from odoo import api, fields, models, _
from odoo.exceptions import UserError

class ProductUomChangeWizard(models.TransientModel):
    _name = 'product.uom.change.wizard'
    _description = 'Change Product UOM Wizard'

    product_tmpl_id = fields.Many2one('product.template', string='Product', required=True, readonly=True)
    current_uom_id = fields.Many2one('uom.uom', related='product_tmpl_id.uom_id', string='Current UOM', readonly=True)
    allowed_uom_ids = fields.Many2many('uom.uom', string='Allowed UOMs', compute='_compute_allowed_uom_ids')
    new_uom_id = fields.Many2one('uom.uom', string='New UOM', required=True)
    new_uom_po_id = fields.Many2one('uom.uom', string='New Purchase UOM')

    @api.depends('product_tmpl_id.uom_id')
    def _compute_allowed_uom_ids(self):
        for record in self:
            if record.product_tmpl_id.uom_id:
                # Find all UOMs that share the same root reference as the current UOM
                # uom.uom model now uses _has_common_reference logic, but simpler to search by root category if possible.
                # Since category_id is gone, we can group by root UoM if that concept exists, or rely on _has_common_reference.
                # However, for a domain, we need a list of IDs.
                # We can iterate all UOMs and check _has_common_reference, OR traverse up to the root and back down.
                # Looking at uom_uom.py: _order = 'sequence, relative_uom_id, id'.
                # fields: relative_uom_id (Reference Unit), related_uom_ids (Related UoMs).
                # To get all in "category", we need to find the root.
                
                # Let's traverse up to find the root.
                uom = record.product_tmpl_id.uom_id
                while uom.relative_uom_id:
                    uom = uom.relative_uom_id
                
                # uom is now the root. Now find all descendants.
                # A recursive search or using parent_path would be ideal if available/indexed.
                # uom.uom has parent_path.
                # parent_path structure: "root_id/child_id/..."
                # So all UOMs in same category start with same root_id in parent_path.
                root_id = uom.id
                domain = [('parent_path', '=like', f'{root_id}/%')]
                # Also include the root itself if it doesn't match the like pattern (which it usually doesn't as it is just "id/")
                # Wait, parent_path is updated by standard valid Parent/Child implementation.
                # Actually, simpler: search for uoms where root is the same.
                # But we don't have a stored 'root_id'.
                # Let's use the fact that we have the root uom 'uom'.
                # We can search for all uoms that have this root as ancestor?
                # Actually, standard Odoo usually just does `uom.search([])` and filters in python if the set is small, 
                # but UOMs can be many.
                # Let's look at uom_uom.py again. 
                # It has `_has_common_reference`.
                
                # A safer approach for now: Get all UOMs and filter. UOM table is usually small < 100.
                all_uoms = self.env['uom.uom'].search([])
                allowed = all_uoms.filtered(lambda u: u._has_common_reference(record.product_tmpl_id.uom_id))
                record.allowed_uom_ids = allowed
            else:
                record.allowed_uom_ids = False

    @api.model
    def default_get(self, fields):
        res = super(ProductUomChangeWizard, self).default_get(fields)
        if self.env.context.get('active_model') == 'product.template' and self.env.context.get('active_id'):
            res['product_tmpl_id'] = self.env.context['active_id']
        elif self.env.context.get('active_model') == 'product.product' and self.env.context.get('active_id'):
            product = self.env['product.product'].browse(self.env.context['active_id'])
            res['product_tmpl_id'] = product.product_tmpl_id.id
        return res

    def action_change_uom(self):
        self.ensure_one()
        if not self.new_uom_id._has_common_reference(self.product_tmpl_id.uom_id):
            raise UserError(_("New UOM must be in the same category as the current UOM."))

        # Update UOM via SQL to bypass the constraint check in product.template write
        self.env.cr.execute("UPDATE product_template SET uom_id = %s WHERE id = %s", (self.new_uom_id.id, self.product_tmpl_id.id))
        
        # Also update Purchase UOM if specified
        if self.new_uom_po_id:
            if not self.new_uom_po_id._has_common_reference(self.product_tmpl_id.uom_po_id):
                 raise UserError(_("New Purchase UOM must be in the same category as the current Purchase UOM."))
            self.env.cr.execute("UPDATE product_template SET uom_po_id = %s WHERE id = %s", (self.new_uom_po_id.id, self.product_tmpl_id.id))

        # Invalidate cache to ensure the new value is read
        self.product_tmpl_id.invalidate_recordset(['uom_id', 'uom_po_id'])
        
        # Log note in chatter
        self.product_tmpl_id.message_post(body=f"UOM forcefully changed from {self.current_uom_id.name} to {self.new_uom_id.name} via Wizard.")

        return {'type': 'ir.actions.act_window_close'}