Limnoria/src/utils/httpserver.py

###
# Copyright (c) 2011, Valentin Lorentz
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###

"""
An embedded and centralized HTTP server for Supybot's plugins.
"""

from threading import Event, Thread
from cStringIO import StringIO
from SocketServer import ThreadingMixIn
from BaseHTTPServer import HTTPServer, BaseHTTPRequestHandler

import supybot.log as log
import supybot.conf as conf
import supybot.world as world

configGroup = conf.supybot.servers.http

if world.testing:
    class TestHTTPServer(HTTPServer):
        """A fake HTTP server for testing purpose."""
        def __init__(self, address, handler):
            self.server_address = address
            self.RequestHandlerClass = handler
            self.socket = StringIO()
            self._notServing = Event()
            self._notServer.set()

        def fileno(self):
            return hash(self)

        def serve_forever(self, poll_interval=None):
            self._notServing.clear()
            self._notServing.wait()

        def shutdown(self):
            self._notServing.set()

    HTTPServer = TestHTTPServer

class SupyHTTPServer(HTTPServer):
    # TODO: make this configurable
    timeout = 0.5
    callbacks = {}
    running = False
    def hook(self, subdir, callback):
        if subdir in self.callbacks:
            raise KeyError('This subdir is already hooked.')
        else:
            self.callbacks[subdir] = callback
    def unhook(self, subdir):
        callback = self.callbacks.pop(subdir) # May raise a KeyError. We don't care.
        callback.doUnhook(self)
        return callback

class SupyHTTPRequestHandler(BaseHTTPRequestHandler):
    def do_GET(self):
        if self.path == '/':
            callback = SupyIndex()
        else:
            subdir = self.path.split('/')[1]
            try:
                callback = self.server.callbacks[subdir]
            except KeyError:
                callback = Supy404()

        # Some shortcuts
        for name in ('send_response', 'send_header', 'end_headers', 'rfile',
                'wfile'):
            setattr(callback, name, getattr(self, name))
        # We call doGet, because this is more supybotic than do_GET.
        callback.doGet(self, '/'.join(self.path[2:]))

    def log_message(self, format, *args):
        log.info('HTTP request: %s - %s' %
                (self.address_string(), format % args))


class SupyHTTPServerCallback:
    """This is a base class that should be overriden by any plugin that want
    to have a Web interface."""
    name = "Unnamed plugin"
    defaultResponse = """
    This is a default response of the Supybot HTTP server. If you see this
    message, it probably means you are developping a plugin, and you have
    neither overriden this message or defined an handler for this query."""

    def doGet(self, handler, path):
        handler.send_response(400)
        self.send_header('Content_type', 'text/plain')
        self.send_header('Content-Length', len(self.defaultResponse))
        self.end_headers()
        self.wfile.write(self.defaultResponse)

    def doUnhook(self, handler):
        """Method called when unhooking this callback."""
        pass

class Supy404(SupyHTTPServerCallback):
    """A 404 Not Found error."""
    name = "Error 404"
    response = """
    I am a pretty clever IRC bot, but I suck at serving Web pages, particulary
    if I don't know what to serve.
    What I'm saying is you just triggered a 404 Not Found, and I am not
    trained to help you in such a case."""
    def doGet(self, handler, path):
        handler.send_response(404)
        self.send_header('Content_type', 'text/plain')
        self.send_header('Content-Length', len(self.response))
        self.end_headers()
        self.wfile.write(self.response)

class SupyIndex(SupyHTTPServerCallback):
    """Displays the index of available plugins."""
    name = "index"
    defaultResponse = "Request not handled."""
    template = """
    <html>
     <head>
      <title>Supybot Web server index</title>
     </head>
     <body>
      <p>Here is a list of the plugins that have a Web interface:</p>
      %s
     </body>
    </html>"""
    def doGet(self, handler, path):
        plugins = [x for x in handler.server.callbacks.items()]
        if plugins == []:
            plugins = 'No plugins available.'
        else:
            plugins = '<ul><li>%s</li></ul>' % '</li><li>'.join(
                    ['<a href="/%s">%s</a>' % (x,y.name) for x,y in plugins])
        response = self.template % plugins
        handler.send_response(200)
        self.send_header('Content_type', 'text/html')
        self.send_header('Content-Length', len(response))
        self.end_headers()
        self.wfile.write(response)

httpServer = None

def startServer():
    """Starts the HTTP server. Shouldn't be called from other modules.
    The callback should be an instance of a child of SupyHTTPServerCallback."""
    global httpServer
    log.info('Starting HTTP server.')
    address = (configGroup.host(), configGroup.port())
    httpServer = SupyHTTPServer(address, SupyHTTPRequestHandler)
    Thread(target=httpServer.serve_forever, name='HTTP Server').start()

def stopServer():
    """Stops the HTTP server. Should be run only from this module or from
    when the bot is dying (ie. from supybot.world)"""
    global httpServer
    log.info('Stopping HTTP server.')
    httpServer.shutdown()
    httpServer = None

if configGroup.keepAlive():
    startServer()

def hook(subdir, callback):
    """Sets a callback for a given subdir."""
    if httpServer is None:
        startServer()
    httpServer.hook(subdir, callback)

def unhook(subdir):
    """Unsets the callback assigned to the given subdir, and return it."""
    global httpServer
    assert httpServer is not None
    callback = httpServer.unhook(subdir)
    if len(httpServer.callbacks) <= 0 and not configGroup.keepAlive():
        stopServer()