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web/http.py

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+"""
+HTTP Utilities
+(from web.py)
+"""
+
+__all__ = [
+    "expires",
+    "lastmodified",
+    "prefixurl",
+    "modified",
+    "changequery",
+    "url",
+    "profiler",
+]
+
+import datetime
+
+from . import net, utils
+from . import webapi as web
+from .py3helpers import iteritems
+
+try:
+    from urllib.parse import urlencode as urllib_urlencode
+except ImportError:
+    from urllib import urlencode as urllib_urlencode
+
+
+def prefixurl(base=""):
+    """
+    Sorry, this function is really difficult to explain.
+    Maybe some other time.
+    """
+    url = web.ctx.path.lstrip("/")
+    for i in range(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):
+        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):
+    """
+    Checks to see if the page has been modified since the version in the
+    requester's cache.
+
+    When you publish pages, you can include `Last-Modified` and `ETag`
+    with the date the page was last modified and an opaque token for
+    the particular version, respectively. When readers reload the page,
+    the browser sends along the modification date and etag value for
+    the version it has in its cache. If the page hasn't changed,
+    the server can just return `304 Not Modified` and not have to
+    send the whole page again.
+
+    This function takes the last-modified date `date` and the ETag `etag`
+    and checks the headers to see if they match. If they do, it returns
+    `True`, or otherwise it raises NotModified error. It also sets
+    `Last-Modified` and `ETag` output headers.
+    """
+    n = {x.strip('" ') for x in web.ctx.env.get("HTTP_IF_NONE_MATCH", "").split(",")}
+    m = net.parsehttpdate(web.ctx.env.get("HTTP_IF_MODIFIED_SINCE", "").split(";")[0])
+    validate = False
+    if etag:
+        if "*" in n or etag in n:
+            validate = True
+    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 date:
+        lastmodified(date)
+    if etag:
+        web.header("ETag", '"' + etag + '"')
+    if validate:
+        raise web.notmodified()
+    else:
+        return True
+
+
+def urlencode(query, doseq=0):
+    """
+    Same as urllib.urlencode, but supports unicode strings.
+
+        >>> urlencode({'text':'foo bar'})
+        'text=foo+bar'
+        >>> urlencode({'x': [1, 2]}, doseq=True)
+        'x=1&x=2'
+    """
+
+    def convert(value, doseq=False):
+        if doseq and isinstance(value, list):
+            return [convert(v) for v in value]
+        else:
+            return utils.safestr(value)
+
+    query = {k: convert(v, doseq) for k, v in query.items()}
+    return urllib_urlencode(query, doseq=doseq)
+
+
+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.rawinput(method="get")
+    for k, v in iteritems(kw):
+        if v is None:
+            query.pop(k, None)
+        else:
+            query[k] = v
+    out = web.ctx.path
+    if query:
+        out += "?" + urlencode(query, doseq=True)
+    return out
+
+
+def url(path=None, doseq=False, **kw):
+    """
+    Makes url by concatenating 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, doseq=doseq)
+
+    return out
+
+
+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 list(out) + ["<pre>" + net.websafe(result) + "</pre>"]
+
+    return profile_internal
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()