From d93ba45b0a952dea06f5cc5326eefb0818525912 Mon Sep 17 00:00:00 2001
From: Greg Brown <gmb60@cam.ac.uk>
Date: Fri, 30 Apr 2021 14:36:54 +0100
Subject: Move items in `nibble::cst` to `nibble`

---
 src/nibble/mod.rs | 474 +++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 473 insertions(+), 1 deletion(-)

(limited to 'src/nibble/mod.rs')

diff --git a/src/nibble/mod.rs b/src/nibble/mod.rs
index 41e895c..3f5c892 100644
--- a/src/nibble/mod.rs
+++ b/src/nibble/mod.rs
@@ -1,2 +1,474 @@
 pub mod convert;
-pub mod cst;
+
+use std::fmt;
+
+use proc_macro2::Span;
+use syn::{
+    bracketed,
+    ext::IdentExt,
+    parenthesized,
+    parse::{Parse, ParseStream},
+    punctuated::{Pair, Punctuated},
+    token::{Bracket, Comma, Let, Match, Paren},
+    LitStr, Token,
+};
+
+use crate::chomp::{ast, Name};
+
+use convert::{Context, Convert, ConvertError};
+
+pub type Epsilon = Token![_];
+
+pub type Ident = syn::Ident;
+
+pub type Literal = LitStr;
+
+#[derive(Clone)]
+pub struct ArgList<T> {
+    paren_token: Paren,
+    args: Punctuated<T, Comma>,
+}
+
+impl<T> ArgList<T> {
+    pub fn span(&self) -> Span {
+        self.paren_token.span
+    }
+
+    pub fn len(&self) -> usize {
+        self.args.len()
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.args.is_empty()
+    }
+}
+
+impl<T> IntoIterator for ArgList<T> {
+    type Item = T;
+
+    type IntoIter = <Punctuated<T, Comma> as IntoIterator>::IntoIter;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.args.into_iter()
+    }
+}
+
+impl<T: Parse> Parse for ArgList<T> {
+    fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
+        let args;
+        let paren_token = parenthesized!(args in input);
+        let args = args.call(Punctuated::parse_terminated)?;
+        Ok(Self { paren_token, args })
+    }
+}
+
+impl<T: fmt::Debug> fmt::Debug for ArgList<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "ArgList")?;
+        f.debug_list().entries(self.args.iter()).finish()
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct Call {
+    pub name: Ident,
+    pub args: ArgList<Expression>,
+}
+
+impl Call {
+    pub fn span(&self) -> Option<Span> {
+        self.name.span().join(self.args.span())
+    }
+}
+
+impl Parse for Call {
+    fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
+        let name = input.call(Ident::parse_any)?;
+        let args = input.parse()?;
+        Ok(Self { name, args })
+    }
+}
+
+#[derive(Clone)]
+pub struct Fix {
+    bracket_token: Bracket,
+    pub arg: Ident,
+    paren_token: Paren,
+    pub expr: Expression,
+}
+
+impl Fix {
+    pub fn span(&self) -> Option<Span> {
+        self.bracket_token.span.join(self.paren_token.span)
+    }
+}
+
+impl Parse for Fix {
+    fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
+        let arg;
+        let bracket_token = bracketed!(arg in input);
+        let arg = arg.call(Ident::parse_any)?;
+        let expr;
+        let paren_token = parenthesized!(expr in input);
+        let expr = expr.parse()?;
+        Ok(Self {
+            bracket_token,
+            arg,
+            paren_token,
+            expr,
+        })
+    }
+}
+
+impl fmt::Debug for Fix {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Fix")
+            .field("arg", &self.arg)
+            .field("expr", &self.expr)
+            .finish()
+    }
+}
+
+#[derive(Clone)]
+pub struct ParenExpression {
+    paren_token: Paren,
+    pub expr: Expression,
+}
+
+impl Parse for ParenExpression {
+    fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
+        let expr;
+        let paren_token = parenthesized!(expr in input);
+        let expr = expr.parse()?;
+        Ok(Self { paren_token, expr })
+    }
+}
+
+impl fmt::Debug for ParenExpression {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("ParenExpression")
+            .field("expr", &self.expr)
+            .finish()
+    }
+}
+
+#[derive(Clone)]
+pub enum Term {
