rebel-parse, rebel-lang: implement if-else expressions

2 files changed, 29 insertions, 3 deletions

diff --git a/crates/rebel-parse/src/ast/expr.rs b/crates/rebel-parse/src/ast/expr.rs
index 2e8d750..3994296 100644
--- a/crates/rebel-parse/src/ast/expr.rs
+++ b/crates/rebel-parse/src/ast/expr.rs
@@ -34,6 +34,10 @@ pub enum Expr<'a> {
 		field: Ident<'a>,
 	},
 	Block(Block<'a>),
+	IfElse {
+		if_blocks: Vec<(Expr<'a>, Block<'a>)>,
+		else_block: Option<Box<Block<'a>>>,
+	},
 	Paren(Box<Expr<'a>>),
 	Path(Path<'a>),
 	Literal(Literal<'a>),
@@ -129,6 +133,19 @@ impl<'a> Expr<'a> {
 				}
 				Ok(())
 			}
+			Expr::IfElse {
+				if_blocks,
+				else_block,
+			} => {
+				for (cond, block) in if_blocks {
+					cond.validate()?;
+					block.validate()?;
+				}
+				if let Some(block) = else_block {
+					block.validate()?;
+				}
+				Ok(())
+			}
 			Expr::Paren(expr) => expr.validate(),
 			Expr::Path(_) => Ok(()),
 			Expr::Literal(lit) => lit.validate(),
diff --git a/crates/rebel-parse/src/grammar/recipe.rs b/crates/rebel-parse/src/grammar/recipe.rs
index 11f1ce6..1ada80c 100644
--- a/crates/rebel-parse/src/grammar/recipe.rs
+++ b/crates/rebel-parse/src/grammar/recipe.rs
@@ -133,15 +133,24 @@ peg::parser! {
 			}
 			base:@ p('.') field:field() { Expr::field(base, field) }
 			--
-			p('(') e:expr() p(')') { Expr::paren(e) }
-			p('{') block:block() p('}') { Expr::Block(block) }
 			e:atom() { e }
 		}
 
 		rule atom() -> Expr<'a>
-			= lit:literal() { Expr::Literal(lit) }
+			= p('(') e:expr() p(')') { Expr::paren(e) }
+			/ [Token::Keyword(Keyword::If)]
+				if_blocks:(cond_block() ++ ([Token::Keyword(Keyword::Else)] [Token::Keyword(Keyword::If)]))
+				else_block:([Token::Keyword(Keyword::Else)] p('{') block:block() p('}') { Box::new(block) })?
+			{
+				Expr::IfElse { if_blocks, else_block }
+			}
+			/ p('{') block:block() p('}') { Expr::Block(block) }
+			/ lit:literal() { Expr::Literal(lit) }
 			/ path:path() { Expr::Path(path) }
 
+		rule cond_block() -> (Expr<'a>, ast::Block<'a>)
+			= cond:expr() p('{') block:block() p('}') { (cond, block) }
+
 		rule call_params() -> Vec<expr::Expr<'a>>
 			= args:delimited(<expr()>, <p(',')>) { args }