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/*
* WebSocket message handlers
*
* 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"
"fmt"
"strconv"
"strings"
"time"
"github.com/coder/websocket"
"github.com/jackc/pgx/v5"
"github.com/jackc/pgx/v5/pgconn"
)
func messageHello(ctx context.Context, c *websocket.Conn, mar []string, userID string, session string) error {
_, _ = mar, session
rows, err := db.Query(
ctx,
"SELECT courseid FROM choices WHERE userid = $1",
userID,
)
if err != nil {
return protocolError(ctx, c, "error fetching choices")
}
courseIDs, err := pgx.CollectRows(rows, pgx.RowTo[string])
if err != nil {
return protocolError(ctx, c, "error collecting choices")
}
err = writeText(ctx, c, "HI :"+strings.Join(courseIDs, ","))
if err != nil {
return fmt.Errorf("error replying to HELLO: %w", err)
}
return nil
}
func messageChooseCourse(ctx context.Context, c *websocket.Conn, mar []string, userID string, session string) error {
_ = session
if len(mar) != 2 {
return protocolError(ctx, c, "Invalid number of arguments for Y")
}
_courseID, err := strconv.ParseInt(mar[1], 10, strconv.IntSize)
if err != nil {
return protocolError(ctx, c, "Course ID must be an integer")
}
courseID := int(_courseID)
course := func() *courseT {
coursesLock.RLock()
defer coursesLock.RUnlock()
return courses[courseID]
}()
err = func() (returnedError error) { /* Named returns so I could modify them in defer */
tx, err := db.Begin(ctx)
if err != nil {
return protocolError(ctx, c, "Database error while beginning transaction")
}
defer func() {
err := tx.Rollback(ctx)
if err != nil && (!errors.Is(err, pgx.ErrTxClosed)) {
returnedError = protocolError(ctx, c, "Database error while rolling back transaction in defer block")
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 == "23505" {
err := writeText(ctx, c, "Y "+mar[1])
if err != nil {
return fmt.Errorf("error reaffirming course choice: %w", err)
}
return nil
}
return protocolError(ctx, c, "Database error while inserting course choice")
}
ok := func() bool {
course.SelectedLock.Lock()
defer course.SelectedLock.Unlock()
if course.Selected < course.Max {
course.Selected++
go propagateIgnoreFailures(fmt.Sprintf("N %d %d", courseID, course.Selected))
return true
}
return false
}()
if ok {
err := tx.Commit(ctx)
if err != nil {
go func() { /* Separate goroutine because we don't need a response from this operation */
course.SelectedLock.Lock()
defer course.SelectedLock.Unlock()
course.Selected--
propagateIgnoreFailures(fmt.Sprintf("N %d %d", courseID, course.Selected))
}()
return protocolError(ctx, c, "Database error while committing transaction")
}
err = writeText(ctx, c, "Y "+mar[1])
if err != nil {
return fmt.Errorf("error affirming course choice: %w", err)
}
} else {
err := tx.Rollback(ctx)
if err != nil {
return protocolError(ctx, c, "Database error while rolling back transaction due to course limit")
}
err = writeText(ctx, c, "R "+mar[1]+" :Full")
if err != nil {
return fmt.Errorf("error rejecting course choice: %w", err)
}
}
return nil
}()
if err != nil {
return err
}
return nil
}
func messageUnchooseCourse(ctx context.Context, c *websocket.Conn, mar []string, userID string, session string) error {
_ = session
if len(mar) != 2 {
return protocolError(ctx, c, "Invalid number of arguments for N")
}
_courseID, err := strconv.ParseInt(mar[1], 10, strconv.IntSize)
if err != nil {
return protocolError(ctx, c, "Course ID must be an integer")
}
courseID := int(_courseID)
course := func() *courseT {
coursesLock.RLock()
defer coursesLock.RUnlock()
return courses[courseID]
}()
ct, err := db.Exec(
ctx,
"DELETE FROM choices WHERE userid = $1 AND courseid = $2",
userID,
courseID,
)
if err != nil {
return protocolError(ctx, c, "Database error while deleting course choice")
}
if ct.RowsAffected() != 0 {
go func() { /* Separate goroutine because we don't need a response from this operation */
course.SelectedLock.Lock()
defer course.SelectedLock.Unlock()
course.Selected--
propagateIgnoreFailures(fmt.Sprintf("N %d %d", courseID, course.Selected))
}()
}
err = writeText(ctx, c, "N "+mar[1])
if err != nil {
return fmt.Errorf("error replying that course has been deselected: %w", err)
}
return nil
}
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