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== Outdated egg!

This is an egg for CHICKEN 4, the unsupported old release.  You're almost certainly looking for [[/eggref/5/spiffy-dynamic-handlers|the CHICKEN 5 version of this egg]], if it exists.

If it does not exist, there may be equivalent functionality provided by another egg; have a look at the [[https://wiki.call-cc.org/chicken-projects/egg-index-5.html|egg index]]. Otherwise, please consider porting this egg to the current version of CHICKEN.

[[tags: egg]]

== Spiffy-dynamic-handlers

[[toc:]]

=== Description

Deprecated [[Spiffy]] handlers for dynamic file-based website scripting.

These handlers are deprecated for two reasons, so please reconsider
before relying on them:

First (this goes for both handlers), it's a potential security hazard
as it requires you to put code in your documentroot which often needs
to be writable in order to store user-uploaded assets.  Protecting
only those directories is tricky and easily forgotten.

Second, SSP pages are a very ugly style in that it is
presentation-first (code needs to be "escaped" into) and thereby
encourages mixing code and presentation.

At some point these handlers will be completely dropped and no longer
supported.

=== Author

[[/users/felix-winkelmann|Felix Winkelmann]].
Currently maintained by [[/users/peter-bex|Peter Bex]].

=== Requirements

Requires the [[spiffy]] and [[intarweb]] extensions.

=== Handlers

These two handlers (both in a module of the same name) are supplied by the egg.

==== ssp-handler

SSP, or Scheme Server Pages, are a way to embed Scheme in HTML
pages. Files with an extension of {{.ssp}} are handled specifically,
by replacing occurrences of certain reserved tags with Scheme code.
There are two possible forms, either the long version, where all
output is redirected to the HTTP response port, or the short, where
the result of the embedded expression is displayed in the response.
The tags default to {{<?scheme}} and {{<?}}, see Configuration for how
to change them.

Here's an example:

would generate for example something like this:

1. 0
     2. 1
     3. 2
     4. 3
     5. 4

(felix x 500 100 /home/felix /bin/bash)

When a {{.ssp}} file is loaded the first time, or when it has been
modified, then a translation takes place that generates a loadable
Scheme source file (with the extension {{.sspx}}, in the same
directory as the original file) from the original data, so in the
above example something like this would be generated:

<enscript highlight=scheme>
 (let ()
 (display "<html><body>\n<ol>")
 (for-each (lambda (i) (printf "<li>~S~%" i)) (iota 5))
 (display "</ol>\n \n")
 (display (call-with-values (lambda () (user-information (current-user-id))) (lambda (name . _) name)))
 (display "\n</body></html>\n") )
</enscript>

Note that the body is evaluated in a {{(let () ...)}} form.

Note: each request runs in a separate thread, so code in {{.ssp}}
pages should take care when using global variables.

===== Configuration

The SSP handler can be configured with the following options:

<parameter>(ssp-short-open-tag [tag-regexp])</parameter>

The opening tag for short fragments. Default: {{<?}}

<parameter>(ssp-long-open-tag [tag-regexp])</parameter>

The opening tag for long fragments. Default: {{<?scheme}}

<parameter>(ssp-close-tag [tag-regexp])</parameter>

The closing tag for Scheme fragments in {{.ssp}} files. Default: {{?>}}

<parameter>(ssp-eval-environment [environment])</parameter>

The environment passed to {{eval}} when evaluating Scheme code inside
{{.ssp}}-pages.  Default: {{interaction-environment}}

<parameter>(ssp-cache-dir [directory-name])</parameter>

The directory under which to store cached .ssp files (these end in .sspx
and are pure Scheme files).  Useful if you want to block write access to
the webserver under your docroot.  Default: {{"."}}

If it's a relative path, it is relative to {{root-path}}, if absolute
it's taken to be relative to the filesystem root.  A directory structure
similar to the docroot will be created underneath this path, so for
example if the file {{/foo/bar/qux.ssp}} exists, and the cache dir is
set to {{/cache}}, it will create the file {{/cache/foo/bar/qux.sspx}}.

===== Runtime information

For the duration of evaluating a SSP page, the following parameters
will have a value assigned to them:

<parameter>(current-workdir [path])</parameter>

During execution, the current working directory of the SSP handler.
Any of the "include" procedures (ssp-include, ssp-stringize) will
interpret their file arguments to be relative to this directory.

<parameter>(ssp-exit-handler [handler])</parameter>

During execution of an ssp page, {{ssp-exit-handler}} is bound to a
procedure that will finish the current page, ignoring any further
content or code.

===== Procedures

The ssp-handler module adds the following procedures to the environment:

<procedure>(ssp-handler filename)</procedure>

The handler itself, which should be used in the {{file-extension-handlers}}
parameter list.

<procedure>(ssp-include filename)</procedure>

Translates the file {{filename}} into Scheme by replacing {{<?scheme ... ?>}}
and {{<? ... ?>}} sequences (if needed) and writes the translated contents
to the current output-port.

<procedure>(ssp-stringize FILENAME)</procedure>

Similar to {{ssp-include}}, but instead of writing the translated
text, the text is returned as a string.

==== web-scheme-handler

Another way of executing Scheme code to produce content are {{.ws}}
files: these should contain a Scheme expression that is expected to
evaluate to a string which will be directly written as the response to
the current request. This facility is intended for Scheme code that
uses the [[web-scheme]] extension.

You can use the {{web-scheme-handler}} for any Scheme file which
returns HTML as a string or which has a side-effect of outputting the
HTML. If it's the latter, make sure the final statement in your file
does not return a string or it will be appended to the output (just
like in the {{csi}} REPL).

'''Tip''' This handler type is perfect not only for web-scheme but
also for when you're using {{SRV:send-reply}} with SXML or for example a
wiki-to-string translator.

Note: each request runs in a separate thread, so code in {{.ws}} pages
should take care when using global variables.

Note: web-scheme-handler is a separate extension and must be imported
as such.

<enscript highlight=scheme>
(require-extension web-scheme-handler)
</enscript>

===== Configuration

The Web-scheme handler can be configured with the following options:

<parameter>(web-scheme-eval-environment [environment])</parameter>

The environment passed to {{eval}} when evaluating Scheme code inside
{{.ws}}-pages.  Default: {{interaction-environment}}

===== Procedures

The Web-scheme handler adds only one procedure to the environment:

<procedure>(web-scheme-handler filename)</procedure>

The handler itself, which should be used in the {{file-extension-handlers}}
parameter list.

=== Changelog

0.1 Moved deprecated {{ssp-handler}} and {{web-scheme-handler}} from [[spiffy]] to their own egg.  Finally wrote some regression tests.

=== License

Copyright (c) 2007-2012, Peter Bex
  Copyright (c) 2000-2005, Felix L. Winkelmann
  All rights reserved.
  
  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are
  met:
  
  Redistributions of source code must retain the above copyright
  notice, this list of conditions and the following disclaimer.
  
  Redistributions in binary form must reproduce the above copyright
  notice, this list of conditions and the following disclaimer in the
  documentation and/or other materials provided with the distribution.
  
  Neither the name of the author nor the names of its contributors may
  be used to endorse or promote products derived from this software
  without specific prior written permission.
  
  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
  INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  OF THE POSSIBILITY OF SUCH DAMAGE.

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