wildhaber/gluebert

/**
 * Class represents ElementBuilder
 * @class ElementBuilder
 */
class ElementBuilder {

    /**
     * Create ElementBuilder instance
     * @param {ElementSignature[]} signatures
     * @param {function} templateEngine
     * @param {function} schemaValidator
     * @param {object} options
     */
    constructor(signatures = [], templateEngine = null, schemaValidator = null, options = {}) {

        this._schemaValidator = (
            schemaValidator &&
            typeof schemaValidator === 'function'
        )
            ? new schemaValidator()
            : null;

        this._templateEngine = (typeof templateEngine === 'object')
            ? templateEngine
            : null;

        this._signatures = (signatures instanceof Array)
            ? this._transformToObject(signatures)
            : {};

        this._elements = {};

        this._options = options;

    }

    /**
     * transform signatures array to {name: signature} object
     * @param {ElementSignature[]} signatures
     * @returns {object}
     * @private
     */
    _transformToObject(signatures) {
        let obj = {};

        if(signatures instanceof Array) {
            signatures.forEach((signature) => {
                if(signature && typeof signature.name === 'string') {
                    obj[signature.name] = signature;
                }
            });
        }

        return obj;
    }

    /**
     * checks if element exists
     * @param {ElementSignature.<name>} name
     * @return {boolean}
     * @private
     */
    _elementExists(name) {
        return (
            !!name &&
            typeof name === 'string' &&
            typeof this._elements[name] === 'object' &&
            !!this._elements[name]
        );
    }

    /**
     * get registered element
     * @param {ElementSignature.<name>} name
     * @return {object|null}
     */
    getElement(name) {
        return (this._elementExists(name))
            ? this._elements[name]
            : null;
    }

    /**
     * get signature
     * @param {ElementSignature.<name>} name
     * @return {object|null}
     */
    getSignature(name) {
        return (this._signatureExists(name))
            ? this._signatures[name]
            : null;
    }

    /**
     * remove signature from registry
     * @param {ElementSignature.<name>} name
     * @return {ElementBuilder}
     */
    removeSignature(name) {
        if(this._signatureExists(name)) {
            delete this._signatures[name];
        }
        return this;
    }

    /**
     * checks if signature exists
     * @param {ElementSignature.<name>} name
     * @return {boolean}
     * @private
     */
    _signatureExists(name) {
        return (
            typeof this._signatures[name] === 'object' &&
            !!this._signatures[name] &&
            typeof this._signatures[name].name === 'string'
        );
    }

    /**
     * checks if signature is currently loading
     * @param {ElementSignature.<name>} name
     * @return {boolean}
     */
    isBusySignature(name) {
        let signature = this.getSignature(name);
        return !!(signature && signature.busy);
    }

    /**
     * sets busy flag to
     * @param {ElementSignature.<name>} name
     * @return {ElementBuilder}
     */
    setBusySignature(name) {
        let signature = this.getSignature(name);
        if(signature) {
            this._signatures[name].busy = true;
        }
        return this;
    }

    /**
     * get template innter html
     * @param {string} template
     * @param {object} data
     * @return {string}
     */
    getTemplateInnerHtml(template, data) {
        return (
            this._templateEngine &&
            typeof this._templateEngine === 'object' &&
            typeof this._templateEngine.render === 'function'
        )
            ? this._templateEngine.render(template, data)
            : template;
    }

    /**
     * get template without shadow dom support
     * @param {string} template
     * @param {object} data
     * @return {Node}
     * @private
     */
    getTemplateElement(template, data) {
        const templateFeature = ('content' in document.createElement('template'));
        const templateElement = (templateFeature)
            ? document.createElement('template')
            : document.createDocumentFragment();

        templateElement.innerHTML = this.getTemplateInnerHtml(template, data);

        return (templateFeature)
            ? templateElement.content
            : templateElement;
    }

