/**
 * Request Analyzer
 * Belongs to Decentraleyes.
 *
 * @author      Thomas Rientjes
 * @since       2016-04-11
 * @license     MPL 2.0
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/.
 */

'use strict';

/**
 * Request Analyzer
 */

var requestAnalyzer = {};

/**
 * Public Methods
 */

requestAnalyzer.isValidCandidate = function (requestDetails, tabDetails) {

    let initiatorDomain, isWhitelisted;

    initiatorDomain = helpers.extractDomainFromUrl(tabDetails.url, true);

    if (initiatorDomain === null) {
        initiatorDomain = Address.EXAMPLE;
    }

    isWhitelisted = requestAnalyzer.whitelistedDomains[initiatorDomain];

    if (isWhitelisted) {
        return false;
    }

    // Only requests of type GET can be valid candidates.
    return requestDetails.method === WebRequest.GET;
};

requestAnalyzer.getLocalTarget = function (requestDetails) {

    let destinationUrl, destinationHost, destinationPath, hostMappings, basePath, resourceMappings;

    destinationUrl = new URL(requestDetails.url);

    destinationHost = destinationUrl.host;
    destinationPath = destinationUrl.pathname;

    // Use the proper mappings for the targeted host.
    hostMappings = mappings[destinationHost];

    // Resource mapping files are never locally available.
    if (Resource.MAPPING_EXPRESSION.test(destinationPath)) {
        return false;
    }

    basePath = requestAnalyzer._matchBasePath(hostMappings, destinationPath);
    resourceMappings = hostMappings[basePath];

    if (!resourceMappings) {
        return false;
    }

    // Return either the local target's path or false.
    return requestAnalyzer._findLocalTarget(resourceMappings, basePath, destinationHost, destinationPath);
};

/**
 * Private Methods
 */

requestAnalyzer._matchBasePath = function (hostMappings, channelPath) {

    for (let basePath of Object.keys(hostMappings)) {

        if (channelPath.startsWith(basePath)) {
            return basePath;
        }
    }

    return false;
};

requestAnalyzer._findLocalTarget = function (resourceMappings, basePath, channelHost, channelPath) {

    let resourcePath, versionNumber, resourcePattern, filename;

    chrome.storage.local.get(Setting.LOGGING, function (items) {
        requestAnalyzer.logging = items.enableLogging;
    });

    resourcePath = channelPath.replace(basePath, '');
    versionNumber = resourcePath.match(Resource.VERSION_EXPRESSION);
    resourcePattern = resourcePath.replace(versionNumber, Resource.VERSION_PLACEHOLDER);

    /*
        NOTE:
        jsDelivr allows to load several files in one request
        This is just a workaround. If there are more websites which use this, we will have to do crazy things here to find and redirect these files.

        It's not possible to respond to a request with multiple redirections
        https://gitlab.com/nobody42/localcdn/-/issues/45
    */
    let regexJsDelivr = RegExp(/\/combine.*jquery.*hogan.*algoliasearch.*autocomplete.*/);
    if (channelHost.includes('cdn.jsdelivr.net') && regexJsDelivr.test(channelPath)) {
        return {
            'source': channelHost,
            'version': 'beta',
            'path': 'resources/jsdelivr-combine-jquery-hogan-algoliasearch-autocomplete.jsm',
            'bundle': ''
        };
    }



    for (let resourceMold of Object.keys(resourceMappings)) {

        if (resourcePattern.startsWith(resourceMold)) {

            let targetPath, hostShorthands, version;

            targetPath = resourceMappings[resourceMold].path;
            targetPath = targetPath.replace(Resource.VERSION_PLACEHOLDER, versionNumber);

            // Replace the requested version with the latest depending on major version
            version = helpers.setLastVersion(targetPath, versionNumber).toString();
            targetPath = targetPath.replace(versionNumber, version);

            hostShorthands = shorthands[channelHost];

            if (hostShorthands && hostShorthands[targetPath]) {

                let shorthand = hostShorthands[targetPath];

                targetPath = shorthand.path;
                version = shorthand.version;

            } else {
                version = versionNumber && versionNumber[0] || targetPath.match(Resource.VERSION_EXPRESSION);
            }

            // Get bundle name
            let bundle = helpers.determineBundle(channelPath);
            if(bundle !== '') {
                filename = channelPath.split('/').pop();
                targetPath = ( RegExp('.*\.css$').test(filename) ) ? targetPath + filename : targetPath + filename + 'm';
            }

            if (requestAnalyzer.logging) {
                console.log('[ LocalCDN ] Replaced resource: ' + targetPath);
            }
            // Prepare and return a local target.
            return {
                'source': channelHost,
                'version': version,
                'path': targetPath,
                'bundle': bundle
            };
        }
    }
    if (requestAnalyzer.logging) {
        console.warn('[ LocalCDN ] Missing resource: ' + channelHost + channelPath);
    }
    return false;
};

requestAnalyzer._applyWhitelistedDomains = function () {

    chrome.storage.local.get(Setting.WHITELISTED_DOMAINS, function (items) {
        requestAnalyzer.whitelistedDomains = items.whitelistedDomains || {};
    });
};

/**
 * Initializations
 */

requestAnalyzer.whitelistedDomains = {};
requestAnalyzer._applyWhitelistedDomains();

/**
 * Event Handlers
 */

chrome.storage.onChanged.addListener(requestAnalyzer._applyWhitelistedDomains);