What is the statute of limitations for an attorney malpractice action?

Finally, the malpractice complaint is not barred by the statute of limitations on its face. Pursuant to section 340.6, subdivision (a), an attorney malpractice action "shall be commenced within one year after the plaintiff discovers, or through the use of reasonable diligence should have discovered, the facts constituting the wrongful act or omission, or four years from the date of the wrongful act or omission, whichever occurs first." On its face, section 340.6, subdivision (a) states "'two distinct and alternative limitation periods: one year after actual or constructive discovery, or four years after occurrence (the date of the wrongful act or omission), whichever occurs first.'" (Samuels v. Mix (1999) 22 Cal.4th 1, 7.)