Sputnik: Actions

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Page Parameters

Page Name (for URL)

Page Title

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Page Content

<span class="teaser">
  Sputnik requests identify a node and an command to be sent by the node.  The node responds
  to the command by executing an action.  The mapping between commands and actions is defined
  by the node.
</span>

Each Sputnik node can perform actions in respond to commands.  (If you like, you can think of
pages as "nouns" and commands as "verbs".) For instance, you can get this node to sent you its
raw representation by asking for:

http://sputnik.freewisdom.org/en/Actions.raw

which consists of three parts:

http://sputnik.freewisdom.org/en/
    Actions
    raw

This means:

1. Call the instance of Sputnik at "http://sputnik.freewisdom.org/en/"
2. Tell it to get the node called "Actions"
3. Tell it to send this node the command "raw"

If command is not specified, then it
assumed to be "show". So, the following two requests are equivalent:

http://sputnik.freewisdom.org/en/Actions
    http://sputnik.freewisdom.org/en/Actions.show

What commands the node can understand and how it interprets them depends on the node.
Some nodes can understand commands that other nodes don't understand.  For instance,
the node [[Raw_Dot_File|Raw\_Dot\_File]], which contains a graph expressed in
GraphViz's "dot" format understands commands [[Raw_Dot_File.svg|svg]] and
[[Raw_Dot_File.png|png]].  Most
other nodes do not know how to respond to a "png" command.  Additionally, a node may
use interpret differently some of the standard actions.  For instance, most nodes
respond to "show" by running their content through [[Markdown]].  (This node does this.)
Nodes that contain Lua code (e.g., [[_navigation]]) do not do that: they display their
content as code instead.

## Defining actions

Each action is a function that takes three parameters and returns content (as a string) and
(optionally) a content type.  (If the action does not return a content type, it's assumed to
be "text/html".)  It can also set some attributes of the node.  The three parameters to the
action function are:

* `node` - the node specified by the request,
* `request` - a [[WSAPI]] request table, preprocessed by Sputnik to unhash parameters,
* `sputnik` - the instance of "Sputnik" that is dispatching the request.

Here is a really simple action:

actions.raw_content = function(node, request, sputnik)
       return node.content, "text/plain"
    end

Or a slightly more complicated one:

actions.code = function(node, request, sputnik)
       page.inner_html = "<pre><code>" .. sputnik.escape(node.content)
          .. "</code></pre>"
       return node.wrappers.default(node, request, sputnik)
    end

Actions can be provided in modules, which must all be in the "sputnik.actions" namespace for security reasons.  Sputnik comes with a default set of actions, provided in the "sputnik.actions.wiki" module.  It includes the following action functions among others:

* `show()` - display the page as HTML, with a navigation bar, etc.
* `edit()` - display the edit form for the page
* `save()` - save the page (when submitted by the edit form)
* `history()` - show page history
* `diff()` - show a diff from an earlier version
* `show_inner()` - display just the content part of HTML (no menus, etc.)
* `raw()` - show the content of the page "as is" - in plain text

## Mapping commands to actions

Commands can be mapped to actions in the "actions" field of the node or its [[Prototypes]].  The default mappings look as follows:

actions= [[
      show  = "wiki.show"
      show_content    = "wiki.show_content"
      history         = "wiki.history"
      edit            = "wiki.edit"
      post            = "wiki.post"
      rss             = "wiki.rss"
      diff            = "wiki.diff"
      code            = "wiki.code"
      raw             = "wiki.raw"
      raw_content     = "wiki.raw_content"
      login           = "wiki.show_login_form"
      sputnik_version = "wiki.sputnik_version"
      save            = "wiki.save"
      preview         = "wiki.preview"
      preview_content = "wiki.preview_content"
    ]]

Configuration pages, however, override this setting because "actions" is set as follows in [[@Lua_Config]]:

actions= [[
      show_content="wiki.show_content_as_lua_code"
    ]]

This means, that all nodes that inherit from @Lua_Config respond to "show_content" by running `sputnik.actions.wiki.actions.show_content_as_lua_code()` instead of the regular `sputnik.actions.wiki.actions.show_content_as_lua_code()`.

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