from odoo import api, fields, models
from odoo.exceptions import ValidationError


class McAcademicYear(models.Model):
    _name = "mc.academic.year"
    _inherit = ["mail.thread"]
    _description = "Academic Year"
    _order = "date_start desc"
    _rec_name = "name"

    name = fields.Char(
        string="Name", required=True, tracking=True,
        help="School-facing label, e.g. 2026-27.",
    )
    date_start = fields.Date(string="Start Date", required=True, tracking=True)
    date_end = fields.Date(string="End Date", required=True, tracking=True)
    is_current = fields.Boolean(string="Current Year", default=False, tracking=True)
    term_ids = fields.One2many("mc.academic.term", "year_id", string="Terms")
    company_id = fields.Many2one(
        "res.company", string="Company", required=True,
        default=lambda self: self.env.company,
    )

    _name_company_uniq = models.Constraint(
        "unique(name, company_id)",
        "An academic year with this name already exists for this company.",
    )

    def init(self):
        # Belt-and-suspenders on top of the create/write auto-toggle below:
        # a partial unique index guarantees at most one current year per
        # company even if a write bypasses the ORM (direct SQL, a future
        # bug in the toggle logic, concurrent transactions).
        self.env.cr.execute(
            "CREATE UNIQUE INDEX IF NOT EXISTS mc_academic_year_one_current_per_company "
            "ON mc_academic_year (company_id) WHERE is_current = true"
        )

    @api.constrains("date_start", "date_end")
    def _check_dates(self):
        for year in self:
            if year.date_start and year.date_end and year.date_end <= year.date_start:
                raise ValidationError(
                    "Academic year '%s' end date must be after its start date." % year.name
                )

    def _unset_other_current_years(self):
        for year in self:
            others = self.search([
                ("id", "!=", year.id),
                ("company_id", "=", year.company_id.id),
                ("is_current", "=", True),
            ])
            if others:
                others.write({"is_current": False})

    @api.model_create_multi
    def create(self, vals_list):
        # Unset the existing current year for each affected company BEFORE
        # inserting the new one, and flush immediately: create() issues a
        # direct SQL INSERT that does not wait for unrelated pending writes
        # in the ORM cache, so without the flush here the old row is still
        # True in the database when the new row is inserted, tripping the
        # partial unique index mid-transaction.
        for vals in vals_list:
            if vals.get("is_current"):
                company_id = vals.get("company_id", self.env.company.id)
                self.search([
                    ("company_id", "=", company_id),
                    ("is_current", "=", True),
                ]).write({"is_current": False})
        self.env.flush_all()
        return super().create(vals_list)

    def write(self, vals):
        if vals.get("is_current"):
            self._unset_other_current_years()
        return super().write(vals)