Parse expiry timestamp from spotifycdn.com CDN URLs (Fixes #1182) (#1183)

The CDN URLs list now includes spotifycdn.com which has a different
format. It was being erroneously interpreted using the scdn.co format
and trying to parse non-digit characters as a timestamp.

Also ignore expiry timestamps we can't parse for future new URLs.

core/src/cdn_url.rs

@@ -5,6 +5,7 @@ use std::{
 
 use protobuf::Message;
 use thiserror::Error;
+use time::Duration;
 use url::Url;
 
 use super::{date::Date, Error, FileId, Session};
@@ -16,6 +17,8 @@ use protocol::storage_resolve::StorageResolveResponse as CdnUrlMessage;
 #[derive(Debug, Clone)]
 pub struct MaybeExpiringUrl(pub String, pub Option<Date>);
 
+const CDN_URL_EXPIRY_MARGIN: Duration = Duration::seconds(5 * 60);
+
 #[derive(Debug, Clone)]
 pub struct MaybeExpiringUrls(pub Vec<MaybeExpiringUrl>);
 
@@ -114,55 +117,96 @@ impl TryFrom<CdnUrlMessage> for MaybeExpiringUrls {
             .iter()
             .map(|cdn_url| {
                 let url = Url::parse(cdn_url)?;
+                let mut expiry: Option<Date> = None;
 
                 if is_expiring {
-                    let expiry_str = if let Some(token) = url
+                    let mut expiry_str: Option<String> = None;
+                    if let Some(token) = url
                         .query_pairs()
                         .into_iter()
                         .find(|(key, _value)| key == "__token__")
                     {
+                        //"https://audio-ak-spotify-com.akamaized.net/audio/4712bc9e47f7feb4ee3450ef2bb545e1d83c3d54?__token__=exp=1688165560~hmac=4e661527574fab5793adb99cf04e1c2ce12294c71fe1d39ffbfabdcfe8ce3b41",
                         if let Some(mut start) = token.1.find("exp=") {
                             start += 4;
                             if token.1.len() >= start {
                                 let slice = &token.1[start..];
                                 if let Some(end) = slice.find('~') {
                                     // this is the only valid invariant for akamaized.net
-                                    String::from(&slice[..end])
+                                    expiry_str = Some(String::from(&slice[..end]));
                                 } else {
-                                    String::from(slice)
+                                    expiry_str = Some(String::from(slice));
                                 }
-                            } else {
-                                String::new()
                             }
-                        } else {
-                            String::new()
+                        }
+                    } else if let Some(token) = url
+                        .query_pairs()
+                        .into_iter()
+                        .find(|(key, _value)| key == "Expires")
+                    {
+                        //"https://audio-gm-off.spotifycdn.com/audio/4712bc9e47f7feb4ee3450ef2bb545e1d83c3d54?Expires=1688165560~FullPath~hmac=IIZA28qptl8cuGLq15-SjHKHtLoxzpy_6r_JpAU4MfM=",
+                        if let Some(end) = token.1.find('~') {
+                            // this is the only valid invariant for spotifycdn.com
+                            let slice = &token.1[..end];
+                            expiry_str = Some(String::from(&slice[..end]));
                         }
                     } else if let Some(query) = url.query() {
+                        //"https://audio4-fa.scdn.co/audio/4712bc9e47f7feb4ee3450ef2bb545e1d83c3d54?1688165560_0GKSyXjLaTW1BksFOyI4J7Tf9tZDbBUNNPu9Mt4mhH4=",
                         let mut items = query.split('_');
                         if let Some(first) = items.next() {
                             // this is the only valid invariant for scdn.co
-                            String::from(first)
+                            expiry_str = Some(String::from(first));
+                        }
+                    }
+
+                    if let Some(exp_str) = expiry_str {
+                        if let Ok(expiry_parsed) = exp_str.parse::<i64>() {
+                            if let Ok(expiry_at) = Date::from_timestamp_ms(expiry_parsed * 1_000) {
+                                let with_margin = expiry_at.saturating_sub(CDN_URL_EXPIRY_MARGIN);
+                                expiry = Some(Date::from(with_margin));
+                            }
                         } else {
-                            String::new()
+                            warn!("Cannot parse CDN URL expiry timestamp '{exp_str}' from '{cdn_url}'");
                         }
                     } else {
-                        String::new()
-                    };
-
-                    let mut expiry: i64 = expiry_str.parse()?;
-
-                    expiry -= 5 * 60; // seconds
-
-                    Ok(MaybeExpiringUrl(
-                        cdn_url.to_owned(),
-                        Some(Date::from_timestamp_ms(expiry * 1000)?),
-                    ))
-                } else {
-                    Ok(MaybeExpiringUrl(cdn_url.to_owned(), None))
+                        warn!("Unknown CDN URL format: {cdn_url}");
+                    }
                 }
+                Ok(MaybeExpiringUrl(cdn_url.to_owned(), expiry))
             })
             .collect::<Result<Vec<MaybeExpiringUrl>, Error>>()?;
 
         Ok(Self(result))
     }
 }
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_maybe_expiring_urls() {
+        let timestamp = 1688165560;
+        let mut msg = CdnUrlMessage::new();
+        msg.result = StorageResolveResponse_Result::CDN.into();
+        msg.cdnurl = vec![
+            format!("https://audio-ak-spotify-com.akamaized.net/audio/foo?__token__=exp={timestamp}~hmac=4e661527574fab5793adb99cf04e1c2ce12294c71fe1d39ffbfabdcfe8ce3b41"),
+            format!("https://audio-gm-off.spotifycdn.com/audio/foo?Expires={timestamp}~FullPath~hmac=IIZA28qptl8cuGLq15-SjHKHtLoxzpy_6r_JpAU4MfM="),
+            format!("https://audio4-fa.scdn.co/audio/foo?{timestamp}_0GKSyXjLaTW1BksFOyI4J7Tf9tZDbBUNNPu9Mt4mhH4="),
+            "https://audio4-fa.scdn.co/foo?baz".to_string(),
+        ];
+        msg.fileid = vec![0];
+
+        let urls = MaybeExpiringUrls::try_from(msg).expect("valid urls");
+        assert_eq!(urls.len(), 4);
+        assert!(urls[0].1.is_some());
+        assert!(urls[1].1.is_some());
+        assert!(urls[2].1.is_some());
+        assert!(urls[3].1.is_none());
+        let timestamp_margin = Duration::seconds(timestamp) - CDN_URL_EXPIRY_MARGIN;
+        assert_eq!(
+            urls[0].1.unwrap().as_timestamp_ms() as i128,
+            timestamp_margin.whole_milliseconds()
+        );
+    }
+}