feat: Add JSON configuration parser

json/parse.go

@@ -0,0 +1,106 @@
+package json
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"os"
+)
+
+type Parser struct {
+	path *string
+
+	conv    func(any) string
+	awaited map[string]bool
+}
+
+func New(path *string) *Parser {
+	return &Parser{path: path}
+}
+
+func (p *Parser) Type() string {
+	if p.path == nil || *p.path == "" {
+		return "json"
+	}
+	return fmt.Sprintf("json[%s]", *p.path)
+}
+
+func (p *Parser) Parse(keys map[string]bool, conv func(any) string) (found, unknown map[string]string, err error) {
+	found = make(map[string]string)
+	unknown = make(map[string]string)
+
+	if p.path == nil || *p.path == "" {
+		return found, unknown, nil
+	}
+
+	data, err := os.ReadFile(*p.path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return found, unknown, nil
+		}
+		return nil, nil, fmt.Errorf("read json file %q: %w", *p.path, err)
+	}
+
+	if len(data) == 0 {
+		return found, unknown, nil
+	}
+
+	p.conv = conv
+	p.awaited = keys
+
+	return p.parse(data)
+}
+
+func (p *Parser) parse(data []byte) (found, unknown map[string]string, err error) {
+	var settings any
+
+	decoder := json.NewDecoder(bytes.NewReader(data))
+	decoder.UseNumber()
+	if err = decoder.Decode(&settings); err != nil {
+		if err.Error() == "EOF" && len(data) == 0 {
+			return make(map[string]string), make(map[string]string), nil
+		}
+		return nil, nil, fmt.Errorf("unmarshal json: %w", err)
+	}
+
+	settingsMap, ok := settings.(map[string]any)
+	if !ok {
+		return make(map[string]string), make(map[string]string), nil
+	}
+
+	found, unknown = p.flatten(settingsMap)
+
+	return found, unknown, nil
+}
+
+func (p *Parser) flatten(settings map[string]any) (found, unknown map[string]string) {
+	found, unknown = make(map[string]string), make(map[string]string)
+	p.flattenDFS(settings, "", found, unknown)
+	return found, unknown
+}
+
+func (p *Parser) flattenDFS(m map[string]any, prefix string, found, unknown map[string]string) {
+	for k, v := range m {
+
+		if v == nil {
+			continue
+		}
+
+		newKey := k
+		if prefix != "" {
+			newKey = prefix + "." + k
+		}
+
+		if p.awaited[newKey] {
+			found[newKey] = p.conv(v)
+			continue
+		}
+
+		if subMap, ok := v.(map[string]any); ok {
+			p.flattenDFS(subMap, newKey, found, unknown)
+			continue
+		}
+
+		unknown[newKey] = p.conv(v)
+	}
+}

json/parse_test.go

@@ -0,0 +1,163 @@
+package json_test
+
+import (
+	"os"
+	"testing"
+
+	zfg "github.com/chaindead/zerocfg"
+	"github.com/chaindead/zerocfg/json"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestParse(t *testing.T) {
+	tests := []struct {
+		name    string
+		input   string
+		awaited map[string]bool
+		found   map[string]string
+		unknown map[string]string
+		wantErr bool
+	}{
+		{
+			name:  "simple key-value",
+			input: `{"str": "name", "int": 1}`,
+			awaited: map[string]bool{
+				"str": true,
+			},
+			found: map[string]string{
+				"str": `name`,
+			},
+			unknown: map[string]string{
+				"int": `1`,
+			},
+		},
+		{
+			name: "nested",
+			input: `{
+                "host": "localhost",
+                "database": {
+                    "port": 5432,
+                    "credentials": {
+                        "username": "admin"
+                    }
+                }
+            }`,
+			awaited: map[string]bool{
+				"database.credentials.username": true,
+			},
+			found: map[string]string{
+				"database.credentials.username": `admin`,
+			},
+			unknown: map[string]string{
+				"host":          `localhost`,
+				"database.port": `5432`,
+			},
+		},
+		{
+			name:  "array",
+			input: `{"tags": ["a", "b"]}`,
+			awaited: map[string]bool{
+				"tags": true,
+			},
+			found: map[string]string{
+				"tags": `["a","b"]`,
+			},
+			unknown: map[string]string{},
+		},
+		{
+			name:  "map",
+			input: `{"options": {"k1": 1, "k2": "v2"}}`,
+			awaited: map[string]bool{
+				"options": true,
+			},
+			found: map[string]string{
+				"options": `{"k1":1,"k2":"v2"}`,
+			},
+			unknown: map[string]string{},
+		},
+		{
+			name:  "null value is skipped",
+			input: `{"key1": "value1", "key2": null, "key3": 123}`,
+			awaited: map[string]bool{
+				"key1": true,
+				"key2": true,
+				"key3": true,
+			},
+			found: map[string]string{
+				"key1": `value1`,
+				"key3": `123`,
+			},
+			unknown: map[string]string{},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if tt.found == nil {
+				tt.found = map[string]string{}
+			}
+			if tt.unknown == nil {
+				tt.unknown = map[string]string{}
+			}
+
+			path := tempFile(t, tt.input)
+			p := json.New(&path)
+
+			found, unknown, err := p.Parse(tt.awaited, zfg.ToString)
+
+			if tt.wantErr {
+				assert.Error(t, err)
+			} else {
+				require.NoError(t, err)
+				assert.Equal(t, tt.found, found, "Found map mismatch")
+				assert.Equal(t, tt.unknown, unknown, "Unknown map mismatch")
+			}
+		})
+	}
+}
+
+func TestParse_Error(t *testing.T) {
+	path := tempFile(t, `{"invalid": "json",}`)
+	p := json.New(&path)
+
+	_, _, err := p.Parse(map[string]bool{}, zfg.ToString)
+	assert.Error(t, err)
+	assert.Contains(t, err.Error(), "unmarshal json")
+}
+
+func TestParse_EmptyInputNoError(t *testing.T) {
+	path := tempFile(t, ``)
+	p := json.New(&path)
+
+	found, unknown, err := p.Parse(map[string]bool{}, zfg.ToString)
+	assert.NoError(t, err)
+	assert.Empty(t, found)
+	assert.Empty(t, unknown)
+}
+
+func TestParse_FileNotExist(t *testing.T) {
+	nonExistentPath := "no_such_file.json"
+	p := json.New(&nonExistentPath)
+
+	found, unknown, err := p.Parse(map[string]bool{"some.key": true}, zfg.ToString)
+	require.NoError(t, err)
+	assert.Empty(t, found)
+	assert.Empty(t, unknown)
+}
+
+func tempFile(t *testing.T, data string) string {
+	f, err := os.CreateTemp("", "tmpjson-")
+	require.NoError(t, err)
+	t.Cleanup(func() {
+		f.Close()
+		os.Remove(f.Name())
+	})
+
+	_, err = f.WriteString(data)
+	require.NoError(t, err)
+
+	require.NoError(t, f.Close())
+
+	return f.Name()
+}