"""Base classes for server/gateway implementations"""

from types import StringType

from util import FileWrapper, guess_scheme, is_hop_by_hop

from headers import Headers

import sys, os, time

__all__ = ['BaseHandler', 'SimpleHandler', 'BaseCGIHandler', 'CGIHandler']

try:

    dict

except NameError:

    def dict(items):

        d = {}

        for k,v in items:

            d[k] = v

        return d

# Uncomment for 2.2 compatibility.

#try:

#    True

#    False

#except NameError:

#    True = not None

#    False = not True

# Weekday and month names for HTTP date/time formatting; always English!

_weekdayname = ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"]

_monthname = [None, # Dummy so we can use 1-based month numbers

              "Jan", "Feb", "Mar", "Apr", "May", "Jun",

              "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"]

def format_date_time(timestamp):

    year, month, day, hh, mm, ss, wd, y, z = time.gmtime(timestamp)

    return "%s, %02d %3s %4d %02d:%02d:%02d GMT" % (

        _weekdayname[wd], day, _monthname[month], year, hh, mm, ss

    )

class BaseHandler:

    """Manage the invocation of a WSGI application"""

    # Configuration parameters; can override per-subclass or per-instance

    wsgi_version = (1,0)

    wsgi_multithread = True

    wsgi_multiprocess = True

    wsgi_run_once = False

    origin_server = True    # We are transmitting direct to client

    http_version  = "1.0"   # Version that should be used for response

    server_software = None  # String name of server software, if any

    # os_environ is used to supply configuration from the OS environment:

    # by default it's a copy of 'os.environ' as of import time, but you can

    # override this in e.g. your __init__ method.

    os_environ = dict(os.environ.items())

    # Collaborator classes

    wsgi_file_wrapper = FileWrapper     # set to None to disable

    headers_class = Headers             # must be a Headers-like class

    # Error handling (also per-subclass or per-instance)

    traceback_limit = None  # Print entire traceback to self.get_stderr()

    error_status = "500 Dude, this is whack!"

    error_headers = [('Content-Type','text/plain')]

    error_body = "A server error occurred.  Please contact the administrator."

    # State variables (don't mess with these)

    status = result = None

    headers_sent = False

    headers = None

    bytes_sent = 0

    def run(self, application):

        """Invoke the application"""

        # Note to self: don't move the close()!  Asynchronous servers shouldn't

        # call close() from finish_response(), so if you close() anywhere but

        # the double-error branch here, you'll break asynchronous servers by

        # prematurely closing.  Async servers must return from 'run()' without

        # closing if there might still be output to iterate over.

        try:

            self.setup_environ()

            self.result = application(self.environ, self.start_response)

            self.finish_response()

        except:

            try:

                self.handle_error()

            except:

                # If we get an error handling an error, just give up already!

                self.close()

                raise   # ...and let the actual server figure it out.

    def setup_environ(self):

        """Set up the environment for one request"""

        env = self.environ = self.os_environ.copy()

        self.add_cgi_vars()

        env['wsgi.input']        = self.get_stdin()

        env['wsgi.errors']       = self.get_stderr()

        env['wsgi.version']      = self.wsgi_version

        env['wsgi.run_once']     = self.wsgi_run_once

        env['wsgi.url_scheme']   = self.get_scheme()

        env['wsgi.multithread']  = self.wsgi_multithread

        env['wsgi.multiprocess'] = self.wsgi_multiprocess

        if self.wsgi_file_wrapper is not None:

            env['wsgi.file_wrapper'] = self.wsgi_file_wrapper

        if self.origin_server and self.server_software:

            env.setdefault('SERVER_SOFTWARE',self.server_software)

    def finish_response(self):

        """Send any iterable data, then close self and the iterable

        Subclasses intended for use in asynchronous servers will

        want to redefine this method, such that it sets up callbacks

        in the event loop to iterate over the data, and to call

        'self.close()' once the response is finished.

        """

        if not self.result_is_file() or not self.sendfile():

            for data in self.result:

                self.write(data)

            self.finish_content()

        self.close()

    def get_scheme(self):

        """Return the URL scheme being used"""

        return guess_scheme(self.environ)

    def set_content_length(self):

        """Compute Content-Length or switch to chunked encoding if possible"""

        try:

            blocks = len(self.result)

        except (TypeError,AttributeError,NotImplementedError):

            pass

        else:

            if blocks==1:

                self.headers['Content-Length'] = str(self.bytes_sent)

                return

        # XXX Try for chunked encoding if origin server and client is 1.1

    def cleanup_headers(self):

        """Make any necessary header changes or defaults

        Subclasses can extend this to add other defaults.

