from odoo import fields, models


class McGradingScale(models.Model):
    _name = "mc.grading.scale"
    _description = "Grading Scale"
    _order = "name"
    _rec_name = "name"

    name = fields.Char(
        string="Name", required=True,
        help="e.g. CBSE, ICSE, IB, Cambridge, Ontario, Percentage.",
    )
    interval_ids = fields.One2many("mc.grading.interval", "scale_id", string="Grade Intervals")

    _name_uniq = models.Constraint(
        "unique(name)",
        "A grading scale with this name already exists.",
    )

    def get_grade_interval(self, percentage):
        """The grade for a percentage is the interval with the highest
        threshold at or below it - e.g. "90 and above = A1", "80-89 = A2".
        Grading rules live here, as data on mc.grading.interval, so a
        different board is configuration, never a code change (O6 spec,
        shared/DOMAIN_MODEL.md sec 5 - the moment you write `if board ==
        "CBSE"` you have already gotten this wrong).
        """
        self.ensure_one()
        candidates = self.interval_ids.filtered(lambda i: percentage >= i.threshold)
        return candidates.sorted("threshold", reverse=True)[:1]


class McGradingInterval(models.Model):
    _name = "mc.grading.interval"
    _description = "Grading Interval"
    _order = "threshold desc"
    _rec_name = "letter"

    scale_id = fields.Many2one("mc.grading.scale", string="Scale", required=True, ondelete="cascade")
    threshold = fields.Float(string="Threshold %", required=True)
    letter = fields.Char(string="Letter", required=True)
    point = fields.Float(string="Grade Point")
    description = fields.Char(string="Description")

    _scale_threshold_uniq = models.Constraint(
        "unique(scale_id, threshold)",
        "This scale already has an interval at this threshold.",
    )
    _threshold_range = models.Constraint(
        "check(threshold >= 0 and threshold <= 100)",
        "A threshold must be between 0 and 100.",
    )