"""
HTTP Utilities
(from web.py)
"""

__all__ = [
  "expires", "lastmodified", 
  "prefixurl", "modified", 
  "redirect", "found", "seeother", "tempredirect", 
  "write",
  "changequery", "url",
  "background", "backgrounder",
  "Reloader", "reloader", "profiler",
]

import sys, os, threading, urllib, urlparse
try: import datetime
except ImportError: pass
import net, utils, webapi as web

def prefixurl(base=''):
    """
    Sorry, this function is really difficult to explain.
    Maybe some other time.
    """
    url = web.ctx.path.lstrip('/')
    for i in xrange(url.count('/')): 
        base += '../'
    if not base: 
        base = './'
    return base

def expires(delta):
    """
    Outputs an `Expires` header for `delta` from now. 
    `delta` is a `timedelta` object or a number of seconds.
    """
    if isinstance(delta, (int, long)):
        delta = datetime.timedelta(seconds=delta)
    date_obj = datetime.datetime.utcnow() + delta
    web.header('Expires', net.httpdate(date_obj))

def lastmodified(date_obj):
    """Outputs a `Last-Modified` header for `datetime`."""
    web.header('Last-Modified', net.httpdate(date_obj))

def modified(date=None, etag=None):
    n = web.ctx.env.get('HTTP_IF_NONE_MATCH')
    m = net.parsehttpdate(web.ctx.env.get('HTTP_IF_MODIFIED_SINCE', '').split(';')[0])
    validate = False
    if etag:
        raise NotImplementedError, "no etag support yet"
        # should really be a warning
    if date and m:
        # we subtract a second because 
        # HTTP dates don't have sub-second precision
        if date-datetime.timedelta(seconds=1) <= m:
            validate = True

    if validate: web.ctx.status = '304 Not Modified'
    return not validate

"""
By default, these all return simple error messages that send very short messages 
(like "bad request") to the user. They can and should be overridden 
to return nicer ones.
"""
def redirect(url, status='301 Moved Permanently'):
    """
    Returns a `status` redirect to the new URL. 
    `url` is joined with the base URL so that things like 
    `redirect("about") will work properly.
    """
    newloc = urlparse.urljoin(web.ctx.path, url)

    # if newloc is relative then make it absolute
    if newloc.startswith('/'):
        newloc = web.ctx.home + newloc

    web.ctx.status = status
    web.ctx.output = ''    
    web.header('Content-Type', 'text/html')
    web.header('Location', newloc)
    # seems to add a three-second delay for some reason:
    # web.output('<a href="'+ newloc + '">moved permanently</a>')

def found(url):
    """A `302 Found` redirect."""
    return redirect(url, '302 Found')

def seeother(url):
    """A `303 See Other` redirect."""
    return redirect(url, '303 See Other')

def tempredirect(url):
    """A `307 Temporary Redirect` redirect."""
    return redirect(url, '307 Temporary Redirect')

def write(cgi_response):
    """
    Converts a standard CGI-style string response into `header` and 
    `output` calls.
    """
    cgi_response = str(cgi_response)
    cgi_response.replace('\r\n', '\n')
    head, body = cgi_response.split('\n\n', 1)
    lines = head.split('\n')

    for line in lines:
        if line.isspace(): 
            continue
        hdr, value = line.split(":", 1)
        value = value.strip()
        if hdr.lower() == "status": 
            web.ctx.status = value
        else: 
            web.header(hdr, value)

    web.output(body)

def urlencode(query):
    """
    Same as urllib.urlencode, but supports unicode strings.
    
