Merge pull request 'bibfetch: a cover whole to its end marker, and relative redirects with an address in the query (#4, #5)' (#13) from issues-3-6 into main

# Conflicts:
#	crates/bibfetch/src/source.rs

crates/bibfetch/README.md

@@ -86,7 +86,7 @@ is a failure — nobody replied, and the identifier may be perfectly good.
 |---|---|---|
 | `doi` | Crossref | It assigns most scholarly DOIs |
 | `arxiv` | the arXiv | Its own register of preprints |
-| `isbn` | OpenLibrary's edition record, then its index, then Google Books | Books, without a key |
+| `isbn` | OpenLibrary's index, then its edition record, then Google Books | Books, without a key |
 
 One register is enough for a DOI or a preprint: the body that assigns the
 identifier is the only one that has it. A book is different. An ISBN is
@@ -97,6 +97,14 @@ names them. So the registers are asked in turn and the first complete answer
 wins. An incomplete one is kept in case nothing better comes, and a register
 being down is a failure only when every register is.
 
+OpenLibrary's index answers about the work, not the edition: its publishers,
+languages, years and page counts are every edition's at once, and the first
+of each is usually another edition's. So for a book it gives only the title,
+the authors and the subjects, and the `container`, `language`, `year` and
+`pages` of a record come from the edition record for that ISBN, or from
+Google Books when the edition record does not say. A field neither gives is
+left out rather than filled from the work.
+
 Google Books is asked last because it answers anonymous callers only until a
 daily quota runs out, after which it replies `429` to everyone sharing the
 address.
@@ -127,7 +135,8 @@ id is asked only when every form of the ISBN asked was answered with no cover; i
 asking by ISBN failed, that failure is the result.
 
 What comes back is checked before it is written: a JPEG or PNG by its bytes
-as well as by what the server says, no larger than ten megabytes, reached in at
+as well as by what the server says, whole to its end marker (`FF D9` for a
+JPEG, `IEND` for a PNG), no larger than ten megabytes, reached in at
 most three redirects, each over HTTPS to `covers.openlibrary.org`,
 `archive.org` or a host under `archive.org`, and never to an address by number.
 One request is made at a time, a `429` or `503` is waited out for as long as

crates/bibfetch/src/cover.rs

@@ -386,6 +386,23 @@ by ISBN every five minutes from one address"
     }
 }
 
+/// Whether an image's bytes run to its end marker: `FF D9` for a JPEG, which
+/// some encoders follow with zero padding, and the `IEND` chunk for a PNG,
+/// which is its last twelve bytes.
+fn ends_whole(media_type: &str, bytes: &[u8]) -> bool {
+    match media_type {
+        "image/jpeg" => {
+            let end = bytes.iter().rposition(|&b| b != 0).map_or(0, |at| at + 1);
+            end >= 5 && bytes[..end].ends_with(&[0xFF, 0xD9])
+        }
+        _ => {
+            bytes.len() >= 8 + 12
+                && bytes[bytes.len() - 12..].starts_with(&[0, 0, 0, 0])
+                && &bytes[bytes.len() - 8..bytes.len() - 4] == b"IEND"
+        }
+    }
+}
+
 /// Read and check a body that is meant to be a cover.
 fn read(mut response: ureq::http::Response<ureq::Body>, address: &str) -> Result<Answer, Error> {
     let declared = header(&response, "content-type")
@@ -438,6 +455,14 @@ fn read(mut response: ureq::http::Response<ureq::Body>, address: &str) -> Result
             "{address}: said {media_type} but is not one"
         )));
     }
+    // The start of an image is not an image. A body sent with no length,
+    // or a stub, can begin right and stop short; what ends it says it is
+    // whole.
+    if !ends_whole(media_type, &bytes) {
+        return Err(Error::Shape(format!(
+            "{address}: a {media_type} that stops before its end"
+        )));
+    }
     // No floor on the size. Open Library's stand-in for a missing cover is a
     // 43-byte, one-pixel GIF, and it serves that only when `default=false`
     // is left off: with it, as every address here has it, a missing cover is
@@ -512,7 +537,12 @@ fn origin(url: &str) -> Option<&str> {
 
 /// Where a `Location` points, read against the address that sent it.
 fn resolve(from: &str, location: &str) -> String {
-    if location.contains("://") {
+    // Absolute only when the scheme comes first: a relative address can
+    // carry another address in its query.
+    if location
+        .find("://")
+        .is_some_and(|at| !location[..at].contains(['/', '?', '#']))
+    {
         return location.to_string();
     }
     if let Some(rest) = location.strip_prefix("//") {
@@ -670,15 +700,19 @@ mod tests {
         .agent()
     }
 
