const dispatch = require('../dispatch/central-dispatch');
const log = require('../util/log');
const maybeFormatMessage = require('../util/maybe-format-message');

const BlockType = require('./block-type');

// These extensions are currently built into the VM repository but should not be loaded at startup.
// TODO: move these out into a separate repository?
// TODO: change extension spec so that library info, including extension ID, can be collected through static methods
const Scratch3PenBlocks = require('../extensions/scratch3_pen');
const Scratch3WeDo2Blocks = require('../extensions/scratch3_wedo2');
const Scratch3MusicBlocks = require('../extensions/scratch3_music');
const Scratch3MicroBitBlocks = require('../extensions/scratch3_microbit');
const Scratch3TranslateBlocks = require('../extensions/scratch3_translate');
const Scratch3VideoSensingBlocks = require('../extensions/scratch3_video_sensing');

const builtinExtensions = {
    pen: Scratch3PenBlocks,
    wedo2: Scratch3WeDo2Blocks,
    music: Scratch3MusicBlocks,
    microbit: Scratch3MicroBitBlocks,
    translate: Scratch3TranslateBlocks,
    videoSensing: Scratch3VideoSensingBlocks
};

/**
 * @typedef {object} ArgumentInfo - Information about an extension block argument
 * @property {ArgumentType} type - the type of value this argument can take
 * @property {*|undefined} default - the default value of this argument (default: blank)
 */

/**
 * @typedef {object} ConvertedBlockInfo - Raw extension block data paired with processed data ready for scratch-blocks
 * @property {ExtensionBlockMetadata} info - the raw block info
 * @property {object} json - the scratch-blocks JSON definition for this block
 * @property {string} xml - the scratch-blocks XML definition for this block
 */

/**
 * @typedef {object} CategoryInfo - Information about a block category
 * @property {string} id - the unique ID of this category
 * @property {string} name - the human-readable name of this category
 * @property {string|undefined} blockIconURI - optional URI for the block icon image
 * @property {string} color1 - the primary color for this category, in '#rrggbb' format
 * @property {string} color2 - the secondary color for this category, in '#rrggbb' format
 * @property {string} color3 - the tertiary color for this category, in '#rrggbb' format
 * @property {Array.<ConvertedBlockInfo>} blocks - the blocks, separators, etc. in this category
 * @property {Array.<object>} menus - the menus provided by this category
 */

/**
 * @typedef {object} PendingExtensionWorker - Information about an extension worker still initializing
 * @property {string} extensionURL - the URL of the extension to be loaded by this worker
 * @property {Function} resolve - function to call on successful worker startup
 * @property {Function} reject - function to call on failed worker startup
 */

class ExtensionManager {
    constructor (runtime) {
        /**
         * The ID number to provide to the next extension worker.
         * @type {int}
         */
        this.nextExtensionWorker = 0;

        /**
         * FIFO queue of extensions which have been requested but not yet loaded in a worker,
         * along with promise resolution functions to call once the worker is ready or failed.
         *
         * @type {Array.<PendingExtensionWorker>}
         */
        this.pendingExtensions = [];

        /**
         * Map of worker ID to workers which have been allocated but have not yet finished initialization.
         * @type {Array.<PendingExtensionWorker>}
         */
        this.pendingWorkers = [];

        /**
         * Set of loaded extension URLs/IDs (equivalent for built-in extensions).
         * @type {Set.<string>}
         * @private
         */
        this._loadedExtensions = new Map();

        /**
         * Keep a reference to the runtime so we can construct internal extension objects.
         * TODO: remove this in favor of extensions accessing the runtime as a service.
         * @type {Runtime}
         */
        this.runtime = runtime;

        dispatch.setService('extensions', this).catch(e => {
            log.error(`ExtensionManager was unable to register extension service: ${JSON.stringify(e)}`);
        });
    }

    /**
     * Check whether an extension is registered or is in the process of loading. This is intended to control loading or
     * adding extensions so it may return `true` before the extension is ready to be used. Use the promise returned by
     * `loadExtensionURL` if you need to wait until the extension is truly ready.
     * @param {string} extensionID - the ID of the extension.
     * @returns {boolean} - true if loaded, false otherwise.
     */
    isExtensionLoaded (extensionID) {
        return this._loadedExtensions.has(extensionID);
    }

