feat: add get contact by id endpoint

cmd/camp/main.go

@@ -24,6 +24,7 @@ func main() {
 	contactHandler := contact.NewHandler(contactRepository)
 
 	http.HandleFunc("POST /api/contacts", contactHandler.Create)
+	http.HandleFunc("GET /api/contacts/{id}", contactHandler.GetByID)
 
 	log.Fatal(http.ListenAndServe(":8080", nil))
 }

internal/contact/handler.go

@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"net/http"
+	"strconv"
 )
 
 type Handler struct {
@@ -43,3 +44,32 @@ func (h *Handler) Create(w http.ResponseWriter, r *http.Request) {
 	}
 	json.NewEncoder(w).Encode(resp)
 }
+
+func (h *Handler) GetByID(w http.ResponseWriter, r *http.Request) {
+	idStr := r.PathValue("id")
+	if idStr == "" {
+		http.Error(w, "missing contact id", http.StatusBadRequest)
+		return
+	}
+
+	id, err := strconv.ParseInt(idStr, 10, 64)
+	if err != nil {
+		http.Error(w, "invalid contact id", http.StatusBadRequest)
+		return
+	}
+
+	contact, err := h.repo.GetContactByID(id)
+	if err != nil {
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+
+	if contact == nil {
+		http.Error(w, "contact not found", http.StatusNotFound)
+		return
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(http.StatusOK)
+	json.NewEncoder(w).Encode(contact)
+}

internal/contact/repository.go

@@ -221,3 +221,73 @@ func createContact(txn *sql.Tx, c *Contact) (int64, error) {
 
 	return lastId, nil
 }
+
+func (r *Repository) GetContactByID(id int64) (*Contact, error) {
+	query := `
+		SELECT
+			id,
+			fname,
+			lname,
+			email,
+			phone,
+			created_at,
+			updated_at
+		FROM contacts
+		WHERE id = ?
+		LIMIT 1
+`
+
+	var contact Contact
+	err := r.db.QueryRow(query, id).Scan(
+		&contact.ID,
+		&contact.FirstName,
+		&contact.LastName,
+		&contact.Email,
+		&contact.Phone,
+		&contact.CreatedAt,
+		&contact.UpdatedAt,
+	)
+
+	if err != nil {
+		if err == sql.ErrNoRows {
+			return nil, nil
+		}
+		return nil, fmt.Errorf("failed to get contact: %w", err)
+	}
+
+	tagsQuery := `
+		SELECT
+			t.id,
+			t.text,
+			t.created_at,
+			t.updated_at
+		FROM tags t
+		INNER JOIN contact_tag ct
+		ON t.id = ct.tag_id
+		WHERE ct.contact_id = ?
+`
+
+	rows, err := r.db.Query(tagsQuery, id)
+
+	if err != nil {
+		return nil, fmt.Errorf("failed to get tags: %w", err)
+	}
+	defer rows.Close()
+
+	var tags []Tag
+	for rows.Next() {
+		var tag Tag
+		if err := rows.Scan(&tag.ID, &tag.Text, &tag.CreatedAt, &tag.UpdatedAt); err != nil {
+			return nil, fmt.Errorf("failed to scan tag: %w", err)
+		}
+		tags = append(tags, tag)
+	}
+
+	if err := rows.Err(); err != nil {
+		return nil, fmt.Errorf("error iterating tags: %w", err)
+	}
+
+	contact.Tags = tags
+
+	return &contact, nil
+}

internal/contact/repository_test.go

@@ -162,6 +162,94 @@ func TestContactRepositoryThrowErrorIfTagsNotSent(t *testing.T) {
 	}
 }
 
+func TestContactRepositoryGetByID(t *testing.T) {
+	testDB = setupDB(t)
+	repo := NewRepository(testDB)
+
+	t.Run("get existing contact with all fields", func(t *testing.T) {
+		contact := &Contact{
+			FirstName: "John",
+			LastName:  "Doe",
+			Email:     "john@codersgyan.com",
+			Tags:      []Tag{{Text: "Tag1"}, {Text: "Tag2"}},
+			Phone:     "000-1234",
+		}
+
+		id, err := repo.CreateContactOrUpsertTags(contact)
+		if err != nil {
+			t.Fatalf("Failed to create contact: %v", err)
+		}
+
+		retrievedContact, err := repo.GetContactByID(id)
+		if err != nil {
+			t.Fatalf("Failed to get contact by ID: %v", err)
+		}
+
+		if retrievedContact == nil {
+			t.Fatal("Expected contact, got nil")
+		}
+
+		if retrievedContact.ID != id {
+			t.Errorf("Expected ID %d, got %d", id, retrievedContact.ID)
+		}
+		if retrievedContact.FirstName != contact.FirstName {
+			t.Errorf("Expected FirstName '%s', got '%s'", contact.FirstName, retrievedContact.FirstName)
+		}
+		if retrievedContact.LastName != contact.LastName {
+			t.Errorf("Expected LastName '%s', got '%s'", contact.LastName, retrievedContact.LastName)
+		}
+		if retrievedContact.Email != contact.Email {
+			t.Errorf("Expected Email '%s', got '%s'", contact.Email, retrievedContact.Email)
+		}
+		if retrievedContact.Phone != contact.Phone {
+			t.Errorf("Expected Phone '%s', got '%s'", contact.Phone, retrievedContact.Phone)
+		}
+		if len(retrievedContact.Tags) != len(contact.Tags) {
+			t.Fatalf("Expected %d tags, got %d", len(contact.Tags), len(retrievedContact.Tags))
+		}
+
+		tagTexts := make(map[string]bool)
+		for _, tag := range retrievedContact.Tags {
+			tagTexts[tag.Text] = true
+		}
+		for _, expectedTag := range contact.Tags {
+			if !tagTexts[expectedTag.Text] {
+				t.Errorf("Expected tag '%s' not found in retrieved tags", expectedTag.Text)
+			}
+		}
+	})
+
+	t.Run("non-existing contact with negative ID", func(t *testing.T) {
+		notFound, err := repo.GetContactByID(-1)
+		if err != nil {
+			t.Fatalf("Expected no error for non-existing contact, got: %v", err)
+		}
+		if notFound != nil {
+			t.Error("Expected nil for non-existing contact")
+		}
+	})
+
+	t.Run("non-existing contact with zero ID", func(t *testing.T) {
+		notFound, err := repo.GetContactByID(0)
+		if err != nil {
+			t.Fatalf("Expected no error for non-existing contact, got: %v", err)
+		}
+		if notFound != nil {
+			t.Error("Expected nil for non-existing contact")
+		}
+	})
+
+	t.Run("non-existing contact with large ID", func(t *testing.T) {
+		notFound, err := repo.GetContactByID(999999)
+		if err != nil {
+			t.Fatalf("Expected no error for non-existing contact, got: %v", err)
+		}
+		if notFound != nil {
+			t.Error("Expected nil for non-existing contact")
+		}
+	})
+}
+
 func setupDB(t *testing.T) *sql.DB {
 	db, err := sql.Open("sqlite3", ":memory:")
 	if err != nil {