Initial project import

tools/v/vlib/veb/sse/sse.v

@@ -0,0 +1,92 @@
+module sse
+
+import veb
+import net
+import strings
+
+// This module implements the server side of `Server Sent Events`.
+// See https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events/Using_server-sent_events#event_stream_format
+// as well as https://html.spec.whatwg.org/multipage/server-sent-events.html#server-sent-events
+// for detailed description of the protocol, and a simple web browser client example.
+//
+// > Event stream format
+// > The event stream is a simple stream of text data which must be encoded using UTF-8.
+// > Messages in the event stream are separated by a pair of newline characters.
+// > A colon as the first character of a line is in essence a comment, and is ignored.
+// > Note: The comment line can be used to prevent connections from timing out;
+// > a server can send a comment periodically to keep the connection alive.
+// >
+// > Each message consists of one or more lines of text listing the fields for that message.
+// > Each field is represented by the field name, followed by a colon, followed by the text
+// > data for that field's value.
+
+@[params]
+pub struct SSEMessage {
+pub mut:
+	id    string
+	event string
+	data  string
+	retry int
+}
+
+@[heap]
+pub struct SSEConnection {
+pub mut:
+	conn &net.TcpConn @[required]
+}
+
+// start an SSE connection
+pub fn start_connection(mut ctx veb.Context) &SSEConnection {
+	if ctx.conn == unsafe { nil } {
+		eprintln('[veb.sse] WARNING: SSE requires a direct TCP connection (ctx.conn) which is not available. Use `ctx.takeover_conn()` before starting an SSE connection.')
+		return &SSEConnection{
+			conn: unsafe { nil }
+		}
+	}
+	// Build and send HTTP response headers directly.
+	// SSE responses must NOT include Content-Length since data is streamed.
+	mut sb := strings.new_builder(256)
+	sb.write_string('HTTP/1.1 200 OK\r\n')
+	sb.write_string('Content-Type: text/event-stream\r\n')
+	sb.write_string('Connection: keep-alive\r\n')
+	sb.write_string('Cache-Control: no-cache\r\n')
+	sb.write_string('Server: veb\r\n')
+	sb.write_string('\r\n')
+	ctx.conn.write(sb) or {}
+
+	return &SSEConnection{
+		conn: ctx.conn
+	}
+}
+
+// send_message sends a single message to the http client that listens for SSE.
+// It does not close the connection, so you can use it many times in a loop.
+pub fn (mut sse SSEConnection) send_message(message SSEMessage) ! {
+	if sse.conn == unsafe { nil } {
+		return error('SSE connection is not available (no TCP connection)')
+	}
+	mut sb := strings.new_builder(512)
+	if message.id != '' {
+		sb.write_string('id: ${message.id}\n')
+	}
+	if message.event != '' {
+		sb.write_string('event: ${message.event}\n')
+	}
+	if message.data != '' {
+		sb.write_string('data: ${message.data}\n')
+	}
+	if message.retry != 0 {
+		sb.write_string('retry: ${message.retry}\n')
+	}
+	sb.write_string('\n')
+	sse.conn.write(sb)!
+}
+
+// send a 'close' event and close the tcp connection.
+pub fn (mut sse SSEConnection) close() {
+	if sse.conn == unsafe { nil } {
+		return
+	}
+	sse.send_message(event: 'close', data: 'Closing the connection', retry: -1) or {}
+	sse.conn.close() or {}
+}