fennel repl on a unix socket

README.md

@@ -25,6 +25,13 @@ As of 2022 these principles are more aspirational than actual.
 is suboptimally hairy, at least for the moment: Nix makes a wrapper
 script for the Lua executable that has appropriate `LUA_PATH` and
 `LUA_CPATH` settings, but it doesn't do the same for kiwmi.
+## Connecting to the repl
+
+If you are using the example rc.fnl, it opens a Unix socket that you
+can connect to and interact with a Fennel REPL. I use
+[socat](http://www.dest-unreach.org/socat/) for this purpose:
+
+    $ socat - unix-connect:${XDG_RUNTIME_DIR}/kiwmi-repl.wayland-1.socket
 
 
 # TODO

rc.fnl

@@ -1,7 +1,16 @@
 (local { : GdkPixbuf } (require :lgi))
 (local { : view } (require :fennel))
 
+(local socket-repl (require :socket-repl))
 
+(let [repl-socket-name
+      (..
+       (: (os.getenv "XDG_RUNTIME_DIR") :gsub "/$" "")
+       "/kiwmi-repl."
+       (os.getenv "WAYLAND_DISPLAY")
+       ".socket"
+       )]
+  (socket-repl.start repl-socket-name))
 
 
 (fn texture-from-file [renderer filename]

shell.nix

@@ -1,7 +1,7 @@
 with import <nixpkgs> {} ;
 let p = callPackage ./. {};
 in (p.overrideAttrs (o:{
-  nativeBuildInputs =  [pkgs.gdb];
+  nativeBuildInputs =  with pkgs; [gdb socat];
   shellHook = ''
     export LUA_PATH=`lua -e 'print(package.path)'`
     export LUA_CPATH=`lua -e 'print(package.cpath)'`

socket-repl.fnl

@@ -0,0 +1,52 @@
+(local { : fdopen } (require "posix.stdio"))
+(local fcntl (require "posix.fcntl"))
+(local unistd (require "posix.unistd"))
+(local socket (require "posix.sys.socket"))
+(local { : repl } (require :fennel))
+
+(fn watch-fd [fd mode handler]
+  (kiwmi:event_loop_add_fd fd mode handler))
+
+(fn unix-socket-listener [pathname on-connected]
+  (let [sa {:family socket.AF_UNIX
+            :path pathname
+            }
+        fd (socket.socket socket.AF_UNIX socket.SOCK_STREAM 0)]
+    (socket.bind fd sa)
+    (socket.listen fd 5)
+    (watch-fd
+     fd fcntl.O_RDWR
+     #(let [connected-fd (socket.accept $1)]
+        (on-connected connected-fd)))
+    ))
+
+(fn start [pathname]
+  (print pathname)
+  (unistd.unlink pathname)
+  (unix-socket-listener
+   pathname
+   (fn [fd]
+     (let [sock (fdopen fd "w+")
+           repl-coro (coroutine.create repl)]
+       (print :fd fd :sock sock)
+       (watch-fd fd fcntl.O_RDONLY
+                 #(coroutine.resume repl-coro (unistd.read $1 1024)))
+       (coroutine.resume repl-coro
+                         {:readChunk
+                          (fn [{: stack-size}]
+                            (sock:write
+                             (if (> stack-size 0) ".." ">> "))
+                            (sock:flush)
+                            (coroutine.yield))
+                          :onValues
+                          (fn [vals]
+                            (sock:write (table.concat vals "\t"))
+                            (sock:write "\n"))
+                          :onError
+                          (fn [errtype err]
+                            (sock:write
+                             (.. errtype " error: " (tostring err) "\n")))
+                          })))))
+
+
+{ : start }