soundSource.rate,
            sampleCount: soundSource.sampleCount,
            name: soundSource.name,
            // TODO we eventually want this property to be called md5ext,
            // but there are many things relying on this particular name at the
            // moment, so this translation is very important
            md5: soundSource.md5ext,
            dataFormat: soundSource.dataFormat,
            data: null
        };
        // deserializeSound should be called on the sound object we're
        // creating above instead of the source sound object, because this way
        // we're always loading the 'sb3' representation of the costume
        // any translation that needs to happen will happen in the process
        // of building up the costume object into an sb3 format
        return deserializeSound(sound, runtime, zip)
            .then(() => loadSound(sound, runtime));
        // Only attempt to load the sound after the deserialization
        // process has been completed.
    });
    // Create the first clone, and load its run-state from JSON.
    const target = sprite.createClone();
    // Load target properties from JSON.
    if (object.hasOwnProperty('variables')) {
        for (const j in object.variables) {
            const variable = object.variables[j];
            const newVariable = new Variable(
                variable.id,
                variable.name,
                variable.type,
                variable.isPersistent
            );
            newVariable.value = variable.value;
            target.variables[newVariable.id] = newVariable;
        }
    }
    if (object.hasOwnProperty('x')) {
        target.x = object.x;
    }
    if (object.hasOwnProperty('y')) {
        target.y = object.y;
    }
    if (object.hasOwnProperty('direction')) {
        target.direction = object.direction;
    }
    if (object.hasOwnProperty('size')) {
        target.size = object.size;
    }
    if (object.hasOwnProperty('visible')) {
        target.visible = object.visible;
    }
    if (object.hasOwnProperty('currentCostume')) {
        target.currentCostume = object.currentCostume;
    }
    if (object.hasOwnProperty('rotationStyle')) {
        target.rotationStyle = object.rotationStyle;
    }
    if (object.hasOwnProperty('isStage')) {
        target.isStage = object.isStage;
    }
    Promise.all(costumePromises).then(costumes => {
        sprite.costumes = costumes;
    });
    Promise.all(soundPromises).then(sounds => {
        sprite.sounds = sounds;
    });
    return Promise.all(costumePromises.concat(soundPromises)).then(() => target);
};

/**
 * Deserialize the specified representation of a VM runtime and loads it into the provided runtime instance.
 * TODO: parse extension info (also, design extension info storage...)
 * @param  {object} json - JSON representation of a VM runtime.
 * @param  {Runtime} runtime - Runtime instance
 * @param {JSZip} zip - Sb3 file describing this project (to load assets from)
 * @returns {Promise.<ImportedProject>} Promise that resolves to the list of targets after the project is deserialized
 */
const deserialize = function (json, runtime, zip) {
    const extensions = {
        extensionIDs: new Set(),
        extensionURLs: new Map()
    };
    return Promise.all(
        (json.targets || []).map(target => parseScratchObject(target, runtime, extensions, zip))
    ).then(targets => ({
        targets,
        extensions
    }));
};

module.exports = {
    serialize: serialize,
    deserialize: deserialize
};