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-rw-r--r--state.go160
1 files changed, 160 insertions, 0 deletions
diff --git a/state.go b/state.go
new file mode 100644
index 0000000..48b8907
--- /dev/null
+++ b/state.go
@@ -0,0 +1,160 @@
+/*
+ * 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"
+ "fmt"
+ "net/http"
+ "strconv"
+ "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 fmt.Errorf("%w: %w", errUnexpectedDBError, err)
+ }
+ } else {
+ return fmt.Errorf("%w: %w", 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 fmt.Errorf("%w: %w", errUnexpectedDBError, err)
+ }
+ return nil
+}
+
+func setState(ctx context.Context, newState uint32) error {
+ if newState > 2 {
+ return fmt.Errorf("%w: %d", errInvalidState, newState)
+ }
+ err := saveStateValue(ctx, newState)
+ if err != nil {
+ return err
+ }
+ atomic.StoreUint32(&state, newState)
+ return nil
+}
+
+func handleState(w http.ResponseWriter, req *http.Request) {
+ sessionCookie, err := req.Cookie("session")
+ if errors.Is(err, http.ErrNoCookie) {
+ wstr(
+ w,
+ http.StatusUnauthorized,
+ "No session cookie, which is required for this endpoint",
+ )
+ return
+ } else if err != nil {
+ wstr(w, http.StatusBadRequest, "Error: Unable to check cookie.")
+ return
+ }
+
+ var userID, userName, userDepartment string
+ err = db.QueryRow(
+ req.Context(),
+ "SELECT id, name, department FROM users WHERE session = $1",
+ sessionCookie.Value,
+ ).Scan(&userID, &userName, &userDepartment)
+ if err != nil {
+ if errors.Is(err, pgx.ErrNoRows) {
+ wstr(
+ w,
+ http.StatusForbidden,
+ "Invalid session cookie",
+ )
+ return
+ }
+ wstr(
+ w,
+ http.StatusInternalServerError,
+ fmt.Sprintf(
+ "Error: Unexpected database error: %s",
+ err,
+ ),
+ )
+ return
+ }
+
+ if userDepartment != staffDepartment {
+ wstr(
+ w,
+ http.StatusForbidden,
+ "You are not authorized to view this page",
+ )
+ return
+ }
+
+ basePath := req.PathValue("s")
+ newState, err := strconv.ParseUint(basePath, 10, 32)
+ if err != nil {
+ wstr(
+ w,
+ http.StatusBadRequest,
+ "State must be an unsigned 32-bit integer",
+ )
+ return
+ }
+ err = setState(req.Context(), uint32(newState))
+ if err != nil {
+ wstr(
+ w,
+ http.StatusInternalServerError,
+ "Failed setting state, please return to previous page; are you sure it's within limits?",
+ )
+ return
+ }
+
+ http.Redirect(w, req, "/", http.StatusSeeOther)
+}