library/library_checkout/models/library_checkout.py

from odoo import api, exceptions, fields, models

class Checkout(models.Model):
    _name = 'library.checkout'
    _description = 'Checkout Request'
    _inherit = ['mail.thread', 'mail.activity.mixin']
    
    member_id = fields.Many2one(
        'library.member',
        required=True)
    user_id = fields.Many2one(
        'res.users',
        'Librarian',
        default=lambda s: s.env.uid)
    request_date = fields.Date(
        default=lambda s: fields.Date.today())
    line_ids = fields.One2many(
        'library.checkout.line',
        'checkout_id',
        string='Borrowed Books',)
    stage_id = fields.Many2one(
        'library.checkout.stage',
        default='_default_stage',
        group_expand='_group_expand_stage_id')
    state = fields.Selection(related='stage_id.state')   
    checkout_date = fields.Date(readonly=True)
    closed_date = fields.Date(readonly=True)
    member_image = fields.Binary(related='member_id.partner_id.image_128')
    num_other_checkouts = fields.Integer(
        compute='_compute_num_other_checkouts')
    num_books = fields.Integer(compute='_compute_num_books',store=True)
    priority = fields.Selection(
        [('0', 'Low'),
        ('1', 'Normal'),
        ('2', 'High')],
        'Priority',
        default='1')
    kanban_state = fields.Selection(
        [('normal', 'In Progress'),
        ('blocked', 'Blocked'),
        ('done', 'Ready for next stage')],
        'Kanban State',
        default='normal')
    color = fields.Integer('Color Index')

    @api.depends('line_ids')
    def _compute_num_books(self):
        for book in self:
            book.num_books = len(book.line_ids)

    def _compute_num_other_checkouts(self):
        for rec in self:
            domain = [
                ('member_id', '=', rec.member_id.id),
                ('state', 'in', ['open']),
                ('id', '!=', rec.id)]
            rec.num_other_checkouts = self.search_count(domain)

    @api.model
    def create(self, vals):
        # Code before create: should use the `vals` dict
        if 'stage_id' in vals:
            Stage = self.env['library.checkout.stage']
            new_state = Stage.browse(vals['stage_id']).state
            if new_state == 'open':
                vals['checkout_date'] = fields.Date.today()
        new_record = super().create(vals)
        # Code after create: can use the `new_record` created
        if new_record.state == 'done':
            raise exceptions.UserError(
                'Not allowed to create a checkout in the done state.')
        return new_record
    
    def write(self, vals):
        # Code before write: can use `self`, with the old values
        if 'stage_id' in vals:
            Stage = self.env['library.checkout.stage']
            new_state = Stage.browse(vals['stage_id']).state
            if new_state == 'open' and self.state != 'open':
                vals['checkout_date'] = fields.Date.today()
            if new_state == 'done' and self.state != 'done':
                vals['closed_date'] = fields.Date.today()
        super().write(vals)
        # Code after write: can use `self`, with the updated values
        return True

    @api.model
    def _default_stage(self):
        Stage = self.env['library.checkout.stage']
        return Stage.search([], limit=1)

    @api.model
    def _group_expand_stage_id(self, stages, domain, order):
        return stages.search([], order=order)

    @api.onchange('member_id')
    def onchange_member_id(self):
        today = fields.Date.today()
        if self.request_date != today:
            self.request_date = fields.Date.today()
            return {
                'warning':{
                    'title': 'Changed Request Date',
                    'message': 'Request date changed to today.'
                }
            }

    def button_done(self):
        Stage = self.env['library.checkout.stage']
        done_stage = Stage.search(
            [('state', '=', 'done')],
            limit=1)
        for checkout in self:
            checkout.stage_id = done_stage
        return True



class CheckoutLine(models.Model):
    _name = 'library.checkout.line'
    _description = 'Borrow Request Line'
    checkout_id = fields.Many2one('library.checkout')
    book_id = fields.Many2one('library.book')