'use strict';
/*
 * Copyright (c) 2015-2016, Willem Cazander
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification, are permitted provided
 * that the following conditions are met:
 *
 * * Redistributions of source code must retain the above copyright notice, this list of conditions and the
 *   following disclaimer.
 * * Redistributions in binary form must reproduce the above copyright notice, this list of conditions and
 *   the following disclaimer in the documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
 * THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
 * TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */


// TODO:
// set tag.media = 'only you';
// add media in resouces 
// check supported browsers

/**
 * FFSpaLoader is an assets loader for single page applications.
 * Its build around the concept the there is only a single static index.html which
 * synces all its assets to local cache for offline and or fast page loads. 
 * 
 * Features:
 * - Assets caching for offline use.
 * - Assets hashing for fast syncing.
 * - Assets types: js,css,cssData
 * - Caching backends: null,localStorage,webSqlDB,sqllite
 * - Optional ask and cache server assets url. 
 * - Cordova deviceready event booting.
 *
 * @module FFSpaLoader
 */
var FFSpaLoader = (/** @lends module:FFSpaLoader */function () {
	
	var options = {
		debug:        false,
		errorHandler: null,
		bootDevice: {
			timeout:    4096,
			windowFlag: 'FFCordovaDevice'
		},
		askUrl: {
			urlTransport:  'http://',
			questionText:  'Please provide the server name;',
			cssText:       '.ffAskUrl { font-size: 1em;margin: auto;width: 50%;border: 3px solid #73AD21;padding: 1em;} .ffAskUrl > div {font-size: 0.8em;color: #ccc;} .ffAskUrl > div > * {} .ffAskUrl > div > input {} .ffAskUrlError{ color: red}',
		},
		server: {
			url:      null,
			urlPath:  null,
			timeout:  4096,
			windowFlag: 'FFServerUrl',
			header: {
				request: {
					'X-FFSpaLoader': '42'
				},
				response: {
				}
			}
		},
		cache: {
			factory: null,
			meta:    null,
			js:      null,
			css:     null,
			cssData: null
		}
	};
	
	/**
     * Prints debug message to the console if options.debug is true.
     * @param {String} message	The message to log.
     * @private
     */
	var utilDebug = function (message) {
		if (options.debug !== true) {
			return;
		}
		console.log('FFSpaLoader.'+message);
	};
	
