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

WEEKDAYS = [
    ("mon", "Monday"),
    ("tue", "Tuesday"),
    ("wed", "Wednesday"),
    ("thu", "Thursday"),
    ("fri", "Friday"),
    ("sat", "Saturday"),
]


class McTimetableSlot(models.Model):
    _name = "mc.timetable.slot"
    _description = "Timetable Slot"
    _order = "year_id desc, weekday, period"
    _rec_name = "display_name"

    batch_id = fields.Many2one("mc.batch", string="Batch", required=True, ondelete="cascade")
    weekday = fields.Selection(WEEKDAYS, string="Weekday", required=True)
    period = fields.Integer(string="Period", required=True)
    subject_id = fields.Many2one("mc.subject", string="Subject", required=True, ondelete="restrict")
    teacher_id = fields.Many2one("hr.employee", string="Teacher", ondelete="restrict")
    room_id = fields.Many2one("mc.room", string="Room", ondelete="restrict")
    year_id = fields.Many2one("mc.academic.year", string="Academic Year", required=True, ondelete="restrict")
    term_id = fields.Many2one("mc.academic.term", string="Term", ondelete="restrict")

    @api.depends("batch_id.name", "weekday", "period", "subject_id.name")
    def _compute_display_name(self):
        weekday_labels = dict(self._fields["weekday"].selection)
        for slot in self:
            slot.display_name = "%s - %s P%s - %s" % (
                slot.batch_id.name or "?",
                weekday_labels.get(slot.weekday, "?"),
                slot.period,
                slot.subject_id.name or "?",
            )

    def init(self):
        # A teacher or a room cannot hold two slots in the same
        # weekday+period (O5 spec, verbatim). Partial unique indexes are
        # the actual guarantee; _check_no_conflict below only exists to
        # turn the same violation into a message a scheduler can read,
        # and - same lesson as mc.enrollment - has to run BEFORE the
        # insert/update, because the index fires first otherwise.
        self.env.cr.execute(
            "CREATE UNIQUE INDEX IF NOT EXISTS mc_timetable_slot_teacher_no_clash "
            "ON mc_timetable_slot (teacher_id, weekday, period, year_id) "
            "WHERE teacher_id IS NOT NULL"
        )
        self.env.cr.execute(
            "CREATE UNIQUE INDEX IF NOT EXISTS mc_timetable_slot_room_no_clash "
            "ON mc_timetable_slot (room_id, weekday, period, year_id) "
            "WHERE room_id IS NOT NULL"
        )
        self.env.cr.execute(
            "CREATE UNIQUE INDEX IF NOT EXISTS mc_timetable_slot_batch_no_clash "
            "ON mc_timetable_slot (batch_id, weekday, period, year_id)"
        )

    def _check_no_conflict(self, vals, exclude_id=None):
        weekday = vals.get("weekday")
        period = vals.get("period")
        year_id = vals.get("year_id")
        if not (weekday and period and year_id):
            return
        base_domain = [
            ("weekday", "=", weekday), ("period", "=", period), ("year_id", "=", year_id),
        ]
        if exclude_id:
            base_domain.append(("id", "!=", exclude_id))

        batch_id = vals.get("batch_id")
        if batch_id and self.search_count(base_domain + [("batch_id", "=", batch_id)]):
            raise ValidationError(_(
                "This batch already has a slot on this weekday and period."
            ))
        teacher_id = vals.get("teacher_id")
        if teacher_id and self.search_count(base_domain + [("teacher_id", "=", teacher_id)]):
            raise ValidationError(_(
                "This teacher already has a slot on this weekday and period."
            ))
        room_id = vals.get("room_id")
        if room_id and self.search_count(base_domain + [("room_id", "=", room_id)]):
            raise ValidationError(_(
                "This room is already booked for this weekday and period."
            ))

    @api.model_create_multi
    def create(self, vals_list):
        for vals in vals_list:
            self._check_no_conflict(vals)
        return super().create(vals_list)

    def write(self, vals):
        if any(key in vals for key in ("weekday", "period", "year_id", "batch_id", "teacher_id", "room_id")):
            for slot in self:
                merged = {
                    "weekday": vals.get("weekday", slot.weekday),
                    "period": vals.get("period", slot.period),
                    "year_id": vals.get("year_id", slot.year_id.id),
                    "batch_id": vals.get("batch_id", slot.batch_id.id),
                    "teacher_id": vals.get("teacher_id", slot.teacher_id.id),
                    "room_id": vals.get("room_id", slot.room_id.id),
                }
                self._check_no_conflict(merged, exclude_id=slot.id)
        return super().write(vals)