const handlebars = require("handlebars") const { registerAll, registerMinimum } = require("./helpers/index") const processors = require("./processors") const { atob, btoa } = require("./utilities") const manifest = require("../manifest.json") const { FIND_HBS_REGEX, FIND_ANY_HBS_REGEX, findDoubleHbsInstances, } = require("./utilities") const { convertHBSBlock } = require("./conversion") const hbsInstance = handlebars.create() registerAll(hbsInstance) const hbsInstanceNoHelpers = handlebars.create() registerMinimum(hbsInstanceNoHelpers) const defaultOpts = { noHelpers: false, cacheTemplates: false, noEscaping: false, escapeNewlines: false, noFinalise: false, } /** * Utility function to check if the object is valid. */ function testObject(object) { // JSON stringify will fail if there are any cycles, stops infinite recursion try { JSON.stringify(object) } catch (err) { throw "Unable to process inputs to JSON, cannot recurse" } } /** * Creates a HBS template function for a given string, and optionally caches it. */ let templateCache = {} function createTemplate(string, opts) { opts = { ...defaultOpts, ...opts } // Finalising adds a helper, can't do this with no helpers const key = `${string}-${JSON.stringify(opts)}` // Reuse the cached template is possible if (opts.cacheTemplates && templateCache[key]) { return templateCache[key] } string = processors.preprocess(string, opts) // Optionally disable built in HBS escaping if (opts.noEscaping) { string = exports.disableEscaping(string) } // This does not throw an error when template can't be fulfilled, // have to try correct beforehand const instance = opts.noHelpers ? hbsInstanceNoHelpers : hbsInstance const template = instance.compile(string, { strict: false, }) templateCache[key] = template return template } /** * Given an input object this will recurse through all props to try and update any handlebars statements within. * @param {object|array} object The input structure which is to be recursed, it is important to note that * if the structure contains any cycles then this will fail. * @param {object} context The context that handlebars should fill data from. * @param {object|undefined} [opts] optional - specify some options for processing. * @returns {Promise} The structure input, as fully updated as possible. */ module.exports.processObject = async (object, context, opts) => { testObject(object) for (let key of Object.keys(object || {})) { if (object[key] != null) { let val = object[key] if (typeof val === "string") { object[key] = await module.exports.processString( object[key], context, opts ) } else if (typeof val === "object") { object[key] = await module.exports.processObject( object[key], context, opts ) } } } return object } /** * This will process a single handlebars containing string. If the string passed in has no valid handlebars statements * then nothing will occur. * @param {string} string The template string which is the filled from the context object. * @param {object} context An object of information which will be used to enrich the string. * @param {object|undefined} [opts] optional - specify some options for processing. * @returns {Promise} The enriched string, all templates should have been replaced if they can be. */ module.exports.processString = async (string, context, opts) => { // TODO: carry out any async calls before carrying out async call return module.exports.processStringSync(string, context, opts) } /** * Given an input object this will recurse through all props to try and update any handlebars statements within. This is * a pure sync call and therefore does not have the full functionality of the async call. * @param {object|array} object The input structure which is to be recursed, it is important to note that * if the structure contains any cycles then this will fail. * @param {object} context The context that handlebars should fill data from. * @param {object|undefined} [opts] optional - specify some options for processing. * @returns {object|array} The structure input, as fully updated as possible. */ module.exports.processObjectSync = (object, context, opts) => { testObject(object) for (let key of Object.keys(object || {})) { let val = object[key] if (typeof val === "string") { object[key] = module.exports.processStringSync(object[key], context, opts) } else if (typeof val === "object") { object[key] = module.exports.processObjectSync(object[key], context, opts) } } return object } /** * This will process a single handlebars containing string. If the string passed in has no valid handlebars statements * then nothing will occur. This is a pure sync call and therefore does not have the full functionality of the async call. * @param {string} string The template string which is the filled from the context object. * @param {object} context An object of information which will be used to enrich the string. * @param {object|undefined} [opts] optional - specify some options for processing. * @returns {string} The enriched string, all templates should have been replaced if they can be. */ module.exports.processStringSync = (string, context, opts) => { // Take a copy of input in case of error const input = string if (typeof string !== "string") { throw "Cannot process non-string types." } try { const template = createTemplate(string, opts) const now = Math.floor(Date.now() / 1000) * 1000 return processors.postprocess( template({ now: new Date(now).toISOString(), __opts: opts, ...context, }) ) } catch (err) { return input } } /** * By default with expressions like {{ name }} handlebars will escape various * characters, which can be problematic. To fix this we use the syntax {{{ name }}}, * this function will find any double braces and switch to triple. * @param string the string to have double HBS statements converted to triple. */ module.exports.disableEscaping = string => { const matches = findDoubleHbsInstances(string) if (matches == null) { return string } // find the unique set const unique = [...new Set(matches)] for (let match of unique) { // add a negative lookahead to exclude any already const regex = new RegExp(`${match}(?!