    /**
     * Load an extension by URL or internal extension ID
     * @param {string} extensionURL - the URL for the extension to load OR the ID of an internal extension
     * @returns {Promise} resolved once the extension is loaded and initialized or rejected on failure
     */
    loadExtensionURL (extensionURL) {
        if (builtinExtensions.hasOwnProperty(extensionURL)) {
            /** @TODO dupe handling for non-builtin extensions. See commit 670e51d33580e8a2e852b3b038bb3afc282f81b9 */
            if (this.isExtensionLoaded(extensionURL)) {
                const message = `Rejecting attempt to load a second extension with ID ${extensionURL}`;
                log.warn(message);
                return Promise.reject(new Error(message));
            }

            const extension = builtinExtensions[extensionURL];
            const extensionInstance = new extension(this.runtime);
            return this._registerInternalExtension(extensionInstance).then(serviceName => {
                this._loadedExtensions.set(extensionURL, serviceName);
            });
        }

        return new Promise((resolve, reject) => {
            // If we `require` this at the global level it breaks non-webpack targets, including tests
            const ExtensionWorker = require('worker-loader?name=extension-worker.js!./extension-worker');

            this.pendingExtensions.push({extensionURL, resolve, reject});
            dispatch.addWorker(new ExtensionWorker());
        });
    }

    /**
    * regenerate blockinfo for any loaded extensions
    */
    refreshBlocks () {
        this._loadedExtensions.forEach(serviceName => {
            dispatch.call(serviceName, 'getInfo')
                .then(info => {
                    dispatch.call('runtime', '_refreshExtensionPrimitives', info);
                })
                .catch(e => {
                    log.error(`Failed to refresh buildtin extension primitives: ${JSON.stringify(e)}`);
                });
        });
    }

    allocateWorker () {
        const id = this.nextExtensionWorker++;
        const workerInfo = this.pendingExtensions.shift();
        this.pendingWorkers[id] = workerInfo;
        return [id, workerInfo.extensionURL];
    }

    /**
     * Collect extension metadata from the specified service and begin the extension registration process.
     * @param {string} serviceName - the name of the service hosting the extension.
     */
    registerExtensionService (serviceName) {
        dispatch.call(serviceName, 'getInfo').then(info => {
            this._registerExtensionInfo(serviceName, info);
        });
    }

    /**
     * Called by an extension worker to indicate that the worker has finished initialization.
     * @param {int} id - the worker ID.
     * @param {*?} e - the error encountered during initialization, if any.
     */
    onWorkerInit (id, e) {
        const workerInfo = this.pendingWorkers[id];
        delete this.pendingWorkers[id];
        if (e) {
            workerInfo.reject(e);
        } else {
            workerInfo.resolve(id);
        }
    }

    /**
     * Register an internal (non-Worker) extension object
     * @param {object} extensionObject - the extension object to register
     * @returns {Promise} resolved once the extension is fully registered or rejected on failure
     */
    _registerInternalExtension (extensionObject) {
        const extensionInfo = extensionObject.getInfo();
        const fakeWorkerId = this.nextExtensionWorker++;
        const serviceName = `extension_${fakeWorkerId}_${extensionInfo.id}`;
        return dispatch.setService(serviceName, extensionObject)
            .then(() => {
                dispatch.call('extensions', 'registerExtensionService', serviceName);
                return serviceName;
            });
    }

    /**
     * Sanitize extension info then register its primitives with the VM.
     * @param {string} serviceName - the name of the service hosting the extension
     * @param {ExtensionInfo} extensionInfo - the extension's metadata
     * @private
     */
    _registerExtensionInfo (serviceName, extensionInfo) {
        extensionInfo = this._prepareExtensionInfo(serviceName, extensionInfo);
        dispatch.call('runtime', '_registerExtensionPrimitives', extensionInfo).catch(e => {
            log.error(`Failed to register primitives for extension on service ${serviceName}:`, e);
        });
    }

    /**
     * Modify the provided text as necessary to ensure that it may be used as an attribute value in valid XML.
     * @param {string} text - the text to be sanitized
     * @returns {string} - the sanitized text
     * @private
     */
    _sanitizeID (text) {
        return text.toString().replace(/[<"&]/, '_');
    }

    /**
     * Apply minor cleanup and defaults for optional extension fields.
     * TODO: make the ID unique in cases where two copies of the same extension are loaded.
     * @param {string} serviceName - the name of the service hosting this extension block
     * @param {ExtensionInfo} extensionInfo - the extension info to be sanitized
     * @returns {ExtensionInfo} - a new extension info object with cleaned-up values
     * @private
     */
    _prepareExtensionInfo (serviceName, extensionInfo) {
        extensionInfo = Object.assign({}, extensionInfo);
        if (!/^[a-z0-9]+$/i.test(extensionInfo.id)) {
            throw new Error('Invalid extension id');
        }
        extensionInfo.name = extensionInfo.name || extensionInfo.id;
        extensionInfo.blocks = extensionInfo.blocks || [];
        extensionInfo.targetTypes = extensionInfo.targetTypes || [];
        extensionInfo.blocks = extensionInfo.blocks.reduce((results, blockInfo) => {
            try {
                let result;
                switch (blockInfo) {
                case '---': // separator
                    result = '---';
                    break;
                default: // an ExtensionBlockMetadata object
                    result = this._prepareBlockInfo(serviceName, blockInfo);
                    break;
                }
                results.push(result);
            } catch (e) {
                // TODO: more meaningful error reporting
                log.error(`Error processing block: ${e.message}, Block:\n${JSON.stringify(blockInfo)}`);
            }
            return results;
        }, []);
        extensionInfo.menus = extensionInfo.menus || [];
        extensionInfo.menus = this._prepareMenuInfo(serviceName, extensionInfo.menus);
        return extensionInfo;
    }

