diff --git a/complete.go b/complete.go
index 94adb11..8ee823d 100644
--- a/complete.go
+++ b/complete.go
@@ -9,56 +9,13 @@ import (
 )
 
 type AutoCompleter interface {
-	GetName() []rune
-	GetChildren() []AutoCompleter
-}
-
-func Do(ac AutoCompleter, line []rune, pos int) (newLine [][]rune, offset int) {
-	line = line[:pos]
-	goNext := false
-	var lineCompleter AutoCompleter
-
-	for _, child := range ac.GetChildren() {
-		childName := child.GetName()
-		if len(line) >= len(childName) {
-			if runes.HasPrefix(line, childName) {
-				if len(line) == len(childName) {
-					newLine = append(newLine, []rune{' '})
-				} else {
-					newLine = append(newLine, childName)
-				}
-				offset = len(childName)
-				lineCompleter = child
-				goNext = true
-			}
-		} else {
-			if runes.HasPrefix(childName, line) {
-				newLine = append(newLine, childName[len(line):])
-				offset = len(line)
-				lineCompleter = child
-			}
-		}
-	}
-
-	if len(newLine) != 1 {
-		return
-	}
-
-	tmpLine := make([]rune, 0, len(line))
-	for i := offset; i < len(line); i++ {
-		if line[i] == ' ' {
-			continue
-		}
-
-		tmpLine = append(tmpLine, line[i:]...)
-		return Do(lineCompleter, tmpLine, len(tmpLine))
-	}
-
-	if goNext {
-		return Do(lineCompleter, nil, 0)
-	}
-
-	return
+	// Readline will pass the whole line and current offset to it
+	// Completer need to pass all the candidates, and how long they shared the same characters in line
+	// Example:
+	//   Do("g", 1) => ["o", "it", "it-shell", "rep"], 1
+	//   Do("gi", 2) => ["t", "t-shell"], 1
+	//   Do("git", 3) => ["", "-shell"], 0
+	Do(line []rune, pos int) (newLine [][]rune, length int)
 }
 
 type opCompleter struct {
@@ -118,7 +75,7 @@ func (o *opCompleter) OnComplete() {
 
 	o.ExitCompleteSelectMode()
 	o.candidateSource = rs
-	newLines, offset := Do(o.ac, rs, buf.idx)
+	newLines, offset := o.ac.Do(rs, buf.idx)
 	if len(newLines) == 0 {
 		o.ExitCompleteMode(false)
 		return
diff --git a/complete_helper.go b/complete_helper.go
index b74e6d5..7e8a807 100644
--- a/complete_helper.go
+++ b/complete_helper.go
@@ -1,27 +1,92 @@
 package readline
 
+import (
+	"bytes"
+	"strings"
+
+	"github.com/chzyer/readline/runes"
+)
+
 type PrefixCompleter struct {
 	Name     []rune
-	Children []AutoCompleter
+	Children []*PrefixCompleter
 }
 
-func (p PrefixCompleter) GetName() []rune {
-	return p.Name
+func (p *PrefixCompleter) Tree(prefix string) string {
+	buf := bytes.NewBuffer(nil)
+	p.Print(prefix, 0, buf)
+	return buf.String()
 }
 
-func (p PrefixCompleter) GetChildren() []AutoCompleter {
-	return p.Children
+func (p *PrefixCompleter) Print(prefix string, level int, buf *bytes.Buffer) {
+	if strings.TrimSpace(string(p.Name)) != "" {
+		buf.WriteString(prefix)
+		if level > 0 {
+			buf.WriteString("├")
+			buf.WriteString(strings.Repeat("─", (level*4)-2))
+			buf.WriteString(" ")
+		}
+		buf.WriteString(string(p.Name) + "\n")
+		level++
+	}
+	for _, ch := range p.Children {
+		ch.Print(prefix, level, buf)
+	}
 }
 
-func NewPrefixCompleter(pc ...AutoCompleter) AutoCompleter {
+func NewPrefixCompleter(pc ...*PrefixCompleter) *PrefixCompleter {
 	return PcItem("", pc...)
 }
 
