const utilLib = require('/lib/enonic/util');

const cacheLib = require('/lib/cache');
const pageContributionsCache = cacheLib.newCache({
    size: 100,
    expire: 10800 // 30 hours
});

const { normalizeEntryNames, getAllUrls } = require('./dependencies');


/** Wraps a url in a script tag and appends it to pageContributions.js.bodyEnd with an async tag. The reason for choosing
 *  bodyEnd is that this allows display of server-side-rendered content or placeholders before starting to load the
 *  acrtive components. The component-render-triggering <script> tag should have a defer attribute in order to wait for
 *  these to load. */
const appendToBodyEnd = (url, pageContributions) => {
    pageContributions.bodyEnd = [
        ...(pageContributions.bodyEnd || []),
        `<script src="${url}" ></script>\n`,
    ];
};


/** Use the json files built by webpack in other libraries (react4xp-build-components, react4xp-runtime-externals, react4xp-runtime-client)
 *  to fetch items of <script src="url" /> for common chunks:
 *   -the dependency chunks of specific entries (array of entry names in the argument, gets all of the dependencies if empty),
 *   -an optional Externals chunk,
 *   -and an optional frontend-client chunk (which falls back to the built-in client url if missing)?
 * @param entries An array (also accepts string, if only one item) of Entry names for React4xp components, for which we want to build the set
 * of dependencies.
 * @returns an object ready to be returned as a pageContributions.js from an XP component. Puts dependencies into the bodyEnd attribute. */
const buildPageContributions = (entries) => {

    const chunkUrls = getAllUrls(entries);

    const pageContributions = {};
    chunkUrls.forEach(chunkUrl => appendToBodyEnd(chunkUrl, pageContributions));

    return pageContributions;
};



// ---------------------------------------------------------------


const getUniqueEntries = (arrayOfArrays, controlSet) => {
    const uniqueEntries = [];
    arrayOfArrays.forEach(arr => {
        utilLib.data.forceArray(arr).forEach(item => {
            if (controlSet.indexOf(item) === -1) {
                uniqueEntries.push(item);
                controlSet.push(item);
            }
        });
    });
    return uniqueEntries;
};


/** Adds page contributions for an (optional) set of entries.  Merges different pageContributions.js objects into one. Prevents duplicates: no single pageContribution entry is
 * repeated, this prevents resource-wasting by loading/running the same script twice).
 *
 * @param incomingPgContrib incoming pageContributions.js (from other components / outside / previous this rendering)
 * @param newPgContrib pageContributions.js that this specific component will add.
 *
 * Also part of the merge: PAGE_CONTRIBUTIONS, the common standard React4xp page contributions
 */
const getAndMergePageContributions = (entryNames, incomingPgContrib, newPgContrib) => {
    entryNames = normalizeEntryNames(entryNames);
    const entriesPgContrib = pageContributionsCache.get(entryNames.join("*"), ()=> buildPageContributions(entryNames));

    if (!incomingPgContrib && !newPgContrib) {
        return entriesPgContrib;
    }
    incomingPgContrib = incomingPgContrib || {};
    newPgContrib = newPgContrib || {};

    // Keeps track of already-added entries across headBegin, headEnd, bodyBegin and bodyEnd
    const controlSet = [];

    return {
        headBegin: getUniqueEntries([entriesPgContrib.headBegin, incomingPgContrib.headBegin, newPgContrib.headBegin], controlSet),
        headEnd: getUniqueEntries([entriesPgContrib.headEnd, incomingPgContrib.headEnd, newPgContrib.headEnd], controlSet),
        bodyBegin: getUniqueEntries([entriesPgContrib.bodyBegin, incomingPgContrib.bodyBegin, newPgContrib.bodyBegin], controlSet),
        bodyEnd: getUniqueEntries([entriesPgContrib.bodyEnd, incomingPgContrib.bodyEnd, newPgContrib.bodyEnd], controlSet)
    };
};



// ------------------------------------------------------------------

module.exports = {
    getAndMergePageContributions,
};