1 files changed, 134 insertions, 0 deletions
diff --git a/src/ast.rs b/src/ast.rs
new file mode 100644
index 0000000..dc0aa79
--- /dev/null
+++ b/src/ast.rs
@@ -0,0 +1,134 @@
+use super::lparser::Rule;
+use std::rc::Rc;
+
+pub fn from_parse_tree(parse_tree: &mut pest::iterators::Pairs<Rule>) -> Program {
+    let root = parse_tree.next().unwrap();
+
+    match root.as_rule() {
+        Rule::program => {
+            let statements_with_eoi: Vec<pest::iterators::Pair<Rule>> = root.into_inner().collect();
+            let statements_split = statements_with_eoi.split_last().unwrap();
+            let statements = statements_split.1.to_vec();
+
+            statements
+                .iter()
+                .map(|s| Statement::from_pair(s.clone()))
+                .collect()
+        }
+        _ => panic!("[ast] first Pair is not a program"),
+    }
+}
+
+pub type Program = Vec<Statement>;
+
+#[derive(Debug)]
+pub enum Statement {
+    Definition {
+        symbol: Symbol,
+        expression: Rc<Expression>,
+    },
+    Expression(Rc<Expression>),
+}
+
+impl Statement {
+    fn from_pair(pair: pest::iterators::Pair<Rule>) -> Statement {
+        let def_or_expr = pair.into_inner().next().unwrap();
+
+        fn definition_from_pair(pair: pest::iterators::Pair<Rule>) -> Statement {
+            let mut inner = pair.into_inner();
+            let symbol = inner.next().unwrap().as_span().as_str();
+            let expression = inner.next().unwrap();
+            let expression_inners: Vec<ExpressionInner> = expression
+                .into_inner()
+                .map(ExpressionInner::from_pair)
+                .collect();
+
+            Statement::Definition {
+                symbol: String::from(symbol),
+                expression: expression_vec_to_tuple(&expression_inners),
+            }
+        }
+
+        match def_or_expr.as_rule() {
+            Rule::definition => definition_from_pair(def_or_expr),
+            Rule::expression => {
+                let expression_inners: Vec<ExpressionInner> = def_or_expr
+                    .into_inner()
+                    .map(ExpressionInner::from_pair)
+                    .collect();
+                Statement::Expression(expression_vec_to_tuple(&expression_inners))
+            }
+            rule => panic!("[ast] can't make a statement from {:#?}", rule),
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub enum ExpressionInner {
+    Symbol(Symbol),
+    IntegerLiteral(IntegerLiteral),
+    StringLiteral(StringLiteral),
+    Expression(Rc<Expression>),
+}
+
+impl ExpressionInner {
+    fn from_pair(pair: pest::iterators::Pair<Rule>) -> ExpressionInner {
+        match pair.as_rule() {
+            Rule::symbol => ExpressionInner::Symbol(string_from_pair(pair)),
+            Rule::integer_literal => ExpressionInner::IntegerLiteral(integer_from_pair(pair)),
+            Rule::string_literal => {
+                let s_with_quotes = string_from_pair(pair);
+                let mut chars = s_with_quotes.chars();
+                chars.next();
+                chars.next_back();
+                let s = chars.as_str();
+                ExpressionInner::StringLiteral(String::from(s))
+            }
+            Rule::expression => {
+                let expression_inners: Vec<ExpressionInner> =
+                    pair.into_inner().map(ExpressionInner::from_pair).collect();
+                ExpressionInner::Expression(expression_vec_to_tuple(&expression_inners))
+            }
+            rule => panic!("[ast] can't make an expression element from {:#?}", rule),
+        }
+    }
+}
+
+#[derive(Debug)]
+pub enum Expression {
+    Unary(ExpressionInner),
+    Binary(ExpressionInner, ExpressionInner),
+}
+
+fn expression_vec_to_tuple(v: &Vec<ExpressionInner>) -> Rc<Expression> {
+    match v.len() {
+        1 => Rc::new(Expression::Unary(v[0].clone())),
+        2 => Rc::new(Expression::Binary(v[0].clone(), v[1].clone())),
+        _ => {
+            let combined = ExpressionInner::Expression(Rc::new(Expression::Binary(
+                v[0].clone(),
+                v[1].clone(),
+            )));
+
+            let mut new_v = vec![combined];
+            for e in &v[2..] {
+                new_v.push(e.clone());
+            }
+
+            expression_vec_to_tuple(&new_v)
+        }
+    }
+}
+
+pub type IntegerLiteral = i64;
+fn integer_from_pair(pair: pest::iterators::Pair<Rule>) -> i64 {
+    let s = pair.as_span().as_str();
+    s.parse().unwrap()
+}
+
+pub type StringLiteral = String;
+fn string_from_pair(pair: pest::iterators::Pair<Rule>) -> String {
+    String::from(pair.as_span().as_str())
+}
+
+pub type Symbol = String;