From c3d9ea142b1de70e68a53bd704b5554a70b72313 Mon Sep 17 00:00:00 2001
From: deoxxa <deoxxa@fknsrs.biz>
Date: Wed, 27 Apr 2016 16:08:41 +1000
Subject: [PATCH] add tab-complete to repl

---
 repl/autocompleter.go | 57 +++++++++++++++++++++++++++++++++++++++++++
 repl/repl.go          |  7 +++++-
 2 files changed, 63 insertions(+), 1 deletion(-)
 create mode 100644 repl/autocompleter.go

diff --git a/repl/autocompleter.go b/repl/autocompleter.go
new file mode 100644
index 0000000..3256678
--- /dev/null
+++ b/repl/autocompleter.go
@@ -0,0 +1,57 @@
+package repl
+
+import (
+	"regexp"
+	"strings"
+
+	"github.com/robertkrimen/otto"
+)
+
+type autoCompleter struct {
+	vm *otto.Otto
+}
+
+var lastExpressionRegex = regexp.MustCompile(`[a-zA-Z0-9]([a-zA-Z0-9\.]*[a-zA-Z0-9])?\.?$`)
+
+func (a *autoCompleter) Do(line []rune, pos int) ([][]rune, int) {
+	lastExpression := lastExpressionRegex.FindString(string(line))
+
+	bits := strings.Split(lastExpression, ".")
+
+	first := bits[:len(bits)-1]
+	last := bits[len(bits)-1]
+
+	var l []string
+
+	if len(first) == 0 {
+		c := a.vm.Context()
+
+		l = make([]string, len(c.Symbols))
+
+		i := 0
+		for k := range c.Symbols {
+			l[i] = k
+			i++
+		}
+	} else {
+		r, err := a.vm.Eval(strings.Join(bits[:len(bits)-1], "."))
+		if err != nil {
+			return nil, 0
+		}
+
+		if o := r.Object(); o != nil {
+			for _, v := range o.KeysByParent() {
+				l = append(l, v...)
+			}
+		}
+	}
+
+	var r [][]rune
+	for _, s := range l {
+		if strings.HasPrefix(s, last) {
+			r = append(r, []rune(strings.TrimPrefix(s, last)))
+		}
+	}
+
+	return r, len(last)
+}
diff --git a/repl/repl.go b/repl/repl.go
index 0d70cc0..791d336 100644
--- a/repl/repl.go
+++ b/repl/repl.go
@@ -48,7 +48,12 @@ func RunWithPromptAndPrelude(vm *otto.Otto, prompt, prelude string) error {
 	prompt = strings.Trim(prompt, " ")
 	prompt += " "
 
-	rl, err := readline.New(prompt)
+	c := &readline.Config{
+		Prompt:       prompt,
+		AutoComplete: &autoCompleter{vm},
+	}
+
+	rl, err := readline.NewEx(c)
 	if err != nil {
 		return err
 	}