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package main
import (
"bytes"
"encoding/json"
"flag"
"fmt"
"io/ioutil"
"log"
"net/http"
"net/netip"
"path/filepath"
"text/template"
)
var appdata string
type RuntimeConfig struct {
Devices DevicesConfig
Web WebConfig
}
type DevicesConfig struct {
Hs100 []Hs100Conf
}
type WebConfig struct {
Listen netip.AddrPort
}
// main() contains the control flow of this program.
func main() {
configPath := parseFlags()
c := parseConfig(configPath)
http.HandleFunc("/", index(c.Devices, appdata))
http.HandleFunc("/api", api())
http.HandleFunc("/simple.css", css(appdata))
fmt.Printf("Serving at http://%s\n", c.Web.Listen)
log.Fatal(http.ListenAndServe(c.Web.Listen.String(), nil))
}
// parseFlags() handles command line interface (CLI) flags.
func parseFlags() string {
var r string // return value
flag.StringVar(&r, "c", "/etc/webiot/config.json",
"path to configuration file")
flag.StringVar(&appdata, "a", "/usr/share/webiot",
"path to static application data")
flag.Parse()
return r
}
// parseConfig() parses and validates the runtime configuration file and
// returns it as Go datastructure.
func parseConfig(path string) RuntimeConfig {
// read config file and ensure proper JSON formatting
data := mustRead(path)
if !json.Valid(data) {
log.Fatalf("%s contains invalid JSON!", path)
}
// read to RuntimeConfig struct and handle errors
config := RuntimeConfig{}
err := json.Unmarshal(data, &config)
if err != nil {
log.Fatalf("Could not parse configuration file:\n%s\n", err)
}
return config
}
// index() returns a HTTP handler for the index page.
func index(devices DevicesConfig, appdata string) func(http.ResponseWriter, *http.Request) {
// prepare HTML
path := filepath.Join(appdata, "index.html.tmpl")
html := mustRender(path, devices)
return func(w http.ResponseWriter, r *http.Request) {
fmt.Fprint(w, html)
}
}
func css(appdata string) func(http.ResponseWriter, *http.Request) {
// read CSS file
path := filepath.Join(appdata, "simple.css")
css := string(mustRead(path))
return func(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "text/css; charset=utf-8")
fmt.Fprint(w, css)
}
}
// mustRead() reads a file and panics if this is not possible.
func mustRead(path string) []byte {
data, err := ioutil.ReadFile(path)
if err != nil {
log.Fatalf("Could not read '%s'!", path)
}
return data
}
// mustRender() renders a template file with the given data and panics if this
// is not possible.
func mustRender(filepath string, data interface{}) string {
file := mustRead(filepath)
tmpl, err := template.New(filepath).Parse(string(file))
var buffer bytes.Buffer
err = tmpl.Execute(&buffer, data)
if err != nil {
fmt.Println(err)
log.Fatalf("Could not execute template for %s!", filepath)
}
return buffer.String()
}
// api() returns the HTTP handler for the API endpoint.
func api() func(http.ResponseWriter, *http.Request) {
return func(w http.ResponseWriter, r *http.Request) {
// TODO assert correct HTTP method
// read parameters and handle errors
errHost, host := assertSingleParam(r, "host")
errState, state := assertSingleParam(r, "state")
if (errHost != nil) || (errState != nil) {
http.Error(w,
"Provide exactly one host and one state parameter!", 400)
return
}
// set WiFi plug
err := set(host, state)
if err != nil {
http.Error(w, "Could not set WiFi plug.", 500)
} else {
fmt.Fprint(w, "ok")
}
}
}
// assertSingleParam() returns the value of given URL key and panics if there
// is not exactly one match for this key.
func assertSingleParam(r *http.Request, key string) (error, string) {
values := r.URL.Query()[key]
if len(values) != 1 {
return fmt.Errorf("Provide exactly one '%s' parameter!", key), ""
}
return nil, values[0]
}
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