lib: Improve dependency resolution

Rather than doing everything in tedious if blocks written in any order,
I instead resolve dependencies using a much simpler loop.  At the moment
each module only depends on a single other module, so this will have to
be extended if I ever need multiple-dependency resolution.

Signed-off-by: Anna Schumaker <schumaker.anna@gmail.com>

lib/Sconscript

@@ -1,33 +1,56 @@
 #!/usr/bin/python
 Import("env", "CONFIG")
 
+class Module:
+	def __init__(self, source = None, package = "", depends = ""):
+		self.depends = depends
+		self.package = package
+		self.source  = source
+
+
+modules = {
+###########################
+#                         #
+# Define new modules here #
+#                         #
+###########################
+
+	"DATABASE" : Module("database.cpp", depends = "FILE"),
+	"FILE"     : Module("file.cpp", package = "glib-2.0"),
+	"FILTER"   : Module("filter.cpp", depends = "INDEX"),
+	"GROUP"    : Module("group.cpp", depends = "INDEX"),
+	"IDLE"     : Module("idle.cpp"),
+	"INDEX"    : Module("index.cpp", depends = "FILE"),
+
+###########################
+###########################
+}
+
+
 build = []
+enabled = []
 
-if CONFIG.FILTER:
-	CONFIG.INDEX = True
-	build += [ env.Object("filter.cpp") ]
+def resolve(name):
+	CONFIG.__dict__[name] = True
+	mod = modules[name]
 
-if CONFIG.GROUP:
-	CONFIG.INDEX = True
-	build += [ env.Object("group.cpp") ]
+	if mod.package != "":
+		CONFIG.package(mod.package)
 
-####################
+	res = [ env.Object(mod.source) ]
+	if CONFIG.__dict__.get(mod.depends) == False:
+		res += resolve(mod.depends)
 
-if CONFIG.DATABASE:
-	CONFIG.FILE = True
-	build += [ env.Object("database.cpp") ]
+	return res
 
-if CONFIG.INDEX:
-	CONFIG.FILE = True
-	build += [ env.Object("index.cpp") ]
 
-####################
 
-if CONFIG.FILE:
-	CONFIG.package("glib-2.0")
-	build += [ env.Object("file.cpp") ]
+for key in modules.keys():
+	if CONFIG.__dict__[key] == True:
+		enabled += [key]
+
+for mod in enabled:
+	build += resolve(mod)
 
-if CONFIG.IDLE:
-	build += [ env.Object("idle.cpp") ]
 
 Return("build")