fix(indexer): harden capability discovery

crates/arr-indexer/src/lib.rs

@@ -1,7 +1,8 @@
 //! arr-indexer — see DESIGN.md.
 
-use std::collections::BTreeSet;
+use std::{collections::BTreeSet, time::Duration};
 
+use quick_xml::events::Event;
 use reqwest::Client;
 use serde::Deserialize;
 use thiserror::Error;
@@ -13,6 +14,7 @@ pub struct Indexer {
     pub id: i64,
     pub name: String,
     pub capabilities: Capabilities,
+    pub capabilities_error: Option<CapabilityError>,
 }
 
 /// Search operations supported by one Torznab indexer.
@@ -34,9 +36,13 @@ impl SearchMode {
     /// Returns whether this operation supports an ID-based lookup.
     #[must_use]
     pub fn supports_id_search(&self) -> bool {
-        self.supported_parameters
-            .iter()
-            .any(|parameter| parameter.ends_with("id"))
+        self.available
+            && self.supported_parameters.iter().any(|parameter| {
+                matches!(
+                    parameter.as_str(),
+                    "imdbid" | "tmdbid" | "tvdbid" | "tvmazeid" | "rid" | "traktid"
+                )
+            })
     }
 
     /// Returns whether the indexer accepts a particular Torznab parameter.
@@ -56,13 +62,21 @@ pub struct ProwlarrClient {
 
 impl ProwlarrClient {
     /// Creates a client using Prowlarr's API key for its REST and Torznab APIs.
-    #[must_use]
-    pub fn new(base_url: impl Into<String>, api_key: impl Into<String>) -> Self {
-        Self {
+    ///
+    /// # Errors
+    ///
+    /// Returns an error when the HTTP client cannot be created.
+    pub fn new(base_url: impl Into<String>, api_key: impl Into<String>) -> Result<Self, Error> {
+        let client = Client::builder()
+            .timeout(Duration::from_secs(30))
+            .build()
+            .map_err(|_| Error::Client)?;
+
+        Ok(Self {
             base_url: base_url.into().trim_end_matches('/').to_owned(),
             api_key: api_key.into(),
-            client: Client::new(),
-        }
+            client,
+        })
     }
 
     /// Enumerates Prowlarr indexers and loads Torznab capabilities for each.
@@ -80,49 +94,75 @@ impl ProwlarrClient {
             .get(format!("{}/api/v1/indexer", self.base_url))
             .header("X-Api-Key", &self.api_key)
             .send()
-            .await?
-            .error_for_status()?;
-        let indexers: Vec<ProwlarrIndexer> = response.json().await?;
+            .await
+            .map_err(|_| Error::Request)?
+            .error_for_status()
+            .map_err(|_| Error::Request)?;
+        let indexers: Vec<ProwlarrIndexer> = response.json().await.map_err(|_| Error::Response)?;
 
         let mut result = Vec::with_capacity(indexers.len());
-        for indexer in indexers {
-            let capabilities = self.capabilities(indexer.id).await?;
+        for indexer in indexers.into_iter().filter(|indexer| indexer.enabled) {
+            let (capabilities, capabilities_error) = match self.capabilities(indexer.id).await {
+                Ok(capabilities) => (capabilities, None),
+                Err(error) => (Capabilities::default(), Some(error)),
+            };
             result.push(Indexer {
                 id: indexer.id,
                 name: indexer.name,
                 capabilities,
+                capabilities_error,
             });
         }
 
         Ok(result)
     }
 
-    async fn capabilities(&self, indexer_id: i64) -> Result<Capabilities, Error> {
+    async fn capabilities(&self, indexer_id: i64) -> Result<Capabilities, CapabilityError> {
         let response = self
             .client
             .get(format!("{}/{indexer_id}/api", self.base_url))
             .query(&[("apikey", self.api_key.as_str()), ("t", "caps")])
             .send()
-            .await?
-            .error_for_status()?;
-        let body = response.text().await?;
-        Ok(parse_capabilities(&body)?)
+            .await
+            .map_err(|_| CapabilityError::Request)?
+            .error_for_status()
+            .map_err(|_| CapabilityError::Request)?;
+        let body = response
+            .text()
+            .await
+            .map_err(|_| CapabilityError::Request)?;
+        parse_capabilities(&body)
     }
 }
 
 /// Errors returned while discovering Prowlarr indexers.
 #[derive(Debug, Error)]
 pub enum Error {
-    #[error("Prowlarr request failed: {0}")]
-    Request(#[from] reqwest::Error),
-    #[error("invalid Torznab capabilities response: {0}")]
-    Capabilities(#[from] quick_xml::DeError),
+    #[error("could not create Prowlarr HTTP client")]
+    Client,
+    #[error("Prowlarr indexer request failed")]
+    Request,
+    #[error("could not parse Prowlarr indexer response")]
+    Response,
+}
+
+/// A failed capabilities request for an otherwise usable Prowlarr indexer.
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub enum CapabilityError {
+    Request,
+    InvalidResponse,
+    Torznab {
+        code: Option<u16>,
+        description: String,
+    },
 }
 
 #[derive(Deserialize)]
 struct ProwlarrIndexer {
     id: i64,
     name: String,
+    #[serde(rename = "enable")]
+    enabled: bool,
 }
 
