1 files changed, 93 insertions, 0 deletions
diff --git a/background/reverse_use_info.mjs b/background/reverse_use_info.mjs
new file mode 100644
index 0000000..c38c52f
--- /dev/null
+++ b/background/reverse_use_info.mjs
@@ -0,0 +1,93 @@
+/**
+* Myext scripts and bundles usage index
+*
+* Copyright (C) 2021 Wojtek Kosior
+*
+* Dual-licensed under:
+*   - 0BSD license
+*   - GPLv3 or (at your option) any later version
+*/
+
+import TYPE_PREFIX from '/common/stored_types.mjs';
+import get_storage from './storage.mjs';
+import make_once from '/common/once.mjs';
+
+"use strict";
+
+/*
+ * We want to count referenes to scripts and bundles in order to know,
+ * for example, whether one can be safely deleted.
+ */
+
+var component_uses = new Map();
+var storage;
+
+function add_use_info_by_item(prefix, item, components)
+{
+    for (let component of components) {
+	component = component.join("");
+
+	let used_by_info = component_uses.get(component);
+
+	if (used_by_info === undefined) {
+	    used_by_info = {};
+	    component_uses.set(component, used_by_info);
+	}
+
+	if (used_by_info[prefix] === undefined)
+	    used_by_info[prefix] = new Set();
+
+	used_by_info[prefix].add(item);
+    }
+}
+
+function remove_use_info_by_item(prefix, item, components)
+{
+    for (let component of components) {
+	used_by_info = component_uses.get(component.join(""));
+	if (used_by_info === undefined || used_by_info[prefix] === undefined)
+	    return;
+
+	used_by_info[prefix].delete(item);
+    }
+}
+
+function build_reverse_uses_info(entries_it, type_prefix)
+{
+    for (let [item, components] of storage.get_all_it(type_prefix))
+	add_use_info_by_item(type_prefix, item, components);
+}
+
+function handle_change(change)
+{
+    if (change.old_val !== undefined)
+	remove_use_info_by_item(change.prefix, change.item, change.old_val);
+
+    if (change.new_val !== undefined)
+	add_use_info_by_item(change.prefix, change.item, change.new_val);
+}
+
+function get_uses(arg1, arg2=undefined)
+{
+    let [prefix, item] = [arg1, arg2];
+
+    if (arg2 === undefined)
+	[prefix, item] = arg1;
+
+    return component_uses.get(prefix + item);
+}
+
+async function init()
+{
+    storage = await get_storage();
+
+    prefixes = [TYPE_PREFIX.PAGE, TYPE_PREFIX.BUNDLE];
+    for (let prefix of prefixes)
+	build_reverse_uses_info(prefix);
+
+    storage.add_change_listener(handle_change, prefixes);
+
+    return get_uses;
+}
+
+export default make_once(init);