chore: move all source files to new folder

Update the project structure to move all golang files to a new `src/`
folder. This keeps all the code located in the same place and easier to
work with.
Update the Makefile and goreleaser config to continue to work with the new
folder structure.

src/exporter.go

@@ -0,0 +1,103 @@
+package main
+
+import (
+	"fail2ban-prometheus-exporter/cfg"
+	fail2banDb "fail2ban-prometheus-exporter/db"
+	"fmt"
+	_ "github.com/mattn/go-sqlite3"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"log"
+	"net/http"
+)
+
+const namespace = "fail2ban"
+
+var (
+	version = "dev"
+	commit  = "none"
+	date    = "unknown"
+	builtBy = "unknown"
+
+	metricUp = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, "", "up"),
+		"Was the last fail2ban query successful.",
+		nil, nil,
+	)
+	metricBannedIpsPerJail = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, "", "banned_ips"),
+		"Number of banned IPs stored in the database (per jail).",
+		[]string{"jail"}, nil,
+	)
+	metricBadIpsPerJail = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, "", "bad_ips"),
+		"Number of bad IPs stored in the database (per jail).",
+		[]string{"jail"}, nil,
+	)
+)
+
+type Exporter struct {
+	db *fail2banDb.Fail2BanDB
+}
+
+func (e *Exporter) Describe(ch chan<- *prometheus.Desc) {
+	ch <- metricUp
+	ch <- metricBadIpsPerJail
+	ch <- metricBannedIpsPerJail
+}
+
+func (e *Exporter) Collect(ch chan<- prometheus.Metric) {
+	ch <- prometheus.MustNewConstMetric(
+		metricUp, prometheus.GaugeValue, 1,
+	)
+	e.collectBadIpsPerJailMetrics(ch)
+	e.collectBannedIpsPerJailMetrics(ch)
+}
+
+func (e *Exporter) collectBadIpsPerJailMetrics(ch chan<- prometheus.Metric) {
+	jailNameToCountMap, err := e.db.CountBadIpsPerJail()
+	if err != nil {
+		log.Print(err)
+	}
+
+	for jailName, count := range jailNameToCountMap {
+		ch <- prometheus.MustNewConstMetric(
+			metricBadIpsPerJail, prometheus.GaugeValue, float64(count), jailName,
+		)
+	}
+}
+
+func (e *Exporter) collectBannedIpsPerJailMetrics(ch chan<- prometheus.Metric) {
+	jailNameToCountMap, err := e.db.CountBannedIpsPerJail()
+	if err != nil {
+		log.Print(err)
+	}
+
+	for jailName, count := range jailNameToCountMap {
+		ch <- prometheus.MustNewConstMetric(
+			metricBannedIpsPerJail, prometheus.GaugeValue, float64(count), jailName,
+		)
+	}
+}
+
+func printAppVersion() {
+	fmt.Println(version)
+	fmt.Printf("    build date:  %s\r\n    commit hash: %s\r\n    built by:    %s\r\n", date, commit, builtBy)
+}
+
+func main() {
+	appSettings := cfg.Parse()
+	if appSettings.VersionMode {
+		printAppVersion()
+	} else {
+		log.Print("starting fail2ban exporter")
+
+		exporter := &Exporter{
+			db: fail2banDb.MustConnectToDb(appSettings.Fail2BanDbPath),
+		}
+		prometheus.MustRegister(exporter)
+
+		http.Handle("/metrics", promhttp.Handler())
+		log.Fatal(http.ListenAndServe(fmt.Sprintf(":%d", appSettings.MetricsPort), nil))
+	}
+}