libgluonutil: merge domain and site configs

package/libgluonutil/Makefile

@@ -16,7 +16,7 @@ define Package/libgluonutil
   SECTION:=libs
   CATEGORY:=Libraries
   TITLE:=Gluon utility library
-  DEPENDS:=+libjson-c
+  DEPENDS:=+libjson-c +libuci
 endef
 
 CMAKE_OPTIONS += \

package/libgluonutil/src/CMakeLists.txt

@@ -7,14 +7,15 @@ project(libgluonutil C)
 set(LIBDIR "lib${LIB_SUFFIX}")
 
 find_package(JSON_C REQUIRED)
+find_package(UCI REQUIRED)
 
 set_property(DIRECTORY PROPERTY COMPILE_DEFINITIONS _GNU_SOURCE)
 
 add_library(gluonutil SHARED libgluonutil.c)
 set_property(TARGET gluonutil PROPERTY COMPILE_FLAGS "-Wall -std=c99 ${JSON_C_CFLAGS_OTHER}")
 set_property(TARGET gluonutil PROPERTY LINK_FLAGS "${JSON_C_LDFLAGS_OTHER}")
-set_property(TARGET gluonutil APPEND PROPERTY INCLUDE_DIRECTORIES ${JSON_C_INCLUDE_DIR})
-target_link_libraries(gluonutil ${JSON_C_LIBRARIES})
+set_property(TARGET gluonutil APPEND PROPERTY INCLUDE_DIRECTORIES ${JSON_C_INCLUDE_DIR} ${UCI_INCLUDE_DIR})
+target_link_libraries(gluonutil ${JSON_C_LIBRARIES} ${UCI_LIBRARIES})
 install(TARGETS gluonutil
   ARCHIVE DESTINATION ${LIBDIR}
   LIBRARY DESTINATION ${LIBDIR}

package/libgluonutil/src/FindUCI.cmake

@@ -0,0 +1,21 @@
+# UCI_FOUND - true if library and headers were found
+# UCI_INCLUDE_DIRS - include directories
+# UCI_LIBRARIES - library directories
+
+find_package(PkgConfig)
+pkg_check_modules(PC_UCI QUIET uci)
+
+find_path(UCI_INCLUDE_DIR uci.h
+	HINTS ${PC_UCI_INCLUDEDIR} ${PC_UCI_INCLUDE_DIRS})
+
+find_library(UCI_LIBRARY NAMES uci libuci
+	HINTS ${PC_UCI_LIBDIR} ${PC_UCI_LIBRARY_DIRS})
+
+set(UCI_LIBRARIES ${UCI_LIBRARY})
+set(UCI_INCLUDE_DIRS ${UCI_INCLUDE_DIR})
+
+include(FindPackageHandleStandardArgs)
+
+find_package_handle_standard_args(UCI DEFAULT_MSG UCI_LIBRARY UCI_INCLUDE_DIR)
+
+mark_as_advanced(UCI_INCLUDE_DIR UCI_LIBRARY)

package/libgluonutil/src/libgluonutil.c

@@ -31,7 +31,41 @@
 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>
+#include <unistd.h>
+#include <uci.h>
 
+/**
+ * Merges two JSON objects
+ *
+ * On conflicts, object a will be preferred.
+ *
+ * Internally, this functions merges all entries from object a into object b,
+ * so merging a small object a with a big object b is faster than vice-versa.
+ */
+static struct json_object * merge_json(struct json_object *a, struct json_object *b) {
+	if (!json_object_is_type(a, json_type_object) || !json_object_is_type(b, json_type_object)) {
+		json_object_put(b);
+		return a;
+	}
+
+	json_object_object_foreach(a, key, val_a) {
+		struct json_object *val_b;
+
+		json_object_get(val_a);
+
+		if (!json_object_object_get_ex(b, key, &val_b)) {
+			json_object_object_add(b, key, val_a);
+			continue;
+		}
+
+		json_object_get(val_b);
+
+		json_object_object_add(b, key, merge_json(val_a, val_b));
+	}
+
+	json_object_put(a);
+	return b;
+}
 
 char * gluonutil_read_line(const char *filename) {
 	FILE *f = fopen(filename, "r");
@@ -140,7 +174,122 @@ bool gluonutil_get_node_prefix6(struct in6_addr *prefix) {
 	return true;
 }
 
