-ikiwiki should support writing plugins in other languages
+ikiwiki should support [[writing plugins in other languages|plugins/write/external]]
+
+> [[done]] !!
While it should be possible to call ikiwiki from C, doing the callbacks in C is
probably hard. And accessing perl at all from C is ugly. It also doesn't
Instead, I'm considering using XML RPC to let ikiwiki communicate with a
child process that it can spawn. The child could then be any program,
-written in any language. It could talk XML RPC via stdio.
+written in any language. It could talk XML RPC via stdio. (This assumes
+that most languages allow easily serialising XML::RPC calls and responses
+to a file descriptor. Some XML RPC implementations may be hardcoded to use
+http..) For ease of implementation, each rpc request sent via stio should
+end with a newline, and begin with "<?xml ..>".
Here's how it would basically look, not showing the actual XML RPC used to
pass values.
- -> init
- <- 1
- <- hook type => preprocess, id => foo
- -> 1
- <- done 1
- -> 1
-
- -> callback type => preprocess id => foo, page => bar
- <- 1
- <- getconfig url
- -> "http://example.com", ...
- <- debug "foo"
- -> 1
- <- done "my return value"
- -> 1
+ -> call import
+ <- call hook type => preprocess, id => foo, call => plugin_preprocess
+ -> result 1
+ <- result 1
+
+ -> call plugin_preprocess page => bar
+ <- call getconfig url
+ -> result "http://example.com", ...
+ <- call debug "foo"
+ -> result 1
+ <- result done "my return value"
From ikiwiki's POV:
* ikiwiki always initiates each conversation with a command
* After sending a command, ikiwiki reads commands, dispatches them, and
- returns the results, in a loop.
-* The loop continues until the plugin calls the "done" command, with a value
- that is the return value for the command that initiated the conversation.
+ returns the results, in a loop, until it gets a result for the command it
+ called.
From the plugin's POV:
* It's probably sitting in an XML::RPC loop.
* Get a command from ikiwiki.
-* Call the appropriate callback.
-* The callback can use XML::RPC to communicate with ikiwiki to get things
+* Dispatch the command to the appropriate function.
+* The function can use XML::RPC to communicate with ikiwiki to get things
like config values; and to call ikiwiki functions.
-* When the callback returns, use XML::RPC to send a "done" command to ikiwiki.
+* Send the function's return value back to ikiwiki.
+
+Simple enough, really. ikiwiki would need to add accessor functions for
+all important variables, such as "getconfig" and "setconfig". It would
+probably be easiest for ikiwiki to dispatch a command by just evaling
+IkiWiki::$command.
+
+Plugin programs could be dropped into /usr/share/ikiwiki/plugins/, and
+load_plugin() would just open2 the plugin program and call import.