"""HTTP server base class.

Note: the class in this module doesn't implement any HTTP request; see
SimpleHTTPServer for simple implementations of GET, HEAD and POST
(including CGI scripts).  It does, however, optionally implement HTTP/1.1
persistent connections, as of version 0.3.

Contents:

- BaseHTTPRequestHandler: HTTP request handler base class
- test: test function

XXX To do:

- log requests even later (to capture byte count)
- log user-agent header and other interesting goodies
- send error log to separate file
"""


# See also:
#
# HTTP Working Group										T. Berners-Lee
# INTERNET-DRAFT											R. T. Fielding
# <draft-ietf-http-v10-spec-00.txt>					 H. Frystyk Nielsen
# Expires September 8, 1995								  March 8, 1995
#
# URL: http://www.ics.uci.edu/pub/ietf/http/draft-ietf-http-v10-spec-00.txt
#
# and
#
# Network Working Group									  R. Fielding
# Request for Comments: 2616									   et al
# Obsoletes: 2068											  June 1999
# Category: Standards Track
#
# URL: http://www.faqs.org/rfcs/rfc2616.html

# Log files
# ---------
#
# Here's a quote from the NCSA httpd docs about log file format.
#
# | The logfile format is as follows. Each line consists of:
# |
# | host rfc931 authuser [DD/Mon/YYYY:hh:mm:ss] "request" ddd bbbb
# |
# |		host: Either the DNS name or the IP number of the remote client
# |		rfc931: Any information returned by identd for this person,
# |				- otherwise.
# |		authuser: If user sent a userid for authentication, the user name,
# |				  - otherwise.
# |		DD: Day
# |		Mon: Month (calendar name)
# |		YYYY: Year
# |		hh: hour (24-hour format, the machine's timezone)
# |		mm: minutes
# |		ss: seconds
# |		request: The first line of the HTTP request as sent by the client.
# |		ddd: the status code returned by the server, - if not available.
# |		bbbb: the total number of bytes sent,
# |			  *not including the HTTP/1.0 header*, - if not available
# |
# | You can determine the name of the file accessed through request.
#
# (Actually, the latter is only true if you know the server configuration
# at the time the request was made!)

__version__ = "0.3"

__all__ = ["HTTPServer", "BaseHTTPRequestHandler"]

import sys
import time
import socket # For gethostbyaddr()
import mimetools
import SocketServer

# Default error message
DEFAULT_ERROR_MESSAGE = """\
<head>
<title>Error response</title>
</head>
<body>
<h1>Error response</h1>
<p>Error code %(code)d.
<p>Message: %(message)s.
<p>Error code explanation: %(code)s = %(explain)s.
</body>
"""

def _quote_html(html):
	return html.replace("&", "&amp;").replace("<", "&lt;").replace(">", "&gt;")

class HTTPServer(SocketServer.TCPServer):

	allow_reuse_address = 1	# Seems to make sense in testing environment

	def server_bind(self):
		"""Override server_bind to store the server name."""
		SocketServer.TCPServer.server_bind(self)
		host, port = self.socket.getsockname()[:2]
		self.server_name = socket.getfqdn(host)
		self.server_port = port


class BaseHTTPRequestHandler(SocketServer.StreamRequestHandler):

	"""HTTP request handler base class.

	The following explanation of HTTP serves to guide you through the
	code as well as to expose any misunderstandings I may have about
	HTTP (so you don't need to read the code to figure out I'm wrong
	:-).

	HTTP (HyperText Transfer Protocol) is an extensible protocol on
	top of a reliable stream transport (e.g. TCP/IP).  The protocol
	recognizes three parts to a request:

	1. One line identifying the request type and path
	2. An optional set of RFC-822-style headers
	3. An optional data part

	The headers and data are separated by a blank line.

	The first line of the request has the form

	<command> <path> <version>

	where <command> is a (case-sensitive) keyword such as GET or POST,
	<path> is a string containing path information for the request,
	and <version> should be the string "HTTP/1.0" or "HTTP/1.1".
	<path> is encoded using the URL encoding scheme (using %xx to signify
	the ASCII character with hex code xx).

	The specification specifies that lines are separated by CRLF but
	for compatibility with the widest range of clients recommends
	servers also handle LF.  Similarly, whitespace in the request line
	is treated sensibly (allowing multiple spaces between components
	and allowing trailing whitespace).

	Similarly, for output, lines ought to be separated by CRLF pairs
	but most clients grok LF characters just fine.

