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


class McFeeConcession(models.Model):
    _name = "mc.fee.concession"
    _inherit = ["mail.thread"]
    _description = "Fee Concession"
    _order = "student_id"
    _rec_name = "display_name"

    student_id = fields.Many2one("mc.student", string="Student", required=True, ondelete="cascade")
    concession_type = fields.Selection(
        [
            ("sibling", "Sibling"),
            ("merit", "Merit"),
            ("staff", "Staff"),
            ("need_based", "Need-based"),
        ],
        string="Type", required=True, tracking=True,
    )
    computation = fields.Selection(
        [("percent", "Percentage"), ("fixed", "Fixed Amount")],
        string="Computed As", required=True, default="percent", tracking=True,
    )
    value = fields.Float(string="Value", required=True, tracking=True,
                          help="A percentage (0-100) if computed as Percentage, otherwise a fixed amount.")
    reason = fields.Char(string="Reason", required=True)
    approver_id = fields.Many2one("res.users", string="Approved By", required=True, tracking=True)
    active = fields.Boolean(string="Active", default=True)

    @api.depends("student_id.name", "concession_type", "value", "computation")
    def _compute_display_name(self):
        for concession in self:
            value_label = "%.0f%%" % concession.value if concession.computation == "percent" else str(concession.value)
            concession.display_name = "%s - %s (%s)" % (
                concession.student_id.name or "?",
                dict(concession._fields["concession_type"].selection).get(concession.concession_type, "?"),
                value_label,
            )

    @api.constrains("computation", "value")
    def _check_percent_range(self):
        for concession in self:
            if concession.computation == "percent" and not (0 < concession.value <= 100):
                raise ValidationError(
                    "A percentage concession's value must be between 0 and 100."
                )
            if concession.value <= 0:
                raise ValidationError("A concession's value must be greater than zero.")