[parsing/mfm] Add simple MFM parser

Iceshrimp.Parsing/Mfm.fs

@@ -188,6 +188,7 @@ module private MfmParser =
     // References
     let node, nodeRef = createParserForwardedToRef ()
     let inlineNode, inlineNodeRef = createParserForwardedToRef ()
+    let simple, simpleRef = createParserForwardedToRef ()
 
     let seqFlatten items =
         seq {
@@ -380,6 +381,11 @@ module private MfmParser =
           fnNode
           charNode ]
 
+    let simpleNodeSeq =
+        [ plainNode
+          emojiCodeNode
+          charNode ]
+
     let blockNodeSeq =
         [ plainNode; centerNode; smallNode; codeBlockNode; mathBlockNode; quoteNode ]
 
@@ -390,9 +396,13 @@ module private MfmParser =
 
     do inlineNodeRef.Value <- choice <| (seqAttempt inlineNodeSeq) |>> fun v -> v :?> MfmInlineNode
     
+    do simpleRef.Value <- choice <| seqAttempt simpleNodeSeq
+
     // Final parse command
     let parse = spaces >>. manyTill node eof .>> spaces
     
+    let parseSimple = spaces >>. manyTill simple eof .>> spaces
+
 open MfmParser
 
 module Mfm =
@@ -400,3 +410,8 @@ module Mfm =
         match runParserOnString parse 0 "" str with
         | Success(result, _, _) -> aggregateText result
         | Failure(s, _, _) -> failwith $"Failed to parse MFM: {s}"
+
+    let parseSimple str =
+        match runParserOnString parseSimple 0 "" str with
+        | Success(result, _, _) -> aggregateText result
+        | Failure(s, _, _) -> failwith $"Failed to parse MFM: {s}"