})`, "g") string = string.replace(regex, `{${match}}`) } return string } /** * Simple utility function which makes sure that a templating property has been wrapped in literal specifiers correctly. * @param {string} property The property which is to be wrapped. * @returns {string} The wrapped property ready to be added to a templating string. */ module.exports.makePropSafe = property => { return `[${property}]`.replace("[[", "[").replace("]]", "]") } /** * Checks whether or not a template string contains totally valid syntax (simply tries running it) * @param string The string to test for valid syntax - this may contain no templates and will be considered valid. * @param [opts] optional - specify some options for processing. * @returns {boolean} Whether or not the input string is valid. */ module.exports.isValid = (string, opts) => { const validCases = [ "string", "number", "object", "array", "cannot read property", "undefined", "json at position 0", ] // this is a portion of a specific string always output by handlebars in the case of a syntax error const invalidCases = [`expecting '`] // don't really need a real context to check if its valid const context = {} try { const template = createTemplate(string, { ...opts, noFinalise: true, }) template(context) return true } catch (err) { const msg = err && err.message ? err.message : err if (!msg) { return false } const invalidCase = invalidCases.some(invalidCase => msg.toLowerCase().includes(invalidCase) ) const validCase = validCases.some(validCase => msg.toLowerCase().includes(validCase) ) // special case for maths functions - don't have inputs yet return validCase && !invalidCase } } /** * We have generated a static manifest file from the helpers that this string templating package makes use of. * This manifest provides information about each of the helpers and how it can be used. * @returns The manifest JSON which has been generated from the helpers. */ module.exports.getManifest = () => { return manifest } /** * Checks if a HBS expression is a valid JS HBS expression * @param handlebars the HBS expression to check * @returns {boolean} whether the expression is JS or not */ module.exports.isJSBinding = handlebars => { return module.exports.decodeJSBinding(handlebars) != null } /** * Encodes a raw JS string as a JS HBS expression * @param javascript the JS code to encode * @returns {string} the JS HBS expression */ module.exports.encodeJSBinding = javascript => { return `{{ js "${btoa(javascript)}" }}` } /** * Decodes a JS HBS expression to the raw JS code * @param handlebars the JS HBS expression * @returns {string|null} the raw JS code */ module.exports.decodeJSBinding = handlebars => { if (!handlebars || typeof handlebars !== "string") { return null } // JS is only valid if it is the only HBS expression if (!handlebars.trim().startsWith("{{ js ")) { return null } const captureJSRegex = new RegExp(/{{ js "(.*)" }}/) const match = handlebars.match(captureJSRegex) if (!match || match.length < 2) { return null } return atob(match[1]) } /** * Same as the doesContainString function, but will check for all the strings * before confirming it contains. * @param {string} template The template string to search. * @param {string[]} strings The strings to look for. * @returns {boolean} Will return true if all strings found in HBS statement. */ module.exports.doesContainStrings = (template, strings) => { let regexp = new RegExp(FIND_HBS_REGEX) let matches = template.match(regexp) if (matches == null) { return false } for (let match of matches) { let hbs = match if (exports.isJSBinding(match)) { hbs = exports.decodeJSBinding(match) } let allFound = true for (let string of strings) { if (!hbs.includes(string)) { allFound = false } } if (allFound) { return true } } return false } /** * Given a string, this will return any {{ binding }} or {{{ binding }}} type * statements. * @param {string} string The string to search within. * @return {string[]} The found HBS blocks. */ module.exports.findHBSBlocks = string => { if (!string || typeof string !== "string") { return [] } let regexp = new RegExp(FIND_ANY_HBS_REGEX) let matches = string.match(regexp) if (matches == null) { return [] } return matches } /** * This function looks in the supplied template for handlebars instances, if they contain * JS the JS will be decoded and then the supplied string will be looked for. For example * if the template "Hello, your name is {{ related }}" this function would return that true * for the string "related" but not for "name" as it is not within the handlebars statement. * @param {string} template A template string to search for handlebars instances. * @param {string} string The word or sentence to search for. * @returns {boolean} The this return true if the string is found, false if not. */ module.exports.doesContainString = (template, string) => { return exports.doesContainStrings(template, [string]) } module.exports.convertToJS = hbs => { const blocks = exports.findHBSBlocks(hbs) let js = "return `", prevBlock = null const variables = {} if (blocks.length === 0) { js += hbs } let count = 1 for (let block of blocks) { let stringPart = hbs if (prevBlock) { stringPart = stringPart.split(prevBlock)[1] } stringPart = stringPart.split(block)[0] prevBlock = block const { variable, value } = convertHBSBlock(block, count++) variables[variable] = value js += `${stringPart.split()}\${${variable}}` } let varBlock = "" for (let [variable, value] of Object.entries(variables)) { varBlock += `const ${variable} = ${value};\n` } js += "`;" return `${varBlock}${js}` }