+    Epsilon(Epsilon),
+    Ident(Ident),
+    Literal(Literal),
+    Call(Call),
+    Fix(Fix),
+    Parens(ParenExpression),
+}
+
+impl Term {
+    pub fn span(&self) -> Option<Span> {
+        match self {
+            Self::Epsilon(e) => Some(e.span),
+            Self::Ident(i) => Some(i.span()),
+            Self::Literal(l) => Some(l.span()),
+            Self::Call(c) => c.span(),
+            Self::Fix(f) => f.span(),
+            Self::Parens(p) => Some(p.paren_token.span),
+        }
+    }
+}
+
+impl Parse for Term {
+    fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
+        let lookahead = input.lookahead1();
+
+        if lookahead.peek(Token![_]) {
+            input.parse().map(Self::Epsilon)
+        } else if lookahead.peek(LitStr) {
+            input.parse().map(Self::Literal)
+        } else if lookahead.peek(Bracket) {
+            input.parse().map(Self::Fix)
+        } else if lookahead.peek(Paren) {
+            input.parse().map(Self::Parens)
+        } else if lookahead.peek(Ident::peek_any) {
+            let name = input.call(Ident::parse_any)?;
+
+            if input.peek(Paren) {
+                input.parse().map(|args| Self::Call(Call { name, args }))
+            } else {
+                Ok(Self::Ident(name))
+            }
+        } else {
+            Err(lookahead.error())
+        }
+    }
+}
+
+impl fmt::Debug for Term {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Term::Epsilon(_) => write!(f, "Term::Epsilon"),
+            Term::Ident(i) => write!(f, "Term::Ident({:?})", i),
+            Term::Literal(l) => write!(f, "Term::Literal({:?})", l.value()),
+            Term::Call(c) => write!(f, "Term::Call({:?})", c),
+            Term::Fix(x) => write!(f, "Term::Fix({:?})", x),
+            Term::Parens(p) => write!(f, "Term::Parens({:?})", p),
+        }
+    }
+}
+
+#[derive(Clone)]
+pub struct Cat(pub Punctuated<Term, Token![.]>);
+
+impl Parse for Cat {
+    fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
+        input.call(Punctuated::parse_separated_nonempty).map(Self)
+    }
+}
+
+impl Cat {
+    pub fn span(&self) -> Option<Span> {
+        let mut iter = self.0.pairs();
+        let span = match iter.next()? {
+            Pair::Punctuated(t, p) => t.span().and_then(|s| s.join(p.span)),
+            Pair::End(t) => t.span(),
+        }?;
+
+        iter.try_fold(span, |span, pair| match pair {
+            Pair::Punctuated(t, p) => t
+                .span()
+                .and_then(|s| span.join(s))
+                .and_then(|s| s.join(p.span)),
+            Pair::End(t) => t.span().and_then(|s| span.join(s)),
+        })
+    }
+}
+
+impl fmt::Debug for Cat {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "Cat")?;
+        f.debug_list().entries(self.0.iter()).finish()
+    }
+}
+
+#[derive(Clone)]
+pub struct Label {
+    colon_tok: Token![:],
+    pub label: Ident,
+}
+
+impl Label {
+    pub fn span(&self) -> Option<Span> {
+        self.colon_tok.span.join(self.label.span())
+    }
+}
+
+impl Parse for Label {
+    fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
+        let colon_tok = input.parse()?;
+        let label = input.call(Ident::parse_any)?;
+        Ok(Self { colon_tok, label })
+    }
+}
+
+impl fmt::Debug for Label {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Label").field("label", &self.label).finish()
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct Labelled {
+    pub cat: Cat,
+    pub label: Option<Label>,
+}
+
+impl Labelled {
+    pub fn span(&self) -> Option<Span> {
+        self.cat.span().and_then(|s| {
+            self.label
+                .as_ref()
+                .and_then(|l| l.span().and_then(|t| s.join(t)))
+        })
+    }
+}
+
+impl Parse for Labelled {
+    fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
+        let cat = input.parse()?;
+        let label = if input.peek(Token![:]) {
+            Some(input.parse()?)