        """

        if not self.headers.has_key('Content-Length'):

            self.set_content_length()

    def start_response(self, status, headers,exc_info=None):

        """'start_response()' callable as specified by PEP 333"""

        if exc_info:

            try:

                if self.headers_sent:

                    # Re-raise original exception if headers sent

                    raise exc_info[0], exc_info[1], exc_info[2]

            finally:

                exc_info = None        # avoid dangling circular ref

        elif self.headers is not None:

            raise AssertionError("Headers already set!")

        assert type(status) is StringType,"Status must be a string"

        assert len(status)>=4,"Status must be at least 4 characters"

        assert int(status[:3]),"Status message must begin w/3-digit code"

        assert status[3]==" ", "Status message must have a space after code"

        if __debug__:

            for name,val in headers:

                assert type(name) is StringType,"Header names must be strings"

                assert type(val) is StringType,"Header values must be strings"

                assert not is_hop_by_hop(name),"Hop-by-hop headers not allowed"

        self.status = status

        self.headers = self.headers_class(headers)

        return self.write

    def send_preamble(self):

        """Transmit version/status/date/server, via self._write()"""

        if self.origin_server:

            if self.client_is_modern():

                self._write('HTTP/%s %s\r\n' % (self.http_version,self.status))

                if not self.headers.has_key('Date'):

                    self._write(

                        'Date: %s\r\n' % format_date_time(time.time())

                    )

                if self.server_software and not self.headers.has_key('Server'):

                    self._write('Server: %s\r\n' % self.server_software)

        else:

            self._write('Status: %s\r\n' % self.status)

    def write(self, data):

        """'write()' callable as specified by PEP 333"""

        assert type(data) is StringType,"write() argument must be string"

        if not self.status:

            raise AssertionError("write() before start_response()")

        elif not self.headers_sent:

            # Before the first output, send the stored headers

            self.bytes_sent = len(data)    # make sure we know content-length

            self.send_headers()

        else:

            self.bytes_sent += len(data)

        # XXX check Content-Length and truncate if too many bytes written?

        self._write(data)

        self._flush()

    def sendfile(self):

        """Platform-specific file transmission

        Override this method in subclasses to support platform-specific

        file transmission.  It is only called if the application's

        return iterable ('self.result') is an instance of

        'self.wsgi_file_wrapper'.

        This method should return a true value if it was able to actually

        transmit the wrapped file-like object using a platform-specific

        approach.  It should return a false value if normal iteration

        should be used instead.  An exception can be raised to indicate

        that transmission was attempted, but failed.

        NOTE: this method should call 'self.send_headers()' if

        'self.headers_sent' is false and it is going to attempt direct

        transmission of the file.

        """

        return False   # No platform-specific transmission by default

    def finish_content(self):

        """Ensure headers and content have both been sent"""

        if not self.headers_sent:

            self.headers['Content-Length'] = "0"

            self.send_headers()

        else:

            pass # XXX check if content-length was too short?

    def close(self):

        """Close the iterable (if needed) and reset all instance vars

        Subclasses may want to also drop the client connection.

        """

        try:

            if hasattr(self.result,'close'):

                self.result.close()

        finally:

            self.result = self.headers = self.status = self.environ = None

            self.bytes_sent = 0; self.headers_sent = False

    def send_headers(self):

        """Transmit headers to the client, via self._write()"""

        self.cleanup_headers()

        self.headers_sent = True

        if not self.origin_server or self.client_is_modern():

            self.send_preamble()

            self._write(str(self.headers))

    def result_is_file(self):

        """True if 'self.result' is an instance of 'self.wsgi_file_wrapper'"""

        wrapper = self.wsgi_file_wrapper

        return wrapper is not None and isinstance(self.result,wrapper)

    def client_is_modern(self):

        """True if client can accept status and headers"""

        return self.environ['SERVER_PROTOCOL'].upper() != 'HTTP/0.9'

    def log_exception(self,exc_info):

        """Log the 'exc_info' tuple in the server log

        Subclasses may override to retarget the output or change its format.

