3 files changed, 229 insertions, 13 deletions

diff --git a/src/ast.rs b/src/ast.rs
index 35bf6c3..fe986da 100644
--- a/src/ast.rs
+++ b/src/ast.rs
@@ -59,14 +59,15 @@ pub enum Statement {
 #[derive(Debug, Eq, PartialEq, Clone)]
 pub enum Expr {
     Node,
-    FieldAccess(Box<Expr>, Identifier),
     Unit,
     Lit(Literal),
     Ident(Identifier),
-    // List(Vec<Expr>),
+    FieldAccess(Box<Expr>, Identifier),
+    Index(Box<Expr>, Box<Expr>),
     Bin(Box<Expr>, BinOp, Box<Expr>),
     Unary(Box<Expr>, UnaryOp),
     Call(Call),
+    List(List),
     If(IfExpr),
     Block(Block),
 }
@@ -154,6 +155,18 @@ impl From<Call> for Expr {
     }
 }
 
+/// A list construction expression
+#[derive(Debug, Eq, PartialEq, Clone)]
+pub struct List {
+    pub items: Vec<Expr>,
+}
+
+impl From<List> for Expr {
+    fn from(list: List) -> Expr {
+        Expr::List(list)
+    }
+}
+
 #[derive(Debug, PartialEq, Eq, Clone, Copy)]
 pub enum Type {
     Unit,
@@ -161,6 +174,7 @@ pub enum Type {
     String,
     Boolean,
     Node,
+    List,
 }
 
 #[derive(Debug, PartialEq, Eq, Clone)]
diff --git a/src/eval.rs b/src/eval.rs
index 7822419..104571b 100644
--- a/src/eval.rs
+++ b/src/eval.rs
@@ -15,17 +15,17 @@ impl Variable {
         &self.value
     }
 
-    fn ty(&self) -> ast::Type {
-        self.ty
+    fn ty(&self) -> &ast::Type {
+        &self.ty
     }
 
     fn assign(&mut self, value: Value) -> Result {
-        if self.ty() == value.ty() {
+        if self.ty() == &value.ty() {
             self.value = value;
             Ok(self.value.clone())
         } else {
             Err(Error::TypeMismatch {
-                expected: self.ty(),
+                expected: self.ty().clone(),
                 got: value.ty(),
             })
         }
@@ -39,6 +39,7 @@ pub enum Value {
     String(String),
     Boolean(bool),
     Node(NodeId),
+    List(Vec<Value>),
 }
 
 type NodeId = usize;
@@ -51,6 +52,7 @@ impl Value {
             Self::String(_) => ast::Type::String,
             Self::Boolean(_) => ast::Type::Boolean,
             Self::Node(_) => ast::Type::Node,
+            Self::List(_) => ast::Type::List,
         }
     }
 
@@ -61,6 +63,7 @@ impl Value {
             ast::Type::String => Self::default_string(),
             ast::Type::Boolean => Self::default_bool(),
             ast::Type::Node => unreachable!(),
+            ast::Type::List => Self::default_list(),
         }
     }
 
@@ -76,6 +79,10 @@ impl Value {
         Self::String(String::default())
     }
 
+    fn default_list() -> Self {
+        Self::List(Vec::new())
+    }
+
     fn as_boolean(&self) -> std::result::Result<bool, Error> {
         match self {
             Self::Boolean(b) => Ok(*b),
@@ -116,6 +123,16 @@ impl Value {
         }
     }
 
+    fn as_list(&self) -> std::result::Result<Vec<Value>, Error> {
+        match self {
+            Self::List(values) => Ok(values.clone()),
+            v => Err(Error::TypeMismatch {
+                expected: ast::Type::List,
+                got: v.ty(),
+            }),
+        }
+    }
+
     fn add(&self, other: &Self) -> Result {
         match (self, other) {
             (Self::Integer(s), Self::Integer(o)) => Ok(Self::Integer(*s + *o)),
@@ -278,6 +295,13 @@ impl fmt::Display for Value {
             Self::String(s) => write!(f, "{s}"),
             Self::Boolean(b) => write!(f, "{b}"),
             Self::Node(id) => write!(f, "<node #{id}>"),
+            Self::List(items) => {
+                write!(f, "[")?;
+                for i in items {
+                    write!(f, "{i}")?;
+                }
+                write!(f, "]")
+            }
         }
     }
 }
@@ -300,6 +324,12 @@ impl From<&str> for Value {
     }
 }
 
+impl From<Vec<Value>> for Value {
+    fn from(value: Vec<Value>) -> Self {
+        Self::List(value)
+    }
+}
+
 type NodeKind = u16;
 