+        } else {
+            None
+        };
+        Ok(Self { cat, label })
+    }
+}
+
+#[derive(Clone)]
+pub struct Alt(pub Punctuated<Labelled, Token![|]>);
+
+impl Alt {
+    pub fn span(&self) -> Option<Span> {
+        let mut iter = self.0.pairs();
+        let span = match iter.next()? {
+            Pair::Punctuated(t, p) => t.span().and_then(|s| s.join(p.span)),
+            Pair::End(t) => t.span(),
+        }?;
+
+        iter.try_fold(span, |span, pair| match pair {
+            Pair::Punctuated(t, p) => t
+                .span()
+                .and_then(|s| span.join(s))
+                .and_then(|s| s.join(p.span)),
+            Pair::End(t) => t.span().and_then(|s| span.join(s)),
+        })
+    }
+}
+
+impl Parse for Alt {
+    fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
+        input.call(Punctuated::parse_separated_nonempty).map(Self)
+    }
+}
+
+impl fmt::Debug for Alt {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "Alt")?;
+        f.debug_list().entries(self.0.iter()).finish()
+    }
+}
+
+pub type Expression = Alt;
+
+#[derive(Clone)]
+pub struct LetStatement {
+    let_token: Token![let],
+    name: Ident,
+    args: Option<ArgList<Ident>>,
+    eq_token: Token![=],
+    expr: Expression,
+    semi_token: Token![;],
+}
+
+impl LetStatement {
+    pub fn span(&self) -> Option<Span> {
+        self.let_token.span.join(self.semi_token.span)
+    }
+}
+
+impl Parse for LetStatement {
+    fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
+        let let_token = input.parse()?;
+        let name = input.call(Ident::parse_any)?;
+        let args = if input.peek(Paren) {
+            Some(input.parse()?)
+        } else {
+            None
+        };
+        let eq_token = input.parse()?;
+        let expr = input.parse()?;
+        let semi_token = input.parse()?;
+
+        Ok(Self {
+            let_token,
+            name,
+            args,
+            eq_token,
+            expr,
+            semi_token,
+        })
+    }
+}
+
+impl fmt::Debug for LetStatement {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("LetStatement")
+            .field("name", &self.name)
+            .field("args", &self.args)
+            .field("expr", &self.expr)
+            .finish()
+    }
+}
+
+#[derive(Clone)]
+pub struct GoalStatement {
+    match_token: Token![match],
+    expr: Expression,
+    semi_token: Token![;],
+}
+
+impl Parse for GoalStatement {
+    fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
+        let match_token = input.parse()?;
+        let expr = input.parse()?;
+        let semi_token = input.parse()?;
+
+        Ok(Self {
+            match_token,
+            expr,
+            semi_token,
+        })
+    }
+}
+
+impl fmt::Debug for GoalStatement {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("GoalStatement")
+            .field("expr", &self.expr)
+            .finish()
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct File {
+    lets: Vec<LetStatement>,
+    goal: GoalStatement,
+}
+
+impl File {
+    pub fn convert(self) -> Result<(Vec<ast::Function>, ast::NamedExpression), ConvertError> {
+        let mut names = Vec::new();
+        let mut map = Vec::new();
+        for stmt in self.lets {
+            let span = stmt.span();
+            let name: Name = stmt.name.into();
+            let params = stmt
+                .args
+                .into_iter()
+                .flat_map(ArgList::into_iter)
+                .map(Name::from);
+            let mut context = Context::new(&names, params.clone());
+            let mut expr = stmt.expr.convert(&mut context)?;
+            names.push(name.clone());
+            expr.name = Some(name.clone());
+            map.push(ast::Function {
+                name,
+                params: params.map(Some).collect(),
+                expr,
+                span,
+            });
+        }
+
+        let mut context = Context::new(&names, Vec::new());
+        let goal = self.goal.expr.convert(&mut context)?;
+        Ok((map, goal))
+    }
+}
+
+impl Parse for File {
+    fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
+        let mut lets = Vec::new();
+        let mut lookahead = input.lookahead1();
+
+        while lookahead.peek(Let) {
+            lets.push(input.parse()?);
+            lookahead = input.lookahead1();
+        }
+
+        let goal = if lookahead.peek(Match) {
+            input.parse()?
+        } else {
+            return Err(lookahead.error());
+        };
+
+        Ok(Self { lets, goal })
+    }
+}
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