feat: add sink for commanders to write output/read input

to write output, you would usually just use the print builtin
since commanders are just lua custom commands but this does not
consider the fact of pipes or other shell operators being used
to redirect or whatever.

this adds readable/writable "sinks" which is a type for input
or output and is currently only used for commanders but can be
used for other hilbish things in the future

exec.go

@@ -323,8 +323,18 @@ func execHandle(bg bool) interp.ExecHandlerFunc {
 			luacmdArgs.Set(rt.IntValue(int64(i + 1)), rt.StringValue(str))
 		}
 
+		hc := interp.HandlerCtx(ctx)
 		if commands[args[0]] != nil {
-			luaexitcode, err := rt.Call1(l.MainThread(), rt.FunctionValue(commands[args[0]]), rt.TableValue(luacmdArgs))
+			stdin := newSinkInput(hc.Stdin)
+			stdout := newSinkOutput(hc.Stdout)
+			stderr := newSinkOutput(hc.Stderr)
+
+			sinks := rt.NewTable()
+			sinks.Set(rt.StringValue("in"), rt.UserDataValue(stdin.ud))
+			sinks.Set(rt.StringValue("out"), rt.UserDataValue(stdout.ud))
+			sinks.Set(rt.StringValue("err"), rt.UserDataValue(stderr.ud))
+
+			luaexitcode, err := rt.Call1(l.MainThread(), rt.FunctionValue(commands[args[0]]), rt.TableValue(luacmdArgs), rt.TableValue(sinks))
 			if err != nil {
 				fmt.Fprintln(os.Stderr, "Error in command:\n" + err.Error())
 				return interp.NewExitStatus(1)
@@ -364,7 +374,6 @@ func execHandle(bg bool) interp.ExecHandlerFunc {
 		killTimeout := 2 * time.Second
 		// from here is basically copy-paste of the default exec handler from
 		// sh/interp but with our job handling
-		hc := interp.HandlerCtx(ctx)
 		path, err := interp.LookPathDir(hc.Dir, hc.Env, args[0])
 		if err != nil {
 			fmt.Fprintln(hc.Stderr, err)

lua.go

@@ -23,6 +23,7 @@ func luaInit() {
 		MessageHandler: debuglib.Traceback,
 	})
 	lib.LoadAll(l)
+	setupSinkType(l)
 
 	lib.LoadLibs(l, hilbishLoader)
 	// yes this is stupid, i know

nature/commands/cat.lua

@@ -1,7 +1,7 @@
 local commander = require 'commander'
 local fs = require 'fs'
 
-commander.register('cat', function(args)
+commander.register('cat', function(args, sinks)
 	local exit = 0
 
 	if #args == 0 then
@@ -17,7 +17,7 @@ usage: cat [file]...]]
 			goto continue
 		end
 
-		io.write(f:read '*a')
+		sinks.out:write(f:read '*a')
 		::continue::
 	end
 	io.flush()

sink.go

@@ -0,0 +1,101 @@
+package main
+
+import (
+	"fmt"
+	"io"
+
+	"hilbish/util"
+
+	rt "github.com/arnodel/golua/runtime"
+)
+
+var sinkMetaKey = rt.StringValue("hshsink")
+
+// a sink is a structure that has input and/or output
+// it is like a lua file when used in popen, but specific to hilbish
+type sink struct{
+	writer io.Writer
+	reader io.Reader
+	ud *rt.UserData
+}
+
+func setupSinkType(rtm *rt.Runtime) {
+	sinkMeta := rt.NewTable()
+
+	sinkMethods := rt.NewTable()
+	sinkFuncs := map[string]util.LuaExport{
+		"write": {luaSinkWrite, 2, false},
+	}
+	util.SetExports(l, sinkMethods, sinkFuncs)
+
+	sinkIndex := func(t *rt.Thread, c *rt.GoCont) (rt.Cont, error) {
+		arg := c.Arg(1)
+		val := sinkMethods.Get(arg)
+
+		return c.PushingNext1(t.Runtime, val), nil
+	}
+
+	sinkMeta.Set(rt.StringValue("__index"), rt.FunctionValue(rt.NewGoFunction(sinkIndex, "__index", 2, false)))
+	l.SetRegistry(sinkMetaKey, rt.TableValue(sinkMeta))
+}
+
+func luaSinkWrite(t *rt.Thread, c *rt.GoCont) (rt.Cont, error) {
+	if err := c.CheckNArgs(2); err != nil {
+		return nil, err
+	}
+
+	s, err := sinkArg(c, 0)
+	if err != nil {
+		return nil, err
+	}
+	data, err := c.StringArg(1)
+	if err != nil {
+		return nil, err
+	}
+
+	s.writer.Write([]byte(data))
+
+	return c.Next(), nil
+}
+
+func newSinkInput(r io.Reader) *sink {
+	s := &sink{
+		reader: r,
+	}
+	s.ud = sinkUserData(s)
+
+	return s
+}
+
+func newSinkOutput(w io.Writer) *sink {
+	s := &sink{
+		writer: w,
+	}
+	s.ud = sinkUserData(s)
+
+	return s
+}
+
+func sinkArg(c *rt.GoCont, arg int) (*sink, error) {
+	s, ok := valueToSink(c.Arg(arg))
+	if !ok {
+		return nil, fmt.Errorf("#%d must be a sink", arg + 1)
+	}
+
+	return s, nil
+}
+
+func valueToSink(val rt.Value) (*sink, bool) {
+	u, ok := val.TryUserData()
+	if !ok {
+		return nil, false
+	}
+
+	s, ok := u.Value().(*sink)
+	return s, ok
+}
+
+func sinkUserData(s *sink) *rt.UserData {
+	sinkMeta := l.Registry(sinkMetaKey)
+	return rt.NewUserData(s, sinkMeta.AsTable())
+}