 #[derive(Debug, Default)]
@@ -371,11 +401,16 @@ pub enum Error {
     AlreadyBound(ast::Identifier),
     MalformedExpr(String),
     InvalidNodeKind(String),
+    NoParentNode(tree_sitter::Node<'static>),
     InvalidStringSlice {
         length: usize,
         start: i128,
         end: i128,
     },
+    ArrayOutOfBounds {
+        idx: i128,
+        len: usize
+    },
     // current node is only set in visitors, not in BEGIN or END blocks
     CurrentNodeNotPresent,
 }
@@ -484,6 +519,8 @@ impl Context {
             ast::Expr::Bin(lhs, op, rhs) => self.eval_bin(&*lhs, *op, &*rhs),
             ast::Expr::Unary(expr, op) => self.eval_unary(&*expr, *op),
             ast::Expr::Call(call) => self.eval_call(&*call),
+            ast::Expr::List(list) => self.eval_list(&*list),
+            ast::Expr::Index(target, idx) => self.eval_index(&*target, &*idx),
             ast::Expr::If(if_expr) => self.eval_if(if_expr),
             ast::Expr::Block(block) => self.eval_block(block),
             ast::Expr::Node => self.eval_node(),
@@ -704,10 +741,40 @@ impl Context {
                     .unwrap();
                 Ok(Value::String(text.to_owned()))
             }
+            ("parent", [arg]) => {
+                let v = self.eval_expr(arg)?;
+                let id = v.as_node()?;
+                let node = self.get_node_by_id(id).unwrap();
+                let parent = node.parent();
+                parent
+                    .map(|n| Value::Node(n.id()))
+                    .ok_or(Error::NoParentNode(node))
+            }
             (s, _) => Err(Error::FailedLookup(s.to_owned())),
         }
     }
 
+    fn eval_list(&mut self, list: &ast::List) -> Result {
+        let mut vals = vec![];
+        for i in &list.items {
+            vals.push(self.eval_expr(i)?);
+        }
+        Ok(vals.into())
+    }
+
+    fn eval_index(&mut self, target: &ast::Expr, idx: &ast::Expr) -> Result {
+        let mut target = self.eval_expr(target)?.as_list()?;
+        let idx = self.eval_expr(idx)?.as_int()?;
+        if idx < 0 || idx >= target.len() as i128 {
+            Err(Error::ArrayOutOfBounds {
+                idx,
+                len: target.len()
+            })
+        } else {
+            Ok(target.remove(idx as usize))
+        }
+    }
+
     fn eval_declaration(&mut self, decl: &ast::Declaration) -> Result {
         let initial_value = match decl.init.as_ref() {
             Some(init) => Some(self.eval_expr(&*init)?),
@@ -986,4 +1053,35 @@ mod test {
             }
         );
     }
+
+    #[test]
+    fn test_list() {
+        let language = tree_sitter_python::language();
+        let mut ctx = Context::new(language)
+            .with_program(ast::Program::new())
+            .unwrap();
+        assert_eq!(
+            ctx.eval_block(&ast::Block {
+                body: vec![ast::Statement::Declaration(ast::Declaration {
+                    ty: ast::Type::List,
+                    name: "a".to_owned(),
+                    init: Some(
+                        ast::Expr::List(ast::List {
+                            items: vec![ast::Expr::int(5)]
+                        })
+                        .boxed()
+                    ),
+                }),]
+            }),
+            Ok(Value::Unit)
+        );
+        assert_eq!(
+            ctx.lookup(&String::from("a")).unwrap().clone(),
+            Variable {
+                ty: ast::Type::List,
+                name: "a".to_owned(),
+                value: vec![5.into()].into(),
+            }
+        );
+    }
 }
diff --git a/src/parser.rs b/src/parser.rs
index 4ec8e57..15d03fe 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -169,28 +169,51 @@ fn parse_mul<'a>(i: &'a str) -> IResult<&'a str, Expr> {
     let div = parse_op("/", BinOp::Arith(ArithOp::Div));
     let mod_ = parse_op("%", BinOp::Arith(ArithOp::Mod));
     let op = alt((mul, div, mod_));
-    let recursive = parse_binary(parse_field_access, op, parse_mul);
-    let base = parse_field_access;
+    let recursive = parse_binary(parse_field_or_index, op, parse_mul);
+    let base = parse_field_or_index;
     alt((recursive, base)).parse(i)
 }
 
-fn parse_field_access<'a>(i: &'a str) -> IResult<&'a str, Expr> {
-    let trailing = map(tuple((ws(char('.')), ws(parse_ident))), |(_, i)| i);
+fn parse_field_or_index<'a>(i: &'a str) -> IResult<&'a str, Expr> {
+    enum FieldOrIndex {
+        Field(String),
+        Index(Expr),
+    }
+
     let (i, base) = parse_atom(i)?;
 
