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use super::data::{Atom, GroupKind};
use super::loc::{Position, Span, Spanned};
use super::tokenizer::{Token, TokenError, Tokenizer, TokenizerConfig};
/// Element of S-Expr
#[derive(Debug, Clone)]
pub enum Element<'a> {
Group(GroupKind, Vec<SpannedElement<'a>>),
Atom(Atom<'a>),
Comment(&'a str),
}
impl<'a> Element<'a> {
/// Return the atom if the element is an atom, otherwise None
pub fn atom(&self) -> Option<&Atom<'a>> {
match self {
Element::Group(_, _) => None,
Element::Comment(_) => None,
Element::Atom(a) => Some(a),
}
}
/// Return the group elements if the element is a group of the right type, otherwise None
pub fn group(&self, grp: GroupKind) -> Option<&[SpannedElement<'a>]> {
match self {
Element::Group(got_grp, elements) if *got_grp == grp => Some(elements),
Element::Group(_, _) => None,
Element::Comment(_) => None,
Element::Atom(_) => None,
}
}
/// Return the group elements if the element is a paren group, otherwise None
pub fn paren(&self) -> Option<&[SpannedElement<'a>]> {
self.group(GroupKind::Paren)
}
/// Return the group elements if the element is a bracket group, otherwise None
pub fn bracket(&self) -> Option<&[SpannedElement<'a>]> {
self.group(GroupKind::Bracket)
}
/// Return the group elements if the element is a brace group, otherwise None
pub fn brace(&self) -> Option<&[SpannedElement<'a>]> {
self.group(GroupKind::Brace)
}
}
/// Spanned Element
pub type SpannedElement<'a> = Spanned<Element<'a>>;
/// S-Expr Parser
pub struct Parser<'a> {
tokenizer: Tokenizer<'a>,
}
/// Parser Error, which are either token error or some error related to group balancing
/// like unterminated group, or mismatch of group
#[derive(Debug, Clone)]
pub enum ParserError {
UnbalancedEmpty(Position, GroupKind),
UnbalancedMismatch {
span: Span,
expected: GroupKind,
got: GroupKind,
},
UnfinishedGroup(GroupKind),
TokenizerError(TokenError),
}
impl From<TokenError> for ParserError {
fn from(t: TokenError) -> ParserError {
ParserError::TokenizerError(t)
}
}
impl<'a> Parser<'a> {
pub fn new_with_config(data: &'a str, cfg: TokenizerConfig) -> Self {
Parser {
tokenizer: Tokenizer::new_with_config(data, cfg),
}
}
pub fn new(data: &'a str) -> Self {
Parser {
tokenizer: Tokenizer::new(data),
}
}
pub fn next(&mut self) -> Result<Option<SpannedElement<'a>>, ParserError> {
let mut out: Vec<(GroupKind, Span, Vec<SpannedElement<'a>>)> = vec![];
loop {
match self.tokenizer.next()? {
None => match out.last() {
None => return Ok(None),
Some((grp, _, _)) => return Err(ParserError::UnfinishedGroup(*grp)),
},
Some(tok) => match tok.inner {
Token::Comment(comment) => {
let el = Spanned {
span: tok.span,
inner: Element::Comment(comment),
};
match out.last_mut() {
None => return Ok(Some(el)),
Some((_, _, elements)) => {
elements.push(el);
}
}
}
Token::Atom(atom) => {
let el = Spanned {
span: tok.span,
inner: Element::Atom(atom),
};
match out.last_mut() {
None => return Ok(Some(el)),
Some((_, _, elements)) => {
elements.push(el);
}
}
}
Token::Left(grp) => {
// create a new group
out.push((grp, tok.span, Vec::new()));
}
Token::Right(grp) => match out.pop() {
None => {
return Err(ParserError::UnbalancedEmpty(tok.span.start, grp));
}
Some((inner_grp, inner_start, inner_elements)) => {
if inner_grp != grp {
return Err(ParserError::UnbalancedMismatch {
span: inner_start.extend(&tok.span),
expected: inner_grp,
got: grp,
});
}
let inner = Spanned {
span: inner_start.extend(&tok.span),
inner: Element::Group(grp, inner_elements),
};
match out.last_mut() {
None => return Ok(Some(inner)),
Some((_, _, elements)) => {
elements.push(inner);
}
}
}
},
},
}
}
}
}