patches for #60 and #56 (#68)

* add graphql query for user info

* add parser for graphql user info

* return `CookieError` when leetcode rejects exec/test `Run`

* add the `is_session_bad` method to somewhat-accurately determine when a LEETCODE_SESSION becomes invalid

* When json parsing fails, if the underlying request requires user authentication, use `is_session_bad()` to check if LEETCODE_SESSION is valid.

* get rid of ZWSPs in problem descriptions (see #56)

* add Error::PremiumError

* throw PremiumError when locked questions are queried for details

src/cache/mod.rs

@@ -177,7 +177,16 @@ impl Cache {
                 .json()
                 .await?;
             debug!("{:#?}", &json);
-            parser::desc(&mut rdesc, json).ok_or(Error::NoneError)?;
+            match parser::desc(&mut rdesc, json) {
+                None => return Err(Error::NoneError),
+                Some(false) => return
+                    if self.is_session_bad().await {
+                        Err(Error::CookieError)
+                    } else {
+                        Err(Error::PremiumError)
+                    },
+                Some(true) => ()
+            }
 
             // update the question
             let sdesc = serde_json::to_string(&rdesc)?;

src/cache/parser.rs

@@ -29,14 +29,22 @@ pub fn problem(problems: &mut Vec<Problem>, v: Value) -> Option<()> {
 }
 
 /// desc parser
-pub fn desc(q: &mut Question, v: Value) -> Option<()> {
+pub fn desc(q: &mut Question, v: Value) -> Option<bool> {
+    /* None - parsing failed
+     * Some(false) - content was null (premium?)
+     * Some(true) - content was parsed
+     */
     let o = &v
         .as_object()?
         .get("data")?
         .as_object()?
         .get("question")?
         .as_object()?;
 
+    if *o.get("content")? == Value::Null {
+        return Some(false);
+    }
+
     *q = Question {
         content: o.get("content")?.as_str().unwrap_or("").to_string(),
         stats: serde_json::from_str(o.get("stats")?.as_str()?).ok()?,
@@ -55,7 +63,7 @@ pub fn desc(q: &mut Question, v: Value) -> Option<()> {
             .to_string(),
     };
 
-    Some(())
+    Some(true)
 }
 
 /// tag parser

src/err.rs

@@ -14,6 +14,7 @@ pub enum Error {
     FeatureError(String),
     ScriptError(String),
     CookieError,
+    PremiumError,
     DecryptError,
     SilentError,
     NoneError,
@@ -37,6 +38,13 @@ impl std::fmt::Debug for Error {
                     .yellow()
                     .bold(),
             ),
+            Error::PremiumError => write!(
+                f,
+                "{} \
+                Your leetcode account lacks a premium subscription, which the given problem requires.\n \
+                If this looks like a mistake, please open a new issue at: {}",
+                e,
+                "https://github.com/clearloop/leetcode-cli/".underline()),
             Error::DownloadError(s) => write!(f, "{} Download {} failed, please try again", e, s),
             Error::NetworkError(s) => write!(f, "{} {}, please try again", e, s),
             Error::ParseError(s) => write!(f, "{} {}", e, s),

src/helper.rs

@@ -147,7 +147,11 @@ mod html {
     impl HTML for String {
         fn ser(&self) -> Vec<Token> {
             // empty tags
-            let tks = self.to_string();
+            let tks = {
+                let mut s = self.clone();
+                // some problems (e.g. 1653) have ZWSPs.
+                s.retain(|x| x != '\u{200B}');
+                s };
             let res: Vec<Token>;
             // styled
             {