docs: update README for TARGETS config and add pre-1.0 notice

Single DNSWATCHER_TARGETS env var replaces the separate DOMAINS and
HOSTNAMES variables. Classification is automatic via the PSL.

Closes #10

README.md

@@ -1,5 +1,8 @@
 # dnswatcher
 
+> ⚠️ **Pre-1.0 software.** APIs, configuration, and behavior may change
+> without notice.
+
 dnswatcher is a production DNS and infrastructure monitoring daemon written in
 Go.  It watches configured DNS domains and hostnames for changes, monitors TCP
 port availability, tracks TLS certificate expiry, and delivers real-time
@@ -16,10 +19,19 @@ without requiring an external database.
 
 ## Features
 
+### Target Classification
+
+All monitored DNS names are provided via a single `DNSWATCHER_TARGETS`
+list.  dnswatcher uses the [Public Suffix List](https://publicsuffix.org/)
+to automatically classify each entry as an apex domain (eTLD+1, e.g.
+`example.com`, `example.co.uk`) or a hostname (subdomain, e.g.
+`www.example.com`).  Apex domains receive NS delegation monitoring;
+hostnames receive per-nameserver record monitoring.  Both receive port
+and TLS checks.
+
 ### DNS Domain Monitoring (Apex Domains)
 
-- Accepts a list of DNS domain names (apex domains, identified via the
-  [Public Suffix List](https://publicsuffix.org/)).
+- Apex domains are identified automatically via the PSL.
 - Every **1 hour**, performs a full iterative trace from root servers to
   discover all authoritative nameservers (NS records) for each domain.
 - Queries **every** discovered authoritative nameserver independently.
@@ -195,8 +207,7 @@ the following precedence (highest to lowest):
 | `PORT`                          | HTTP listen port                           | `8080`      |
 | `DNSWATCHER_DEBUG`              | Enable debug logging                       | `false`     |
 | `DNSWATCHER_DATA_DIR`           | Directory for state file                   | `./data`    |
-| `DNSWATCHER_DOMAINS`            | Comma-separated list of apex domains       | `""`        |
-| `DNSWATCHER_HOSTNAMES`          | Comma-separated list of hostnames          | `""`        |
+| `DNSWATCHER_TARGETS`            | Comma-separated list of DNS names to monitor | `""`      |
 | `DNSWATCHER_SLACK_WEBHOOK`      | Slack incoming webhook URL                 | `""`        |
 | `DNSWATCHER_MATTERMOST_WEBHOOK` | Mattermost incoming webhook URL            | `""`        |
 | `DNSWATCHER_NTFY_TOPIC`         | ntfy topic URL                             | `""`        |
@@ -214,8 +225,7 @@ the following precedence (highest to lowest):
 PORT=8080
 DNSWATCHER_DEBUG=false
 DNSWATCHER_DATA_DIR=./data
-DNSWATCHER_DOMAINS=example.com,example.org
-DNSWATCHER_HOSTNAMES=www.example.com,api.example.com,mail.example.org
+DNSWATCHER_TARGETS=example.com,example.org,www.example.com,api.example.com,mail.example.org
 DNSWATCHER_SLACK_WEBHOOK=https://hooks.slack.com/services/T.../B.../xxx
 DNSWATCHER_MATTERMOST_WEBHOOK=https://mattermost.example.com/hooks/xxx
 DNSWATCHER_NTFY_TOPIC=https://ntfy.sh/my-dns-alerts
@@ -352,8 +362,7 @@ docker build -t dnswatcher .
 docker run -d \
   -p 8080:8080 \
   -v dnswatcher-data:/var/lib/dnswatcher \
-  -e DNSWATCHER_DOMAINS=example.com \
-  -e DNSWATCHER_HOSTNAMES=www.example.com \
+  -e DNSWATCHER_TARGETS=example.com,www.example.com \
   -e DNSWATCHER_NTFY_TOPIC=https://ntfy.sh/my-alerts \
   dnswatcher
 ```

go.mod

@@ -9,16 +9,20 @@ require (
 	github.com/joho/godotenv v1.5.1
 	github.com/prometheus/client_golang v1.23.2
 	github.com/spf13/viper v1.21.0
+	github.com/stretchr/testify v1.11.1
