Simplify SSE parsing

openai/init.moon

@@ -97,27 +97,6 @@ parse_completion_chunk = types.partial {
   }
 }
 
--- lpeg pattern to read a json data block from the front of a string, returns
--- the json blob and the rest of the string if it could parse one
-consume_json_head = do
-  import C, S, P from require "lpeg"
-
-  -- this pattern reads from the front just enough characters to consume a
-  -- valid json object
-  consume_json = P (str, pos) ->
-    str_len = #str
-    for k=pos+1,str_len
-      candidate = str\sub pos, k
-      parsed = false
-      pcall -> parsed = cjson.decode candidate
-      if parsed
-        return k + 1
-
-    return nil -- fail
-
-  S("\t\n\r ")^0 * P("data: ") * C(consume_json) * C(P(1)^0)
-
-
 parse_error_message = types.partial {
   error: types.partial {
     message: types.string\tag "message"
@@ -240,21 +219,36 @@ class OpenAI
     assert types.function(chunk_callback), "Must provide chunk_callback function when streaming response"
 
     accumulation_buffer = ""
+    streamed = false
 
     (...) ->
       chunk = ...
 
-      if type(chunk) == "string"
+      if chunk == nil
+        assert not streamed or accumulation_buffer\match"^%s*$", "buffer not empty"
+      elseif type(chunk) == "string"
         accumulation_buffer ..= chunk
 
         while true
-          json_blob, rest = consume_json_head\match accumulation_buffer
-          unless json_blob
+          event, rest = accumulation_buffer\match "^(.-)\r?\n\r?\n(.-)$"
+          unless event
             break
 
           accumulation_buffer = rest
-          if chunk = parse_completion_chunk cjson.decode json_blob
-            chunk_callback chunk
+          while event and #event>0
+            field, value, rest_evt = event\match "^(.-):%s+([^\r\n]+)(.-)$"
+            switch field
+              when "data"
+                streamed = true
+                unless value=="[DONE]"
+                  chunk_callback (cjson.decode value)
+              when "event","id","retry","" --comment
+                nil -- noop
+              when nil
+                error "Cannot parse SSE event: "..event
+              else
+                error ('Unknown field "%s" with value "%s"')\format(field, value)
+            event = #rest_evt>0 and rest_evt\match"^\r?\n(.*)"
 
       ...