Impl "web" subcommand for opening TreeMaker (#174)

* impl "web" subcommand for opening TreeMaker

* fix windows

* wsl用にブラウザで開きたいため

* update help

* update readme

* nits

README.md

@@ -39,6 +39,11 @@ Also, once loaded, you can enjoy offline!<br>
 
 ![](web_example.gif)
 
+You can open it in your browser with
+```console
+$ gtree web
+```
+
 [source code](cmd/gtree-wasm/)
 
 
@@ -111,7 +116,7 @@ gtree
 ```console
 $ gtree --help
 NAME:
-   gtree - This CLI outputs tree or makes directories from markdown.
+   gtree - This CLI generates directory trees and the directories itself using Markdown.
 
 USAGE:
    gtree [global options] command [command options] [arguments...]
@@ -120,11 +125,12 @@ COMMANDS:
    output, o, out     Output tree from markdown. Let's try 'gtree template | gtree output'. Output format is tree or yaml or toml or json. Default tree.
    mkdir, m           Make directories(and files) from markdown. It is possible to dry run. Let's try 'gtree template | gtree mkdir -e .go -e .md -e Makefile'.
    template, t, tmpl  Output markdown template.
+   web, w, www        Open "Tree Maker" in your browser. If it doesn't open, it will display the url.
    version, v         Output gtree version.
    help, h            Shows a list of commands or help for one command
 
 GLOBAL OPTIONS:
-   --help, -h  show help (default: false)
+   --help, -h  show help
 ```
 
 - The symbols that can be used in Markdown are `*`, `-`, `+`, and `#`.

cmd/gtree/main.go

@@ -85,9 +85,16 @@ func main() {
 		},
 	}
 
+	webFlags := []cli.Flag{
+		&cli.BoolFlag{
+			Name:  "wsl",
+			Usage: "Specify this option if you are using WSL.",
+		},
+	}
+
 	app := &cli.App{
 		Name:  "gtree",
-		Usage: "This CLI outputs tree or makes directories from markdown.",
+		Usage: "This CLI generates directory trees and the directories itself using Markdown.",
 		Commands: []*cli.Command{
 			{
 				Name:    "output",
@@ -113,6 +120,14 @@ func main() {
 				Before:  notExistArgs,
 				Action:  actionTemplate,
 			},
+			{
+				Name:    "web",
+				Aliases: []string{"w", "www"},
+				Usage:   "Open \"Tree Maker\" in your browser. If it doesn't open, it will display the url.",
+				Flags:   webFlags,
+				Before:  notExistArgs,
+				Action:  actionWeb,
+			},
 			{
 				Name:    "version",
 				Aliases: []string{"v"},
@@ -221,3 +236,14 @@ func actionTemplate(c *cli.Context) error {
 
 	return directory.println()
 }
+
+const treeMakerURL = "https://ddddddo.github.io/gtree/"
+
+func actionWeb(c *cli.Context) error {
+	if err := openWeb(treeMakerURL, c.Bool("wsl")); err != nil {
+		fmt.Println(treeMakerURL)
+		return nil
+	}
+
+	return nil
+}

cmd/gtree/web.go

@@ -0,0 +1,49 @@
+package main
+
+import (
+	"errors"
+	"os/exec"
+	"runtime"
+)
+
+var openFuncs = map[string]func(string) error{
+	"windows": openWebByWindows,
+	"linux":   openWebByLinux,
+	"wsl":     openWebByWSL,
+	"darwin":  openWebByMac,
+}
+
+func openWeb(url string, isWSL bool) error {
+	runtimeOS := runtime.GOOS
+	if isWSL {
+		runtimeOS = "wsl"
+	}
+
+	openFunc, ok := openFuncs[runtimeOS]
+	if !ok {
+		return errors.New("That OS is not yet supported....")
+	}
+	return openFunc(url)
+}
+
+func openWebByWindows(url string) error {
+	_, err := exec.Command("cmd.exe", "/c", "start", url).CombinedOutput()
+	return err
+}
+
+func openWebByLinux(url string) error {
+	// TODO: インタラクティブモードで開かれた場合どうするか。errはnil
+	//       戻り値に返ってきてるっぽい
+	_, err := exec.Command("xdg-open", url).CombinedOutput()
+	return err
+}
+
+func openWebByWSL(url string) error {
+	_, err := exec.Command("cmd.exe", "/c", "start", url).CombinedOutput()
+	return err
+}
+
+func openWebByMac(url string) error {
+	_, err := exec.Command("open", url).CombinedOutput()
+	return err
+}