    /**
     * Prepare extension menus. e.g. setup binding for dynamic menu functions.
     * @param {string} serviceName - the name of the service hosting this extension block
     * @param {Array.<MenuInfo>} menus - the menu defined by the extension.
     * @returns {Array.<MenuInfo>} - a menuInfo object with all preprocessing done.
     * @private
     */
    _prepareMenuInfo (serviceName, menus) {
        const menuNames = Object.getOwnPropertyNames(menus);
        for (let i = 0; i < menuNames.length; i++) {
            const item = menuNames[i];
            // If the value is a string, it should be the name of a function in the
            // extension object to call to populate the menu whenever it is opened.
            // Set up the binding for the function object here so
            // we can use it later when converting the menu for Scratch Blocks.
            if (typeof menus[item] === 'string') {
                const serviceObject = dispatch.services[serviceName];
                const menuName = menus[item];
                menus[item] = this._getExtensionMenuItems.bind(this, serviceObject, menuName);
            }
        }
        return menus;
    }

    /**
     * Fetch the items for a particular extension menu, providing the target ID for context.
     * @param {object} extensionObject - the extension object providing the menu.
     * @param {string} menuName - the name of the menu function to call.
     * @returns {Array} menu items ready for scratch-blocks.
     * @private
     */
    _getExtensionMenuItems (extensionObject, menuName) {
        // Fetch the items appropriate for the target currently being edited. This assumes that menus only
        // collect items when opened by the user while editing a particular target.
        const editingTarget = this.runtime.getEditingTarget() || this.runtime.getTargetForStage();
        const editingTargetID = editingTarget ? editingTarget.id : null;
        const extensionMessageContext = this.runtime.makeMessageContextForTarget(editingTarget);

        // TODO: Fix this to use dispatch.call when extensions are running in workers.
        const menuFunc = extensionObject[menuName];
        const menuItems = menuFunc.call(extensionObject, editingTargetID).map(
            item => {
                item = maybeFormatMessage(item, extensionMessageContext);
                if (typeof item === 'object') {
                    return [
                        maybeFormatMessage(item.text, extensionMessageContext),
                        item.value
                    ];
                }
                return item;
            });

        if (!menuItems || menuItems.length < 1) {
            throw new Error(`Extension menu returned no items: ${menuName}`);
        }
        return menuItems;
    }

    /**
     * Apply defaults for optional block fields.
     * @param {string} serviceName - the name of the service hosting this extension block
     * @param {ExtensionBlockMetadata} blockInfo - the block info from the extension
     * @returns {ExtensionBlockMetadata} - a new block info object which has values for all relevant optional fields.
     * @private
     */
    _prepareBlockInfo (serviceName, blockInfo) {
        blockInfo = Object.assign({}, {
            blockType: BlockType.COMMAND,
            terminal: false,
            blockAllThreads: false,
            arguments: {}
        }, blockInfo);
        blockInfo.opcode = this._sanitizeID(blockInfo.opcode);
        blockInfo.text = blockInfo.text || blockInfo.opcode;

        if (blockInfo.blockType !== BlockType.EVENT) {
            blockInfo.func = blockInfo.func ? this._sanitizeID(blockInfo.func) : blockInfo.opcode;

            /**
             * This is only here because the VM performs poorly when blocks return promises.
             * @TODO make it possible for the VM to resolve a promise and continue during the same Scratch "tick"
             */
            if (dispatch._isRemoteService(serviceName)) {
                blockInfo.func = dispatch.call.bind(dispatch, serviceName, blockInfo.func);
            } else {
                const serviceObject = dispatch.services[serviceName];
                const func = serviceObject[blockInfo.func];
                if (func) {
                    blockInfo.func = func.bind(serviceObject);
                } else if (blockInfo.blockType !== BlockType.EVENT) {
                    throw new Error(`Could not find extension block function called ${blockInfo.func}`);
                }
            }
        } else if (blockInfo.func) {
            log.warn(`Ignoring function "${blockInfo.func}" for event block ${blockInfo.opcode}`);
        }

        return blockInfo;
    }
}

module.exports = ExtensionManager;