feat: expose syntax highlighting (closes #125)

api.go

@@ -28,6 +28,7 @@ var exports = map[string]lua.LGFunction {
 	"exec": hlexec,
 	"runnerMode": hlrunnerMode,
 	"goro": hlgoro,
+	"highlighter": hlhighlighter,
 	"hinter": hlhinter,
 	"multiprompt": hlmlprompt,
 	"prependPath": hlprependPath,
@@ -517,3 +518,10 @@ func hlhinter(L *lua.LState) int {
 	
 	return 0
 }
+
+func hlhighlighter(L *lua.LState) int {
+	highlighterCb := L.CheckFunction(1)
+	highlighter = highlighterCb
+
+	return 0
+}

rl.go

@@ -14,6 +14,7 @@ type lineReader struct {
 }
 var fileHist *fileHistory
 var hinter lua.LValue = lua.LNil
+var highlighter lua.LValue = lua.LNil
 
 // other gophers might hate this naming but this is local, shut up
 func newLineReader(prompt string, noHist bool) *lineReader {
@@ -68,6 +69,28 @@ func newLineReader(prompt string, noHist bool) *lineReader {
 		
 		return []rune(hintText)
 	}
+	rl.SyntaxHighlighter = func(line []rune) string {
+		if highlighter == lua.LNil {
+			return string(line)
+		}
+		err := l.CallByParam(lua.P{
+			Fn: highlighter,
+			NRet: 1,
+			Protect: true,
+		}, lua.LString(string(line)))
+		if err != nil {
+			fmt.Println(err)
+			return string(line)
+		}
+		
+		retVal := l.Get(-1)
+		highlighted := ""
+		if luaStr, ok := retVal.(lua.LString); retVal != lua.LNil && ok {
+			highlighted = luaStr.String()
+		}
+		
+		return highlighted
+	}
 	rl.TabCompleter = func(line []rune, pos int, _ readline.DelayedTabContext) (string, []*readline.CompletionGroup) {
 		ctx := string(line)
 		var completions []string