	var factory = {
		detect: {
			localStorage: function() {
			    try {
			    	var testData = 'localStorageDetect';
			        localStorage.setItem(testData, testData);
			        localStorage.removeItem(testData);
			        return true;
			    } catch(e) {
			        return false;
			    }
			},
			openDatabase: function() {
				return 'openDatabase' in window;
			},
			sqlitePlugin: function() {
				return 'sqlitePlugin' in window;
			},
			cordova: function() {
				return 'cordova' in window;
			},
			cordovaDevice: function() {
				return options.bootDevice.windowFlag in window;
			},
			mobileAgent: function() {
				return navigator.userAgent.match(/(iPhone|iPod|iPad|Android|BlackBerry|IEMobile)/);
			}
		},
		cache: {
			localStorage: function() {
				return {
					cacheGetValue: function(key, cb) {
						try {
							var dataRaw = localStorage.getItem(key);
							var data = JSON.parse(dataRaw); 
							cb(null, data);
						} catch(e) {
							cb(e);
						}
					},
					cacheSetValue: function(key, value, cb) {
						try {
							localStorage.setItem(key,JSON.stringify(value));
							cb(null);
						} catch(e) {
							cb(e);
						}
					},
					cacheDeleteValue: function(key, cb) {
						try {
							localStorage.removeItem(key);
							cb(null);
						} catch(e) {
							cb(e);
						}
					}
				}
			},
			websql: function(opt) {
				if (opt === undefined)              { opt = {}; }
				if (opt.name === undefined)         { opt.name = 'ffSpaLoader.db'; }
				if (opt.size === undefined)         { opt.size = -1;  }
				if (opt.version === undefined)      { opt.version = '1.0';      }
				if (opt.openDatabase === undefined) { opt.openDatabase = window.openDatabase; }
				var nullDataHandler = function(cb) {
					return function (tx, results) {
						cb(null);
					};
				};
				var sqlErrorHandler = function(cb) {
					return function (tx, err) {
						cb(err.message+' code: '+err.code);
					};
				};
				var cacheDB = window.openDatabase(opt.name, opt.version, opt.name, opt.size);
				cacheDB.transaction(function(tx) {
					var query = 'SELECT value FROM cache_store WHERE key = \"test-for-table\"';
					utilDebug('websql.init query: '+query);
					tx.executeSql(query, [], function(tx,res) {}, function(tx,errorNoTable) {
						var query = 'CREATE TABLE cache_store(id INTEGER PRIMARY KEY AUTOINCREMENT, key TEXT NOT NULL, value TEXT NOT NULL)';
						utilDebug('websql.init query: '+query);
						tx.executeSql(query, [], function(tx,res) {
							var query = 'CREATE UNIQUE INDEX cache_store__key__udx ON cache_store (key)';
							utilDebug('websql.init query: '+query);
							tx.executeSql(query, [], function(tx,res) {}, sqlErrorHandler(options.errorHandler)); // FIX<E: asyns error ?
						}, sqlErrorHandler(options.errorHandler));	
					});
				});
				return {
					cacheGetValue: function(key, cb) {
						cacheDB.transaction(function(tx) {
							var query = 'SELECT value FROM cache_store WHERE key = ?';
							utilDebug('websql.cacheGetValue query: '+query);
							tx.executeSql(query,[key], function(tx, res) {
								if (res.rows.length === 0) {
									cb(null, null);
								} else {
									var value = res.rows.item(0).value;
									cb(null, JSON.parse(value));
								}
							}, sqlErrorHandler(cb));
						});
					},
					cacheSetValue: function(key, value, cb) {
						cacheDB.transaction(function(tx) {
							var query = 'SELECT value FROM cache_store WHERE key = ?';
							utilDebug('websql.cacheSetValue query: '+query);
							tx.executeSql(query,[key], function(tx, res) {
								if (res.rows.length === 0) {
									var query = 'INSERT INTO cache_store (key,value) VALUES (?,?)';
									utilDebug('websql.cacheSetValue query: '+query);
									tx.executeSql(query, [key,JSON.stringify(value)], nullDataHandler(cb), sqlErrorHandler(cb));		
								} else {
									var query = 'UPDATE cache_store SET value = ? WHERE key = ?';
									utilDebug('websql.cacheSetValue query: '+query);
									tx.executeSql(query, [JSON.stringify(value),key], nullDataHandler(cb), sqlErrorHandler(cb));
								}
							}, sqlErrorHandler(cb));
						});
					},
					cacheDeleteValue: function(key, cb) {
						cacheDB.transaction(function(tx) {
							var query = 'DELETE FROM cache_store WHERE key = ?';
							utilDebug('websql.cacheDeleteValue query: '+query);
							tx.executeSql(query, [key], nullDataHandler(cb), sqlErrorHandler(cb));
						});						
					}
				}
			},
		}
	};
	
	/**
     * The default error handler which renders the error in the browser.
     * @param {String|Error} err	The error message.
     * @private
     */
	var utilErrorHandler = function(err) {
		utilDebug('utilErrorHandler error: '+err);
		
		var rootTag = document.createElement('div');
		rootTag.setAttribute('class','ffError');
		
		var cssTag = document.createElement("style");
		cssTag.type = "text/css";
		cssTag.innerHTML = '.ffError { margin: auto;width: 50%;border: 3px solid red;padding: 1em;} .ffAskUrl > div {font-size: 0.8em;color: red;}';
		rootTag.appendChild(cssTag);

		var titleTag = document.createElement('h1');
		titleTag.appendChild(document.createTextNode('Error'));
		rootTag.appendChild(titleTag);
		
		var questionTag = document.createElement('p');
		questionTag.appendChild(document.createTextNode(err));
		rootTag.appendChild(questionTag);
		
		document.getElementsByTagName('body')[0].appendChild(rootTag);
	};
	options.errorHandler = utilErrorHandler;
	
