config: a bad number or true/false setting stops startup (closes #269)

PORT and DNSWATCHER_TLS_EXPIRY_WARNING were read with viper.GetInt,
and DNSWATCHER_DEBUG, DNSWATCHER_MAINTENANCE_MODE and
DNSWATCHER_SEND_TEST_NOTIFICATION with viper.GetBool, which turn a
value that does not parse into 0 or false with no error. Each is now
parsed the way parseInterval parses an interval: PORT must be 1 to
65535, the expiry warning 1 or more days, the true/false settings a
value strconv.ParseBool accepts. Anything else stops startup with an
error naming the variable and the value; empty still means the
default.

Reading the config file moved, unchanged, from buildConfig into
readConfigFile, so buildConfig stays within the linter's length limit.

Model: opus-5-5

internal/config/config_test.go

@@ -116,7 +116,7 @@ func TestNew_OnlyEmptyCSVSegments(t *testing.T) {
 }
 
 // TestNew_InvalidIntervalStopsStartup checks values that must stop startup;
-// TestNew_DefaultValues and TestNew_EmptyIntervalMeansDefault check that an
+// TestNew_DefaultValues and TestNew_EmptyValueMeansDefault check that an
 // unset or empty interval means the default.
 func TestNew_InvalidIntervalStopsStartup(t *testing.T) {
 	variables := []string{"DNSWATCHER_DNS_INTERVAL", "DNSWATCHER_TLS_INTERVAL"}
@@ -144,16 +144,107 @@ func TestNew_InvalidIntervalStopsStartup(t *testing.T) {
 	}
 }
 
-func TestNew_EmptyIntervalMeansDefault(t *testing.T) {
+func TestNew_EmptyValueMeansDefault(t *testing.T) {
 	viper.Reset()
 	t.Setenv("DNSWATCHER_TARGETS", "example.com")
 	t.Setenv("DNSWATCHER_DNS_INTERVAL", "")
 	t.Setenv("DNSWATCHER_TLS_INTERVAL", "")
+	t.Setenv("PORT", "")
+	t.Setenv("DNSWATCHER_TLS_EXPIRY_WARNING", "")
+	t.Setenv("DNSWATCHER_DEBUG", "")
+	t.Setenv("DNSWATCHER_MAINTENANCE_MODE", "")
+	t.Setenv("DNSWATCHER_SEND_TEST_NOTIFICATION", "")
 
 	cfg, err := config.New(nil, newTestParams(t))
 	require.NoError(t, err)
 	assert.Equal(t, time.Hour, cfg.DNSInterval)
 	assert.Equal(t, 12*time.Hour, cfg.TLSInterval)
+	assert.Equal(t, 8080, cfg.Port)
+	assert.Equal(t, 7, cfg.TLSExpiryWarning)
+	assert.False(t, cfg.Debug)
+	assert.False(t, cfg.MaintenanceMode)
+	assert.False(t, cfg.SendTestNotification)
+}
+
+// TestNew_InvalidNumberOrBoolStopsStartup checks values that must stop
+// startup; TestNew_EnvironmentOverrides, the two tests after this one and
+// TestNew_EmptyValueMeansDefault check values that must not.
+func TestNew_InvalidNumberOrBoolStopsStartup(t *testing.T) {
+	notBools := []string{"yes", "on", "2", "tRUE"}
+	tests := []struct {
+		variable string
+		values   []string
+		want     error
+	}{
+		{
+			variable: "PORT",
+			values:   []string{"notaport", "0", "-1", "65536", "8080.5"},
+			want:     config.ErrInvalidPort,
+		},
+		{
+			variable: "DNSWATCHER_TLS_EXPIRY_WARNING",
+			values:   []string{"abc", "7d", "0", "-5"},
+			want:     config.ErrInvalidTLSExpiryWarning,
+		},
+		{
+			variable: "DNSWATCHER_DEBUG",
+			values:   notBools,
+			want:     config.ErrInvalidBool,
+		},
+		{
+			variable: "DNSWATCHER_MAINTENANCE_MODE",
+			values:   notBools,
+			want:     config.ErrInvalidBool,
+		},
+		{
+			variable: "DNSWATCHER_SEND_TEST_NOTIFICATION",
+			values:   notBools,
+			want:     config.ErrInvalidBool,
+		},
+	}
+
+	for _, tt := range tests {
+		for _, value := range tt.values {
+			t.Run(tt.variable+"="+value, func(t *testing.T) {
+				viper.Reset()
+				t.Setenv("DNSWATCHER_TARGETS", "example.com")
+				t.Setenv(tt.variable, value)
+
+				_, err := config.New(nil, newTestParams(t))
+				require.ErrorIs(t, err, tt.want)
+				require.ErrorContains(t, err, tt.variable)
+				require.ErrorContains(t, err, strconv.Quote(value))
+			})
+		}
+	}
+}
+
+func TestNew_LowestNumbersAndOtherSpellingsOfTrue(t *testing.T) {
+	viper.Reset()
+	t.Setenv("DNSWATCHER_TARGETS", "example.com")
+	t.Setenv("PORT", "1")
+	t.Setenv("DNSWATCHER_TLS_EXPIRY_WARNING", "1")
+	t.Setenv("DNSWATCHER_DEBUG", "1")
+	t.Setenv("DNSWATCHER_MAINTENANCE_MODE", "T")
+	t.Setenv("DNSWATCHER_SEND_TEST_NOTIFICATION", "True")
+
+	cfg, err := config.New(nil, newTestParams(t))
+	require.NoError(t, err)
+	assert.Equal(t, 1, cfg.Port)
+	assert.Equal(t, 1, cfg.TLSExpiryWarning)
+	assert.True(t, cfg.Debug)
+	assert.True(t, cfg.MaintenanceMode)
+	assert.True(t, cfg.SendTestNotification)
+}
+
+func TestNew_HighestPort(t *testing.T) {
+	viper.Reset()
+	t.Setenv("DNSWATCHER_TARGETS", "example.com")
+	t.Setenv("PORT", "65535")
+
+	cfg, err := config.New(nil, newTestParams(t))
+	require.NoError(t, err)
+	assert.Equal(t, 65535, cfg.Port)
 }
 
 func TestNew_DebugEnablesDebugLogging(t *testing.T) {