-func PcItem(name string, pc ...AutoCompleter) AutoCompleter {
+func PcItem(name string, pc ...*PrefixCompleter) *PrefixCompleter {
 	name += " "
-	result := AutoCompleter(PrefixCompleter{
+	return &PrefixCompleter{
 		Name:     []rune(name),
 		Children: pc,
-	})
-	return result
+	}
+}
+
+func (p *PrefixCompleter) Do(line []rune, pos int) (newLine [][]rune, offset int) {
+	line = line[:pos]
+	goNext := false
+	var lineCompleter *PrefixCompleter
+	for _, child := range p.Children {
+		if len(line) >= len(child.Name) {
+			if runes.HasPrefix(line, child.Name) {
+				if len(line) == len(child.Name) {
+					newLine = append(newLine, []rune{' '})
+				} else {
+					newLine = append(newLine, child.Name)
+				}
+				offset = len(child.Name)
+				lineCompleter = child
+				goNext = true
+			}
+		} else {
+			if runes.HasPrefix(child.Name, line) {
+				newLine = append(newLine, child.Name[len(line):])
+				offset = len(line)
+				lineCompleter = child
+			}
+		}
+	}
+
+	if len(newLine) != 1 {
+		return
+	}
+
+	tmpLine := make([]rune, 0, len(line))
+	for i := offset; i < len(line); i++ {
+		if line[i] == ' ' {
+			continue
+		}
+
+		tmpLine = append(tmpLine, line[i:]...)
+		return lineCompleter.Do(tmpLine, len(tmpLine))
+	}
+
+	if goNext {
+		return lineCompleter.Do(nil, 0)
+	}
+	return
 }
diff --git a/complete_helper_ext.go b/complete_helper_ext.go
new file mode 100644
index 0000000..ef86153
--- /dev/null
+++ b/complete_helper_ext.go
@@ -0,0 +1,110 @@
+package readline
+
+import (
+	"bytes"
+	"strings"
+
+	"github.com/chzyer/readline/runes"
+)
+
+type PrefixCompleterInterface interface {
+	Print(prefix string, level int, buf *bytes.Buffer)
+	Do(line []rune, pos int) (newLine [][]rune, length int)
+	GetName() []rune
+	GetChildren() []PrefixCompleterInterface
+}
+
+type PrefixCompleterExt struct {
+	Name     []rune
+	Children []PrefixCompleterInterface
+}
+
+func Print(p PrefixCompleterInterface, prefix string, level int, buf *bytes.Buffer) {
+	if strings.TrimSpace(string(p.GetName())) != "" {
+		buf.WriteString(prefix)
+		if level > 0 {
+			buf.WriteString("├")
+			buf.WriteString(strings.Repeat("─", (level*4)-2))
+			buf.WriteString(" ")
+		}
+		buf.WriteString(string(p.GetName()) + "\n")
+		level++
+	}
+	for _, ch := range p.GetChildren() {
+		ch.Print(prefix, level, buf)
+	}
+}
+
+func (p *PrefixCompleterExt) Print(prefix string, level int, buf *bytes.Buffer) {
+	Print(p, prefix, level, buf)
+}
+
+func (p *PrefixCompleterExt) GetName() []rune {
+	return p.Name
+}
+
+func (p *PrefixCompleterExt) GetChildren() []PrefixCompleterInterface {
+	return p.Children
+}
+
+func NewPrefixCompleterExt(pc ...PrefixCompleterInterface) *PrefixCompleterExt {
+	return PceItem("", pc...)
+}
+
+func PceItem(name string, pc ...PrefixCompleterInterface) *PrefixCompleterExt {
+	name += " "
+	return &PrefixCompleterExt{
+		Name:     []rune(name),
+		Children: pc,
+	}
+}
+
+func (p *PrefixCompleterExt) Do(line []rune, pos int) (newLine [][]rune, offset int) {
+	return Do(p, line, pos)
+}
+
+func Do(p PrefixCompleterInterface, line []rune, pos int) (newLine [][]rune, offset int) {
+	line = line[:pos]
+	goNext := false
+	var lineCompleter PrefixCompleterInterface
+	for _, child := range p.GetChildren() {
+		childName := child.GetName()
+		if len(line) >= len(childName) {
+			if runes.HasPrefix(line, childName) {
+				if len(line) == len(childName) {
+					newLine = append(newLine, []rune{' '})
+				} else {
+					newLine = append(newLine, childName)
+				}
+				offset = len(childName)
+				lineCompleter = child
+				goNext = true
+			}
+		} else {
+			if runes.HasPrefix(childName, line) {
+				newLine = append(newLine, childName[len(line):])
+				offset = len(line)
+				lineCompleter = child
+			}
+		}
+	}
+
+	if len(newLine) != 1 {
+		return
+	}
+
+	tmpLine := make([]rune, 0, len(line))
+	for i := offset; i < len(line); i++ {
+		if line[i] == ' ' {
+			continue
+		}
+
+		tmpLine = append(tmpLine, line[i:]...)
+		return lineCompleter.Do(tmpLine, len(tmpLine))
+	}
+
+	if goNext {
+		return lineCompleter.Do(nil, 0)
+	}
+	return
+}