	/**
     * Fetches an url resource with a XMLHttpRequest.
     * @param {String} url	The url to fetch.
     * @param {function} cb	The callback for error and request if ready.
     * @private
     */
	var utilHttpFetch = function (url, cb) {
		var startTime = new Date().getTime();
		var httpRequest = new XMLHttpRequest();
		httpRequest.onreadystatechange = function() {
			if (httpRequest.readyState == 4 && httpRequest.status === 200) {
				utilDebug('utilHttpFetch url: '+url+' done in '+(new Date().getTime()-startTime)+' ms.');
				cb(null, httpRequest);
			} else if (httpRequest.readyState == 4) {
				cb('Wrong status: '+httpRequest.status);
			}
		}
		httpRequest.open('GET', url, true);
		httpRequest.timeout = options.server.timeout; // ieX: after open()
		httpRequest.ontimeout = function() {
			cb('timeout after '+options.server.timeout+' of url: '+url);
		};
		httpRequest.send();
	};

	var cacheGetService = function (type) {
		if (options.cache[type]) {
			return options.cache[type];
		}
		if (options.cache['factory']) {
			return options.cache['factory'];
		}
		return null;
	};
	
	var cacheHasService = function (type) {
		return cacheGetService(type) !== null;
	};

	var cacheCheckType = function (type, cb, action) {
		cacheHasService(type)?action():cb('No caching for: '+type);
	};
	
	var cacheGetValue = function(type, key , cb) {
		cacheCheckType(type, cb, function() {
			var cacheKey = type+'_'+key;
			utilDebug('cacheGetValue key: '+cacheKey);
			cacheGetService(type).cacheGetValue(cacheKey,cb);	
		});
	};
	
	var cacheSetValue = function(type, key, value, cb) {
		cacheCheckType(type, cb, function() {
			var cacheKey = type+'_'+key;
			utilDebug('cacheSetValue key: '+cacheKey);
			cacheGetService(type).cacheSetValue(cacheKey,value,cb);	
		});
	};
	
	var cacheDeleteValue = function(type, key, cb) {
		cacheCheckType(type, cb, function() {
			var cacheKey = type+'_'+key;
			utilDebug('cacheDeleteValue key: '+cacheKey);
			cacheGetService(type).cacheDeleteValue(cacheKey,cb);	
		});
	};
	
	var cleanupCache = function (resources, cb) {
		utilDebug('cleanupCache TODO cacheList: '+0+' resources: '+resources.length);
		
		// TODO: impl for removes in resource lists
		cb(null);
	};
	
	var injectResourceData = function(resource, data, cb) {
		utilDebug('injectResourceData resource: '+JSON.stringify(resource)+' data: '+data.length);
		var tag = null;
		if (resource.type === 'css' || resource.type === 'cssData') {
			tag = document.createElement('style');
			tag.type = 'text/css';
		}
		if (resource.type === 'js') {
			tag = document.createElement('script');
			tag.type = 'text/javascript';
		}
		tag.appendChild(document.createTextNode(data));
		
		document.getElementsByTagName('head')[0].appendChild(tag);
		//var ref = document.getElementsByTagName('script')[0];
		//ref.parentNode.insertBefore(tag, ref); // note in reverse order	
		cb(null);
	};
	
	var storeResourceKey = function (resource, cb) {
		// Add all cache keys in central list so we can clear the cache item if resources are removed.
		var cacheKey = resource.type+'_keys';
		cacheGetValue('meta',cacheKey,function (err,value) {
			if (err !== null) {
				cb(err);
				return;
			}
			if (value === null) {
				value = [];
			}
			value.push(resource.hash);
			cacheSetValue('meta',cacheKey,value, cb);
		});
	}
	
