13. Income Taxes (Details) - Schedule of Deferred Tax Assets and Liabilities - USD ($) $ in Thousands	Apr. 30, 2019	Apr. 30, 2018
Deferred tax assets:
Employee benefits	$ 5,092	$ 5,078
Inventory	1,649	1,129
Accounts receivable	204	213
Tax credits	1,300	1,213
Other assets	148	139
Capital Loss carry-forward	2,455	1,385
Net operating loss carry-forwards	5,556	6,451
Total deferred tax asset	16,404	15,608
Deferred tax liabilities:
Property, plant and equipment	(1,344)	(1,639)
Other liabilities	(343)	(821)
Deferred state income tax	(767)	(727)
Net deferred tax asset	13,950	12,421
Valuation allowance	(13,950)	(12,688)
Net deferred tax liability	0	(267)
Gross deferred assets	13,950	12,421
Valuation allowance	(13,950)	(12,688)
Net deferred tax (liability) asset	$ 0	$ (267)