feat: Added standalone property and tweaked xmldecl parsing

src/glxml.gleam

@@ -1,16 +1,16 @@
+import gleam/option.{type Option, None}
 import gleam/result
 
 pub type Declaration {
-  Declaration(versioninfo: String, encoding: String)
+  Declaration(versioninfo: String, encoding: String, standalone: Bool)
 }
 
 pub type DocType {
-  None
   DocType(name: String)
 }
 
 pub type Document {
-  Document(decl: Declaration, doctype: DocType)
+  Document(decl: Declaration, doctype: Option(DocType))
 }
 
 pub fn main() {
@@ -23,8 +23,13 @@ fn parse_document(doc: String) -> Result(Document, Nil) {
   Ok(Document(decl, doctype))
 }
 
-fn parse_prolog(doc: String) -> Result(#(Declaration, DocType, String), Nil) {
-  use #(decl, doc) <- result.try(parse_decl(doc))
+fn parse_prolog(
+  doc: String,
+) -> Result(#(Declaration, Option(DocType), String), Nil) {
+  let #(decl, doc) = case parse_decl(doc) {
+    Ok(#(decl, doc)) -> #(decl, doc)
+    _ -> #(Declaration("1.0", "UTF-8", False), doc)
+  }
 
   Ok(#(decl, None, doc))
 }
@@ -37,9 +42,14 @@ fn parse_decl(doc: String) -> Result(#(Declaration, String), Nil) {
         Ok(e) -> e
         Error(_) -> #("", doc)
       }
+      let #(standalone, doc) = case parse_standalone(doc) {
+        Ok(e) -> e
+        Error(_) -> #(False, doc)
+      }
 
       case trim_space(doc) {
-        "?>" <> tail -> Ok(#(Declaration(versioninfo:, encoding:), tail))
+        "?>" <> tail ->
+          Ok(#(Declaration(versioninfo:, encoding:, standalone:), tail))
         _ -> Error(Nil)
       }
     }
@@ -142,6 +152,17 @@ fn parse_encoding(doc: String) -> Result(#(String, String), Nil) {
   }
 }
 
+fn parse_standalone(doc: String) -> Result(#(Bool, String), Nil) {
+  use #(_, doc) <- result.try(parse_space(doc))
+
+  case doc {
+    "standalone=\"yes\"" <> tail | "standalone='yes'" <> tail ->
+      Ok(#(True, tail))
+    "standalone=\"no\"" <> tail | "standalone='no'" <> tail -> Ok(#(True, tail))
+    _ -> Error(Nil)
+  }
+}
+
 fn do_parse_digit(doc: String) -> Result(#(String, String), Nil) {
   case doc {
     "0" as digit <> tail