/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/**
 * This (and the crawler subfolder) is an ES6 version of the following crawler
 * /node_modules/es6-crawler-detect (dependency is kept to have the source close)
 * This is used to be able to babelize wem.js making it compatible with IE11
 */

import {Crawlers}  from './crawler/crawlers';
import {Exclusions}  from './crawler/exclusions';
import {Headers}  from './crawler/headers';

export class Crawler
{
	constructor(request, headers, userAgent)
	{
		/**
		 * Init classes
		 */
		this._init();

		/**
		 * This request must be an object
		 */
		this.request = typeof request === 'object' ? request : {};

		// The regex-list must not be used with g-flag!
		// See: https://stackoverflow.com/questions/1520800/why-does-a-regexp-with-global-flag-give-wrong-results
		this.compiledRegexList = this.compileRegex(this.crawlers.getAll(), 'i');

		// The exclusions should be used with g-flag in order to remove each value.
		this.compiledExclusions = this.compileRegex(this.exclusions.getAll(), 'g');

		/**
		 * Set http headers
		 */
		this.setHttpHeaders(headers);

		/**
		 * Set userAgent
		 */
		this.userAgent = this.setUserAgent(userAgent);
	}

	/**
	 * Init Classes Instances
	 */
	_init()
	{
		this.crawlers   = new Crawlers();
		this.headers    = new Headers();
		this.exclusions = new Exclusions();
	}

	compileRegex(patterns, flags) {
		return new RegExp(patterns.join('|').trim(), flags);
	}

	/**
	 * Set HTTP headers.
	 */
	setHttpHeaders(headers)
	{
		// Use the Request headers if httpHeaders is not defined
        if ( typeof headers === 'undefined' || Object.keys(headers).length === 0 )
        {
        	headers = Object.keys(this.request).length ? this.request.headers : {};
        }

		// Clear existing headers.
		this.httpHeaders = [];

        // Only save HTTP headers.
		for ( const key in headers )
		{
			this.httpHeaders[key] = headers[key];
		}
	}

	/**
	 * Set user agent
	 */
	setUserAgent(userAgent)
	{
		if ( typeof userAgent === 'undefined' || userAgent === null || ! userAgent.length )
		{
			for ( const header of this.getUaHttpHeaders() )
			{
				if ( Object.keys(this.httpHeaders).indexOf(header.toLowerCase()) >= 0 )
				{
					userAgent += this.httpHeaders[header] + ' ';
				}
			}
		}

		return userAgent;
	}

	/**
	 * Get user agent headers
	 */
	getUaHttpHeaders()
	{
		return this.headers.getAll();
	}

	/**
	 * Check user agent string against the regex.
	 */
	isCrawler(userAgent = undefined)
	{
		var agent = (typeof userAgent === 'undefined' || userAgent === null ? this.userAgent : userAgent);

		// test on compiled regx
		agent = agent.replace(this.compiledExclusions, '');

		if ( agent.trim().length === 0 )
		{
			return false;
		}

		var matches = this.compiledRegexList.exec(agent.trim());

		if ( matches )
		{
			this.matches = matches;
		}

		return matches !== null ? (matches.length ? true : false) : false;
	}

	/**
	 * Return the matches.
	 */
	getMatches()
	{
		return this.matches !== undefined ? (this.matches.length ? this.matches[0] : null) : {};
	}
}