utilize Pattern Tree to decide the policy to use and modify HTTP response headers according to that policy

This commit also enhances the build script so that preprocessor conditionals can now use operators '&&' and '||'.
The features being developed are not yet included in the actual Haketilo build.
Some of the new source files contain similar functionality to other ones already existing in the source tree. At some point the latter will be removed.

1 files changed, 44 insertions, 22 deletions

diff --git a/common/indexeddb.js b/common/indexeddb.js
index 096391a..e54d1ca 100644
--- a/common/indexeddb.js
+++ b/common/indexeddb.js
@@ -62,7 +62,8 @@ const stores = 	[
     ["files",     {keyPath: "hash_key"}],
     ["file_uses", {keyPath: "hash_key"}],
     ["resources", {keyPath: "identifier"}],
-    ["mappings",  {keyPath: "identifier"}]
+    ["mappings",  {keyPath: "identifier"}],
+    ["settings",  {keyPath: "name"}]
 ];
 
 let db = null;
@@ -207,7 +208,7 @@ async function incr_file_uses(context, file_ref, by=1)
 
 const decr_file_uses = (ctx, file_ref) => incr_file_uses(ctx, file_ref, -1);
 
-async function finalize_items_transaction(context)
+async function finalize_transaction(context)
 {
     for (const uses of Object.values(context.file_uses)) {
 	if (uses.uses < 0)
@@ -248,7 +249,7 @@ async function finalize_items_transaction(context)
 
     return context.result;
 }
-#EXPORT finalize_items_transaction
+#EXPORT finalize_transaction
 
 /*
  * How a sample data argument to the function below might look like:
@@ -304,7 +305,7 @@ async function _save_items(resources, mappings, context)
     for (const item of resources.concat(mappings))
 	await save_item(item, context);
 
-    await finalize_items_transaction(context);
+    await finalize_transaction(context);
 }
 
 /*
@@ -314,9 +315,9 @@ async function _save_items(resources, mappings, context)
  * object with keys being of the form `sha256-<file's-sha256-sum>`.
  *
  * context should be one returned from start_items_transaction() and should be
- * later passed to finalize_items_transaction() so that files depended on are
- * added to IndexedDB and files that are no longer depended on after this
- * operation are removed from IndexedDB.
+ * later passed to finalize_transaction() so that files depended on are added to
+ * IndexedDB and files that are no longer depended on after this operation are
+ * removed from IndexedDB.
  */
 async function save_item(item, context)
 {
@@ -346,9 +347,9 @@ async function _remove_item(store_name, identifier, context)
  * Remove definition of a resource/mapping from IndexedDB.
  *
  * context should be one returned from start_items_transaction() and should be
- * later passed to finalize_items_transaction() so that files depended on are
- * added to IndexedDB and files that are no longer depended on after this
- * operation are removed from IndexedDB.
+ * later passed to finalize_transaction() so that files depended on are added to
+ * IndexedDB and files that are no longer depended on after this operation are
+ * removed from IndexedDB.
  */
 async function remove_item(store_name, identifier, context)
 {
@@ -363,26 +364,49 @@ const remove_resource = (id, ctx) => remove_item("resources", id, ctx);
 const remove_mapping = (id, ctx) => remove_item("mappings",  id, ctx);
 #EXPORT remove_mapping
 
+/* A simplified kind of transaction for modifying just the "settings" store. */
+async function start_settings_transaction()
+{
+    const db = await get_db();
+    return make_context(db.transaction("settings", "readwrite"), {});
+}
+
+async function set_setting(name, value)
+{
+    const context = await start_settings_transaction();
+    broadcast.prepare(context.sender, `idb_changes_settings`, name);
+    await idb_put(context.transaction, "settings", {name, value});
+    return finalize_transaction(context);
+}
+#EXPORT set_setting
+
+async function get_setting(name)
+{
+    const transaction = (await get_db()).transaction("settings");
+    return ((await idb_get(transaction, "settings", name)) || {}).value;
+}
+#EXPORT get_setting
+
 /* Callback used when listening to broadcasts while tracking db changes. */
-async function track_change(tracking, identifier)
+async function track_change(tracking, key)
 {
     const transaction = (await get_db()).transaction([tracking.store_name]);
-    const new_val = await idb_get(transaction, tracking.store_name, identifier);
+    const new_val = await idb_get(transaction, tracking.store_name, key);
 
-    tracking.onchange({identifier, new_val});
+    tracking.onchange({key, new_val});
 }
 
 /*
  * Monitor changes to `store_name` IndexedDB object store.
  *
- * `store_name` should be either "resources" or "mappings".
+ * `store_name` should be either "resources", "mappings" or "settings".
  *
  * `onchange` should be a callback that will be called when an item is added,
  * modified or removed from the store. The callback will be passed an object
  * representing the change as its first argument. This object will have the
  * form:
  * {
- *     identifier: "the identifier of modified resource/mapping",
+ *     key: "the identifier of modified resource/mapping or settings key",
  *     new_val: undefined // `undefined` if item removed, item object otherwise
  * }
  *
@@ -395,7 +419,7 @@ async function track_change(tracking, identifier)
  * actually modified or that it only gets called once after multiple quick
  * changes to an item.
  */
-async function track(store_name, onchange)
+async function start_tracking(store_name, onchange)
 {
     const tracking = {store_name, onchange};
     tracking.listener =
@@ -408,12 +432,10 @@ async function track(store_name, onchange)
     return [tracking, (await wait_request(all_req)).target.result];
 }
 
-const track_resources = onchange => track("resources", onchange);
-#EXPORT track_resources
-
-const track_mappings = onchange => track("mappings",  onchange);
-#EXPORT track_mappings
+const track = {};
+for (const store_name of ["resources", "mappings", "settings"])
+    track[store_name] = onchange => start_tracking(store_name, onchange);
+#EXPORT track
 
 const untrack = tracking => broadcast.close(tracking.listener);
 #EXPORT untrack
-