    /**
     * get schema reference
     * @param {ElementSignature.<name>} name
     * @return {object}
     */
    getSchema(name) {
        const element = this.getElement(name);
        return (
            element &&
            typeof element === 'object' &&
            typeof element.schema !== 'undefined'
        )
            ? element.schema
            : null;
    }

    /**
     * validate data against schema
     * @param {ElementSignature.<name>} elementName
     * @param {*} data
     * @return {boolean}
     * @private
     */
    _validate(elementName, data) {
        if(!this._elementExists(elementName)) {
            return false;
        }

        const schema = this.getSchema(elementName);

        if(
            this._schemaValidator &&
            schema
        ) {
            return this._schemaValidator.validate(schema, data);
        } else {
            return true;
        }
    }

    /**
     * adds element to registry
     * @param {ElementSignature.<name>} name
     * @param {object} schema
     * @param {string} template
     * @param {ElementAbstract} module
     * @return {ElementBuilder}
     */
    addElement(name, schema, template, module) {

        const templateView = (
            this._templateEngine &&
            typeof this._templateEngine === 'object'
        )
            ? this._templateEngine.createView(template)
            : template;

        this._elements[name] = {
            schema,
            template: templateView,
            module,
        };

        return this;
    }

    /**
     * generate element instance
     * @param {ElementSignature.<name>} name
     * @param {object} data
     * @private
     */
    _generateElement(name, data) {
        if(this._validate(name, data)) {
            const element = this.getElement(name, data);

            const elementInstance = new element.module(
                data,
                this.getTemplateElement(element.template, data),
            );

            return elementInstance.create();
        } else {
            throw new Error(`Create Element ${name} failed. Given data do not match given schema.`);
        }
    }

    /**
     * load element module
     * @param {ElementSignature.<name>} name
     * @param {object} data
     * @return {Promise.<TResult>}
     * @private
     */
    async _loadElementModule(name, data) {
        const signature = this.getSignature(name);
        this.setBusySignature(name);

        return await Promise.all([
            signature.importSchema(),
            signature.importTemplate(),
            signature.importElement(),
        ])
            .then((imports) => {
                this.addElement(name, imports[0], imports[1], imports[2]);

                if(this._elementExists(name)) {
                    this.removeSignature(name);
                    return this.create(name, data);
                } else {
                    throw new Error(`Unfortunately Element ${name} could not have been instanciated.`);
                }
            })
            .catch((err) => {
                throw new Error(`Unfortunately Element ${name} could not have been instanciated. ${err}`);
            });
    }

    /**
     * retry create element loop when
     * same element signature has to load
     * multiple times at the same time
     * @param {Elementsignature.<name>} name
     * @param {object} data
     * @return {Promise}
     * @private
     */
    _retryCreate(name, data) {
        return new Promise((resolve, reject) => {
            window.setTimeout(() => {
                try {
                    resolve(this.create(name, data));
                } catch(err) {
                    reject(err);
                }
            }, 100);
        });
    }

    /**
     * loads dependency creates element by name and data
     * @param {ElementSignature.<name>} name
     * @param {*} data
     * @return {Promise}
     */
    async create(name, data) {
        try {
            const elementExists = this._elementExists(name);
            const signatureExists = this._signatureExists(name);
            const signatureIsBusy = this.isBusySignature(name);

            if(!elementExists && !signatureExists) {
                return null;
            }

            if(elementExists) {
                return this._generateElement(name, data);
            }

            return (signatureExists && !signatureIsBusy)
                ? this._loadElementModule(name, data)
                : this._retryCreate(name, data);

        } catch(err) {
            return null;
        }
    }

    /**
     * get options
     * @return {Object}
     */
    getOptions() {
        return this._options;
    }

    /**
     * get element ready class
     * @return {string|null} elementReadyClass
     */
    getElementReadyClass() {
        return (typeof this._options.elementReadyClass === 'string')
            ? this._options.elementReadyClass
            : null;
    }

}

export {
    ElementBuilder,
};