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"""
Package source manager is responsible for selecting the correct source
for a requested package, by a provided string.
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).
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
from pomu.util.result import Result
class PackageDispatcher():
def __init__(self):
self.handlers = []
self.backends = {}
def source(self, cls):
"""
A decorator to mark package source modules
It would register all the methods of the class marked by @handler
with the dispatcher.
"""
try:
from pomu.source.base import BaseSource
except ImportError: #circular import
return cls
if cls == BaseSource:
return cls
self.backends[cls.__name__] = 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():
"""
A decorator to denote package source module handler, which
should attempt to parse a package descriptor. If it succeeds,
the result would be passed to the module for further processing.
"""
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):
"""
Register a package handler for a specified source.
Handlers with lower priority get called first.
"""
i = 0
for i in range(len(self.handlers)):
if self.handlers[0][0] > priority:
break
self.handlers.insert(i, (priority, source, handler))
def get_package_source(self, uri):
"""Get a source which accepts the package"""
for priority, source, handler in self.handlers:
if handler(uri).is_ok():
return Result.Ok(source)
return Result.Err('No handler found for package ' + uri)
def get_package(self, uri):
"""Fetch a package specified by the descriptor"""
for priority, source, handler in self.handlers:
res = handler(uri)
if res.is_ok():
return Result.Ok(source.fetch_package(res.ok()))
return Result.Err('No handler found for package ' + uri)
def install_package(self, repo, uri):
"""Install a package specified by the descriptor into the repository"""
pkg = self.get_package(uri).unwrap()
return repo.merge(pkg)
def uninstall_package(self, repo, uri):
"""Uninstall a package specified by the descriptor"""
pkg = self.get_package(uri).unwrap()
return repo.unmerge(pkg)
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