new simpler setup method, readme and doc update

src/setup.go

@@ -0,0 +1,115 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"net/url"
+	"os"
+	"path"
+
+	. "github.com/yusing/go-proxy/common"
+)
+
+var branch = GetEnv("GOPROXY_BRANCH", "v0.5")
+var baseUrl = fmt.Sprintf("https://github.com/yusing/go-proxy/raw/%s", branch)
+var requiredConfigs = []Config{
+	{ConfigBasePath, true, false, ""},
+	{ComposeFileName, false, true, ComposeExampleFileName},
+	{path.Join(ConfigBasePath, ConfigFileName), false, true, ConfigExampleFileName},
+}
+
+type Config struct {
+	Pathname         string
+	IsDir            bool
+	NeedDownload     bool
+	DownloadFileName string
+}
+
+func Setup() {
+	log.Println("setting up go-proxy")
+	log.Println("branch:", branch)
+
+	os.Chdir("/setup")
+
+	for _, config := range requiredConfigs {
+		config.setup()
+	}
+
+	log.Println("done")
+}
+
+func (c *Config) setup() {
+	if c.IsDir {
+		mkdir(c.Pathname)
+		return
+	}
+	if !c.NeedDownload {
+		touch(c.Pathname)
+		return
+	}
+
+	fetch(c.DownloadFileName, c.Pathname)
+}
+
+func hasFileOrDir(path string) bool {
+	_, err := os.Stat(path)
+	return err == nil
+}
+
+func mkdir(pathname string) {
+	_, err := os.Stat(pathname)
+	if err != nil && os.IsNotExist(err) {
+		log.Printf("creating directory %q\n", pathname)
+		err := os.MkdirAll(pathname, 0o755)
+		if err != nil {
+			log.Fatalf("failed: %s\n", err)
+		}
+		return
+	}
+	if err != nil {
+		log.Fatalf("failed: %s\n", err)
+	}
+}
+
+func touch(pathname string) {
+	if hasFileOrDir(pathname) {
+		return
+	}
+	log.Printf("creating file %q\n", pathname)
+	_, err := os.Create(pathname)
+	if err != nil {
+		log.Fatalf("failed: %s\n", err)
+	}
+}
+func fetch(remoteFilename string, outFileName string) {
+	if hasFileOrDir(outFileName) {
+		return
+	}
+	log.Printf("downloading %q\n", remoteFilename)
+
+	url, err := url.JoinPath(baseUrl, remoteFilename)
+	if err != nil {
+		log.Fatalf("unexpected error: %s\n", err)
+	}
+
+	resp, err := http.Get(url)
+	if err != nil {
+		log.Fatalf("http request failed: %s\n", err)
+	}
+
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		log.Fatalf("error reading response body: %s\n", err)
+	}
+
+	err = os.WriteFile(outFileName, body, 0o644)
+	if err != nil {
+		log.Fatalf("failed to write to file: %s\n", err)
+	}
+
+	log.Printf("downloaded %q\n", outFileName)
+}