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


class McExam(models.Model):
    _name = "mc.exam"
    _inherit = ["mail.thread"]
    _description = "Exam"
    _order = "date desc"
    _rec_name = "display_name"

    name = fields.Char(string="Name", required=True)
    term_id = fields.Many2one("mc.academic.term", string="Term", required=True, ondelete="restrict")
    batch_id = fields.Many2one("mc.batch", string="Batch", required=True, ondelete="restrict")
    subject_id = fields.Many2one("mc.subject", string="Subject", required=True, ondelete="restrict")
    max_marks = fields.Float(string="Max Marks", required=True, default=100)
    pass_marks = fields.Float(string="Pass Marks", required=True, default=35)
    date = fields.Date(string="Date", required=True)
    mark_ids = fields.One2many("mc.mark", "exam_id", string="Marks")

    _batch_subject_term_uniq = models.Constraint(
        "unique(batch_id, subject_id, term_id, name)",
        "An exam with this name already exists for this batch, subject and term.",
    )

    @api.depends("name", "batch_id.name", "subject_id.name")
    def _compute_display_name(self):
        for exam in self:
            exam.display_name = "%s - %s (%s)" % (
                exam.name, exam.batch_id.name or "?", exam.subject_id.name or "?",
            )

    @api.constrains("max_marks", "pass_marks")
    def _check_marks_positive(self):
        for exam in self:
            if exam.max_marks <= 0:
                raise ValidationError("Max marks must be greater than zero.")
            if exam.pass_marks < 0 or exam.pass_marks > exam.max_marks:
                raise ValidationError("Pass marks must be between 0 and max marks.")

    def action_enter_marks(self):
        self.ensure_one()
        enrollments = self.env["mc.enrollment"].search([
            ("batch_id", "=", self.batch_id.id), ("state", "=", "active"),
        ])
        existing_student_ids = set(self.mark_ids.mapped("student_id").ids)
        to_create = [
            {"exam_id": self.id, "student_id": enrollment.student_id.id, "marks_obtained": 0}
            for enrollment in enrollments
            if enrollment.student_id.id not in existing_student_ids
        ]
        if to_create:
            self.env["mc.mark"].create(to_create)
        return {
            "type": "ir.actions.act_window",
            "name": "Enter Marks - %s" % self.display_name,
            "res_model": "mc.mark",
            "view_mode": "list",
            "domain": [("exam_id", "=", self.id)],
            "context": {"default_exam_id": self.id},
        }