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/*
* Handle the unified global state
*
* Copyright (C) 2024 Runxi Yu <https://runxiyu.org>
* SPDX-License-Identifier: AGPL-3.0-or-later
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
package main
import (
"context"
"errors"
"sync/atomic"
"github.com/jackc/pgx/v5"
)
/*
* 0: Student access is disabled
* 1: Student have read-only access
* 2: Student can choose courses
*/
var state uint32 /* atomic */
func loadState() error {
var _state uint32
err := db.QueryRow(
context.Background(),
"SELECT value FROM misc WHERE key = 'state'",
).Scan(&_state)
if err != nil {
if errors.Is(err, pgx.ErrNoRows) {
_state = 0
_, err := db.Exec(
context.Background(),
"INSERT INTO misc(key, value) VALUES ('state', $1)",
_state,
)
if err != nil {
return wrapError(errUnexpectedDBError, err)
}
} else {
return wrapError(errUnexpectedDBError, err)
}
}
atomic.StoreUint32(&state, _state)
return nil
}
func saveStateValue(ctx context.Context, newState uint32) error {
_, err := db.Exec(
ctx,
"UPDATE misc SET value = $1 WHERE key = 'state'",
newState,
)
if err != nil {
return wrapError(errUnexpectedDBError, err)
}
return nil
}
func setState(ctx context.Context, newState uint32) error {
switch newState {
case 0:
cancelPool.Range(func(_, value interface{}) bool {
cancel, ok := value.(*context.CancelFunc)
if !ok {
panic("chanPool has non-\"*contect.CancelFunc\" values")
}
(*cancel)()
return false
})
case 1:
propagate("STOP")
case 2:
propagate("START")
default:
return errInvalidState
}
err := saveStateValue(ctx, newState)
if err != nil {
return err
}
atomic.StoreUint32(&state, newState)
return nil
}
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