/*\
title: $:/plugins/tiddlywiki/browser-storage/startup.js
type: application/javascript
module-type: startup

Startup initialisation

\*/
(function(){

/*jslint node: true, browser: true */
/*global $tw: false */
"use strict";

// Export name and synchronous status
exports.name = "browser-storage";
exports.platforms = ["browser"];
exports.after = ["startup"];
exports.synchronous = true;

var ENABLED_TITLE = "$:/config/BrowserStorage/Enabled",
	SAVE_FILTER_TITLE = "$:/config/BrowserStorage/SaveFilter",
	PERSISTED_STATE_TITLE = "$:/info/browser/storage/persisted";

var BrowserStorageUtil = require("$:/plugins/tiddlywiki/browser-storage/util.js").BrowserStorageUtil;

exports.startup = function() {
	var self = this;
	
        // If not exists, add ENABLED tiddler with default value "yes"
        if(!$tw.wiki.getTiddler(ENABLED_TITLE)) {
                $tw.wiki.addTiddler({title: ENABLED_TITLE, text: "yes"});
        }
	// Compute our prefix for local storage keys
	var prefix = "tw5#" + window.location.pathname + "#";
	// Make a logger
	var logger = new $tw.utils.Logger("browser-storage",{
			colour: "cyan"
		});
	// Add browserStorage object to $tw
	$tw.browserStorage = new BrowserStorageUtil($tw.wiki,{
		enabledTitle: ENABLED_TITLE,
		prefix: prefix,
		logger: logger
	});
	// Function to compile the filter
	var filterFn,
		compileFilter = function() {
			filterFn = $tw.wiki.compileFilter($tw.wiki.getTiddlerText(SAVE_FILTER_TITLE));
	}
	compileFilter();
	// Listen for tm-clear-browser-storage messages
	$tw.rootWidget.addEventListener("tm-clear-browser-storage",function(event) {
		$tw.wiki.addTiddler({title: ENABLED_TITLE, text: "no"});
		$tw.browserStorage.clearLocalStorage();
	});
	// Helpers for protecting storage from eviction
	var setPersistedState = function(state) {
			$tw.wiki.addTiddler({title: PERSISTED_STATE_TITLE, text: state});
		},
		requestPersistence = function() {
			setPersistedState("requested");
			navigator.storage.persist().then(function(persisted) {
				console.log("Request for persisted storage " + (persisted ? "granted" : "denied"));
				setPersistedState(persisted ? "granted" : "denied");
			});
		},
		persistPermissionRequested = false,
		requestPersistenceOnFirstSave = function() {
			$tw.hooks.addHook("th-saving-tiddler", function(tiddler) {
				if (!persistPermissionRequested) {
					var filteredChanges = filterFn.call($tw.wiki, function(iterator) {
						iterator(tiddler,tiddler.getFieldString("title"));
					});
					if (filteredChanges.length > 0) {
						// The tiddler will be saved to local storage, so request persistence
						requestPersistence();
						persistPermissionRequested = true;
					}
				}
				return tiddler;
			});
		};
	// Request the browser to never evict the localstorage. Some browsers such as firefox
	// will prompt the user. To make the decision easier for the user only prompt them
	// when they click the save button on a tiddler which will be stored to localstorage.
	if (navigator.storage && navigator.storage.persist) {
		navigator.storage.persisted().then(function(isPersisted) {
			if (!isPersisted) {
				setPersistedState("not requested yet");
				requestPersistenceOnFirstSave();
			} else {
				setPersistedState("granted");
			}
		});
	} else {
		setPersistedState("feature not available");
	}
	// Track tiddler changes
	$tw.wiki.addEventListener("change",function(changes) {
		// Bail if browser storage is disabled
		if($tw.wiki.getTiddlerText(ENABLED_TITLE) === "no") {
			return;
		}
		// Recompile the filter if it has changed
		if(changes[SAVE_FILTER_TITLE]) {
			compileFilter();
		}
		// Filter the changes
		var filteredChanges = filterFn.call($tw.wiki,function(iterator) {
			$tw.utils.each(changes,function(change,title) {
				var tiddler = $tw.wiki.getTiddler(title);
				iterator(tiddler,title);
			});
		});
		$tw.utils.each(filteredChanges,function(title) {
			// Don't try to save changes to our enabled status
			// (If it were enabled in the file but disabled in local storage then we might not realise that distributing a copy of the file would have local storage enabled for other users)
			if(title === ENABLED_TITLE) {
				return;
			}
			// This should always be queried from the browser, so don't store it in local storage
			if(title === PERSISTED_STATE_TITLE) {
				return;
			}
			// Save the tiddler
			$tw.browserStorage.saveTiddlerToLocalStorage(title);
		});
	});
};

})();