import sys
import traceback

def simple_app(environ, start_response):
    """Simplest possible application object"""
    status = '200 OK'
    response_headers = [('Content-type','text/plain')]
    start_response(status, response_headers)
    return ['Hello world!\n']

class AppClass:
    def __init__(self, environ, start_response):
        self.environ = environ
        self.start = start_response

    def __iter__(self):
        status = '200 OK'
        response_headers = [('Content-type','text/plain')]
        self.start(status, response_headers)
        yield "Hello world!\n"

################
## Middleware ##
################        

class UpperIter:
    def __init__(self,result,transform_ok):
        if hasattr(result,'close'):
            self.close = result.close
        self._next = iter(result).next
        self.transform_ok = transform_ok

    def __iter__(self):
        return self

    def next(self):
        if self.transform_ok:
            return self._next().upper()
        else:
            return self._next()

class Upperator:
    transform = False

    def __init__(self, application):
        self.application = application

    def __call__(self, environ, start_response):

        transform_ok = []

        def start_upper(status,response_headers,exc_info=None):

            # Reset ok flag, in case this is a repeat call
            transform_ok[:]=[]

            for name,value in response_headers:
                if name.lower()=='content-type' and value=='text/plain':
                    transform_ok.append(True)
                    # Strip content-length if present, else it'll be wrong
                    response_headers = [(name,value)
                        for name,value in response_headers
                            if name.lower()<>'content-length'
                    ]
                    break
                
            write = start_response(status,
                                   response_headers,exc_info)
            
            if exc_info:
                try:
                    write('Errortype:%s\nValue:%s\nTraceback:%s'%
                          (exc_info[0], exc_info[1],
                           traceback.format_tb(exc_info[2]))
                          )
                finally:
                    exec_info = None
            if transform_ok:
                def write_upper(data):
                    write(data.upper())
                return write_upper
            else:
                return write

        return UpperIter(self.application(environ,start_upper),
                         transform_ok)


def e_app(environ, start_response):
    try:
        # regular application code here
        status = "200 Froody"
        response_headers = [("content-type","text/plain")]
        start_response(status, response_headers)
        a = 1/0
        return ["normal body goes here"]
    except:
        # XXX should trap runtime issues like MemoryError, KeyboardInterrupt
        #     in a separate handler before this bare 'except:'...
        status = "500 Oops"
        response_headers = [("content-type","text/plain")]
        start_response(status, response_headers, sys.exc_info())
        return ["\nerror body goes here"]

from pprint import pformat
import cgi
formstr = """
<p>
<form action="/wsgitest" method="post" >
  <p>
  username: 
    <input name="username" type="text">
  <br/>
  password: 
  <input name="passwd" type="password">
  <br/>
  <input name="submit" type="submit" value="submit">
</form>
</p>
<p>
name: %s
pass: %s
</p>
"""
def form_app(environ, start_response):
    status = "200 Froody"
    response_headers = [("content-type","text/html")]
    form = cgi.FieldStorage(fp=environ['wsgi.input'],
                            environ= environ, keep_blank_values=0)
    start_response(status, response_headers)
    name, passwd = '', ''
    if form.has_key('username'):
        name = form['username'].value
    if form.has_key('passwd'):
        passwd = form['passwd'].value
    return [formstr%(name, passwd)]

uapp = Upperator(simple_app)
eapp = Upperator(e_app)