	If the first line of the request has the form

	<command> <path>

	(i.e. <version> is left out) then this is assumed to be an HTTP
	0.9 request; this form has no optional headers and data part and
	the reply consists of just the data.

	The reply form of the HTTP 1.x protocol again has three parts:

	1. One line giving the response code
	2. An optional set of RFC-822-style headers
	3. The data

	Again, the headers and data are separated by a blank line.

	The response code line has the form

	<version> <responsecode> <responsestring>

	where <version> is the protocol version ("HTTP/1.0" or "HTTP/1.1"),
	<responsecode> is a 3-digit response code indicating success or
	failure of the request, and <responsestring> is an optional
	human-readable string explaining what the response code means.

	This server parses the request and the headers, and then calls a
	function specific to the request type (<command>).  Specifically,
	a request SPAM will be handled by a method do_SPAM().  If no
	such method exists the server sends an error response to the
	client.  If it exists, it is called with no arguments:

	do_SPAM()

	Note that the request name is case sensitive (i.e. SPAM and spam
	are different requests).

	The various request details are stored in instance variables:

	- client_address is the client IP address in the form (host,
	port);

	- command, path and version are the broken-down request line;

	- headers is an instance of mimetools.Message (or a derived
	class) containing the header information;

	- rfile is a file object open for reading positioned at the
	start of the optional input data part;

	- wfile is a file object open for writing.

	IT IS IMPORTANT TO ADHERE TO THE PROTOCOL FOR WRITING!

	The first thing to be written must be the response line.  Then
	follow 0 or more header lines, then a blank line, and then the
	actual data (if any).  The meaning of the header lines depends on
	the command executed by the server; in most cases, when data is
	returned, there should be at least one header line of the form

	Content-type: <type>/<subtype>

	where <type> and <subtype> should be registered MIME types,
	e.g. "text/html" or "text/plain".

	"""

	# The Python system version, truncated to its first component.
	sys_version = "Python/" + sys.version.split()[0]

	# The server software version.  You may want to override this.
	# The format is multiple whitespace-separated strings,
	# where each string is of the form name[/version].
	server_version = "BaseHTTP/" + __version__

	def parse_request(self):
		"""Parse a request (internal).

		The request should be stored in self.raw_requestline; the results
		are in self.command, self.path, self.request_version and
		self.headers.

		Return True for success, False for failure; on failure, an
		error is sent back.

		"""
		self.command = None  # set in case of error on the first line
		self.request_version = version = "HTTP/0.9" # Default
		self.close_connection = 1
		requestline = self.raw_requestline
		if requestline[-2:] == '\r\n':
			requestline = requestline[:-2]
		elif requestline[-1:] == '\n':
			requestline = requestline[:-1]
		self.requestline = requestline
		words = requestline.split()
		if len(words) == 3:
			[command, path, version] = words
			if version[:5] != 'HTTP/':
				self.send_error(400, "Bad request version (%r)" % version)
				return False
			try:
				base_version_number = version.split('/', 1)[1]
				version_number = base_version_number.split(".")
				# RFC 2145 section 3.1 says there can be only one "." and
				#   - major and minor numbers MUST be treated as
				#	  separate integers;
				#   - HTTP/2.4 is a lower version than HTTP/2.13, which in
				#	  turn is lower than HTTP/12.3;
				#   - Leading zeros MUST be ignored by recipients.
				if len(version_number) != 2:
					raise ValueError
				version_number = int(version_number[0]), int(version_number[1])
			except (ValueError, IndexError):
				self.send_error(400, "Bad request version (%r)" % version)
				return False
			if version_number >= (1, 1) and self.protocol_version >= "HTTP/1.1":
				self.close_connection = 0
			if version_number >= (2, 0):
				self.send_error(505,
						  "Invalid HTTP Version (%s)" % base_version_number)
				return False
		elif len(words) == 2:
			[command, path] = words
			self.close_connection = 1
			if command != 'GET':
				self.send_error(400,
								"Bad HTTP/0.9 request type (%r)" % command)
				return False
		elif not words:
			return False
		else:
			self.send_error(400, "Bad request syntax (%r)" % requestline)
			return False
		self.command, self.path, self.request_version = command, path, version

		# Examine the headers and look for a Connection directive
		self.headers = self.MessageClass(self.rfile, 0)

		conntype = self.headers.get('Connection', "")
		if conntype.lower() == 'close':
			self.close_connection = 1
		elif (conntype.lower() == 'keep-alive' and
			  self.protocol_version >= "HTTP/1.1"):
			self.close_connection = 0
		return True

	def handle_one_request(self):
		"""Handle a single HTTP request.

