From 7588f29cc98d97b288d4becd337fe59be3a4256c Mon Sep 17 00:00:00 2001
From: "Timothy J. Warren" <tim@timshomepage.net>
Date: Fri, 7 Feb 2020 20:01:10 -0500
Subject: [PATCH] Add some tests

---
 src/lib.rs | 61 ++++++++++++++++++++++++++++++++++++++++++------------
 1 file changed, 48 insertions(+), 13 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index f3009be..496314d 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,6 +1,6 @@
+//! # Naive JSON Parser
 use std::collections::HashMap;
 use std::iter::FromIterator;
-use crate::ParseError::UnexpectedEndOfInput;
 
 #[derive(Debug, PartialEq)]
 pub enum JSONValue {
@@ -13,7 +13,7 @@ pub enum JSONValue {
     Null,
 }
 
-#[derive(Debug)]
+#[derive(Debug, PartialEq)]
 pub enum ParseError {
     UnexpectedEndOfInput(String),
     ExpectedEndOfInput(String),
@@ -25,7 +25,7 @@ pub enum ParseError {
     ExpectedUnicodeEscape(String),
 }
 
-#[derive(Debug)]
+#[derive(Debug, PartialEq)]
 pub struct JSON {
     chars: Vec<char>,
     i: usize
@@ -55,7 +55,7 @@ impl JSON {
 
         match types.next() {
             Some(val) => Ok(val),
-            None => Err(UnexpectedEndOfInput(String::new()))
+            None => Err(ParseError::UnexpectedEndOfInput(String::new()))
         }
     }
 
@@ -76,7 +76,7 @@ impl JSON {
         // we take the path of string -> whitespace -> ':' -> value -> ...
         while self.chars[self.i] != '}' {
             if initial == false {
-                self.eat_char(',')?;
+                self.eat(',')?;
                 self.skip_whitespace();
             }
 
@@ -89,7 +89,7 @@ impl JSON {
             };
 
             self.skip_whitespace();
-            self.eat_char(':')?;
+            self.eat(':')?;
             let value = self.parse_value()?;
 
             result.insert(key, value);
@@ -116,7 +116,7 @@ impl JSON {
 
         while self.chars[self.i] != ']' {
             if initial == false {
-                self.eat_char(',')?;
+                self.eat(',')?;
             }
             let value = self.parse_value()?;
             result.push(value);
@@ -130,15 +130,22 @@ impl JSON {
     }
 
     fn parse_string(&mut self) -> PartialResult {
-        todo!();
+       Ok(None)
     }
 
     fn parse_number(&mut self) -> PartialResult {
-        todo!();
+       Ok(None)
     }
 
     fn parse_keyword(&mut self, search: &str, value: JSONValue) -> PartialResult {
-        let slice = &String::from_iter(&self.chars[self.i..self.i+search.len()]);
+        let start = self.i;
+        let end = if self.i + search.len() > self.chars.len() {
+            self.chars.len()
+        } else {
+            self.i + search.len()
+        };
+
+        let slice = &String::from_iter(&self.chars[start..end]);
         if slice == search {
            self.i += search.len();
 
@@ -154,7 +161,7 @@ impl JSON {
         }
     }
 
-    fn eat_char(&mut self, ch: char) -> Result<(), ParseError> {
+    fn eat(&mut self, ch: char) -> Result<(), ParseError> {
         if self.chars[self.i] != ch {
             let msg = format!(r#"Expected "{}"."#, ch);
             return Err(ParseError::ExpectedToken(msg));
@@ -165,6 +172,7 @@ impl JSON {
         Ok(())
     }
 
+    /// Convert a `&str` containing JSON into a `Result<JSONValue, ParseError>`
     pub fn parse(json: &str) -> JSONResult {
         JSON::new(json).parse_value()
     }
@@ -177,7 +185,34 @@ mod tests {
     use super::*;
 
     #[test]
-    fn it_works() {
-        assert_eq!(2 + 2, 4);
+    fn parse_keyword() {
+        let mut parser = JSON::new(r#""foobarbaz""#);
+        let res = JSON::parse_keyword(&mut parser, "true", JSONValue::True);
+        assert_eq!(res, Ok(None));
+
+        let mut parser = JSON::new("true");
+        let res = JSON::parse_keyword(&mut parser, "true", JSONValue::True);
+        assert_eq!(res, Ok(Some(JSONValue::True)));
+    }
+
+    #[test]
+    fn skip_whitespace() {
+        let mut parser = JSON::new(" \t\r\nx");
+        parser.skip_whitespace();
+        assert_eq!('x', parser.chars[parser.i]);
+    }
+
+    #[test]
+    fn parse_empty_array() {
+        let mut parser = JSON::new("[]");
+        let res = JSON::parse_value(&mut parser);
+        assert_eq!(res, Ok(JSONValue::Array(vec![])));
+    }
+
+    #[test]
+    fn can_parse_array_of_keywords() {
+        let result = JSON::parse("[true,false,null]");
+
+        assert_eq!(result, Ok(JSONValue::Array(vec![JSONValue::True, JSONValue::False, JSONValue::Null])));
     }
 }