Complete foundational data layer with repository implementation

- Add GORM dependencies for SQLite and PostgreSQL
- Create domain models (User, Session, File) with common errors
- Implement repository interfaces and database layer with migrations
- Update WebApp to bootstrap with database and repositories
- Add comprehensive unit tests for repository methods
- Update config structure to support multiple database drivers
- Extend AGENTS.md with debugging principles and dependency rules

internal/repository/user_test.go

@@ -0,0 +1,192 @@
+package repository
+
+import (
+	"context"
+	"testing"
+
+	"gorm.io/driver/sqlite"
+	"gorm.io/gorm"
+
+	"github.com/dhao2001/mygo/internal/model"
+)
+
+func setupUserRepo(t *testing.T) UserRepository {
+	t.Helper()
+
+	db, err := gorm.Open(sqlite.Open(":memory:"), &gorm.Config{})
+	if err != nil {
+		t.Fatalf("open db: %v", err)
+	}
+	if err := db.AutoMigrate(&model.User{}); err != nil {
+		t.Fatalf("migrate: %v", err)
+	}
+
+	return NewUserRepository(db)
+}
+
+func TestUserRepository_Create(t *testing.T) {
+	repo := setupUserRepo(t)
+	ctx := context.Background()
+
+	user := &model.User{
+		ID:           "user-1",
+		Username:     "alice",
+		Email:        "alice@example.com",
+		PasswordHash: "hash",
+	}
+
+	if err := repo.Create(ctx, user); err != nil {
+		t.Fatalf("Create = %v", err)
+	}
+}
+
+func TestUserRepository_CreateDuplicateUsername(t *testing.T) {
+	repo := setupUserRepo(t)
+	ctx := context.Background()
+
+	u1 := &model.User{ID: "user-1", Username: "alice", Email: "alice@example.com", PasswordHash: "hash"}
+	u2 := &model.User{ID: "user-2", Username: "alice", Email: "alice2@example.com", PasswordHash: "hash"}
+
+	if err := repo.Create(ctx, u1); err != nil {
+		t.Fatalf("Create = %v", err)
+	}
+
+	err := repo.Create(ctx, u2)
+	if err != model.ErrDuplicate {
+		t.Fatalf("expected ErrDuplicate, got %v", err)
+	}
+}
+
+func TestUserRepository_FindByID(t *testing.T) {
+	repo := setupUserRepo(t)
+	ctx := context.Background()
+
+	user := &model.User{ID: "user-1", Username: "alice", Email: "alice@example.com", PasswordHash: "hash"}
+	if err := repo.Create(ctx, user); err != nil {
+		t.Fatalf("Create = %v", err)
+	}
+
+	found, err := repo.FindByID(ctx, "user-1")
+	if err != nil {
+		t.Fatalf("FindByID = %v", err)
+	}
+	if found.Username != "alice" {
+		t.Errorf("username = %q, want %q", found.Username, "alice")
+	}
+}
+
+func TestUserRepository_FindByIDNotFound(t *testing.T) {
+	repo := setupUserRepo(t)
+	ctx := context.Background()
+
+	_, err := repo.FindByID(ctx, "nonexistent")
+	if err != model.ErrNotFound {
+		t.Fatalf("expected ErrNotFound, got %v", err)
+	}
+}
+
+func TestUserRepository_FindByEmail(t *testing.T) {
+	repo := setupUserRepo(t)
+	ctx := context.Background()
+
+	user := &model.User{ID: "user-1", Username: "alice", Email: "alice@example.com", PasswordHash: "hash"}
+	if err := repo.Create(ctx, user); err != nil {
+		t.Fatalf("Create = %v", err)
+	}
+
+	found, err := repo.FindByEmail(ctx, "alice@example.com")
+	if err != nil {
+		t.Fatalf("FindByEmail = %v", err)
+	}
+	if found.ID != "user-1" {
+		t.Errorf("id = %q, want %q", found.ID, "user-1")
+	}
+}
+
+func TestUserRepository_FindByUsername(t *testing.T) {
+	repo := setupUserRepo(t)
+	ctx := context.Background()
+
+	user := &model.User{ID: "user-1", Username: "alice", Email: "alice@example.com", PasswordHash: "hash"}
+	if err := repo.Create(ctx, user); err != nil {
+		t.Fatalf("Create = %v", err)
+	}
+
+	found, err := repo.FindByUsername(ctx, "alice")
+	if err != nil {
+		t.Fatalf("FindByUsername = %v", err)
+	}
+	if found.Email != "alice@example.com" {
+		t.Errorf("email = %q, want %q", found.Email, "alice@example.com")
+	}
+}
+
+func TestUserRepository_Update(t *testing.T) {
+	repo := setupUserRepo(t)
+	ctx := context.Background()
+
+	user := &model.User{ID: "user-1", Username: "alice", Email: "alice@example.com", PasswordHash: "hash"}
+	if err := repo.Create(ctx, user); err != nil {
+		t.Fatalf("Create = %v", err)
+	}
+
+	user.Username = "alice2"
+	if err := repo.Update(ctx, user); err != nil {
+		t.Fatalf("Update = %v", err)
+	}
+
+	found, err := repo.FindByID(ctx, "user-1")
+	if err != nil {
+		t.Fatalf("FindByID = %v", err)
+	}
+	if found.Username != "alice2" {
+		t.Errorf("username = %q, want %q", found.Username, "alice2")
+	}
+}
+
+func TestUserRepository_Delete(t *testing.T) {
+	repo := setupUserRepo(t)
+	ctx := context.Background()
+
+	user := &model.User{ID: "user-1", Username: "alice", Email: "alice@example.com", PasswordHash: "hash"}
+	if err := repo.Create(ctx, user); err != nil {
+		t.Fatalf("Create = %v", err)
+	}
+
+	if err := repo.Delete(ctx, "user-1"); err != nil {
+		t.Fatalf("Delete = %v", err)
+	}
+
+	_, err := repo.FindByID(ctx, "user-1")
+	if err != model.ErrNotFound {
+		t.Fatalf("expected ErrNotFound after delete, got %v", err)
+	}
+}
+
+func TestUserRepository_List(t *testing.T) {
+	repo := setupUserRepo(t)
+	ctx := context.Background()
+
+	for i := range 5 {
+		user := &model.User{
+			ID:           "user-" + string(rune('0'+i)),
+			Username:     "user" + string(rune('0'+i)),
+			Email:        "user" + string(rune('0'+i)) + "@example.com",
+			PasswordHash: "hash",
+		}
+		if err := repo.Create(ctx, user); err != nil {
+			t.Fatalf("Create = %v", err)
+		}
+	}
+
+	users, total, err := repo.List(ctx, 0, 3)
+	if err != nil {
+		t.Fatalf("List = %v", err)
+	}
+	if len(users) != 3 {
+		t.Errorf("len(users) = %d, want %d", len(users), 3)
+	}
+	if total != 5 {
+		t.Errorf("total = %d, want %d", total, 5)
+	}
+}