 	go.uber.org/fx v1.24.0
+	golang.org/x/net v0.50.0
 )
 
 require (
 	github.com/beorn7/perks v1.0.1 // indirect
 	github.com/cespare/xxhash/v2 v2.3.0 // indirect
+	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/fsnotify/fsnotify v1.9.0 // indirect
 	github.com/go-viper/mapstructure/v2 v2.4.0 // indirect
 	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
 	github.com/pelletier/go-toml/v2 v2.2.4 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/prometheus/client_model v0.6.2 // indirect
 	github.com/prometheus/common v0.66.1 // indirect
 	github.com/prometheus/procfs v0.16.1 // indirect
@@ -33,7 +37,8 @@ require (
 	go.uber.org/zap v1.26.0 // indirect
 	go.yaml.in/yaml/v2 v2.4.2 // indirect
 	go.yaml.in/yaml/v3 v3.0.4 // indirect
-	golang.org/x/sys v0.35.0 // indirect
-	golang.org/x/text v0.28.0 // indirect
+	golang.org/x/sys v0.41.0 // indirect
+	golang.org/x/text v0.34.0 // indirect
 	google.golang.org/protobuf v1.36.8 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

go.sum

@@ -74,10 +74,12 @@ go.yaml.in/yaml/v2 v2.4.2 h1:DzmwEr2rDGHl7lsFgAHxmNz/1NlQ7xLIrlN2h5d1eGI=
 go.yaml.in/yaml/v2 v2.4.2/go.mod h1:081UH+NErpNdqlCXm3TtEran0rJZGxAYx9hb/ELlsPU=
 go.yaml.in/yaml/v3 v3.0.4 h1:tfq32ie2Jv2UxXFdLJdh3jXuOzWiL1fo0bu/FbuKpbc=
 go.yaml.in/yaml/v3 v3.0.4/go.mod h1:DhzuOOF2ATzADvBadXxruRBLzYTpT36CKvDb3+aBEFg=
-golang.org/x/sys v0.35.0 h1:vz1N37gP5bs89s7He8XuIYXpyY0+QlsKmzipCbUtyxI=
-golang.org/x/sys v0.35.0/go.mod h1:BJP2sWEmIv4KK5OTEluFJCKSidICx8ciO85XgH3Ak8k=
-golang.org/x/text v0.28.0 h1:rhazDwis8INMIwQ4tpjLDzUhx6RlXqZNPEM0huQojng=
-golang.org/x/text v0.28.0/go.mod h1:U8nCwOR8jO/marOQ0QbDiOngZVEBB7MAiitBuMjXiNU=
+golang.org/x/net v0.50.0 h1:ucWh9eiCGyDR3vtzso0WMQinm2Dnt8cFMuQa9K33J60=
+golang.org/x/net v0.50.0/go.mod h1:UgoSli3F/pBgdJBHCTc+tp3gmrU4XswgGRgtnwWTfyM=
+golang.org/x/sys v0.41.0 h1:Ivj+2Cp/ylzLiEU89QhWblYnOE9zerudt9Ftecq2C6k=
+golang.org/x/sys v0.41.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
+golang.org/x/text v0.34.0 h1:oL/Qq0Kdaqxa1KbNeMKwQq0reLCCaFtqu2eNuSeNHbk=
+golang.org/x/text v0.34.0/go.mod h1:homfLqTYRFyVYemLBFl5GgL/DWEiH5wcsQ5gSh1yziA=
 google.golang.org/protobuf v1.36.8 h1:xHScyCOEuuwZEc6UtSOvPbAT4zRh0xcNRYekJwfqyMc=
 google.golang.org/protobuf v1.36.8/go.mod h1:fuxRtAxBytpl4zzqUh6/eyUujkJdNiuEkXntxiD/uRU=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=

internal/config/classify.go

@@ -0,0 +1,61 @@
+// Package config provides application configuration via Viper.
+package config
+
+import (
+	"fmt"
+	"strings"
+
+	"golang.org/x/net/publicsuffix"
+)
+
+// ClassifyTarget determines whether a DNS name is an apex domain
+// (eTLD+1) or a hostname (subdomain of an eTLD+1). Returns
+// "domain" or "hostname". Returns an error if the name is itself
+// a public suffix (e.g. "co.uk") or otherwise invalid.
+func ClassifyTarget(name string) (string, error) {
+	// Normalize: lowercase, strip trailing dot.
+	name = strings.ToLower(strings.TrimSuffix(name, "."))
+
+	if name == "" {
+		return "", fmt.Errorf("empty target name")
+	}
+
+	apex, err := publicsuffix.EffectiveTLDPlusOne(name)
+	if err != nil {
+		return "", fmt.Errorf(
+			"invalid target %q: %w", name, err,
+		)
+	}
+
+	if name == apex {
+		return "domain", nil
+	}
+
+	return "hostname", nil
+}
+
+// classifyTargets splits a list of DNS names into apex domains
+// and hostnames using the Public Suffix List.
+func classifyTargets(
+	targets []string,
+) (domains, hostnames []string, err error) {
+	for _, target := range targets {
+		kind, classifyErr := ClassifyTarget(target)
