Add JSON concept exercise (marshal and unmarshal)

internal/exercises/catalog.yaml

@@ -134,6 +134,14 @@ concepts:
   test_regex: ".*"
   hints:
     - Define a custom error type and return it from a function.
+- slug: json
+  title: JSON
+  test_regex: ".*"
+  hints:
+    - Use the encoding/json package to work with JSON data.
+    - Implement MarshalPerson to convert a struct into JSON using json.Marshal.
+    - Implement UnmarshalPerson to convert a JSON string into a struct using json.Unmarshal.
+    - Handle and return errors properly in both functions.
 
 projects:
 - slug: 28_text_analyzer

internal/exercises/templates/36_json/json.go

@@ -0,0 +1,24 @@
+package json
+
+// Task:
+// Implement JSON encoding and decoding using Go's standard library.
+//
+// 1. Define a struct named Person with fields Name and Email.
+// 2. Implement MarshalPerson to convert a Person struct into JSON.
+// 3. Implement UnmarshalPerson to convert a JSON string into a Person struct.
+// 4. Handle and return errors properly in both functions.
+
+type Person struct {
+	Name  string `json:"name"`
+	Email string `json:"email"`
+}
+
+// MarshalPerson should convert a Person struct to a JSON string.
+func MarshalPerson(p Person) (string, error) {
+	return "", nil
+}
+
+// UnmarshalPerson should convert a JSON string to a Person struct.
+func UnmarshalPerson(jsonStr string) (Person, error) {
+	return Person{}, nil
+}

internal/exercises/templates/36_json/json_test.go

@@ -0,0 +1,33 @@
+package json
+
+import "testing"
+
+func TestMarshalPerson(t *testing.T) {
+	p := Person{Name: "golearn", Email: "golearn@example.com"}
+
+	jsonStr, err := MarshalPerson(p)
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+
+	expected := `{"name":"golearn","email":"golearn@example.com"}`
+	if jsonStr != expected {
+		t.Errorf("Expected %s, got %s", expected, jsonStr)
+	}
+}
+
+func TestUnmarshalPerson(t *testing.T) {
+	jsonStr := `{"name":"golearn","email":"golearn@example.com"}`
+
+	p, err := UnmarshalPerson(jsonStr)
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+
+	if p.Name != "golearn" {
+		t.Errorf("Expected name 'golearn', got %s", p.Name)
+	}
+	if p.Email != "golearn@example.com" {
+		t.Errorf("Expected email 'golearn@example.com', got %s", p.Email)
+	}
+}