From 0993780c897608f58fe2db286d77022cc2810b33 Mon Sep 17 00:00:00 2001
From: "Timothy J. Warren" <tim@timshomepage.net>
Date: Fri, 7 Feb 2020 22:55:09 -0500
Subject: [PATCH] String parsing

---
 src/lib.rs | 57 +++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 54 insertions(+), 3 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index 5569467..f498b55 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -4,6 +4,7 @@
 #![forbid(unsafe_code)]
 use std::collections::HashMap;
 use std::iter::FromIterator;
+use std::{char, u16};
 
 /// The type of JSON value
 #[derive(Debug, PartialEq)]
@@ -194,17 +195,56 @@ impl JSON {
         let mut result = String::new();
 
         while self.chars[self.i] != '"' {
+            // All the escape sequences...
             if self.chars[self.i] == '\\' {
-                todo!();
+                let ch = self.chars[self.i + 1];
+                if ['"', '\\', '/'].contains(&ch) {
+                    let escaped = ch.escape_default().next().unwrap_or(ch);
+
+                    result.push(escaped);
+                    self.i += 1;
+                } else if ['b', 'f', 'n', 'r', 't'].contains(&ch) {
+                    let ch = match ch {
+                        'b' => '\u{8}',
+                        'f' => '\x0C',
+                        'n' => '\n',
+                        'r' => '\r',
+                        't' => '\t',
+                        _ => panic!("Shouldn't be possible!"),
+                    };
+                    result.push(ch);
+                    self.i += 1;
+                } else if ch == 'u'
+                    && self.chars[self.i + 2].is_ascii_hexdigit()
+                    && self.chars[self.i + 3].is_ascii_hexdigit()
+                    && self.chars[self.i + 4].is_ascii_hexdigit()
+                    && self.chars[self.i + 5].is_ascii_hexdigit()
+                {
+                    // Blech, parse out a JSON unicode (utf16) escape code. Handles surrogate pairs
+                    // by giving you the replacement character...because...yeah
+                    let char_str = String::from_iter(&self.chars[self.i + 2..=self.i + 5]);
+                    let code = u16::from_str_radix(&char_str, 16)
+                        .expect("Failed to parse unicode escape number");
+                    let string = String::from_utf16_lossy(&[code]);
+
+                    result.push_str(&string);
+
+                    self.i += 5;
+                }
+            } else {
+                result.push(self.chars[self.i]);
             }
+            self.i += 1;
         }
 
-        Ok(None)
+        self.i += 1;
+
+        Ok(Some(JSONValue::String(result)))
     }
 
     /// See if there's a `JSONValue::Number` next in the JSON
     fn parse_number(&mut self) -> Result<Option<JSONValue>, ParseError> {
-        Ok(None)
+        todo!();
     }
 
     /// See if there's a `JSONValue::True`, `JSONValue::False`, or a `JSONValue::Null` next in the JSON
@@ -281,6 +321,17 @@ mod tests {
         assert_eq!('x', parser.chars[parser.i]);
     }
 
+    #[test]
+    fn parse_string() {
+        let mut parser = JSON::new(r#""\t""#);
+        let res = JSON::parse_string(&mut parser);
+        assert_eq!(res, Ok(Some(JSONValue::String(String::from("\t")))));
+
+        let mut parser = JSON::new(r#""\u203d""#);
+        let res = JSON::parse_string(&mut parser);
+        assert_eq!(res, Ok(Some(JSONValue::String(String::from("‽")))));
+    }
+
     #[test]
     fn parse_empty_array() {
         let mut parser = JSON::new("[]");