Add single quote strings, quote escaping

demo/demo.rpy

@@ -5,6 +5,8 @@ what the heck
 "this is a string over
 multiple lines"
 "this is \"escaped\""
+'this is a single quote string'
+'this also has escaped \'quotes\''
 this is cool # comment
 
 huh

src/lib.rs

@@ -21,7 +21,15 @@ pub fn parse(file_path: &str) {
                         Rule::token => {
                             let token = token.into_inner().next().unwrap();
                             match token.as_rule() {
-                                Rule::string => println!("string: {}", token.as_str()),
+                                Rule::string => {
+                                    let string_data = token.into_inner().next().unwrap();
+                                    let str = string_data.as_str();
+                                    println!("string: {}", match string_data.as_rule() {
+                                        Rule::single_quote_string_data => str.replace("\\'", "'"),
+                                        Rule::double_quote_string_data => str.replace("\\\"", "\""),
+                                        _ => unreachable!(),
+                                    });
+                                },
                                 Rule::keyword => println!("keyword: {}", token.as_str()),
                                 _ => unreachable!(),
                             };

src/rpy.pest

@@ -13,10 +13,18 @@ token = { string | keyword }
 // has to be atomic for no implicit separate (spaces)
 keyword = @{ (!(WHITESPACE | NEWLINE) ~ ANY)+ }
 
-// strings cannot contain quotes
-// TODO: escaped quotes
-string_data = @{ (!"\"" ~ ANY)* }
-string = ${ "\"" ~ string_data ~ "\"" }
+single_quote_string_data = @{ (
+    "\\'" // Escaped single quotes
+    | (!"'" ~ ANY)
+)* }
+double_quote_string_data = @{ (
+    "\\\"" // Escaped double quotes
+    | (!"\"" ~ ANY)
+)* }
+string = ${
+    ("'" ~ single_quote_string_data ~ "'")
+    | ("\"" ~ double_quote_string_data ~ "\"")
+}
 
 // comments are a # followed by
 // any number of non-newline characters