from odoo import api, fields, models


class McStudentGuardian(models.Model):
    _name = "mc.student.guardian"
    _description = "Student Guardian Link"
    _order = "student_id, is_primary desc"

    student_id = fields.Many2one(
        "mc.student", string="Student", required=True, ondelete="cascade",
    )
    guardian_id = fields.Many2one(
        "mc.guardian", string="Guardian", required=True, ondelete="cascade",
    )
    relationship = fields.Selection(
        [
            ("father", "Father"),
            ("mother", "Mother"),
            ("legal_guardian", "Legal Guardian"),
            ("other", "Other"),
        ],
        string="Relationship", required=True,
    )
    is_primary = fields.Boolean(
        string="Primary", default=False,
        help="Notices go to the primary guardian only.",
    )

    _student_guardian_uniq = models.Constraint(
        "unique(student_id, guardian_id)",
        "This guardian is already linked to this student.",
    )

    def init(self):
        # At most one primary guardian per student, enforced at the database
        # level - the same belt-and-suspenders pattern as
        # mc.academic.year.is_current. See that model for why both the
        # ORM toggle and the partial index exist.
        self.env.cr.execute(
            "CREATE UNIQUE INDEX IF NOT EXISTS mc_student_guardian_one_primary_per_student "
            "ON mc_student_guardian (student_id) WHERE is_primary = true"
        )

    @api.depends("student_id.name", "guardian_id.name", "relationship")
    def _compute_display_name(self):
        relationship_labels = dict(self._fields["relationship"].selection)
        for link in self:
            label = relationship_labels.get(link.relationship, "")
            link.display_name = "%s -> %s (%s)" % (
                link.guardian_id.name or "?", link.student_id.name or "?", label,
            )

    def _unset_other_primary_links(self):
        for link in self:
            others = self.search([
                ("id", "!=", link.id),
                ("student_id", "=", link.student_id.id),
                ("is_primary", "=", True),
            ])
            if others:
                others.write({"is_primary": False})

    @api.model_create_multi
    def create(self, vals_list):
        # Unset the existing primary guardian for each affected student
        # BEFORE inserting, and flush immediately - create() issues a
        # direct SQL INSERT that will not wait for this pending write.
        for vals in vals_list:
            if vals.get("is_primary") and vals.get("student_id"):
                self.search([
                    ("student_id", "=", vals["student_id"]),
                    ("is_primary", "=", True),
                ]).write({"is_primary": False})
        self.env.flush_all()
        return super().create(vals_list)

    def write(self, vals):
        if vals.get("is_primary"):
            self._unset_other_primary_links()
        return super().write(vals)