business: fix contact projection and phone sharing

(cherry picked from commit c0a0e5b52240ed415d3b43ba77659821887bf50b)

internal/app/userprojection/projection.go

@@ -0,0 +1,75 @@
+package userprojection
+
+import (
+	"context"
+
+	"telesrv/internal/domain"
+	"telesrv/internal/store"
+)
+
+// ForViewer applies the owner-specific user view that Telegram clients expect.
+// In particular, phone is visible for self and contacts; non-contacts should not
+// receive a phone field because TDesktop will prefer it over the public name.
+func ForViewer(ctx context.Context, contacts store.ContactStore, viewerUserID int64, users []domain.User) ([]domain.User, error) {
+	if contacts == nil || viewerUserID == 0 || len(users) == 0 {
+		return users, nil
+	}
+	out := make([]domain.User, len(users))
+	copy(out, users)
+	cache := make(map[int64]domain.User, len(users))
+	for i := range out {
+		u := out[i]
+		if u.ID == 0 || u.ID == viewerUserID || u.ID == domain.OfficialSystemUserID {
+			continue
+		}
+		if projected, ok := cache[u.ID]; ok {
+			out[i] = projected
+			continue
+		}
+		projected, err := projectOne(ctx, contacts, viewerUserID, u)
+		if err != nil {
+			return nil, err
+		}
+		cache[u.ID] = projected
+		out[i] = projected
+	}
+	return out, nil
+}
+
+// One applies ForViewer to a single user.
+func One(ctx context.Context, contacts store.ContactStore, viewerUserID int64, user domain.User) (domain.User, error) {
+	projected, err := ForViewer(ctx, contacts, viewerUserID, []domain.User{user})
+	if err != nil || len(projected) == 0 {
+		return domain.User{}, err
+	}
+	return projected[0], nil
+}
+
+func projectOne(ctx context.Context, contacts store.ContactStore, viewerUserID int64, user domain.User) (domain.User, error) {
+	contact, found, err := contacts.Get(ctx, viewerUserID, user.ID)
+	if err != nil {
+		return domain.User{}, err
+	}
+	if !found {
+		user.Phone = ""
+		user.Contact = false
+		user.Mutual = false
+		return user, nil
+	}
+	projected := user
+	projected.Contact = true
+	projected.Mutual = contact.Mutual || contact.User.Mutual
+	if contact.User.Phone != "" {
+		projected.Phone = contact.User.Phone
+	} else {
+		projected.Phone = contact.Phone
+	}
+	if contact.User.FirstName != "" || contact.User.LastName != "" {
+		projected.FirstName = contact.User.FirstName
+		projected.LastName = contact.User.LastName
+	} else if contact.FirstName != "" || contact.LastName != "" {
+		projected.FirstName = contact.FirstName
+		projected.LastName = contact.LastName
+	}
+	return projected, nil
+}