rpi-sensors/server.go

package main

import (
	"errors"
	"fmt"
	"github.com/gorilla/mux"
	"html/template"
	"log"
	"net/http"
	"os/exec"
	"strconv"
	"strings"
	"time"
)

const ROOT_URL = ""

func startServer() {
	port := "8001"
	router := mux.NewRouter()
	router.HandleFunc("/", showCharts).Methods("GET")
	router.HandleFunc("/", showCharts).Methods("GET").Queries("show-minutes", "{[0-9]+}")
	router.HandleFunc("/", saveSnapshot).Methods("POST")
	router.HandleFunc("/data", sendData).Methods("GET")
	router.HandleFunc("/data", sendData).Methods("GET").Queries("since", "")
	router.HandleFunc("/data/now", createAndSendSnapshot).Methods("GET")
	router.PathPrefix("/static/").Handler(http.StripPrefix("/static/", http.FileServer(http.Dir("webapp/dist/"))))
	fmt.Printf("Listening on port %s...\n", port)
	log.Fatal(http.ListenAndServe(fmt.Sprintf(":%v", port), router))
}

func showCharts(w http.ResponseWriter, r *http.Request) {
	minutes := r.FormValue("show-minutes")
	if minutes != "" {
		if _, err := strconv.ParseInt(minutes, 10, 0); err != nil {
			http.Redirect(w, r, ROOT_URL, 303)
		}
	}
	templater, err := template.ParseFiles("webapp/dist/charts.html")
	if internalErrorOnErr(fmt.Errorf("couldn't parse the template: %w", err), w, r) { return }
	err = templater.Execute(w, ROOT_URL)
	internalErrorOnErr(err, w, r)
}

func sendData(w http.ResponseWriter, r *http.Request) {
	dateSince := strings.SplitAfter(time.Now().UTC().Format(time.RFC3339Nano), "Z")[0]
	sinceQuery := r.FormValue("since")
	if sinceQuery != "" {
		newDateSince, err := time.Parse(time.RFC3339Nano, sinceQuery)
		if err != nil {
			http.Redirect(w, r, ROOT_URL, 303)
			return
		}
		dateSince = strings.SplitAfter(newDateSince.Format(time.RFC3339Nano), "Z")[0]
	}
	records, err := getSnapshotRecordsFromDb(dateSince)
	if internalErrorOnErr(fmt.Errorf("couldn't get snapshots from db: %w", err), w, r) { return }
	json, err := createJsonFromSnapshotRecords(records)
	if internalErrorOnErr(fmt.Errorf("couldn't create json from snapshots: %w", err), w, r) { return }
	w.Header().Set("Content-Type", "application/json")
	_, err = fmt.Fprintf(w, string(json))
	internalErrorOnErr(err, w, r)
}

func createAndSendSnapshot(w http.ResponseWriter, r *http.Request) {
	snapshot, err := getSnapshotFromPythonScript()
	if internalErrorOnErr(fmt.Errorf("couldn't create a snapshot: %w", err), w, r) { return }
	_, err = writeSnapshotToDb(snapshot)
	if internalErrorOnErr(fmt.Errorf("couldn't save snapshot to db: %w", err), w, r) { return }
	dbSnapshotRecord, err := getLastSnapshotRecordFromDb()
	json, err := createJsonFromSnapshotRecords([]*SnapshotRecord{dbSnapshotRecord})
	if internalErrorOnErr(fmt.Errorf("couldn't create json from last snapshots: %w", err), w, r) { return }
	w.Header().Set("Content-Type", "application/json")
	_, err = fmt.Fprintf(w, string(json))
	internalErrorOnErr(err, w, r)
}

func saveSnapshot(w http.ResponseWriter, r *http.Request) {
	snapshotSub, err := createSnapshotSubFromJsonBodyStream(r.Body)
	if internalErrorOnErr(fmt.Errorf("couldn't create snapshot from JSON: %w", err), w, r) { return }
	newId, err := writeSnapshotToDb(snapshotSub)
	if internalErrorOnErr(fmt.Errorf("couldn't submit snapshot into the database: %w", err), w, r) { return }
	_, err = fmt.Fprintf(w, "{id: %v}", newId)
	internalErrorOnErr(err, w, r)
}

func saveSnapshotOnInterval(seconds int64, stop chan int) {
	for {
		snapshot, err := getSnapshotFromPythonScript()
		if err == nil {
			_, err = writeSnapshotToDb(snapshot)
		}
		if err != nil {
			pythonLogger.Println(err.Error())
		}
		select {
		case <-stop:
			break
		default:
			time.Sleep(time.Duration(seconds) * time.Second)
		}
	}
}

func getSnapshotFromPythonScript() (*SnapshotSubmission, error) {
	output, err := exec.Command("./climate-pinger.py").CombinedOutput()
	if err != nil {
		return nil, fmt.Errorf(
			"Error:\n\t%s%w",
			strings.Replace(string(output), "\n", "\n\t", -1),
			err,
		)
	}
	tokens := strings.Split(string(output), "\n")
	if len(tokens) != 5 {
		return nil, errors.New(fmt.Sprintf("Strange python output: %s", output))
	}
	snapshot := SnapshotSubmission{
		Timestamp: strings.Split(tokens[0], "\t")[1],
		Temp:      strings.Split(tokens[1], "\t")[1],
		Humidity:  strings.Split(tokens[2], "\t")[1],
		Co2:       strings.Split(tokens[3], "\t")[1],
	}
	return &snapshot, nil
}

func internalErrorOnErr(err error, w http.ResponseWriter, r *http.Request) bool {
	if errors.Unwrap(err) != nil {
		errorMessage := "Internal Server Error!"
		if DEBUG {
			errorMessage += fmt.Sprintf(" Happened during %s request for pattern '%s': %s",
				r.Method,
				r.URL,
				err.Error())
		}
		logError(errorMessage)
		http.Error(w, errorMessage, 500)
		return true
	}
	return false
}

func logError(errorMessage string) {
	fmt.Println(errorMessage)
	mainLogger.Println(errorMessage)
}