 #[derive(Deserialize)]
@@ -131,6 +171,14 @@ struct TorznabCapabilities {
     searching: Option<TorznabSearching>,
 }
 
+#[derive(Deserialize)]
+struct TorznabError {
+    #[serde(default, rename = "@code")]
+    code: Option<u16>,
+    #[serde(default, rename = "@description")]
+    description: String,
+}
+
 #[derive(Deserialize)]
 struct TorznabSearching {
     #[serde(default)]
@@ -149,8 +197,18 @@ struct TorznabSearchMode {
     supported_parameters: Option<String>,
 }
 
-fn parse_capabilities(body: &str) -> Result<Capabilities, quick_xml::DeError> {
-    let capabilities: TorznabCapabilities = quick_xml::de::from_str(body)?;
+fn parse_capabilities(body: &str) -> Result<Capabilities, CapabilityError> {
+    if response_root(body)? == "error" {
+        let error: TorznabError =
+            quick_xml::de::from_str(body).map_err(|_| CapabilityError::InvalidResponse)?;
+        return Err(CapabilityError::Torznab {
+            code: error.code,
+            description: error.description,
+        });
+    }
+
+    let capabilities: TorznabCapabilities =
+        quick_xml::de::from_str(body).map_err(|_| CapabilityError::InvalidResponse)?;
     let searching = capabilities.searching;
 
     Ok(Capabilities {
@@ -169,6 +227,23 @@ fn parse_capabilities(body: &str) -> Result<Capabilities, quick_xml::DeError> {
     })
 }
 
+fn response_root(body: &str) -> Result<String, CapabilityError> {
+    let mut reader = quick_xml::Reader::from_str(body);
+    loop {
+        match reader
+            .read_event()
+            .map_err(|_| CapabilityError::InvalidResponse)?
+        {
+            Event::Start(element) | Event::Empty(element) => {
+                return String::from_utf8(element.name().as_ref().to_owned())
+                    .map_err(|_| CapabilityError::InvalidResponse);
+            }
+            Event::Eof => return Err(CapabilityError::InvalidResponse),
+            _ => {}
+        }
+    }
+}
+
 impl From<&TorznabSearchMode> for SearchMode {
     fn from(mode: &TorznabSearchMode) -> Self {
         let supported_parameters = mode
@@ -197,7 +272,7 @@ fn is_available(value: &str) -> bool {
 
 #[cfg(test)]
 mod tests {
-    use super::ProwlarrClient;
+    use super::{Capabilities, CapabilityError, ProwlarrClient};
     use wiremock::{
         matchers::{header, method, path, query_param},
         Mock, MockServer, ResponseTemplate,
@@ -225,13 +300,20 @@ mod tests {
             include_str!("../tests/fixtures/text-only-caps.xml"),
         )
         .await;
+        mount_capabilities(
+            &server,
+            23,
+            include_str!("../tests/fixtures/broken-caps.xml"),
+        )
+        .await;
 
         let indexers = ProwlarrClient::new(server.uri(), API_KEY)
+            .expect("HTTP client can be created")
             .indexers()
             .await
             .expect("recorded Prowlarr responses are valid");
 
-        assert_eq!(indexers.len(), 2);
+        assert_eq!(indexers.len(), 3);
         assert_eq!(indexers[0].id, 3);
         assert_eq!(indexers[0].name, "Alpha Tracker");
         assert!(indexers[0].capabilities.movie.available);
@@ -241,8 +323,20 @@ mod tests {
         assert_eq!(indexers[1].id, 17);
         assert_eq!(indexers[1].name, "Text Only");
         assert!(indexers[1].capabilities.search.available);
+        assert!(!indexers[1].capabilities.search.supports_id_search());
         assert!(!indexers[1].capabilities.movie.supports_id_search());
         assert!(!indexers[1].capabilities.tv.available);
+        assert!(!indexers[1].capabilities.tv.supports_id_search());
+
+        assert_eq!(indexers[2].id, 23);
+        assert_eq!(indexers[2].capabilities, Capabilities::default());
+        assert_eq!(
+            indexers[2].capabilities_error,
+            Some(CapabilityError::Torznab {
+                code: Some(100),
+                description: "Indexer unavailable".to_owned(),
+            })
+        );
     }
 
     async fn mount_capabilities(server: &MockServer, id: i64, body: &str) {

crates/arr-indexer/tests/fixtures/broken-caps.xml

@@ -0,0 +1,2 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<error code="100" description="Indexer unavailable" />

crates/arr-indexer/tests/fixtures/indexers.json

@@ -1,4 +1,6 @@
 [
   { "id": 3, "name": "Alpha Tracker", "enable": true },
-  { "id": 17, "name": "Text Only", "enable": true }
+  { "id": 17, "name": "Text Only", "enable": true },
+  { "id": 23, "name": "Broken Tracker", "enable": true },
+  { "id": 42, "name": "Disabled Tracker", "enable": false }
 ]

crates/arr-indexer/tests/fixtures/text-only-caps.xml

@@ -2,8 +2,8 @@
 <caps>
   <server version="1.0" title="Text Only" />
   <searching>
-    <search available="true" supportedParams="q" />
-    <tv-search available="no" supportedParams="q" />
+    <search available="true" supportedParams="q,categoryid" />
+    <tv-search available="no" supportedParams="q,imdbid" />
     <movie-search available="1" supportedParams="q" />
   </searching>
 </caps>