	var storeResource = function (resource, httpRequest, cb) {
		utilDebug('storeResource url: '+resource.url+' hash: '+resource.hash);
		var item = {
			resource: resource,
			data: httpRequest.responseText
		}
		cacheSetValue(resource.type, resource.hash, item , function(err) {
			if (err !== null) {
				cb(err);
			} else {
				storeResourceKey(resource,cb);
			}
		});
	};
	
	var loadResource = function (resource, cb) {
		var resourceUrl = resource.url;
		if (resourceUrl.indexOf('http') === -1) {
			resourceUrl = options.server.url + resourceUrl;
		}
		utilDebug('loadResource '+JSON.stringify(resource));
		if (cacheHasService(resource.type)) {
			cacheGetValue(resource.type,resource.hash,function(err, value) {
				if (err !== null) {
					cb(err);
					return;
				}
				if (value === null) {
					utilDebug('loadResource cache miss');
				} else if (value.resource === undefined) {
					utilDebug('loadResource cache wrong obj');
				} else if (value.resource.hash !== resource.hash) {
					utilDebug('loadResource cache hash mismatch');
				} else {
					utilDebug('loadResource cache hit');
					injectResourceData(value.resource,value.data,cb);
					return;
				}
				utilHttpFetch(resourceUrl, function(err, httpRequest) {
					if (err !== null) {
						cb(err);
					} else {
						storeResource(resource, httpRequest, function (err) {
							injectResourceData(resource,httpRequest.responseText,cb);
						});
					}
				});
			});
		} else {
			// note: was links but now download + inject so order stays sequenced
			utilHttpFetch(resourceUrl, function(err, httpRequest) {
				if (err !== null) {
					cb(err);
				} else {
					injectResourceData(resource,httpRequest.responseText,cb);
				}
			});
		}
	};
	
	var loadResources = function(resources, cb) {
		var startTime = new Date().getTime();
		utilDebug('loadResources');
		var resourceStack = resources;
		var resourceLoader = function(err) {
			if (err !== null) {
				cb(err);
				return;
			}
			resourceStack = resourceStack.slice(1);
			if (resourceStack.length === 0) {
				utilDebug('loadResources done in '+(new Date().getTime()-startTime)+' ms.');
				cb(null);
			} else {
				loadResource(resourceStack[0],resourceLoader);
			}
		};
		loadResource(resourceStack[0],resourceLoader);
	};

	var injectResources = function(resources, cb) {
		var startTime = new Date().getTime();
		utilDebug('injectResources');
		resources.forEach(function (resource) {
			cacheGetValue(resource.type,resource.hash,function(err,item) {
				// TODO injectResourceData
				
				var tag = null;
				if (resource.type === 'css' || resource.type === 'cssData') {
					tag = document.createElement('style');
					tag.type = 'text/css';
				}
				if (resource.type === 'js') {
					tag = document.createElement('script');
					tag.type = 'text/javascript';
				}
				utilDebug('injectResources resource: '+JSON.stringify(resource));
				
				tag.appendChild(document.createTextNode(item.data));
				
				//document.getElementsByTagName('head')[0].appendChild(tag);
				var ref = document.getElementsByTagName('script')[0];
				ref.parentNode.insertBefore(tag, ref); // note in reverse order	
			});
		});
		utilDebug('injectResources done in '+(new Date().getTime()-startTime)+' ms.');
		cb(null); // FIXME async
	};
	