        >>> urlencode({'text':'foo bar'})
        'text=foo+bar'
    """
    query = dict([(k, utils.utf8(v)) for k, v in query.items()])
    return urllib.urlencode(query)

def changequery(query=None, **kw):
    """
    Imagine you're at `/foo?a=1&b=2`. Then `changequery(a=3)` will return
    `/foo?a=3&b=2` -- the same URL but with the arguments you requested
    changed.
    """
    if query is None:
        query = web.input(_method='get')
    for k, v in kw.iteritems():
        if v is None:
            query.pop(k, None)
        else:
            query[k] = v
    out = web.ctx.path
    if query:
        out += '?' + urlencode(query)
    return out

def url(path=None, **kw):
    """
    Makes url by concatinating web.ctx.homepath and path and the 
    query string created using the arguments.
    """
    if path is None:
        path = web.ctx.path
    if path.startswith("/"):
        out = web.ctx.homepath + path
    else:
        out = path

    if kw:
        out += '?' + urlencode(kw)
    
    return out

def background(func):
    """A function decorator to run a long-running function as a background thread.

    GOTCHA in postgres: Until the foreground task ends, any db access by background 
    task will necessarily get old data from before the foreground task started
    because psycopg2 begins a transaction in the foreground task until it quits.
    """
    def internal(*a, **kw):
        web.data() # cache it

        tmpctx = web._context[threading.currentThread()]
        web._context[threading.currentThread()] = utils.storage(web.ctx.copy())

        def newfunc():
            web._context[threading.currentThread()] = tmpctx
            # Create new db cursor if there is one else background thread
            # overwrites foreground cursor causing rubbish data into dbase
            if web.config.get('db_parameters'):
                import db
                db.connect(**web.config.db_parameters)
            func(*a, **kw)
            myctx = web._context[threading.currentThread()]
            for k in myctx.keys():
                if k not in ['status', 'headers', 'output']:
                    try: del myctx[k]
                    except KeyError: pass
        
        t = threading.Thread(target=newfunc)
        background.threaddb[id(t)] = t
        t.start()
        web.ctx.headers = []
        return seeother(changequery(_t=id(t)))
    return internal
background.threaddb = {}

def backgrounder(func):
    def internal(*a, **kw):
        i = web.input(_method='get')
        if '_t' in i:
            try:
                t = background.threaddb[int(i._t)]
            except KeyError:
                return web.notfound()
            web._context[threading.currentThread()] = web._context[t]
            return
        else:
            return func(*a, **kw)
    return internal

class Reloader:
    """
    Before every request, checks to see if any loaded modules have changed on 
    disk and, if so, reloads them.
    """
    def __init__(self, func):
        self.func = func
        self.mtimes = {}
        # cheetah:
        # b = _compiletemplate.bases
        # _compiletemplate = globals()['__compiletemplate']
        # _compiletemplate.bases = b
        
        web.loadhooks['reloader'] = self.check
        # todo:
        #  - replace relrcheck with a loadhook
        #if reloader in middleware:
        #    relr = reloader(None)
        #    relrcheck = relr.check
        #    middleware.remove(reloader)
        #else:
        #    relr = None
        #    relrcheck = lambda: None
        # if relr:
        #     relr.func = wsgifunc
        #     return wsgifunc
        # 
        
    
    def check(self):
        for mod in sys.modules.values():
            try: 
                mtime = os.stat(mod.__file__).st_mtime
            except (AttributeError, OSError, IOError): 
                continue
            if mod.__file__.endswith('.pyc') and \
               os.path.exists(mod.__file__[:-1]):
                mtime = max(os.stat(mod.__file__[:-1]).st_mtime, mtime)
            if mod not in self.mtimes:
                self.mtimes[mod] = mtime
            elif self.mtimes[mod] < mtime:
                try: 
                    reload(mod)
                    self.mtimes[mod] = mtime
                except ImportError: 
                    pass
        return True
    
    def __call__(self, e, o): 
        self.check()
        return self.func(e, o)

reloader = Reloader

def profiler(app):
    """Outputs basic profiling information at the bottom of each response."""
    from utils import profile
    def profile_internal(e, o):
        out, result = profile(app)(e, o)
        return out + ['<pre>' + net.websafe(result) + '</pre>']
    return profile_internal

if __name__ == "__main__":
    import doctest
    doctest.testmod()