Sse event parser

source/sse-session/constants.ts

@@ -0,0 +1,34 @@
+/**
+ * Regex that splits decoded SSE text into lines.
+ *
+ * The SSE wire format is line-oriented (`field: value` per line). Servers may
+ * send `\r\n` (HTTP default), `\n` (Unix), or `\r` (legacy Mac). Matching all
+ * three keeps parsing correct regardless of platform or server implementation.
+ */
+export const SSE_LINE_ENDINGS = /\r\n|\r|\n/;
+
+/**
+ * Regex that matches the single optional leading space in an SSE field value.
+ *
+ * Per the SSE spec, `field: value` may include one space immediately after the
+ * colon; that space is not part of the value. Used with `.replace()` to strip
+ * it when parsing lines such as `data: hello` → `hello`.
+ */
+export const SSE_FIELD_VALUE_REGEX = /^ /;
+
+/**
+ * Regex that matches a trailing newline at the end of a string.
+ *
+ * Multiple `data:` lines in one event are joined with `\n`. When the event is
+ * completed, this removes any stray trailing newline so callers receive the
+ * payload without an extra line break at the end.
+ */
+export const SSE_TRAILING_NEWLINE_REGEX = /\n$/;
+
+/**
+ * The newline character used when normalizing SSE text internally.
+ *
+ * Used to join consecutive `data:` lines into one payload and to reassemble
+ * buffered partial lines between streamed chunks before the next parse call.
+ */
+export const NEW_LINE = '\n';