From eecde7635c623599a4a5ae8c484313cba2acdf6f Mon Sep 17 00:00:00 2001
From: Erin <erin@erindesu.cz>
Date: Fri, 11 Jun 2021 17:52:47 +0200
Subject: [PATCH] Basic BfFunctio support

---
 src/ast.rs       |  5 +++++
 src/interpret.rs |  1 +
 src/parser.rs    | 50 ++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 56 insertions(+)

diff --git a/src/ast.rs b/src/ast.rs
index 1aa3453f..d599c860 100644
--- a/src/ast.rs
+++ b/src/ast.rs
@@ -63,6 +63,11 @@ pub enum StmtKind {
         args: Vec<Iden>,
         body: Block,
     },
+    BfFunctio {
+        iden: Iden,
+        tape_len: Option<Expr>,
+        code: String,
+    },
     Call {
         iden: Iden,
         args: Vec<Expr>,
diff --git a/src/interpret.rs b/src/interpret.rs
index 3ae0e9d9..5775f738 100644
--- a/src/interpret.rs
+++ b/src/interpret.rs
@@ -208,6 +208,7 @@ impl ExecEnv {
                 args: _,
                 body: _,
             } => todo!(),
+            StmtKind::BfFunctio { .. } => todo!(),
             // This is missing from StmtKind after the interpreter
             // rewrite; presumably, parsing is not yet implemented for
             // it. ~~Alex
diff --git a/src/parser.rs b/src/parser.rs
index 19294c33..15190dfe 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -62,6 +62,7 @@ impl<'source> Parser<'source> {
                 self.functio_flow()?,
                 start..self.lexer.span().end,
             )),
+            Token::Bff => Ok(Stmt::new(self.bff_flow()?, start..self.lexer.span().end)),
             Token::Var => Ok(Stmt::new(self.var_flow()?, start..self.lexer.span().end)),
             Token::Melo => Ok(Stmt::new(self.melo_flow()?, start..self.lexer.span().end)),
             Token::Loop => Ok(Stmt::new(self.loop_flow()?, start..self.lexer.span().end)),
@@ -381,6 +382,55 @@ impl<'source> Parser<'source> {
         Ok(StmtKind::Functio { iden, args, body })
     }
 
+    /// Parse BF function declaration
+    ///
+    /// `bff $iden $((tapelen))? { ... }`
+    fn bff_flow(&mut self) -> Result<StmtKind, Error> {
+        let iden = self.get_iden()?;
+
+        let tape_len = match self
+            .lexer
+            .next()
+            .ok_or(Error::unexpected_eof(self.lexer.span().start))?
+        {
+            Token::LeftParen => {
+                let len = Some(self.expr_flow(Token::RightParen)?);
+                self.require(Token::LeftCurly)?;
+                len
+            }
+            Token::LeftCurly => None,
+            _ => todo!(),
+        };
+
+        let mut code = String::new();
+        loop {
+            code.push_str(
+                match self
+                    .lexer
+                    .next()
+                    .ok_or(Error::unexpected_eof(self.lexer.span().start))?
+                {
+                    Token::Plus
+                    | Token::Minus
+                    | Token::Dot
+                    | Token::Comma
+                    | Token::LeftBracket
+                    | Token::RightBracket
+                    | Token::LessThan
+                    | Token::GreaterThan => self.lexer.slice(),
+                    Token::RightCurly => break,
+                    _ => "",
+                },
+            );
+        }
+
+        Ok(StmtKind::BfFunctio {
+            iden,
+            tape_len,
+            code,
+        })
+    }
+
     /// Parse functio call flow
     fn functio_call_flow(&mut self, iden: Iden) -> Result<StmtKind, Error> {
         let mut args = vec![];