		You normally don't need to override this method; see the class
		__doc__ string for information on how to handle specific HTTP
		commands such as GET and POST.

		"""
		try:
			self.raw_requestline = self.rfile.readline()
			if not self.raw_requestline:
				self.close_connection = 1
				return
			if not self.parse_request(): # An error code has been sent, just exit
				return
			mname = 'do_' + self.command
			if not hasattr(self, mname):
				self.send_error(501, "Unsupported method (%r)" % self.command)
				return
			method = getattr(self, mname)
			method()
		except:
			pass

	def handle(self):
		"""Handle multiple requests if necessary."""
		self.close_connection = 1

		self.handle_one_request()
		while not self.close_connection:
			self.handle_one_request()

	def send_error(self, code, message=None):
		"""Send and log an error reply.

		Arguments are the error code, and a detailed message.
		The detailed message defaults to the short entry matching the
		response code.

		This sends an error response (so it must be called before any
		output has been generated), logs the error, and finally sends
		a piece of HTML explaining the error to the user.

		"""

		try:
			short, long = self.responses[code]
		except KeyError:
			short, long = '???', '???'
		if message is None:
			message = short
		explain = long
		self.log_error("code %d, message %s", code, message)
		# using _quote_html to prevent Cross Site Scripting attacks (see bug #1100201)
		content = (self.error_message_format %
				   {'code': code, 'message': _quote_html(message), 'explain': explain})
		self.send_response(code, message)
		self.send_header("Content-Type", "text/html")
		self.send_header('Connection', 'close')
		self.end_headers()
		if self.command != 'HEAD' and code >= 200 and code not in (204, 304):
			self.wfile.write(content)

	error_message_format = DEFAULT_ERROR_MESSAGE

	def send_response(self, code, message=None):
		"""Send the response header and log the response code.

		Also send two standard headers with the server software
		version and the current date.

		"""
		self.log_request(code)
		if message is None:
			if code in self.responses:
				message = self.responses[code][0]
			else:
				message = ''
		if self.request_version != 'HTTP/0.9':
			self.wfile.write("%s %d %s\r\n" %
							 (self.protocol_version, code, message))
			# print (self.protocol_version, code, message)
		self.send_header('Server', self.version_string())
		self.send_header('Date', self.date_time_string())

	def send_header(self, keyword, value):
		"""Send a MIME header."""
		if self.request_version != 'HTTP/0.9':
			self.wfile.write("%s: %s\r\n" % (keyword, value))

		if keyword.lower() == 'connection':
			if value.lower() == 'close':
				self.close_connection = 1
			elif value.lower() == 'keep-alive':
				self.close_connection = 0

	def end_headers(self):
		"""Send the blank line ending the MIME headers."""
		if self.request_version != 'HTTP/0.9':
			self.wfile.write("\r\n")

	def log_request(self, code='-', size='-'):
		"""Log an accepted request.

		This is called by send_response().

		"""

		self.log_message('"%s" %s %s',
						 self.requestline, str(code), str(size))

	def log_error(self, *args):
		"""Log an error.

		This is called when a request cannot be fulfilled.  By
		default it passes the message on to log_message().

		Arguments are the same as for log_message().

		XXX This should go to the separate error log.

		"""

		self.log_message(*args)

	def log_message(self, format, *args):
		"""Log an arbitrary message.

		This is used by all other logging functions.  Override
		it if you have specific logging wishes.

		The first argument, FORMAT, is a format string for the
		message to be logged.  If the format string contains
		any % escapes requiring parameters, they should be
		specified as subsequent arguments (it's just like
		printf!).

		The client host and current date/time are prefixed to
		every message.

		"""

		sys.stderr.write("%s - - [%s] %s\n" %
						 (self.address_string(),
						  self.log_date_time_string(),
						  format%args))

	def version_string(self):
		"""Return the server software version string."""
		return self.server_version + ' ' + self.sys_version

	def date_time_string(self, timestamp=None):
		"""Return the current date and time formatted for a message header."""
		if timestamp is None:
			timestamp = time.time()
		year, month, day, hh, mm, ss, wd, y, z = time.gmtime(timestamp)
		s = "%s, %02d %3s %4d %02d:%02d:%02d GMT" % (
				self.weekdayname[wd],
				day, self.monthname[month], year,
				hh, mm, ss)
		return s

	def log_date_time_string(self):
		"""Return the current time formatted for logging."""
		now = time.time()
		year, month, day, hh, mm, ss, x, y, z = time.localtime(now)
		s = "%02d/%3s/%04d %02d:%02d:%02d" % (
				day, self.monthname[month], year, hh, mm, ss)
		return s

	weekdayname = ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun']

	monthname = [None,
				 'Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun',
				 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec']

	def address_string(self):
		"""Return the client address formatted for logging.

