fix(sse): handle empty lines and comments in SSE event stream #97

Previously, the SSE parser did not correctly handle empty lines and comments, which could lead to parsing errors. This commit addresses the issue by skipping empty lines and treating lines starting with `:` as comments, as per the SSE format specification. This change ensures that the SSE parser is more robust and adheres to the standard.

Author: phodal

src/main/kotlin/cc/unitmesh/devti/llms/azure/ResponseBodyCallback.kt

@@ -92,13 +92,28 @@ class ResponseBodyCallback(private val emitter: FlowableEmitter<SSE>, private va
                         null
                     }
 
-                    // : ping
+                    // skip `: ping` comments for: https://github.com/sysid/sse-starlette/issues/16
                     line!!.startsWith(": ping") -> {
                         null
                     }
 
                     else -> {
-                        throw SSEFormatException("Invalid sse format! '$line'")
+                        when {
+                            // sometimes the server maybe returns empty line
+                            line == "" -> {
+                                null
+                            }
+
+                            // : is comment
+                            // https://html.spec.whatwg.org/multipage/server-sent-events.html#parsing-an-event-stream
+                            line!!.startsWith(":") -> {
+                                null
+                            }
+
+                            else -> {
+                                throw SSEFormatException("Invalid sse format! '$line'")
+                            }
+                        }
                     }
                 }
             }