+char * get_selected_domain_code(struct json_object * base) {
+	char * domain_path_fmt = "/lib/gluon/domains/%s.json";
+	char domain_path[strlen(domain_path_fmt) + 256];
+	const char * domain_code;
+
+	struct uci_context *ctx = uci_alloc_context();
+	if (!ctx)
+		goto uci_fail;
+
+	ctx->flags &= ~UCI_FLAG_STRICT;
+
+	struct uci_package *p;
+	if (uci_load(ctx, "gluon", &p))
+		goto uci_fail;
+
+	struct uci_section *s = uci_lookup_section(ctx, p, "system");
+	if (!s)
+		goto uci_fail;
+
+	domain_code = uci_lookup_option_string(ctx, s, "domain_code");
+
+	if (!domain_code)
+		goto uci_fail;
+
+	snprintf(domain_path, sizeof domain_path, domain_path_fmt, domain_code);
+
+	if (access(domain_path, R_OK) != -1) {
+		// ${domain_code}.conf exists and is accessible
+		char * domain_code_cpy = strndup(domain_code, 256); // copy before free
+		uci_free_context(ctx);
+		return domain_code_cpy;
+	}
+
+uci_fail:
+	if (ctx)
+		uci_free_context(ctx);
+
+	json_object * default_domain_code;
+
+	// it's okay to pass base == NULL to json_object_object_get_ex()
+	if (!json_object_object_get_ex(base, "default_domain_code", &default_domain_code))
+		return NULL;
+
+	domain_code = json_object_get_string(default_domain_code);
+
+	if (!domain_code)
+		return NULL;
+
+	// the gluon build environment should ensure, that this filename exists,
+	// but to be sure, we check here again.
+	snprintf(domain_path, sizeof domain_path, domain_path_fmt, domain_code);
+
+	if (access(domain_path, R_OK) == -1)
+		return NULL;
+
+	// create a copy so site could be freed before domain_code
+	return strndup(domain_code, 256);
+}
+
+/**
+ * Get selected domain code
+ *
+ * - If NULL is passed to the site parameter, internally only the base part
+ *   (without domain config) is loaded, which is more efficient than calling
+ *   gluonutil_load_site_config() for this job only. Nevertheless if you already
+ *   have an instance of a site object then you should pass it here.
+ * - Returned domain code string has to be freed after use
+ * - Returns NULL in case of error
+ * - If a domain code is returned, it's ensured that the corresponding config
+ *   in /lib/gluon/domains/ exists.
+ */
+char * gluonutil_get_selected_domain_code(struct json_object * site) {
+	if (site)
+		// If the user already has allocated a whole site object, it makes no sense
+		// to load the base object. Taking the site object (merged from domain and
+		// base) should be fine here.
+		return get_selected_domain_code(site);
+
+	// load base
+	struct json_object * base = json_object_from_file("/lib/gluon/site.json");
+
+	if (!base)
+		return NULL;
+
+	return get_selected_domain_code(base);
+}
 
 struct json_object * gluonutil_load_site_config(void) {
-	return json_object_from_file("/lib/gluon/site.json");
+	// load base
+	struct json_object * base = json_object_from_file("/lib/gluon/site.json");
+
+	if (!base)
+		return NULL;
+
+	// load domain
+	char * domain_path_fmt = "/lib/gluon/domains/%s.json";
+	char domain_path[strlen(domain_path_fmt) + 256];
+	char * domain_code = get_selected_domain_code(base);
+
+	if (!domain_code) {
+		// something went horribly wrong here
+		json_object_put(base); // free base
+		return NULL;
+	}
+
+	snprintf(domain_path, sizeof domain_path, domain_path_fmt, domain_code);
+
+	free(domain_code);
+
+	struct json_object * domain = json_object_from_file(domain_path);
+
+	if (!domain) {
+		json_object_put(base);
+		return NULL;
+	}
+
+	// finally merge them
+	return merge_json(domain, base);
 }

package/libgluonutil/src/libgluonutil.h

@@ -42,4 +42,18 @@ struct json_object * gluonutil_wrap_and_free_string(char *str);
 
 struct json_object * gluonutil_load_site_config(void);
 
+/**
+ * Get selected domain code
+ *
+ * - If NULL is passed to the site parameter, internally only the base part
+ *   (without domain config) is loaded, which is more efficient than calling
+ *   gluonutil_load_site_config() for this job only. Nevertheless if you already
+ *   have an instance of a site object then you should pass it here.
+ * - Returned domain code string has to be freed after use
+ * - Returns NULL in case of error
+ * - If a domain code is returned, it's ensured that the corresponding config
+ *   in /lib/gluon/domains/ exists.
+ */
+char * gluonutil_get_selected_domain_code(struct json_object * site);
+
 #endif /* _LIBGLUON_LIBGLUON_H_ */