CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS) (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2021	Jan. 31, 2020
Income Statement [Abstract]
Revenues	$ 21,806	$ 13,585	$ 68,262	$ 47,152
Cost of revenues	15,604	12,800	47,098	41,921
Gross profit	6,202	785	21,164	5,231
Operating expenses:
Selling, general and administrative	4,018	2,996	12,009	10,989
Loss on lease termination	0	0	0	355
Total operating expenses	4,018	2,996	12,009	11,344
Operating income (loss)	2,184	(2,211)	9,155	(6,113)
Interest and other income, net	23	107	66	415
Net income (loss)	2,207	(2,104)	9,221	(5,698)
Comprehensive income (loss)	2,207	(2,104)	9,221	(5,698)
Series E preferred stock accumulated dividends	(1,442)	(1,442)	(3,604)	(3,604)
Net income (loss) attributable to common stockholders	$ 765	$ (3,546)	$ 5,617	$ (9,302)
Net income (loss) per share attributable to common stockholders:
Basic	$ 0.01	$ (0.06)	$ 0.10	$ (0.17)
Diluted	$ 0.01	$ (0.06)	$ 0.10	$ (0.17)
Weighted average common shares outstanding:
Basic	58,865	56,404	57,349	56,275
Diluted	60,097	56,404	58,058	56,275