	/**
     * Starts loader by downloading resource list or using cache version to 
     * load/refresh/inject the resources.
     * 
     * @param {function} cb Callback gets called when loader is done.
     * @private
     */
	var startLoader = function (cb) {
		if (options.server.url === null) {
			cb('Missing options.server.url');
			return;
		}
		if (options.server.urlPath === null) {
			cb('Missing options.server.urlPath');
			return;
		}
		window[options.server.windowFlag] = options.server.url; 
		
		var resourcesUrl = options.server.url + options.server.urlPath;
		utilDebug('startLoader serverUrl: '+resourcesUrl);
		utilHttpFetch(resourcesUrl, function(err, httpRequest) {
			if (err !== null) {
				utilDebug('startLoader fetch error: '+err);
				if (cacheHasService('meta')) {
					cacheGetValue('meta','server_resources',function(err, value) {
						if (err !== null) {
							cb(err);
						} else if (value === null) {
							cb('Have no cache of server resouces from: '+options.server.url);
						} else {
							injectResources(value, cb);
						}
					});
				} else {
					cb('Could not fetch server resouces from: '+options.server.url);
				}
				return;
			}
			var resources = [];
			JSON.parse(httpRequest.responseText).data.resources.forEach(function (r) {
				resources.push(r);
			});
			utilDebug('startLoader resources: '+resources.length);
			if (cacheHasService('meta')) {
				cacheSetValue('meta','server_resources',resources, function (err) {
					if (err !== null) {
						cb(err);
					} else {
						loadResources(resources, cb);
					}
				});
			} else {
				loadResources(resources, cb);				
			}
		});
	};
	
	/**
     * Validates the user input url by downloading it.
     * 
     * @param {function} cb Callback gets called when loader is done.
     * @param {Element} deleteTag The dom element to remove from the body tag after success.
     * @private
     */
	var askUrlValidate = function (cb,deleteTag) {
		var inputTag = document.getElementById('serverInput');
		var inputErrorTag = document.getElementById('serverInputError');
		
		while (inputErrorTag.firstChild) {
			inputErrorTag.removeChild(inputErrorTag.firstChild); // clear error
		}
		
		options.server.url = '';
		if (options.askUrl.urlTransport !== undefined) {
			options.server.url += options.askUrl.urlTransport;
		}
		options.server.url += inputTag.value;
		
		var resourcesUrl = options.server.url + options.server.urlPath;  
		utilDebug('askUrlStart check url: '+resourcesUrl);
		
		// TODO: add+check headers
		utilHttpFetch(resourcesUrl,function(err, req) {
			if (err !== null) {
				inputErrorTag.appendChild(document.createTextNode('Error could not get data.'));
				return;
			}
			document.getElementsByTagName('body')[0].removeChild(deleteTag);
			if (cacheHasService('meta')) {
				cacheSetValue('meta','server_url',options.server.url, function(err) {
					if (err !== null) {
						cb(err);				
					} else {
						startLoader(cb);
					}
				});
			} else {
				startLoader(cb);
			}
		})
	}
	
	/**
     * Creates the ask url ui.
     * 
     * @param {function} cb Callback gets called when loader is done.
     * @private
     */
	var askUrl = function (cb) {
		utilDebug('askUrl create ui');
		
		var rootTag = document.createElement('div');
		rootTag.setAttribute('class','ffAskUrl');
		
		var cssTag = document.createElement("style");
		cssTag.type = "text/css";
		cssTag.innerHTML = options.askUrl.cssText;
		rootTag.appendChild(cssTag);
		
		var questionTag = document.createElement('p');
		questionTag.appendChild(document.createTextNode(options.askUrl.questionText));
		rootTag.appendChild(questionTag);
		
		var formTag = document.createElement('div');
		rootTag.appendChild(formTag);
		
		if (options.urlTransport !== undefined) {
			var transportTag = document.createElement('label');
			rootTag.setAttribute('for','serverInput');
			transportTag.appendChild(document.createTextNode(options.urlTransport));
			formTag.appendChild(transportTag);
		}
		var inputTag = document.createElement('input');
		inputTag.type = 'text';
		inputTag.id = 'serverInput';
		inputTag.setAttribute('autofocus','');
		inputTag.setAttribute('onkeydown','if (event.keyCode == 13) {document.getElementById(\'serverSubmit\').click()}');
		formTag.appendChild(inputTag);
		
		var submitLineTag = document.createElement('br');
		formTag.appendChild(submitLineTag);
		