        """

        try:

            from traceback import print_exception

            stderr = self.get_stderr()

            print_exception(

                exc_info[0], exc_info[1], exc_info[2],

                self.traceback_limit, stderr

            )

            stderr.flush()

        finally:

            exc_info = None

    def handle_error(self):

        """Log current error, and send error output to client if possible"""

        self.log_exception(sys.exc_info())

        if not self.headers_sent:

            self.result = self.error_output(self.environ, self.start_response)

            self.finish_response()

        # XXX else: attempt advanced recovery techniques for HTML or text?

    def error_output(self, environ, start_response):

        """WSGI mini-app to create error output

        By default, this just uses the 'error_status', 'error_headers',

        and 'error_body' attributes to generate an output page.  It can

        be overridden in a subclass to dynamically generate diagnostics,

        choose an appropriate message for the user's preferred language, etc.

        Note, however, that it's not recommended from a security perspective to

        spit out diagnostics to any old user; ideally, you should have to do

        something special to enable diagnostic output, which is why we don't

        include any here!

        """

        start_response(self.error_status,self.error_headers[:],sys.exc_info())

        return [self.error_body]

    # Pure abstract methods; *must* be overridden in subclasses

    def _write(self,data):

        """Override in subclass to buffer data for send to client

        It's okay if this method actually transmits the data; BaseHandler

        just separates write and flush operations for greater efficiency

        when the underlying system actually has such a distinction.

        """

        raise NotImplementedError

    def _flush(self):

        """Override in subclass to force sending of recent '_write()' calls

        It's okay if this method is a no-op (i.e., if '_write()' actually

        sends the data.

        """

        raise NotImplementedError

    def get_stdin(self):

        """Override in subclass to return suitable 'wsgi.input'"""

        raise NotImplementedError

    def get_stderr(self):

        """Override in subclass to return suitable 'wsgi.errors'"""

        raise NotImplementedError

    def add_cgi_vars(self):

        """Override in subclass to insert CGI variables in 'self.environ'"""

        raise NotImplementedError

class SimpleHandler(BaseHandler):

    """Handler that's just initialized with streams, environment, etc.

    This handler subclass is intended for synchronous HTTP/1.0 origin servers,

    and handles sending the entire response output, given the correct inputs.

    Usage::

        handler = SimpleHandler(

            inp,out,err,env, multithread=False, multiprocess=True

        )

        handler.run(app)"""

    def __init__(self,stdin,stdout,stderr,environ,

        multithread=True, multiprocess=False

    ):

        self.stdin = stdin

        self.stdout = stdout

        self.stderr = stderr

        self.base_env = environ

        self.wsgi_multithread = multithread

        self.wsgi_multiprocess = multiprocess

    def get_stdin(self):

        return self.stdin

    def get_stderr(self):

        return self.stderr

    def add_cgi_vars(self):

        self.environ.update(self.base_env)

    def _write(self,data):

        self.stdout.write(data)

        self._write = self.stdout.write

    def _flush(self):

        self.stdout.flush()

        self._flush = self.stdout.flush

class BaseCGIHandler(SimpleHandler):

    """CGI-like systems using input/output/error streams and environ mapping

    Usage::

        handler = BaseCGIHandler(inp,out,err,env)

        handler.run(app)

    This handler class is useful for gateway protocols like ReadyExec and

    FastCGI, that have usable input/output/error streams and an environment

    mapping.  It's also the base class for CGIHandler, which just uses

    sys.stdin, os.environ, and so on.

    The constructor also takes keyword arguments 'multithread' and

    'multiprocess' (defaulting to 'True' and 'False' respectively) to control

    the configuration sent to the application.  It sets 'origin_server' to

    False (to enable CGI-like output), and assumes that 'wsgi.run_once' is

    False.

    """

    origin_server = False

class CGIHandler(BaseCGIHandler):

    """CGI-based invocation via sys.stdin/stdout/stderr and os.environ

    Usage::

        CGIHandler().run(app)

    The difference between this class and BaseCGIHandler is that it always

    uses 'wsgi.run_once' of 'True', 'wsgi.multithread' of 'False', and

    'wsgi.multiprocess' of 'True'.  It does not take any initialization

    parameters, but always uses 'sys.stdin', 'os.environ', and friends.

    If you need to override any of these parameters, use BaseCGIHandler

    instead.

    """

    wsgi_run_once = True

    def __init__(self):

        BaseCGIHandler.__init__(

            self, sys.stdin, sys.stdout, sys.stderr, dict(os.environ.items()),

            multithread=False, multiprocess=True

        )

#