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|
/*
* Handle the "Y" message for choosing a course
*
* 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"
"log/slog"
"strconv"
"sync/atomic"
"time"
"github.com/coder/websocket"
"github.com/jackc/pgx/v5"
"github.com/jackc/pgx/v5/pgconn"
)
func messageChooseCourse(
ctx context.Context,
c *websocket.Conn,
mar []string,
userID string,
userCourseGroups *userCourseGroupsT,
userCourseTypes *userCourseTypesT,
) error {
if atomic.LoadUint32(&state) != 2 {
err := writeText(ctx, c, "E :Course selections are not open")
if err != nil {
return wrapError(
errCannotSend,
err,
)
}
return nil
}
select {
case <-ctx.Done():
return wrapError(
errContextCanceled,
ctx.Err(),
)
default:
}
if len(mar) != 2 {
return errBadNumberOfArguments
}
_courseID, err := strconv.ParseInt(mar[1], 10, strconv.IntSize)
if err != nil {
return errNoSuchCourse
}
courseID := int(_courseID)
_course, ok := courses.Load(courseID)
if !ok {
return errNoSuchCourse
}
course, ok := _course.(*courseT)
if !ok {
panic("courses map has non-\"*courseT\" items")
}
if course == nil {
return errNoSuchCourse
}
if _, ok := (*userCourseGroups)[course.Group]; ok {
err := writeText(ctx, c, "R "+mar[1]+" :Group conflict")
if err != nil {
return wrapError(
errCannotSend,
err,
)
}
return nil
}
err = func() (returnedError error) {
tx, err := db.Begin(ctx)
if err != nil {
return wrapError(errUnexpectedDBError, err)
}
defer func() {
err := tx.Rollback(ctx)
if err != nil && (!errors.Is(err, pgx.ErrTxClosed)) {
returnedError = wrapError(errUnexpectedDBError, err)
return
}
}()
_, err = tx.Exec(
ctx,
"INSERT INTO choices (seltime, userid, courseid) VALUES ($1, $2, $3)",
time.Now().UnixMicro(),
userID,
courseID,
)
if err != nil {
var pgErr *pgconn.PgError
if errors.As(err, &pgErr) &&
pgErr.Code == pgErrUniqueViolation {
err2 := writeText(ctx, c, "Y "+mar[1])
if err2 != nil {
return wrapError(
err2,
wrapError(errUnexpectedDBError, err),
)
}
return nil
}
return wrapError(errUnexpectedDBError, err)
}
ok := func() bool {
course.SelectedLock.Lock()
defer course.SelectedLock.Unlock()
/*
* The read here doesn't have to be atomic because the
* lock guarantees that no other goroutine is writing to
* it.
*/
if course.Selected < course.Max {
atomic.AddUint32(&course.Selected, 1)
return true
}
return false
}()
if ok {
go func() {
defer func() {
if e := recover(); e != nil {
slog.Error("panic", "arg", e)
}
}()
propagateSelectedUpdate(course)
}()
err := tx.Commit(ctx)
if err != nil {
err := course.decrementSelectedAndPropagate(ctx, c)
if err != nil {
return wrapError(
errCannotSend,
err,
)
}
return wrapError(errUnexpectedDBError, err)
}
/*
* This would race if message handlers could run
* concurrently for one connection.
*/
(*userCourseGroups)[course.Group] = struct{}{}
(*userCourseTypes)[course.Type]++
err = writeText(ctx, c, "Y "+mar[1])
if err != nil {
return wrapError(
errCannotSend,
err,
)
}
if config.Perf.PropagateImmediate {
err = sendSelectedUpdate(ctx, c, courseID)
if err != nil {
return wrapError(
errCannotSend,
err,
)
}
}
} else {
err := tx.Rollback(ctx)
if err != nil {
return wrapError(errUnexpectedDBError, err)
}
err = writeText(ctx, c, "R "+mar[1]+" :Full")
if err != nil {
return wrapError(
errCannotSend,
err,
)
}
}
return nil
}()
if err != nil {
return err
}
return nil
}
|
