serve.go

package main

import (
	"encoding/json"
	"flag"
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"os"
)

type (
	onlyFilesFS struct {
		fs    http.FileSystem
		index string
	}

	neuteredReaddirFile struct {
		http.File
	}
)

// Dir returns a http.Filesystem that can be used by http.FileServer().
// if listDirectory == true, then it works the same as http.Dir() otherwise it returns
// a filesystem that prevents http.FileServer() to list the directory files.
func Dir(index, root string, listDirectory bool) http.FileSystem {
	fs := http.Dir(root)
	if listDirectory {
		return fs
	}
	return &onlyFilesFS{fs, index}
}

// Conforms to http.Filesystem
// Tries to open the given file name, otherwise fallback to index.html
// This is required by SPA apps that perform internal routing
func (fs onlyFilesFS) Open(name string) (http.File, error) {
	f, err := fs.fs.Open(name)
	if err != nil {
		f, err = fs.fs.Open(fs.index)
	}

	if err != nil {
		return nil, err
	}
	return neuteredReaddirFile{f}, nil
}

// Overrides the http.File default implementation
func (f neuteredReaddirFile) Readdir(count int) ([]os.FileInfo, error) {
	// this disables directory listing
	return nil, nil
}

// Conforms http.FileSystem interface
type localFileSystem struct {
	http.FileSystem
	root string
}

func LocalFile(index, root string, listDir bool) *localFileSystem {
	return &localFileSystem{
		FileSystem: Dir(index, root, listDir),
		root:       root,
	}
}

func main() {
	dir := flag.String("dir", "/serve", "location of the dir to serve")
	bind := flag.String("bind", ":8005", "bind address")
	cfgFile := flag.String("cfg", "cfg.json", "configuration")
	flag.Parse()

	b, err := ioutil.ReadFile(*cfgFile)
	if err != nil {
		panic(err)
	}
	var cfg *cfg
	if err := json.Unmarshal(b, &cfg); err != nil {
		panic(err)
	}

	for _, ep := range cfg.Endpoints {
		fmt.Println(ep)
		fs := LocalFile(ep.File, *dir, false)
		h := http.FileServer(*fs)
		if ep.StripPattern {
			h = http.StripPrefix(ep.Pattern, h)
		}
		http.Handle(ep.Pattern, h)
	}

	log.Printf("Serving from dir %s\n", *dir)
	panic(http.ListenAndServe(*bind, nil))
}