Add word-level parsing

src/syntax/content/parser/token/span.rs

@@ -0,0 +1,49 @@
+use std::fmt::Display;
+use crate::syntax::content::{Parseable, parser::lexeme::Lexeme};
+
+pub struct Span {
+    open: Option<bool>,
+}
+
+impl Span {
+    pub fn new(open: bool) -> Span {
+        Span { open: Some(open) }
+    }
+}
+
+impl Parseable for Span {
+    fn probe(_lexeme: &Lexeme) -> bool {
+        // there is no lexeme for span
+        false
+    }
+
+    fn lex(_lexeme: &Lexeme) -> Span {
+        Span { open: None }
+    }
+
+    fn render(&self) -> String {
+        if let Some(open) = self.open {
+            if open {
+                "<span>".to_owned()
+            } else {
+                "</span>".to_owned()
+            }
+        } else {
+            panic!("Attempt to render a span tag while open state is unknown")
+        }
+    }
+}
+
+impl Display for Span {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        if let Some(open) = self.open {
+            if open {
+                write!(f, "Open Span")
+            } else {
+                write!(f, "Closed Span")
+            }
+        } else {
+            write!(f, "Span (Unknown open state)")
+        }
+    }
+}