implement html5 localStorage support for client-side cache

functions.js

@@ -2184,3 +2184,10 @@ function backend_sanity_check_callback(transport) {
 	} 
 }
 
+function has_local_storage() {
+	try {
+		return 'localStorage' in window && window['localStorage'] != null;
+	} catch (e) {
+		return false;
+	}
+}

tt-rss.js

@@ -421,6 +421,9 @@ function init_second_stage() {
 
 		enable_offline_reading();
 
+		if (has_local_storage())
+			localStorage.clear();
+
 	} catch (e) {
 		exception_error("init_second_stage", e);
 	}

viewfeed.js

@@ -1696,12 +1696,18 @@ function cache_inject(id, article, param) {
 					[id, article, param, ts]);				
 			} else {
 	
-				var cache_obj = new Array();
+				var cache_obj = {};
 	
 				cache_obj["id"] = id;
 				cache_obj["data"] = article;
 				cache_obj["param"] = param;
+				cache_obj["added"] = new Date();
 
+				if (param) id = id + ":" + param;
+
+				if (has_local_storage()) 
+					localStorage.setItem(id, JSON.stringify(cache_obj));
+				else
 					article_cache.push(cache_obj);
 			}
 	
@@ -1727,6 +1733,18 @@ function cache_find(id) {
 
 		return a;
 
+	} else {
+
+		if (has_local_storage()) {
+			var cache_obj = localStorage.getItem(id);
+	
+			if (cache_obj) {
+				cache_obj = JSON.parse(cache_obj);
+
+				if (cache_obj)
+					return cache_obj['data'];
+			}
+
 		} else {
 			for (var i = 0; i < article_cache.length; i++) {
 				if (article_cache[i]["id"] == id) {
@@ -1734,6 +1752,7 @@ function cache_find(id) {
 				}
 			}
 		}
+	}
 	return false;
 }
 
@@ -1752,6 +1771,18 @@ function cache_find_param(id, param) {
 
 		return a;
 
+	} else {
+
+		if (has_local_storage()) {
+			var cache_obj = localStorage.getItem(id + ":" + param);
+
+			if (cache_obj) {
+				cache_obj = JSON.parse(cache_obj);
+
+				if (cache_obj)
+					return cache_obj['data'];
+			}
+
 		} else {
 			for (var i = 0; i < article_cache.length; i++) {
 				if (article_cache[i]["id"] == id && article_cache[i]["param"] == param) {
@@ -1759,6 +1790,7 @@ function cache_find_param(id, param) {
 				}
 			}
 		}
+	}
 	return false;
 }
 
@@ -1777,6 +1809,10 @@ function cache_check(id) {
 
 		return a;
 
+	} else {
+		if (has_local_storage) {
+			if (localStorage.getItem(id))
+					return true;
 		} else {
 			for (var i = 0; i < article_cache.length; i++) {
 				if (article_cache[i]["id"] == id) {
@@ -1784,6 +1820,7 @@ function cache_check(id) {
 				}
 			}
 		}
+	}
 	return false;
 }
 
@@ -1802,6 +1839,11 @@ function cache_check_param(id, param) {
 
 		return a;
 
+	} else {
+
+		if (has_local_storage) {
+			if (localStorage.getItem(id + ':' + param))
+					return true;
 		} else {
 			for (var i = 0; i < article_cache.length; i++) {
 				if (article_cache[i]["id"] == id && article_cache[i]["param"] == param) {
@@ -1809,6 +1851,7 @@ function cache_check_param(id, param) {
 				}
 			}
 		}
+	}
 	return false;
 }
 
@@ -1822,11 +1865,17 @@ function cache_expire() {
 		db.execute("DELETE FROM cache WHERE added < ? - 86400", [ts]);
 
 
+	} else {
+		if (has_local_storage()) {
+			while (localStorage.length > 25) {
+				localStorage.removeItem(localStorage.key(localStorage.length-1));
+			}
 		} else {
 			while (article_cache.length > 25) {
 				article_cache.shift();
 			}
 		}
+	}
 }
 
 function cache_flush() {
@@ -1841,6 +1890,15 @@ function cache_invalidate(id) {
 			return rs.rowsAffected != 0;
 		} else {
 
+			if (has_local_storage()) {
+				for (var i = 0; i < localStorage.length; i++) {
+					var key = localStorage.key(i);
+
+					if (key == id || key.indexOf(id + ":") == 0)
+						localStorage.removeItem(key);
+
+				}
+			} else {
 				var i = 0
 
 				while (i < article_cache.length) {
@@ -1852,6 +1910,7 @@ function cache_invalidate(id) {
 					i++;
 				}
 			}
+		}
 
 		console.log("cache_invalidate: id not found: " + id);
 		return false;