1 files changed, 59 insertions, 0 deletions
diff --git a/backend/wsx.go b/backend/wsx.go
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+/*
+ * Generic WebSocket auxiliary functions
+ *
+ * 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/>.
+ */
+
+/*
+ * The message format is a WebSocket message separated with spaces.
+ * The contents of each field could contain anything other than spaces,
+ * The first character of each argument cannot be a colon. As an exception, the
+ * last argument may contain spaces and the first character thereof may be a
+ * colon, if the argument is prefixed with a colon. The colon used for the
+ * prefix is not considered part of the content of the message. For example, in
+ *
+ *    SQUISH POP :cat purr!!
+ *
+ * the first field is "SQUISH", the second field is "POP", and the third
+ * field is "cat purr!!".
+ *
+ * It is essentially an RFC 1459 IRC message without trailing CR-LF and
+ * without prefixes. See section 2.3.1 of RFC 1459 for an approximate
+ * BNF representation.
+ *
+ * The reason this was chosen instead of using protobuf etc. is that it
+ * is simple to parse without external libraries, and it also happens to
+ * be a format I'm very familiar with, having extensively worked with the
+ * IRC protocol.
+ */
+
+package main
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/coder/websocket"
+)
+
+func writeText(ctx context.Context, c *websocket.Conn, msg string) error {
+	err := c.Write(ctx, websocket.MessageText, []byte(msg))
+	if err != nil {
+		return fmt.Errorf("error writing to connection: %w", err)
+	}
+	return nil
+}