init work of uptime

internal/monitor/tls.go

@@ -0,0 +1,68 @@
+package monitor
+
+import (
+	"crypto/tls"
+	"fmt"
+	"net"
+	"time"
+
+	"arclineit/arcline-uptime/internal/config"
+)
+
+// TLSChecker dials a TLS endpoint and alerts when the certificate is about
+// to expire (within ExpiryWarningDays days).
+type TLSChecker struct {
+	cfg     config.MonitorConfig
+	timeout time.Duration
+}
+
+func NewTLSChecker(cfg config.MonitorConfig, timeout time.Duration) *TLSChecker {
+	return &TLSChecker{cfg: cfg, timeout: timeout}
+}
+
+func (t *TLSChecker) Name()     string        { return t.cfg.Name }
+func (t *TLSChecker) Interval() time.Duration { return time.Duration(t.cfg.Interval) * time.Second }
+
+func (t *TLSChecker) Check() Result {
+	start := time.Now()
+	result := Result{
+		MonitorName: t.cfg.Name,
+		CheckedAt:   start,
+	}
+
+	addr := fmt.Sprintf("%s:%d", t.cfg.Host, t.cfg.Port)
+	dialer := &tls.Dialer{
+		NetDialer: &net.Dialer{Timeout: t.timeout},
+		Config:    &tls.Config{ServerName: t.cfg.Host},
+	}
+
+	conn, err := dialer.Dial("tcp", addr)
+	result.ResponseTime = time.Since(start)
+	if err != nil {
+		result.Error = err.Error()
+		return result
+	}
+	defer conn.Close()
+
+	tlsConn := conn.(*tls.Conn)
+	state := tlsConn.ConnectionState()
+
+	// Find the earliest-expiring certificate in the chain.
+	var earliest time.Time
+	for _, cert := range state.PeerCertificates {
+		if earliest.IsZero() || cert.NotAfter.Before(earliest) {
+			earliest = cert.NotAfter
+		}
+	}
+
+	daysLeft := int(time.Until(earliest).Hours() / 24)
+	if daysLeft <= t.cfg.ExpiryWarningDays {
+		result.Error = fmt.Sprintf("certificate expires in %d day(s) on %s",
+			daysLeft, earliest.UTC().Format("2006-01-02"))
+		return result
+	}
+
+	result.Up = true
+	applyThreshold(&result, t.cfg.MaxResponseMS)
+	return result
+}