from odoo import models

class StockPicking(models.Model):
    _inherit = 'stock.picking'

    def action_auto_generate_lots_subcontract(self):
        """
        Auto-generate lot names for move lines in this picking that:
        1. Have a product with tracking enabled (serial or lot).
        2. Have an empty 'lot_name' and no 'lot_id'.
        3. Have a product template with a configured 'lot_sequence_id'.
        """
        for picking in self:
            # We iterate over move_line_ids (operations)
            # Filter for lines that need a lot generated
            lines_to_process = picking.move_line_ids.filtered(
                lambda ml: (
                    ml.product_id 
                    and ml.product_id.tracking in ('serial', 'lot')
                    and not ml.lot_name 
                    and not ml.lot_id
                    and getattr(ml.product_id.product_tmpl_id, 'lot_sequence_id', False)
                )
            )

            for line in lines_to_process:
                # Get the sequence from the product template
                seq = line.product_id.product_tmpl_id.lot_sequence_id
                if seq:
                    # strict=True ensures we skip if next_by_id fails, though usually it returns None/False
                    new_lot_name = seq.next_by_id()
                    if new_lot_name:
                        line.lot_name = new_lot_name
        return True