Simplified join with a global code

core/users.go

@@ -1,6 +1,8 @@
 package core
 
 import (
+	"errors"
+
 	"gorm.io/gorm"
 )
 
@@ -14,6 +16,31 @@ func (u *User) GetPlans(orm *gorm.DB) ([]Plan, error) {
 	return plans, err.Error
 }
 
+func (u *User) GetPlan(db *gorm.DB, plan_id uint) (Plan, error) {
+	var plan Plan = Plan{
+		ID: plan_id,
+	}
+	result := db.Take(&plan)
+
+	if errors.Is(result.Error, gorm.ErrRecordNotFound) {
+		return plan, ErrNotFound
+	} else if result.Error != nil {
+		return plan, result.Error
+	}
+
+	if plan.Owner == u.Username {
+		return plan, nil
+	}
+
+	isMember, err := plan.IsMember(db, u)
+
+	if !isMember || err != nil {
+		return plan, err
+	}
+
+	return plan, nil
+}
+
 func GetUser(orm *gorm.DB, username string) (User, error) {
 	user := User{Username: username}
 	if err := orm.Take(&user).Error; err != nil {