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


class McFeeSchedule(models.Model):
    _name = "mc.fee.schedule"
    _description = "Fee Installment Schedule"
    _order = "structure_id"
    _rec_name = "display_name"

    structure_id = fields.Many2one(
        "mc.fee.structure", string="Fee Structure", required=True, ondelete="cascade",
    )
    line_ids = fields.One2many("mc.fee.schedule.line", "schedule_id", string="Installments")
    total_percentage = fields.Float(
        string="Total %", compute="_compute_total_percentage", store=True,
        help="Must reach exactly 100% before this schedule can be used to generate an "
             "invoice - checked at that point, not while you are still building it up "
             "term by term.",
    )

    _structure_uniq = models.Constraint(
        "unique(structure_id)",
        "This fee structure already has an installment schedule.",
    )

    @api.depends("structure_id.display_name")
    def _compute_display_name(self):
        for schedule in self:
            schedule.display_name = "%s installments" % (schedule.structure_id.display_name or "?")

    @api.depends("line_ids.percentage")
    def _compute_total_percentage(self):
        for schedule in self:
            schedule.total_percentage = sum(schedule.line_ids.mapped("percentage"))


class McFeeScheduleLine(models.Model):
    _name = "mc.fee.schedule.line"
    _description = "Fee Installment"
    _order = "due_date"

    schedule_id = fields.Many2one(
        "mc.fee.schedule", string="Schedule", required=True, ondelete="cascade",
    )
    term_id = fields.Many2one("mc.academic.term", string="Term", required=True, ondelete="restrict")
    due_date = fields.Date(string="Due Date", required=True)
    percentage = fields.Float(string="Percentage", required=True)

    _percentage_range = models.Constraint(
        "check(percentage > 0 and percentage <= 100)",
        "An installment percentage must be between 0 and 100.",
    )
    _schedule_term_uniq = models.Constraint(
        "unique(schedule_id, term_id)",
        "This schedule already has an installment for this term.",
    )

    @api.constrains("percentage", "schedule_id")
    def _check_schedule_not_over_100(self):
        # Only guards against clearly-wrong data (allocating more than the
        # whole fee) at write time. Reaching exactly 100% is expected to
        # take several saves as terms are added one at a time - and is
        # enforced instead at the point it actually matters: when the
        # invoice-generation wizard resolves a schedule to use (see
        # wizards/mc_fee_invoice_generate_wizard.py).
        for line in self:
            total = sum(line.schedule_id.line_ids.mapped("percentage"))
            if total > 100.01:
                raise ValidationError(
                    "The installments for '%s' add up to more than 100%% (%.2f%%)." % (
                        line.schedule_id.display_name, total,
                    )
                )