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cachedApi.js
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cachedApi.js
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/* eslint-disable func-names */
/* eslint-disable no-use-before-define */
/**
* Class to handle json api calls
* @type {*}
*/
const apiCaller = require('./api')
module.exports = (function () {
/**
* Wrap our constructor in a factory method.
* @param options our options object
* @returns {CachedApi} a new instance of an Api class
*/
function factory(options) {
return new CachedApi(options)
}
/**
* Constructor for the Api class
* @param options the options object:
* {
* port : int / default: 443
* method : string / default: GET
* host : string / default: none / MANDATORY
* path : string / default: '/'
* debugMode : boolean / default: false
* https : boolean / default: true
* headers : object / default: undefined
* json : boolean / default: false
* }
* @constructor
*/
function CachedApi(options) {
this.api = apiCaller(options)
this.key = options.path
this.log = options.log
this.debugMode = options.debugMode || false
if (!options.cache) {
throw new Error('Cannot create cached API without reference to a cache implementation')
}
this.cache = options.cache
this.debugPrint = function (msg) {
const self = this
if (self.debugMode) {
// eslint-disable-next-line no-console
console.log(msg)
}
}
}
/**
* Sends a GET request to the configured api expecting a text/plain response
*/
CachedApi.prototype.promisedGetText = function () {
const self = this
self.debugPrint('Calling promisedGetText for path: ' + self.key)
return readRedisCache(self).catch(err => {
self.debugPrint('Not found in cache[' + err + '], try data source: ' + self.key)
return self.api.promisedGetText().then(result => storeInRedisAndReturnResult(self, result))
})
}
/**
* Method returning api calls as promise.
* The promise will be resolved with
* - the error if call fails
* - the response object/json
* @return Promise for the api call
*/
CachedApi.prototype.promisedApiCall = function () {
const self = this
self.debugPrint('Calling promisedApiCall for path: ' + self.key)
return readRedisCache(self)
.then(result => {
let jsonResult = result
if (typeof result === 'string') {
jsonResult = JSON.parse(result)
}
return jsonResult
})
.catch(err => {
self.debugPrint('Not found in cache[' + err + '], try data source: ' + self.key)
return self.api.promisedApiCall().then(result => storeInRedisAndReturnResult(self, result))
})
}
// helper functions
// TODO ta in app prefix från package med require(package)
function readRedisCache(self) {
self.debugPrint('Read redis cache for: ' + self.key)
return self.cache.get(self.key)
}
function storeInRedisAndReturnResult(self, result) {
self.debugPrint('Store value in redis cache by: ' + self.key)
let value = result
if (typeof value === 'object') {
value = JSON.stringify(result)
}
self.cache.set(self.key, value)
return result
}
return factory
})()