# -*- coding: utf-8 -*-
# Part of Odoo. See LICENSE file for full copyright and licensing details.

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


class AccountMoveLine(models.Model):
    _inherit = 'account.move.line'
    
    # Override price_unit to use more decimal places
    price_unit = fields.Float(
        string='Unit Price',
        digits=(16, 6),  # Use 6 decimal places instead of the default 2
    )

    @api.onchange('price_subtotal')
    def _onchange_price_subtotal(self):
        """
        Recalculate price_unit when price_subtotal is manually edited.
        
        This method is triggered when a user modifies the price_subtotal field
        on a vendor bill line. It automatically calculates the unit price to
        maintain the exact entered subtotal amount.
        
        Requirements: 1.2, 1.3, 1.4, 3.1, 3.5, 5.3
        """
        for line in self:
            # Skip if not a vendor bill line or if in a computed context
            if line.move_id.move_type not in ('in_invoice', 'in_refund'):
                continue
            
            # Validate quantity is not zero
            if line.quantity == 0:
                raise UserError(_("Cannot calculate unit price: quantity must be greater than zero"))
            
            # Calculate price_unit from price_subtotal
            # Formula: price_unit = price_subtotal / quantity
            new_price_unit = line.price_subtotal / line.quantity
            
            # Set the price_unit - now with 6 decimal precision
            line.price_unit = new_price_unit

    @api.onchange('price_total')
    def _onchange_price_total(self):
        """
        Recalculate price_unit when price_total is manually edited.
        
        This method is triggered when a user modifies the price_total field
        on a vendor bill line. It automatically calculates the unit price by
        first deriving the price_subtotal from the price_total (accounting for
        taxes), then calculating the unit price.
        
        Requirements: 2.2, 2.3, 2.5, 3.1, 3.3, 3.4, 3.5, 5.3
        """
        for line in self:
            # Skip if not a vendor bill line or if in a computed context
            if line.move_id.move_type not in ('in_invoice', 'in_refund'):
                continue
            
            # Validate quantity is not zero
            if line.quantity == 0:
                raise UserError(_("Cannot calculate unit price: quantity must be greater than zero"))
            
            # Handle case with no taxes: price_total equals price_subtotal
            if not line.tax_ids:
                new_price_unit = line.price_total / line.quantity
                line.price_unit = new_price_unit
                continue
            
            # Check if any taxes are price-included
            # For tax-included taxes, the price_unit already includes the tax
            has_price_included_tax = any(tax.price_include for tax in line.tax_ids)
            
            if has_price_included_tax:
                # For tax-included taxes, price_unit = price_total / quantity
                # because the tax is already included in the unit price
                new_price_unit = line.price_total / line.quantity
                line.price_unit = new_price_unit
            else:
                # For tax-excluded taxes, we need to calculate the tax factor
                # Use a temporary price_unit of 1.0 to get the tax multiplier
                tax_results = line.tax_ids.compute_all(
                    price_unit=1.0,
                    currency=line.currency_id,
                    quantity=1.0,
                    product=line.product_id,
                    partner=line.move_id.partner_id
                )
                
                # Calculate the tax factor (total_included / total_excluded)
                # This tells us the multiplier from subtotal to total
                if tax_results['total_excluded'] != 0:
                    tax_factor = tax_results['total_included'] / tax_results['total_excluded']
                else:
                    tax_factor = 1.0
                
                # Derive price_subtotal from price_total
                # Formula: price_subtotal = price_total / tax_factor
                derived_price_subtotal = line.price_total / tax_factor
                
                # Calculate price_unit from derived price_subtotal
                # Formula: price_unit = price_subtotal / quantity
                new_price_unit = derived_price_subtotal / line.quantity
                
                line.price_unit = new_price_unit