+		if classifyErr != nil {
+			return nil, nil, classifyErr
+		}
+
+		switch kind {
+		case "domain":
+			domains = append(domains, strings.ToLower(
+				strings.TrimSuffix(target, "."),
+			))
+		case "hostname":
+			hostnames = append(hostnames, strings.ToLower(
+				strings.TrimSuffix(target, "."),
+			))
+		}
+	}
+
+	return domains, hostnames, nil
+}

internal/config/classify_test.go

@@ -0,0 +1,84 @@
+package config
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestClassifyTarget(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name     string
+		input    string
+		expected string
+		wantErr  bool
+	}{
+		{"apex .com", "example.com", "domain", false},
+		{"apex .org", "example.org", "domain", false},
+		{"apex .co.uk", "example.co.uk", "domain", false},
+		{"apex .com.au", "example.com.au", "domain", false},
+		{"subdomain www", "www.example.com", "hostname", false},
+		{"subdomain api", "api.example.com", "hostname", false},
+		{"deep subdomain", "a.b.c.example.com", "hostname", false},
+		{"subdomain .co.uk", "www.example.co.uk", "hostname", false},
+		{"trailing dot", "example.com.", "domain", false},
+		{"trailing dot sub", "www.example.com.", "hostname", false},
+		{"uppercase", "EXAMPLE.COM", "domain", false},
+		{"mixed case", "Www.Example.Com", "hostname", false},
+		{"public suffix", "co.uk", "", true},
+		{"tld only", "com", "", true},
+		{"empty", "", "", true},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			result, err := ClassifyTarget(tc.input)
+			if tc.wantErr {
+				assert.Error(t, err)
+
+				return
+			}
+
+			require.NoError(t, err)
+			assert.Equal(t, tc.expected, result)
+		})
+	}
+}
+
+func TestClassifyTargets(t *testing.T) {
+	t.Parallel()
+
+	targets := []string{
+		"example.com",
+		"www.example.com",
+		"api.example.com",
+		"example.co.uk",
+		"blog.example.co.uk",
+	}
+
+	domains, hostnames, err := classifyTargets(targets)
+	require.NoError(t, err)
+
+	assert.Equal(
+		t,
+		[]string{"example.com", "example.co.uk"},
+		domains,
+	)
+	assert.Equal(
+		t,
+		[]string{"www.example.com", "api.example.com", "blog.example.co.uk"},
+		hostnames,
+	)
+}
+
+func TestClassifyTargets_RejectsPublicSuffix(t *testing.T) {
+	t.Parallel()
+
+	_, _, err := classifyTargets([]string{"example.com", "co.uk"})
+	assert.Error(t, err)
+}

internal/config/config.go

@@ -89,8 +89,7 @@ func setupViper(name string) {
 	viper.SetDefault("PORT", defaultPort)
 	viper.SetDefault("DEBUG", false)
 	viper.SetDefault("DATA_DIR", "./data")
-	viper.SetDefault("DOMAINS", "")
-	viper.SetDefault("HOSTNAMES", "")
+	viper.SetDefault("TARGETS", "")
 	viper.SetDefault("SLACK_WEBHOOK", "")
 	viper.SetDefault("MATTERMOST_WEBHOOK", "")
 	viper.SetDefault("NTFY_TOPIC", "")
@@ -133,12 +132,19 @@ func buildConfig(
 		tlsInterval = defaultTLSInterval
 	}
 
+	targets := parseCSV(viper.GetString("TARGETS"))
+
+	domains, hostnames, classifyErr := classifyTargets(targets)
+	if classifyErr != nil {
+		return nil, fmt.Errorf("classifying targets: %w", classifyErr)
+	}
+
 	cfg := &Config{
 		Port:              viper.GetInt("PORT"),
 		Debug:             viper.GetBool("DEBUG"),
 		DataDir:           viper.GetString("DATA_DIR"),
-		Domains:           parseCSV(viper.GetString("DOMAINS")),
-		Hostnames:         parseCSV(viper.GetString("HOSTNAMES")),
+		Domains:           domains,
+		Hostnames:         hostnames,
 		SlackWebhook:      viper.GetString("SLACK_WEBHOOK"),
 		MattermostWebhook: viper.GetString("MATTERMOST_WEBHOOK"),
 		NtfyTopic:         viper.GetString("NTFY_TOPIC"),