feat: first commit

backend/internal/adapter/memory/user_repo.go

@@ -0,0 +1,60 @@
+package memory
+
+import (
+	"context"
+	"crypto/rand"
+	"sync"
+
+	"github.com/snip/backend/internal/domain"
+)
+
+type UserRepo struct {
+	mu     sync.RWMutex
+	byID   map[string]*domain.User
+	byKey  map[string]string // provider|subject -> id
+}
+
+func NewUserRepo() *UserRepo {
+	return &UserRepo{byID: make(map[string]*domain.User), byKey: make(map[string]string)}
+}
+
+func (r *UserRepo) Upsert(_ context.Context, u *domain.User) (*domain.User, error) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	key := u.Provider + "|" + u.Subject
+	if id, ok := r.byKey[key]; ok {
+		existing := r.byID[id]
+		existing.Email = u.Email
+		existing.Name = u.Name
+		cp := *existing
+		return &cp, nil
+	}
+	id := randomID()
+	u.ID = id
+	r.byID[id] = u
+	r.byKey[key] = id
+	cp := *u
+	return &cp, nil
+}
+
+func (r *UserRepo) GetByID(_ context.Context, id string) (*domain.User, error) {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+	u, ok := r.byID[id]
+	if !ok {
+		return nil, domain.ErrNotFound
+	}
+	cp := *u
+	return &cp, nil
+}
+
+func randomID() string {
+	const hex = "0123456789abcdef"
+	b := make([]byte, 16)
+	_, _ = rand.Read(b)
+	out := make([]byte, 16)
+	for i := range out {
+		out[i] = hex[int(b[i])%16]
+	}
+	return "u_" + string(out)
+}