libresilient/plugins/cache.js

/* ========================================================================= *\
|* === Stashing plugin using the Cache API                               === *|
\* ========================================================================= */

// no polluting of the global namespace please
(function () {

    /*
     * plugin config settings
     */
    
    // sane defaults
    let defaultConfig = {
        // name of this plugin
        // should not be changed
        name: "cache"
    }
    
    // merge the defaults with settings from LibResilientConfig
    let config = {...defaultConfig, ...self.LibResilientConfig.plugins[defaultConfig.name]}
    
    /**
     * getting content from cache
     */
    let getContentFromCache = (url) => {
        self.log(config.name, `getting from cache: ${url}`)
        return caches.open('v1')
            .then((cache) => {
                return cache.match(url)
            })
            .then((response) => {
                if ((typeof response === 'undefined') || (response === null) ) {
                    throw new Error('Resource not found in cache');
                } else {
                    var msg = 'retrieved cached headers:'
                    response.headers.forEach((v, k)=>{
                        msg += `\n+-- ${k} : ${v}`
                    })
                    self.log(config.name, msg)
                    // return the response
                    return response
                }
            })
    }

    /**
     * add resources to cache
     * 
     * implements the stash() LibResilient plugin method
     * 
     * accepts either a Response
     * or a string containing a URL
     * or an Array of string URLs
     */
    let cacheContent = (resource, key) => {
        return caches.open('v1')
            .then((cache) => {
                if (typeof resource === 'string') {
                    // assume URL
                    self.log(config.name, "caching an URL: " + resource)
                    return cache.add(resource)
                } else if (Array.isArray(resource)) {
                    // assume array of URLs
                    self.log(config.name, "caching an Array of URLs")
                    return cache.addAll(resource)
                } else {
                    // assume a Response
                    // which means we either have a Request in key, a string URL in key,
                    // or we can use the URL in resource.url
                    if ( (typeof key !== 'object') && ( (typeof key !== 'string') || (key === '') ) ) {
                        if (typeof resource.url !== 'string' || resource.url === '') {
                            throw new Error('No URL to work with!')
                        }
                        key = resource.url
                    }
                    
                    // we need to create a new Response object
                    // with all the headers added explicitly
                    // otherwise the x-libresilient-* headers get ignored
                    var init = {
                        status:     resource.status,
                        statusText: resource.statusText,
                        headers: {}
                    };
                    if (typeof resource.url === 'string' && resource.url !== '') {
                        init.url = resource.url
                    }
                    resource.headers.forEach(function(val, header){
                        init.headers[header] = val;
                    });
                    return resource
                            .blob()
                            .then((blob) => {
                                self.log(config.name, "caching a Response to: " + key)
                                return cache.put(key, new Response(
                                    blob,
                                    init
                                ))
                            })
                }
            })
    }

    /**
     * remove resources from cache
     * 
     * implements the unstash() LibResilient plugin method 
     * 
     * accepts either a Response
     * or a string containing a URL
     * or an Array of string URLs
     */
    let clearCachedContent = (resource) => {
        return caches.open('v1')
            .then((cache) => {
                if (typeof resource === 'string') {
                    // assume URL
                    self.log(config.name, "deleting a cached URL")
                    return cache.delete(resource)
                } else if (Array.isArray(resource)) {
                    // assume array of URLs
                    self.log(config.name, "deleting an Array of cached URLs")
                    return Promise.all(
                        resource.map((res)=>{
                            return cache.delete(res)
                        })
                    )
                } else {
                    // assume a Response
                    // which means we have an URL in resource.url
                    self.log(config.name, "removing a Response from cache: " + resource.url)
                    return cache.delete(resource.url)
                }
            })
    }


    // and add ourselves to it
    // with some additional metadata
    self.LibResilientPlugins.push({
        name: config.name,
        description: 'Locally cached responses, using the Cache API.',
        version: 'COMMIT_UNKNOWN',
        fetch: getContentFromCache,
        stash: cacheContent,
        unstash: clearCachedContent
    })

// done with not polluting the global namespace
})()