Add config package (#2)

YAML & JSON configuration handling added

---------

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

config/config.go

@@ -0,0 +1,84 @@
+package config
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/pkg/errors"
+	yaml "gopkg.in/yaml.v3"
+)
+
+type Check struct {
+	Kind string          `json:"kind"`
+	Spec json.RawMessage `json:"spec"`
+}
+
+type Peer struct {
+	Name          string   `json:"name"`
+	RemoteAddress string   `json:"remote_address"`
+	RemoteAS      uint64   `json:"remote_as"`
+	LocalAddress  string   `json:"local_address"`
+	LocalAS       uint64   `json:"local_as"`
+	Routes        []string `json:"routes"`
+}
+
+type Service struct {
+	Name          string   `json:"name"`
+	CheckOperator string   `json:"check_operator"`
+	CheckInterval Duration `json:"check_interval"`
+	Checks        []Check  `json:"checks"`
+	Peers         []Peer   `json:"peers"`
+}
+
+type Metrics struct {
+	Enabled bool   `json:"enabled"`
+	Address string `json:"address"`
+}
+
+type Config struct {
+	Services []Service `json:"services"`
+	Metrics  Metrics   `json:"metrics"`
+}
+
+func NewFromFile(filename string) (*Config, error) {
+	cfg := &Config{}
+
+	data, err := os.ReadFile(filename)
+	if err != nil {
+		return nil, errors.Wrap(err, "error reading configuration file")
+	}
+
+	ext := strings.ToLower(filepath.Ext(filename))
+
+	switch ext {
+	case ".yml", ".yaml":
+		type intermediate struct {
+			Services []any          `yaml:"services"`
+			Metrics  map[string]any `yaml:"metrics"`
+		}
+
+		d := intermediate{}
+
+		err := yaml.Unmarshal(data, &d)
+		if err != nil {
+			return nil, errors.Wrap(err, "error unmarshaling intermediate configuration")
+		}
+
+		data, err = json.Marshal(d)
+		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 {
+		return nil, errors.Wrap(err, "error unmarshaling config")
+	}
+
+	return cfg, nil
+}

config/config_test.go

@@ -0,0 +1,108 @@
+package config
+
+import (
+	"encoding/json"
+	"testing"
+	"time"
+
+	"github.com/pkg/errors"
+	"github.com/stretchr/testify/require"
+)
+
+func TestConfig(t *testing.T) {
+	type testCase struct {
+		name       string
+		samplePath string
+		expOut     Config
+		expError   error
+	}
+
+	sampleConfig := Config{
+		Services: []Service{
+			{
+				Name:          "http",
+				CheckOperator: "and",
+				CheckInterval: Duration(time.Duration(10 * time.Second)),
+				Checks: []Check{
+					{
+						Kind: "dns_lookup",
+						Spec: json.RawMessage(`{"interval":"100ms","query":"example.com","resolver":"127.0.0.1","tries":3}`),
+					},
+					{
+						Kind: "http_2xx",
+						Spec: json.RawMessage(`{"address":"127.0.0.1:8080","interval":"100ms","path":"/","timeout":"2s","tries":3}`),
+					},
+					{
+						Kind: "assigned_address",
+						Spec: json.RawMessage(`{"interface":"dummy0","ipv4":"10.0.0.128"}`),
+					},
+				},
+				Peers: []Peer{
+					{
+						Name:          "some_router_1",
+						RemoteAddress: "10.0.0.252",
+						RemoteAS:      65000,
+						LocalAddress:  "10.0.0.1",
+						LocalAS:       65999,
+						Routes:        []string{"10.0.0.128/32"},
+					},
+					{
+						Name:          "some_router_2",
+						RemoteAddress: "10.0.0.253",
+						RemoteAS:      65000,
+						LocalAddress:  "10.0.0.1",
+						LocalAS:       65999,
+						Routes:        []string{"10.0.0.128/32"},
+					},
+				},
+			},
+		},
+		Metrics: Metrics{
+			Enabled: true,
+			Address: "127.0.0.1:9090",
+		},
+	}
+
+	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/duration.go

@@ -0,0 +1,37 @@
+package config
+
+import (
+	"encoding/json"
+	"time"
+
+	"github.com/pkg/errors"
+)
+
+type Duration time.Duration
+
+func (d Duration) MarshalJSON() ([]byte, error) {
+	return json.Marshal(time.Duration(d).String())
+}
+
+func (d *Duration) UnmarshalJSON(b []byte) error {
+	var v any
+
+	if err := json.Unmarshal(b, &v); err != nil {
+		return err
+	}
+
+	switch value := v.(type) {
+	case float64:
+		*d = Duration(time.Duration(value))
+		return nil
+	case string:
+		tmp, err := time.ParseDuration(value)
+		if err != nil {
+			return err
+		}
+		*d = Duration(tmp)
+		return nil
+	default:
+		return errors.Errorf("invalid value: `%v` (%T)", value, value)
+	}
+}

config/duration_test.go

@@ -0,0 +1,57 @@
+package config
+
+import (
+	"encoding/json"
+	"testing"
+	"time"
+
+	"github.com/pkg/errors"
+	"github.com/stretchr/testify/require"
+)
+
+func TestDuration(t *testing.T) {
+	type testCase struct {
+		name     string
+		in       string
+		expOut   Duration
+		expError error
+	}
+	tcs := []testCase{
+		{
+			name:   "number",
+			in:     "10",
+			expOut: Duration(time.Duration(10)),
+		},
+		{
+			name:   "number w/ suffix",
+			in:     `"10s"`,
+			expOut: Duration(time.Duration(10 * time.Second)),
+		},
+		{
+			name:     "invalid string",
+			in:       `"blah"`,
+			expError: errors.Errorf(`time: invalid duration "blah"`),
+		},
+		{
+			name:     "boolean",
+			in:       "true",
+			expError: errors.Errorf("invalid value: `true` (bool)"),
+		},
+	}
+
+	for _, tc := range tcs {
+		t.Run(tc.name, func(t *testing.T) {
+			r := require.New(t)
+
+			v := new(Duration)
+			err := json.Unmarshal([]byte(tc.in), v)
+			if tc.expError == nil {
+				r.NoError(err)
+				r.Equal(&tc.expOut, v)
+			} 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

config/testdata/sample.yaml

@@ -0,0 +1,41 @@
+---
+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