		This version looks up the full hostname using gethostbyaddr(),
		and tries to find a name that contains at least one dot.

		"""

		host, port = self.client_address[:2]
		return socket.getfqdn(host)

	# Essentially static class variables

	# The version of the HTTP protocol we support.
	# Set this to HTTP/1.1 to enable automatic keepalive
	protocol_version = "HTTP/1.0"

	# The Message-like class used to parse headers
	MessageClass = mimetools.Message

	# Table mapping response codes to messages; entries have the
	# form {code: (shortmessage, longmessage)}.
	# See RFC 2616.
	responses = {
		100: ('Continue', 'Request received, please continue'),
		101: ('Switching Protocols',
			  'Switching to new protocol; obey Upgrade header'),

		200: ('OK', 'Request fulfilled, document follows'),
		201: ('Created', 'Document created, URL follows'),
		202: ('Accepted',
			  'Request accepted, processing continues off-line'),
		203: ('Non-Authoritative Information', 'Request fulfilled from cache'),
		204: ('No Content', 'Request fulfilled, nothing follows'),
		205: ('Reset Content', 'Clear input form for further input.'),
		206: ('Partial Content', 'Partial content follows.'),

		300: ('Multiple Choices',
			  'Object has several resources -- see URI list'),
		301: ('Moved Permanently', 'Object moved permanently -- see URI list'),
		302: ('Found', 'Object moved temporarily -- see URI list'),
		303: ('See Other', 'Object moved -- see Method and URL list'),
		304: ('Not Modified',
			  'Document has not changed since given time'),
		305: ('Use Proxy',
			  'You must use proxy specified in Location to access this '
			  'resource.'),
		307: ('Temporary Redirect',
			  'Object moved temporarily -- see URI list'),

		400: ('Bad Request',
			  'Bad request syntax or unsupported method'),
		401: ('Unauthorized',
			  'No permission -- see authorization schemes'),
		402: ('Payment Required',
			  'No payment -- see charging schemes'),
		403: ('Forbidden',
			  'Request forbidden -- authorization will not help'),
		404: ('Not Found', 'Nothing matches the given URI'),
		405: ('Method Not Allowed',
			  'Specified method is invalid for this server.'),
		406: ('Not Acceptable', 'URI not available in preferred format.'),
		407: ('Proxy Authentication Required', 'You must authenticate with '
			  'this proxy before proceeding.'),
		408: ('Request Timeout', 'Request timed out; try again later.'),
		409: ('Conflict', 'Request conflict.'),
		410: ('Gone',
			  'URI no longer exists and has been permanently removed.'),
		411: ('Length Required', 'Client must specify Content-Length.'),
		412: ('Precondition Failed', 'Precondition in headers is false.'),
		413: ('Request Entity Too Large', 'Entity is too large.'),
		414: ('Request-URI Too Long', 'URI is too long.'),
		415: ('Unsupported Media Type', 'Entity body in unsupported format.'),
		416: ('Requested Range Not Satisfiable',
			  'Cannot satisfy request range.'),
		417: ('Expectation Failed',
			  'Expect condition could not be satisfied.'),

		500: ('Internal Server Error', 'Server got itself in trouble'),
		501: ('Not Implemented',
			  'Server does not support this operation'),
		502: ('Bad Gateway', 'Invalid responses from another server/proxy.'),
		503: ('Service Unavailable',
			  'The server cannot process the request due to a high load'),
		504: ('Gateway Timeout',
			  'The gateway server did not receive a timely response'),
		505: ('HTTP Version Not Supported', 'Cannot fulfill request.'),
		}


def test(HandlerClass = BaseHTTPRequestHandler,
		 ServerClass = HTTPServer, protocol="HTTP/1.0"):
	"""Test the HTTP request handler class.

	This runs an HTTP server on port 8000 (or the first command line
	argument).

	"""

	if sys.argv[1:]:
		port = int(sys.argv[1])
	else:
		port = 8000
	server_address = ('', port)

	HandlerClass.protocol_version = protocol
	httpd = ServerClass(server_address, HandlerClass)

	sa = httpd.socket.getsockname()
	print "Serving HTTP on", sa[0], "port", sa[1], "..."
	httpd.serve_forever()


if __name__ == '__main__':
	test()
