Add TOC support

README.md

@@ -31,9 +31,10 @@ Flags:
 
 ### Available functions
 
-| Name               | Usage |
-|--------------------|---|
-| `printHelp` | `{{printHelp 'hd'}}` |
+| Name               | Usage                | Description                            |
+|--------------------|----------------------|----------------------------------------|
+| `printHelp` | `{{printHelp 'hd'}}` | Print the help text of a command       |
+| `printToc` | `{{printToc}}`       | Print the [TOC](https://en.wikipedia.org/wiki/TOC) of the template file |
 
 ### Ignore particular items
 

main.go

@@ -120,6 +120,9 @@ func (o *option) runE(cmd *cobra.Command, args []string) (err error) {
 			}
 			return
 		},
+		"printToc": func() string {
+			return generateTOC(readmeTpl)
+		},
 	}).Parse(readmeTpl); err != nil {
 		return
 	}
@@ -152,6 +155,34 @@ func sortBy(items []map[string]interface{}, sortBy string, descending bool) {
 	})
 }
 
+func generateTOC(txt string) (toc string) {
+	items := strings.Split(txt, "\n")
+	for i := range items {
+		item := items[i]
+
+		var prefix string
+		var tag string
+		if strings.HasPrefix(item, "## ") {
+			tag = strings.TrimPrefix(item, "## ")
+			prefix = "- "
+		} else if strings.HasPrefix(item, "### ") {
+			tag = strings.TrimPrefix(item, "### ")
+			prefix = " - "
+		} else {
+			continue
+		}
+
+		// not support those titles which have whitespaces
+		tag = strings.TrimSpace(tag)
+		if len(strings.Split(tag, " ")) > 1 {
+			continue
+		}
+
+		toc = toc + fmt.Sprintf("%s[%s](#%s)\n", prefix, tag, strings.ToLower(tag))
+	}
+	return
+}
+
 func main() {
 	opt := &option{}
 	cmd := cobra.Command{

main_test.go

@@ -71,3 +71,44 @@ func Test_sortBy(t *testing.T) {
 		})
 	}
 }
+
+func Test_generateTOC(t *testing.T) {
+	type args struct {
+		txt string
+	}
+	tests := []struct {
+		name    string
+		args    args
+		wantToc string
+	}{{
+		name: "simple text",
+		args: args{
+			txt: `## Good`,
+		},
+		wantToc: `- [Good](#good)
+`,
+	}, {
+		name: "multiple levels of the titles",
+		args: args{
+			txt: `## Good
+content
+### Better`,
+		},
+		wantToc: `- [Good](#good)
+ - [Better](#better)
+`,
+	}, {
+		name: "has whitespace between title",
+		args: args{
+			txt: `## Good
+## This is good`,
+		},
+		wantToc: `- [Good](#good)
+`,
+	}}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equalf(t, tt.wantToc, generateTOC(tt.args.txt), "generateTOC(%v)", tt.args.txt)
+		})
+	}
+}