From 51531b806f4a52a415ad938d9055d3609ba4479f Mon Sep 17 00:00:00 2001
From: Dane Johnson <daneallenjohnson@protonmail.com>
Date: Mon, 14 Feb 2022 10:42:49 -0600
Subject: [PATCH] Conditionals

---
 rust/src/parser.rs | 65 ++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 60 insertions(+), 5 deletions(-)

diff --git a/rust/src/parser.rs b/rust/src/parser.rs
index 8e2fa46..15d3e20 100644
--- a/rust/src/parser.rs
+++ b/rust/src/parser.rs
@@ -1,10 +1,11 @@
-#[derive(Debug,PartialEq)]
+#[derive(Debug,PartialEq,Clone)]
 pub enum Stmt {
     Assignment(String, Expr),
     Funcall(Expr),
+    Conditional(Vec<Expr>, Option<Expr>),
 }
 
-#[derive(Debug,PartialEq)]
+#[derive(Debug,PartialEq,Clone)]
 pub enum Expr {
     Id(String),
     Num(f64),
@@ -15,6 +16,13 @@ pub enum Expr {
     Mult(Box<Expr>, Box<Expr>),
     Div(Box<Expr>, Box<Expr>),
     Block(Vec<Stmt>),
+    GuardedBlock(Box<GuardedBlock>),
+}
+
+#[derive(Debug,PartialEq,Clone)]
+pub struct GuardedBlock {
+    pub guard: Expr,
+    pub block: Vec<Stmt>,
 }
 
 peg::parser! {
@@ -23,7 +31,8 @@ peg::parser! {
             = __*  s:stmt()* { s }
         pub rule stmt() -> Stmt
             = i:id() "<-" _ e:expr() stop() { Stmt::Assignment(i, e) } /
-            f:funcall() stop() { Stmt::Funcall(f) }
+            f:funcall() stop() { Stmt::Funcall(f) } /
+            c:conditional() { c }
         rule expr() -> Expr = precedence! {
             e1:(@) "+" _ e2:@ { Expr::Plus(Box::new(e1), Box::new(e2)) }
             e1:(@) "-" _ e2:@ { Expr::Minus(Box::new(e1), Box::new(e2)) }
@@ -37,8 +46,6 @@ peg::parser! {
             i:id() _ { Expr::Id(i) }
             n:num() _ { Expr::Num(n) }
         }
-        rule block() -> Expr
-            = stop() indent() __* s:stmt()+ dedent() { Expr::Block(s) }
 
         rule id() -> String
             = i:$(letter() (letter() / digit() / ['?'|'.'|'-'])*) _ { i.to_string() }
@@ -48,6 +55,28 @@ peg::parser! {
             = i:id() "(" _ e:(expr() ** ("," _)) ")" _ { Expr::Funcall(i, e) }
         rule funcdef() -> Expr
             = i:id()? "->" _ e:(expr() / block()) { Expr::Funcdef(i, Box::new(e)) }
+        rule conditional() -> Stmt
+            = i:_if() __* ei:elif()* __* e:_else()? __* { Stmt::Conditional([vec![i], ei].concat(), e) }
+        rule _if() -> Expr
+            = "if" _ g:expr() b:indented_block() {
+                Expr::GuardedBlock(Box::new(GuardedBlock {
+                    guard: g,
+                    block: b,
+                }))
+            }
+        rule elif() -> Expr
+            = "elif" _ g:expr() b:indented_block() {
+                Expr::GuardedBlock(Box::new(GuardedBlock {
+                    guard: g,
+                    block: b
+                }))
+            }
+        rule _else() -> Expr
+            = "else" _ b:block() { b }
+        rule block() -> Expr
+            = i:indented_block() { Expr::Block(i) }
+        rule indented_block() -> Vec<Stmt>
+            = stop() indent() __* s:stmt()+ dedent() { s }
 
         rule letter()
             = ['A'..='Z'] / ['a'..='z']
@@ -250,6 +279,32 @@ foo <- x -> y -> x * y";
         ];
         assert_eq!(deelang_parser::program(prgm).unwrap(), expected);
     }
+    #[test]
+    fn test_conditional() {
+        let prgm = r"if foo
+>>>bar()
+<<<
+elif baz
+>>>foobar()
+<<<
+else
+>>>quux()
+<<<";
+        let expected = vec![Stmt::Conditional(
+            vec![
+                Expr::GuardedBlock(Box::new(GuardedBlock {
+                    guard: Expr::Id("foo".to_string()),
+                    block: vec![Stmt::Funcall(Expr::Funcall("bar".to_string(), vec![]))]
+                })),
+                Expr::GuardedBlock(Box::new(GuardedBlock {
+                    guard: Expr::Id("baz".to_string()),
+                    block: vec![Stmt::Funcall(Expr::Funcall("foobar".to_string(), vec![]))]
+                })),
+            ],
+            Some(Expr::Block(vec![Stmt::Funcall(Expr::Funcall("quux".to_string(), vec![]))])),
+        )];
+        assert_eq!(deelang_parser::program(prgm).unwrap(), expected);
+    }
 
     #[test]
     fn test_preprocess() {