chore: reorganize directories

src/syntax/entity.rs

@@ -0,0 +1,120 @@
+use nom::{
+    branch::alt,
+    bytes::complete::{tag, take_while_m_n},
+    character::complete::alphanumeric1,
+    combinator::opt,
+    IResult,
+};
+
+use crate::{
+    entities::ENTITIES,
+    syntax::combinator::{backslash_token, node},
+    SyntaxKind,
+};
+
+use super::{combinator::GreenElement, input::Input};
+
+pub fn entity_node(input: Input) -> IResult<Input, GreenElement, ()> {
+    debug_assert!(input.s.starts_with('\\'));
+    let mut parser = alt((template1, template2));
+    crate::lossless_parser!(parser, input)
+}
+
+// \NAME POST or // \NAME{}
+fn template1(input: Input) -> IResult<Input, GreenElement, ()> {
+    let (input, backslash) = backslash_token(input)?;
+    let (input, name) = alphanumeric1(input)?;
+
+    if ENTITIES.iter().all(|i| i.0 != name.s) {
+        return Err(nom::Err::Error(()));
+    }
+    let (input, brackets) = opt(tag("{}"))(input)?;
+
+    if let Some(brackets) = brackets {
+        return Ok((
+            input,
+            node(
+                SyntaxKind::ENTITY,
+                [backslash, name.text_token(), brackets.text_token()],
+            ),
+        ));
+    }
+
+    if let Some(post) = input.bytes().next() {
+        if post.is_ascii_alphabetic() {
+            return Err(nom::Err::Error(()));
+        }
+    }
+
+    Ok((
+        input,
+        node(SyntaxKind::ENTITY, [backslash, name.text_token()]),
+    ))
+}
+
+// \_SPACES
+fn template2(input: Input) -> IResult<Input, GreenElement, ()> {
+    let (input, backslash) = backslash_token(input)?;
+    let (input, underscore) = tag("_")(input)?;
+    let (input, spaces) = take_while_m_n(1, 20, |c| c == ' ')(input)?;
+    Ok((
+        input,
+        node(
+            SyntaxKind::ENTITY,
+            [
+                backslash,
+                underscore.token(SyntaxKind::UNDERSCORE),
+                spaces.text_token(),
+            ],
+        ),
+    ))
+}
+
+#[test]
+fn parse() {
+    use crate::{ast::Entity, tests::to_ast, ParseConfig};
+
+    let to_entity = to_ast::<Entity>(entity_node);
+
+    insta::assert_debug_snapshot!(
+        to_entity("\\cent").syntax,
+        @r###"
+    ENTITY@0..5
+      BACKSLASH@0..1 "\\"
+      TEXT@1..5 "cent"
+    "###
+    );
+
+    insta::assert_debug_snapshot!(
+        to_entity("\\S").syntax,
+        @r###"
+    ENTITY@0..2
+      BACKSLASH@0..1 "\\"
+      TEXT@1..2 "S"
+    "###
+    );
+
+    insta::assert_debug_snapshot!(
+        to_entity("\\frac12{}test").syntax,
+        @r###"
+    ENTITY@0..9
+      BACKSLASH@0..1 "\\"
+      TEXT@1..7 "frac12"
+      TEXT@7..9 "{}"
+    "###
+    );
+
+    insta::assert_debug_snapshot!(
+        to_entity("\\_                   ").syntax,
+        @r###"
+    ENTITY@0..21
+      BACKSLASH@0..1 "\\"
+      UNDERSCORE@1..2 "_"
+      TEXT@2..21 "                   "
+    "###
+    );
+
+    let c = ParseConfig::default();
+
+    assert!(entity_node(("\\poi", &c).into()).is_err());
+}