Extend this program:

- add a database for devices
- read devices from database and present this data on a simple web/REST
interface

The code or model is from a blog entry from Alex Edward:
https://www.alexedwards.net/blog/organising-database-access

.gitignore

@@ -0,0 +1,15 @@
+# Binaries for programs and plugins
+*.exe
+*.exe~
+*.dll
+*.so
+*.dylib
+
+# Test binary, built with `go test -c`
+*.test
+
+# Output of the go coverage tool, specifically when used with LiteIDE
+*.out
+
+# Dependency directories (remove the comment below to include it)
+# vendor/

config.toml

@@ -0,0 +1,7 @@
+[BROKER]
+Address="s1.mimbach49.de"
+Port=8883
+ClientId = "mqttListener"
+Username = "testuser"
+Password = "xyz123"
+EnableTLS = true

go.mod

@@ -0,0 +1,11 @@
+module mqttListener
+
+go 1.14
+
+require (
+	github.com/eclipse/paho.mqtt.golang v1.2.0
+	github.com/mattn/go-sqlite3 v1.14.2
+	github.com/mmcdole/gofeed v1.0.0
+	github.com/pelletier/go-toml v1.2.0
+	github.com/spf13/cobra v1.0.0
+)

main.go

@@ -2,16 +2,23 @@ package main
 
 import (
 	"mqttListener/Config"
+	"mqttListener/models"
 	"mqttListener/mqtt"
 
-	//"mqttListener/cmd"
+	"fmt"
+	"log"
 
-	//"fmt"
 	"os"
 	"os/signal"
 	"syscall"
+
+	"net/http"
 )
 
+type Env struct {
+	db models.Datastore
+}
+
 func main() {
 
 	c := make(chan os.Signal, 1)
@@ -22,13 +29,38 @@ func main() {
 	// DEBUG Config
 	// fmt.Println("BrokerAddress = ", Config.BrokerAddress)
 
+	db, err := models.NewDB("simple.sqlite")
+	if err != nil {
+		log.Panic(err)
+	}
+
+	env := &Env{db}
+
 	mqtt.Setup()
 	mqtt.Connect()
 	go mqtt.Listen()
 
-	//cmd.Exec()
+	http.HandleFunc("/devices", env.devicesIndex)
+	go http.ListenAndServe(":3000", nil)
 
+	fmt.Println("awaiting signal")
 	<-c // wait for SIGTERM
+	fmt.Println("exiting")
 
 	mqtt.Disconnect()
 }
+
+func (env *Env) devicesIndex(w http.ResponseWriter, r *http.Request) {
+	if r.Method != "GET" {
+		http.Error(w, http.StatusText(405), 405)
+		return
+	}
+	devices, err := env.db.AllDevices()
+	if err != nil {
+		http.Error(w, http.StatusText(500), 500)
+		return
+	}
+	for _, device := range devices {
+		fmt.Fprintf(w, "%s, %s, %s, £%.2f\n", device.ID, device.MAC, device.SN, device.LastMsg)
+	}
+}

models/db.go

@@ -0,0 +1,33 @@
+package models
+
+import (
+	"database/sql"
+
+	_ "github.com/mattn/go-sqlite3"
+)
+
+type Datastore interface {
+	AllDevices() ([]*Device, error)
+}
+
+type DB struct {
+	*sql.DB
+}
+
+func NewDB(dataSourceName string) (*DB, error) {
+	db, err := sql.Open("sqlite3", dataSourceName)
+	if err != nil {
+		return nil, err
+	}
+	if err = db.Ping(); err != nil {
+		return nil, err
+	}
+
+	sqlStmt := "CREATE TABLE IF NOT EXISTS devices (id TEXT not null primary key, mac TEXT, sn TEXT, lastMsg TEXT);"
+	_, err = db.Exec(sqlStmt)
+	if err != nil {
+		return nil, err
+	}
+
+	return &DB{db}, nil
+}

models/devices.go

@@ -0,0 +1,36 @@
+package models
+
+type Device struct {
+	ID string
+	MAC string
+	SN string
+	LastMsg string
+}
+
+
+
+
+
+func (db *DB) AllDevices() ([]*Device, error) {
+    rows, err := db.Query("SELECT * FROM devices")
+    if err != nil {
+        return nil, err
+    }
+    defer rows.Close()
+
+    devices := make([]*Device, 0)
+    for rows.Next() {
+        device := new(Device)
+        err := rows.Scan(&device.ID, &device.MAC, &device.SN, &device.LastMsg)
+        if err != nil {
+            return nil, err
+        }
+        devices = append(devices, device)
+    }
+    if err = rows.Err(); err != nil {
+        return nil, err
+    }
+    return devices, nil
+}
+
+