I need to check in my lines, the products I have, their respective quantities, and know what is the availability of such products in warehouses, the stock.move and stock.picking do something like that, but it's old api, I need a custom method.

This is my method:

class bsi_production_order(models.Model):
_name = 'bsi.production.order'

name = fields.Char('Reference', required=True, index=True, copy=False, readonly='True', default='New')
date = fields.Date(string="Production Date")
production_type = fields.Selection([
        ('budgeted','Budgeted'),
        ('nonbudgeted','Non Budgeted'),
        ('direct','Direct Order'),
    ], string='Type of Order', index=True,  
    track_visibility='onchange', copy=False,
    help=" ")
notes = fields.Text(string="Notes")
order_lines = fields.One2many('bsi.production.order.lines', 'production_order', states={'finished': [('readonly', True)], 'cancel': [('readonly', True)]}, string="Order lines", copy=True)
print_orders = fields.One2many('bsi.print.order', 'production_orders', string="Print Orders")
warehouse_quantity = fields.Char(compute='quantity', string='Quantity per warehouse')

class bsi_production_order_lines(models.Model):
_name = 'bsi.production.order.lines'

production_order = fields.Many2one('bsi.production.order', string="Production Orders")
isbn = fields.Many2one('product.product', string="ISBN", domain="[('is_isbn', '=', True)]")
qty = fields.Integer(string="Quantity")
consumed_qty = fields.Float(string="Consumed quantity")
remaining_qty = fields.Float(string="Remaining quantity")

I need to check from bsi.production.order on the order_lines One2many field, the isbn which is a product, how much of it is available on all the locations of the system, also, compare it to the qty field, so, from there I can go to another state on the object.

Think about the stock.picking or stock.move objects. It's basically the same logic.

So far, I've tried this method, to check if there is any line on the One2many object.

@api.multi
@api.depends('order_lines', 'order_lines.isbn')
def checkit(self):
    #actual_stock = self.env['product.product'].browse(qty_available)
    for record in self:
        if self.order_lines:
            for line in self.order_lines:
                if line.isbn:
                    return line.isbn
        else:
            raise Warning(('Enter​ ​at least​ ​1​ ​ISBN to produce'))

This works so far, to check whether there is a isbn on the line, or not, I'll need to also check if there is enough on warehouse to make the calculation, and if there is, then proceed to the next stage, I'm only tuck on the stock.location part.

I've checked some other modules on stock management OCA repo, although there are similar routines, I couldn't find something really suitable to this.

There is this method, which seems quite likely what I need:

@api.multi
@api.depends('order_lines', 'order_lines.isbn')
def quantity(self):
    for record in self:
        warehouse_quantity_text = ''
        isbn = self.env['product.product'].sudo().search([('product_tmpl_id', '=', record.id)])
        if isbn:
            quant_ids = self.env['stock.quant'].sudo().search([('isbn','=',isbn[0].id),('location_id.usage','=','internal')])
            t_warehouses = {}
            for quant in quant_ids:
                if quant.location_id:
                    if quant.location_id not in t_warehouses:
                        t_warehouses.update({quant.location_id:0})
                    t_warehouses[quant.location_id] += quant.qty

            tt_warehouses = {}
            for location in t_warehouses:
                warehouse = False
                location1 = location
                while (not warehouse and location1):
                    warehouse_id = self.env['stock.warehouse'].sudo().search([('lot_stock_id','=',location1.id)])
                    if len(warehouse_id) > 0:
                        warehouse = True
                    else:
                        warehouse = False
                    location1 = location1.location_id
                if warehouse_id:
                    if warehouse_id.name not in tt_warehouses:
                        tt_warehouses.update({warehouse_id.name:0})
                    tt_warehouses[warehouse_id.name] += t_warehouses[location]

            for item in tt_warehouses:
                if tt_warehouses[item] != 0:
                    warehouse_quantity_text = warehouse_quantity_text + ' ** ' + item + ': ' + str(tt_warehouses[item])
            record.warehouse_quantity = warehouse_quantity_text

But it doesn't works since it needs a field, also, I think it's far complex, there must be an easier way to do this checking.

In a nutshell: I need to check the quantities on the system, compare it to every isbn (product) on the line, which it'll be the qty field, if not enough, do nothing, if there is, then pass to the next state.

Any ideas?