		var submitTag = document.createElement('input');
		submitTag.id = 'serverSubmit';
		submitTag.type = 'submit';
		submitTag.value = 'Start';
		submitTag.onclick = function() {askUrlValidate(cb,rootTag);};
		formTag.appendChild(submitTag);
		
		var serverErrorTag = document.createElement('div');
		serverErrorTag.id = 'serverInputError';
		serverErrorTag.setAttribute('class','ffAskUrlError');
		formTag.appendChild(serverErrorTag);
		
		document.getElementsByTagName('body')[0].appendChild(rootTag);
	};
	
	/**
     * Starts the loader.
     * 
     * @param {function} cb Callback gets called when loader is done.
     */
	var start = function (cbArgu) {
		var startTime = new Date().getTime();
		var cb = function(err) {
			if (err !== null) {
				options.errorHandler(err);
			} else {
				utilDebug('start done in '+(new Date().getTime()-startTime)+' ms.');
				if (typeof cbArgu === "function") {
					cbArgu();
				}		
			}
		}
		utilDebug('start serverUrl: '+options.server.url);
		if (options.server.url !== null) {
			startLoader(cb);
			return;
		}
		if (cacheHasService('meta')) {
			cacheGetValue('meta','server_url',function(err, value) {
				if (err !== null) {
					cb(err);
				} else if (value === undefined || value === null || value === '') {
					askUrl(cb);
				} else {
					options.server.url = value;
					startLoader(cb);
				}
			});
		} else {
			askUrl(cb);
		}
	};
	
	var clearServer = function(cb) {
		if (cb === undefined) {
			cb = function() {};
		}
		if (cacheHasService('meta')) {
			cacheDeleteValue('meta','server_url',function(err) {
				if (err !== null) {
					cb(err);
				} else {
					cb(null);
				}
			});
		} else {
			cb(null);
		}
	}
	
	/**
     * Helper for automatic selecting the best to none cache backend option.
     * 
     * Order of detection; sqllite,openDatabase,localStorage,none.
     */
	var autoSelectCache = function() {
		if (factory.detect.cordovaDevice() && factory.detect.sqlitePlugin()) {
			utilDebug('autoSelectCache sqlitePlugin');
			return factory.cache.websql({openDatabase: window.sqlitePlugin});
		}
		if (factory.detect.openDatabase()) {
			utilDebug('autoSelectCache openDatabase');
			return factory.cache.websql();
		}
		if (factory.detect.localStorage()) {
			utilDebug('autoSelectCache localStorage');
			return factory.cache.localStorage();
		}
		utilDebug('autoSelectCache none');
		return null; // no caching
	}
	
	/**
     * Helper for cordova applications which want to use the sqllite plugin as cache.
     * Note: On none cordova page it will callback directly.
     * Note: On none cordova device page is will timeout. 
     * 
     * @param {function} cb Callback gets called device is ready to use.
     */
	var bootDevice = function(cb) {
		var startTime = new Date().getTime();
		var bootOnce = function() {
			if (typeof cb === "function") {
				var callback = cb;
				cb = null;
				utilDebug('bootDevice done in '+(new Date().getTime()-startTime)+' ms.');
				callback();
			}
		};
		if (!factory.detect.cordova()) {
			utilDebug('bootDevice webapp');
			bootOnce();
			return;
		}
		utilDebug('bootDevice timeout: '+options.bootDeviceTimeout);
		setTimeout ( function () {
			utilDebug('bootDevice timeout');
			bootOnce();
		}, options.bootDevice.timeout);
		document.addEventListener("deviceready", function () {
			window[options.bootDevice.windowFlag] = true;
			utilDebug('bootDevice '+options.bootDevice.windowFlag);
			bootOnce();
	    }, false);
	};
	
	return {
		options: options,
		factory: factory,
		start: start,
		bootDevice: bootDevice,
		autoSelectCache: autoSelectCache,
		clearServer: clearServer
	};
})();