add cnf/json parse() and get() + minimal tests

internal/cnf/json.go

@@ -0,0 +1,54 @@
+package cnf
+
+import (
+	"encoding/json"
+	"io"
+	"strings"
+)
+
+type Json struct {
+	data   interface{}
+	parsed bool
+}
+
+// Parse extract a reader as its JSON representation
+func (d *Json) Parse(_reader io.Reader) error {
+
+	// 1. get json decoder
+	decoder := json.NewDecoder(_reader)
+	err := decoder.Decode(&d.data)
+	if err != nil {
+		return err
+	}
+
+	d.parsed = true
+	return nil
+
+}
+
+// Get returns the value of a dot-separated path, and if it exists
+func (d *Json) Get(_path string) (string, bool) {
+
+	// 1. extract path
+	path := strings.Split(_path, ".")
+
+	// 2. Iterate over path / nested fields
+	current := d.data
+	for _, field := range path {
+		fmap, ok := current.(map[string]interface{})
+		if !ok { // incomplete path
+			return "", false
+		}
+
+		child, ok := fmap[field]
+		if !ok { // incomplete path
+			return "", false
+		}
+
+		current = child
+	}
+
+	// 3. Only return if string value
+	value, ok := current.(string)
+	return value, ok
+}

internal/cnf/json_test.go

@@ -0,0 +1,81 @@
+package cnf
+
+import (
+	"bytes"
+	"testing"
+)
+
+func TestSimpleJson(t *testing.T) {
+
+	tests := []struct {
+		raw string
+		key string
+	}{
+		{`{ "key": "value" }`, "key"},
+		{`{ "ignore": "xxx", "key": "value" }`, "key"},
+		{`{ "parent": { "child": "value" } }`, "parent.child"},
+		{`{ "ignore": "xxx", "parent": { "child": "value" } }`, "parent.child"},
+	}
+
+	for _, test := range tests {
+
+		parser := new(Json)
+		reader := bytes.NewBufferString(test.raw)
+
+		// try to extract value
+		err := parser.Parse(reader)
+		if err != nil {
+			t.Errorf("parse error: %s", err)
+			continue
+		}
+
+		// extract value
+		value, found := parser.Get(test.key)
+		if !found {
+			t.Errorf("expected a result, got none")
+			continue
+		}
+
+		// check value
+		if value != "value" {
+			t.Errorf("expected 'value' got '%s'", value)
+		}
+
+	}
+
+}
+
+func TestNotString(t *testing.T) {
+
+	tests := []struct {
+		raw string
+		key string
+	}{
+		{`{ "key": ["value"] }`, "key"},
+		{`{ "key": {"subkey": "value"} }`, "key"},
+		{`{ "parent": { "child": [ "value" ] } }`, "parent.child"},
+		{`{ "parent": { "child": { "subkey": "value" } } }`, "parent.child"},
+	}
+
+	for _, test := range tests {
+
+		parser := new(Json)
+		reader := bytes.NewBufferString(test.raw)
+
+		// try to extract value
+		err := parser.Parse(reader)
+		if err != nil {
+			t.Errorf("parse error: %s", err)
+			continue
+		}
+
+		// extract value
+		value, found := parser.Get(test.key)
+		if found || len(value) > 0 {
+			t.Errorf("expected no result, got '%s'", value)
+			continue
+		}
+
+	}
+
+}