diff options
Diffstat (limited to 'wsm.go')
| -rw-r--r-- | wsm.go | 177 |
1 files changed, 177 insertions, 0 deletions
@@ -0,0 +1,177 @@ +/* + * 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" + "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, userID, session + err := writeText(ctx, c, "HI") + 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 +} |