From ca6e092b38e49c48023a3f2b749b0a5216d5314a Mon Sep 17 00:00:00 2001
From: Moritz Gmeiner <moritz@gmeiner.net>
Date: Mon, 2 Sep 2024 03:10:00 +0200
Subject: [PATCH] added escape sequences

---
 frontend/src/lexer/_lexer.rs | 52 +++++++++++++++++++++++++++++++-----
 frontend/src/lexer/error.rs  |  2 ++
 2 files changed, 48 insertions(+), 6 deletions(-)

diff --git a/frontend/src/lexer/_lexer.rs b/frontend/src/lexer/_lexer.rs
index b1f7088..f296e47 100644
--- a/frontend/src/lexer/_lexer.rs
+++ b/frontend/src/lexer/_lexer.rs
@@ -238,23 +238,63 @@ impl Lexer {
     }
 
     fn try_parse_string(&mut self) {
+        // first '"' already consumed
+
         // advance until second "
-        while self.advance() != '"' {
+        /* while self.advance() != '"' {
             if self.source_is_empty() {
                 self.errors.push(LexerError::UnterminatedStringLiteral {
                     code_pos: self.code_pos,
                 });
                 return;
             }
+        } */
+
+        let mut s = String::new();
+
+        let starting_pos = self.code_pos;
+
+        loop {
+            if self.source_is_empty() {
+                self.errors.push(LexerError::UnterminatedStringLiteral {
+                    code_pos: starting_pos,
+                });
+                return;
+            }
+
+            match self.advance() {
+                '"' => break,
+                '\\' => {
+                    // escape sequence -> handle later
+                    if self.source_is_empty() {
+                        self.errors.push(LexerError::UnterminatedStringLiteral {
+                            code_pos: starting_pos,
+                        });
+                        return;
+                    }
+
+                    match self.advance() {
+                        'n' => s.push('\n'),
+                        'r' => s.push('\r'),
+                        '\\' => s.push('\\'),
+                        c => self.errors.push(LexerError::InvalidEscapeSequence {
+                            code_pos: self.code_pos,
+                            c,
+                        }),
+                    }
+                }
+                c => {
+                    s.push(c);
+                }
+            }
         }
 
-        let string_literal: Box<str> = self.source[self.start + 1..self.current - 1]
-            .iter()
-            .collect();
+        // let string_literal: Box<str> = self.source[self.start + 1..self.current - 1]
+        //     .iter()
+        //     .collect();
 
         // Some(TokenType::String(Box::new(string_literal)))
-        self.tokens
-            .push(Token::new_string(string_literal, self.code_pos));
+        self.tokens.push(Token::new_string(s, self.code_pos));
     }
 
     fn try_parse_number(&mut self) {
diff --git a/frontend/src/lexer/error.rs b/frontend/src/lexer/error.rs
index 1f382fc..e6ab17f 100644
--- a/frontend/src/lexer/error.rs
+++ b/frontend/src/lexer/error.rs
@@ -8,6 +8,8 @@ pub enum LexerError {
     UnexpectedCharacter { c: char, code_pos: CodePos },
     #[error("unterminated string literal starting at {code_pos}.")]
     UnterminatedStringLiteral { code_pos: CodePos },
+    #[error("invalid escape sequence \\{c} at {code_pos}")]
+    InvalidEscapeSequence { code_pos: CodePos, c: char },
     #[error("unterminated block comment starting at {code_pos}.")]
     UnterminatedBlockComment { code_pos: CodePos },
     #[error("invalid number literal {lexeme} at {code_pos}: {msg}")]