8. Net Income (Loss) Per Common Share (Details - Reconcilation of per share) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Apr. 30, 2021	Jan. 31, 2021	Oct. 31, 2020	Jul. 31, 2020	Apr. 30, 2020	Jan. 31, 2020	Oct. 31, 2019	Jul. 31, 2019	Apr. 30, 2021	Apr. 30, 2020	Apr. 30, 2019
Earnings Per Share [Abstract]
Net income (loss)	$ 1,991	$ 2,207	$ 2,284	$ 4,730	$ (4,768)	$ (2,104)	$ (430)	$ (3,164)	$ 11,212	$ (10,466)	$ (4,215)
Series E preferred stock accumulated dividends	(1,211)	(1,442)	(1,442)	(1,442)	$ (1,442)	$ (1,442)	$ (1,442)	$ (1,442)	(4,455)	(4,686)	(4,686)
Impact of Series E preferred stock redemption	$ (3,439)	$ 0	$ 0	$ 0					(3,439)	0	0
Net income (loss) attributable to common stockholders									$ 3,318	$ (15,152)	$ (8,901)
Weighted average common shares outstanding, basic									58,222	56,326	55,981
Stock options									909	0	0
RSUs									272	0	0
ESPP									23	0	0
Weighted average common shares outstanding, dilutive									59,426	56,326	55,981
Net income (loss) per share, basic									$ 0.06	$ (0.27)	$ (0.16)
Net income (loss) per share, diluted									$ 0.06	$ (0.27)	$ (0.16)