Add JSON configuration support

Signed-off-by: Igor Shishkin <me@teran.dev>

config/config.go

@@ -50,7 +50,9 @@ func NewFromFile(filename string) (*Config, error) {
 		return nil, errors.Wrap(err, "error reading configuration file")
 	}
 
-	switch strings.ToLower(filepath.Ext(filename)) {
+	ext := strings.ToLower(filepath.Ext(filename))
+
+	switch ext {
 	case ".yml", ".yaml":
 		type intermediate struct {
 			Services []any          `yaml:"services"`
@@ -68,6 +70,10 @@ func NewFromFile(filename string) (*Config, error) {
 		if err != nil {
 			return nil, errors.Wrap(err, "error marshaling intermediate configuration")
 		}
+	case ".json":
+		// no additional action needed
+	default:
+		return nil, errors.Errorf("unexpected file format: `%s`", ext)
 	}
 
 	if err := json.Unmarshal(data, &cfg); err != nil {

config/config_test.go

@@ -5,15 +5,19 @@ import (
 	"testing"
 	"time"
 
+	"github.com/pkg/errors"
 	"github.com/stretchr/testify/require"
 )
 
 func TestConfig(t *testing.T) {
-	r := require.New(t)
+	type testCase struct {
+		name       string
+		samplePath string
+		expOut     Config
+		expError   error
+	}
 
-	cfg, err := NewFromFile("testdata/sample.yaml")
-	r.NoError(err)
-	r.Equal(&Config{
+	sampleConfig := Config{
 		Services: []Service{
 			{
 				Name:          "http",
@@ -57,5 +61,48 @@ func TestConfig(t *testing.T) {
 			Enabled: true,
 			Address: "127.0.0.1:9090",
 		},
-	}, cfg)
+	}
+
+	tcs := []testCase{
+		{
+			name:       "YAML configuration",
+			samplePath: "testdata/sample.yaml",
+			expOut:     sampleConfig,
+		},
+		{
+			name:       "JSON configuration",
+			samplePath: "testdata/sample.json",
+			expOut:     sampleConfig,
+		},
+		{
+			name:       "wrong config file extension",
+			samplePath: "testdata/sample.unknown",
+			expError:   errors.New("unexpected file format: `.unknown`"),
+		},
+	}
+
+	for _, tc := range tcs {
+		t.Run(tc.name, func(t *testing.T) {
+			r := require.New(t)
+
+			cfg, err := NewFromFile(tc.samplePath)
+			if tc.expError == nil {
+				r.NoError(err)
+				for i := range tc.expOut.Services {
+					r.Equalf(tc.expOut.Services[i].Name, cfg.Services[i].Name, "svc#%d", i)
+					r.Equalf(tc.expOut.Services[i].CheckInterval, cfg.Services[i].CheckInterval, "svc#%d", i)
+					r.Equalf(tc.expOut.Services[i].CheckOperator, cfg.Services[i].CheckOperator, "svc#%d", i)
+					for j := range tc.expOut.Services[i].Checks {
+						r.Equalf(tc.expOut.Services[i].Checks[j].Kind, cfg.Services[i].Checks[j].Kind, "svc#%d check#%d", i, j)
+						r.JSONEqf(string(tc.expOut.Services[i].Checks[j].Spec), string(cfg.Services[i].Checks[j].Spec), "svc#%d check#%d", i, j)
+					}
+					r.Equalf(tc.expOut.Services[i].Peers, cfg.Services[i].Peers, "svc#%d", i)
+				}
+				r.Equal(tc.expOut.Metrics, cfg.Metrics)
+			} else {
+				r.Error(err)
+				r.Equal(tc.expError.Error(), err.Error())
+			}
+		})
+	}
 }

config/testdata/sample.json

@@ -0,0 +1,63 @@
+{
+  "services": [
+    {
+      "name": "http",
+      "check_operator": "and",
+      "check_interval": "10s",
+      "checks": [
+        {
+          "kind": "dns_lookup",
+          "spec": {
+            "query": "example.com",
+            "resolver": "127.0.0.1",
+            "tries": 3,
+            "interval": "100ms"
+          }
+        },
+        {
+          "kind": "http_2xx",
+          "spec": {
+            "address": "127.0.0.1:8080",
+            "path": "/",
+            "tries": 3,
+            "interval": "100ms",
+            "timeout": "2s"
+          }
+        },
+        {
+          "kind": "assigned_address",
+          "spec": {
+            "interface": "dummy0",
+            "ipv4": "10.0.0.128"
+          }
+        }
+      ],
+      "peers": [
+        {
+          "name": "some_router_1",
+          "remote_address": "10.0.0.252",
+          "remote_as": 65000,
+          "local_address": "10.0.0.1",
+          "local_as": 65999,
+          "routes": [
+            "10.0.0.128/32"
+          ]
+        },
+        {
+          "name": "some_router_2",
+          "remote_address": "10.0.0.253",
+          "remote_as": 65000,
+          "local_address": "10.0.0.1",
+          "local_as": 65999,
+          "routes": [
+            "10.0.0.128/32"
+          ]
+        }
+      ]
+    }
+  ],
+  "metrics": {
+    "enabled": true,
+    "address": "127.0.0.1:9090"
+  }
+}

config/testdata/sample.unknown

@@ -0,0 +1 @@
+nothing here

go.mod

@@ -4,11 +4,13 @@ go 1.22.3
 
 require (
 	github.com/pkg/errors v0.9.1
+	github.com/sirupsen/logrus v1.9.3
 	github.com/stretchr/testify v1.9.0
 	gopkg.in/yaml.v3 v3.0.1
 )
 
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
+	golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8 // indirect
 )

go.sum

@@ -1,12 +1,20 @@
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
 github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/sirupsen/logrus v1.9.3 h1:dueUQJ1C2q9oE3F7wvmSGAaVtTmUizReu6fjN8uqzbQ=
+github.com/sirupsen/logrus v1.9.3/go.mod h1:naHLuLoDiP4jHNo9R0sCBMtWGeIprob74mVsIT4qYEQ=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
 github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8 h1:0A+M6Uqn+Eje4kHMK80dtF3JCXC4ykBgQG4Fe06QRhQ=
+golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=