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)
+}