Implement package source dispatch

2 files changed, 69 insertions, 6 deletions

diff --git a/pomu/source/__init__.py b/pomu/source/__init__.py
new file mode 100644
index 0000000..a86679f
--- /dev/null
+++ b/pomu/source/__init__.py
@@ -0,0 +1,3 @@
+from pomu.source.manager import PackageDispatcher
+
+dispatcher = PackageDispatcher()
diff --git a/pomu/source/manager.py b/pomu/source/manager.py
index a15a427..93c05c0 100644
--- a/pomu/source/manager.py
+++ b/pomu/source/manager.py
@@ -1,8 +1,68 @@
-def register_package_handler(source, handler, priority):
-    pass
+"""
+Package source manager is responsible for selecting the correct source
+for a requested package, by a provided string.
 
-def get_package_source(uri):
-    pass
+Package sources can provide several handlers with different priorities.
+A handler is a String -> Result function, which tries to parse the passed
+value and return Ok(value).
 
-def get_package(uri):
-    pass
+The package would be handled by the handler with the lowest priority, which
+was added the first.
+
+Example:
+    @dispatcher.source
+    class BgoSource():
+        @dispatcher.handler(priority=5)
+        def parse_int(uri):
+            if uri.is_decimal():
+                return Result.Ok(int(uri))
+            elif uri[0] == '#' and uri[1:].is_decimal():
+                return Result.Ok(int(uri[1:]))
+            return Result.Err('NaN')
+
+        @dispatcher.handler(priority=1)
+        def parse_url(uri):
+            if uri.startswith('http://bugs.gentoo.org/'):
+            ...
+"""
+#TODO: efficient sorted insertion
+#import bisect
+import inspect
+
+class PackageDispatcher():
+    def __init__(self):
+        self.handlers = []
+
+    def source(self, cls):
+        for m, obj in inspect.getmembers(cls):
+            if isinstance(obj, self.handler._handler):
+                self.register_package_handler(cls, obj.handler, obj.priority)
+        return cls
+
+    class handler():
+        class _handler():
+            def __init__(self, handler):
+                self.handler = handler
+            def __call__(self, *args):
+                return self.handler(*args)
+
+        def __init__(self, priority=1000, *args, **kwargs):
+            self.priority = priority
+
+        def __call__(self, func, *args, **kwargs):
+            x = self._handler(func)
+            x.priority = self.priority
+            return x
+
+    def register_package_handler(self, source, handler, priority):
+        i = 0
+        for i in range(len(self.handlers)):
+            if self.handlers[0] > priority:
+                break
+        self.handlers.insert(i, (priority, source, handler))
+
+    def get_package_source(self, uri):
+        for priority, source, handler in self.handlers:
+            if handler(uri).is_ok():
+                return source
+        return None