+    let field = map(tuple((ws(char('.')), ws(parse_ident))), |(_, i)| {
+        FieldOrIndex::Field(i)
+    });
+    let index = map(
+        tuple((ws(char('[')), parse_expr, ws(char(']')))),
+        |(_, idx, _)| FieldOrIndex::Index(idx),
+    );
+
     fold_many0(
-        trailing,
+        alt((field, index)),
         move || base.clone(),
-        move |acc, new| Expr::FieldAccess(acc.boxed(), new),
+        move |acc, new| match new {
+            FieldOrIndex::Field(f) => Expr::FieldAccess(acc.boxed(), f),
+            FieldOrIndex::Index(idx) => Expr::Index(acc.boxed(), idx.boxed()),
+        },
     )(i)
 }
 
+fn parse_list<'a>(i: &'a str) -> IResult<&'a str, List> {
+    let open = ws(char('['));
+    let items = separated_list0(char(','), parse_expr);
+    let close = ws(char(']'));
+    map(tuple((open, items, close)), |(_, items, _)| List { items }).parse(i)
+}
+
 fn parse_atom<'a>(i: &'a str) -> IResult<&'a str, Expr> {
     let inner = alt((
         map(tag("node"), |_| Expr::Node),
         map(parse_block, Expr::Block),
         map(parse_if, Expr::If),
         map(parse_call, Expr::Call),
+        map(parse_list, Expr::List),
         map(parse_lit, Expr::Lit),
         map(parse_ident, Expr::Ident),
         map(parse_unit, |_| Expr::Unit),
@@ -254,7 +277,8 @@ fn parse_type<'a>(i: &'a str) -> IResult<&'a str, Type> {
     let int = value(Type::Integer, tag("int"));
     let string = value(Type::String, tag("string"));
     let bool_ = value(Type::Boolean, tag("bool"));
-    alt((int, string, bool_)).parse(i)
+    let list = value(Type::List, tag("list"));
+    alt((int, string, bool_, list)).parse(i)
 }
 
 fn parse_declaration<'a>(i: &'a str) -> IResult<&'a str, Declaration> {
@@ -510,6 +534,27 @@ mod test {
                 )
             ))
         );
+        assert_eq!(
+            parse_expr("a[0]"),
+            Ok((
+                "",
+                Expr::Index(Expr::Ident("a".to_owned()).boxed(), Expr::int(0).boxed())
+            ))
+        );
+        assert_eq!(
+            parse_expr("children(node)[0]"),
+            Ok((
+                "",
+                Expr::Index(
+                    Expr::Call(Call {
+                        function: "children".to_owned(),
+                        parameters: vec![Expr::Node]
+                    })
+                    .boxed(),
+                    Expr::int(0).boxed()
+                )
+            ))
+        );
     }
 
     #[test]
@@ -544,6 +589,22 @@ mod test {
                 })
             ))
         );
+        assert_eq!(
+            parse_statement(r#"list a =["a", "b", "c"]; "#),
+            Ok((
+                "",
+                Statement::Declaration(Declaration {
+                    ty: Type::List,
+                    name: "a".to_owned(),
+                    init: Some(
+                        Expr::List(List {
+                            items: vec![Expr::str("a"), Expr::str("b"), Expr::str("c"),]
+                        })
+                        .boxed()
+                    )
+                })
+            ))
+        );
     }
 
     #[test]
@@ -624,6 +685,49 @@ mod test {
         );
     }
 
+    #[test]
+    fn test_parse_index() {
+        assert_eq!(
+            parse_expr(
+                r#"
+                a[0]
+                "#
+            ),
+            Ok((
+                "",
+                Expr::Index(Expr::Ident("a".to_owned()).boxed(), Expr::int(0).boxed()),
+            ))
+        );
+        assert_eq!(
+            parse_expr(r#"node.children[idx]"#),
+            Ok((
+                "",
+                Expr::Index(
+                    Expr::FieldAccess(Expr::Node.boxed(), Identifier::from("children")).boxed(),
+                    Expr::Ident("idx".to_owned()).boxed()
+                )
+            ))
+        );
+        assert_eq!(
+            parse_expr(r#"foo[i].bar[j]"#),
+            Ok((
+                "",
+                Expr::Index(
+                    Expr::FieldAccess(
+                        Expr::Index(
+                            Expr::Ident("foo".to_owned()).boxed(),
+                            Expr::Ident("i".to_owned()).boxed()
+                        )
+                        .boxed(),
+                        "bar".to_owned()
+                    )
+                    .boxed(),
+                    Expr::Ident("j".to_owned()).boxed()
+                ),
+            ))
+        );
+    }
+
     // #[test]
     // fn test_skip_query() {
     //     assert_eq!(