feat: support subscript and superscript

src/syntax/subscript_superscript.rs

@@ -0,0 +1,162 @@
+use memchr::memchr2_iter;
+use nom::{
+    branch::alt,
+    bytes::complete::{tag, take_while1},
+    combinator::opt,
+    AsBytes, IResult, InputTake,
+};
+
+use crate::{
+    syntax::{
+        combinator::{caret_token, underscore_token},
+        object::object_nodes,
+    },
+    SyntaxKind,
+};
+
+use super::{
+    combinator::{l_curly_token, node, r_curly_token, GreenElement},
+    input::Input,
+};
+
+pub fn superscript_node(input: Input) -> IResult<Input, GreenElement, ()> {
+    let (input, caret) = caret_token(input)?;
+
+    let mut children = vec![caret];
+
+    if let Ok((input, star)) = tag::<&str, Input, ()>("*")(input) {
+        children.push(star.text_token());
+        Ok((input, node(SyntaxKind::SUPERSCRIPT, children)))
+    } else if let Ok((input, (l, contents, r))) = template1(input) {
+        children.push(l);
+        children.extend(object_nodes(contents));
+        children.push(r);
+        Ok((input, node(SyntaxKind::SUPERSCRIPT, children)))
+    } else if let Ok((input, (sign, contents))) = template2(input) {
+        if let Some(s) = sign {
+            children.push(s)
+        }
+        children.push(contents);
+        Ok((input, node(SyntaxKind::SUPERSCRIPT, children)))
+    } else {
+        Err(nom::Err::Error(()))
+    }
+}
+
+pub fn subscript_node(input: Input) -> IResult<Input, GreenElement, ()> {
+    let (input, underscore) = underscore_token(input)?;
+
+    let mut children = vec![underscore];
+
+    if let Ok((input, star)) = tag::<&str, Input, ()>("*")(input) {
+        children.push(star.text_token());
+        Ok((input, node(SyntaxKind::SUBSCRIPT, children)))
+    } else if let Ok((input, (l, contents, r))) = template1(input) {
+        children.push(l);
+        children.extend(object_nodes(contents));
+        children.push(r);
+        Ok((input, node(SyntaxKind::SUBSCRIPT, children)))
+    } else if let Ok((input, (sign, contents))) = template2(input) {
+        if let Some(s) = sign {
+            children.push(s)
+        }
+        children.push(contents);
+        Ok((input, node(SyntaxKind::SUBSCRIPT, children)))
+    } else {
+        Err(nom::Err::Error(()))
+    }
+}
+
+fn template1(input: Input) -> IResult<Input, (GreenElement, Input, GreenElement), ()> {
+    let (input, l) = l_curly_token(input)?;
+    let (input, contents) = balanced_brackets(input)?;
+    let (input, r) = r_curly_token(input)?;
+    Ok((input, (l, contents, r)))
+}
+
+fn template2(input: Input) -> IResult<Input, (Option<GreenElement>, GreenElement), ()> {
+    let (input, sign) = opt(alt((tag("+"), tag("-"))))(input)?;
+
+    let (input, contents) =
+        take_while1(|c: char| c.is_alphanumeric() || c == ',' || c == '\\' || c == '.')(input)?;
+
+    if contents.s.ends_with(|c: char| !c.is_alphanumeric()) {
+        return Err(nom::Err::Error(()));
+    }
+
+    Ok((input, (sign.map(|x| x.text_token()), contents.text_token())))
+}
+
+fn balanced_brackets(input: Input) -> IResult<Input, Input, ()> {
+    let mut pairs = 1;
+    let bytes = input.as_bytes();
+    for i in memchr2_iter(b'{', b'}', bytes) {
+        if bytes[i] == b'{' {
+            pairs += 1;
+        } else if pairs != 1 {
+            pairs -= 1;
+        } else {
+            return Ok(input.take_split(i));
+        }
+    }
+    Err(nom::Err::Error(()))
+}
+
+pub fn verify_pre(s: &str) -> bool {
+    dbg!(&s);
+    if s.is_empty() {
+        return false;
+    }
+    let last = s.as_bytes()[s.len() - 1];
+    last != b' ' && last != b'\t'
+}
+
+#[test]
+fn parse() {
+    use crate::ast::Subscript;
+    use crate::tests::to_ast;
+
+    let to_subscript = to_ast::<Subscript>(subscript_node);
+
+    insta::assert_debug_snapshot!(
+        to_subscript("_*").syntax,
+        @r###"
+    SUBSCRIPT@0..2
+      UNDERSCORE@0..1 "_"
+      TEXT@1..2 "*"
+    "###
+    );
+
+    insta::assert_debug_snapshot!(
+        to_subscript("_{*bo\nld*}").syntax,
+        @r###"
+    SUBSCRIPT@0..10
+      UNDERSCORE@0..1 "_"
+      L_CURLY@1..2 "{"
+      BOLD@2..9
+        STAR@2..3 "*"
+        TEXT@3..8 "bo\nld"
+        STAR@8..9 "*"
+      R_CURLY@9..10 "}"
+    "###
+    );
+
+    insta::assert_debug_snapshot!(
+        to_subscript("_+123").syntax,
+        @r###"
+    SUBSCRIPT@0..5
+      UNDERSCORE@0..1 "_"
+      TEXT@1..2 "+"
+      TEXT@2..5 "123"
+    "###
+    );
+
+    insta::assert_debug_snapshot!(
+        to_subscript("_abc").syntax,
+        @r###"
+    SUBSCRIPT@0..4
+      UNDERSCORE@0..1 "_"
+      TEXT@1..4 "abc"
+    "###
+    );
+}