+    /// A JPEG's start, filler, and its end marker, `len` bytes in all.
     fn jpeg(len: usize) -> Vec<u8> {
         let mut bytes = vec![0xFF, 0xD8, 0xFF, 0xE0];
-        bytes.resize(len, 0x11);
+        bytes.resize(len - 2, 0x11);
+        bytes.extend([0xFF, 0xD9]);
         bytes
     }
 
+    /// A PNG's signature, filler, and its `IEND` chunk, `len` bytes in all.
     fn png(len: usize) -> Vec<u8> {
         let mut bytes = b"\x89PNG\r\n\x1a\n".to_vec();
-        bytes.resize(len, 0x22);
+        bytes.resize(len - 12, 0x22);
+        bytes.extend(b"\0\0\0\0IEND\xAE\x42\x60\x82");
         bytes
     }
 
@@ -1170,6 +1204,38 @@ mod tests {
         assert_eq!(stub.asked(), [ISBN13, ISBN10]);
     }
 
+    #[test]
+    fn a_magic_number_alone_is_not_a_cover() {
+        let mut cut_jpeg = jpeg(4096);
+        cut_jpeg.truncate(4000);
+        let mut cut_png = png(4096);
+        cut_png.truncate(4000);
+        for (media_type, body) in [
+            ("image/jpeg", vec![0xFF, 0xD8, 0xFF]),
+            ("image/png", b"\x89PNG\r\n\x1a\n".to_vec()),
+            ("image/jpeg", cut_jpeg),
+            ("image/png", cut_png),
+        ] {
+            let stub = Stub::start(move |_, _| Reply::image(media_type, body.clone()));
+            let found = stub
+                .covers()
+                .fetch(&agent(), "9780306406157", None, CoverSize::Large)
+                .map(|cover| cover.map(|cover| cover.bytes.len()));
+            assert!(
+                matches!(found, Err(Error::Shape(_))),
+                "{media_type}: {found:?}"
+            );
+        }
+    }
+
+    #[test]
+    fn a_jpeg_padded_after_its_end_marker_is_whole() {
+        let mut padded = jpeg(2048);
+        padded.extend([0, 0, 0]);
+        assert!(ends_whole("image/jpeg", &padded));
+        assert!(!ends_whole("image/jpeg", &[0xFF, 0xD8, 0xFF, 0, 0]));
+    }
+
     #[test]
     fn a_redirect_to_an_address_by_number_is_refused() {
         // A listener standing in for a service on the LAN; it only counts.
@@ -1217,6 +1283,15 @@ mod tests {
         assert_eq!(resolve(from, "//c.example/x"), "https://c.example/x");
         assert_eq!(resolve(from, "/x?y=1"), "https://a.example/x?y=1");
         assert_eq!(resolve(from, "x.jpg"), "https://a.example/b/isbn/x.jpg");
+        // An address in a relative one's query does not make it absolute.
+        assert_eq!(
+            resolve(from, "/view_archive.php?from=https://archive.org/x"),
+            "https://a.example/view_archive.php?from=https://archive.org/x"
+        );
+        assert_eq!(
+            resolve(from, "x?u=https://c.example/"),
+            "https://a.example/b/isbn/x?u=https://c.example/"
+        );
         assert_eq!(
             origin("http://127.0.0.1:8080/a?b"),
             Some("http://127.0.0.1:8080")

crates/bibfetch/src/lib.rs

@@ -265,11 +265,10 @@ mod merge_tests {
         let mut index = rec("openlibrary");
         index.title = Some("The First World War".into());
         index.authors = vec!["Michael Howard".into()];
-        index.year = Some(2007);
 
         edition.fill_from(index);
         assert_eq!(edition.authors, ["Michael Howard"]);
-        assert_eq!(edition.year, Some(2007));
+        assert_eq!(edition.language.as_deref(), Some("eng"));
         // The fuller title arrived first and is not displaced by the shorter.
         assert_eq!(
             edition.title.as_deref(),

crates/bibfetch/src/source.rs

@@ -17,9 +17,10 @@ pub enum Source {
     Arxiv,
     /// OpenLibrary, for books by ISBN.
     OpenLibrary,
-    /// OpenLibrary's index, rather than its edition record. Asked when the
+    /// OpenLibrary's index, rather than its edition record. Asked for what is
-    /// edition record has the book but not who wrote it, which is often: an
+    /// true of the work — the title, the authors by name, the subjects —
-    /// edition names its authors by key, and the index names them.
+    /// because an edition names its authors by key and the index names them.
+    /// Never for what differs between editions.
     OpenLibrarySearch,
     /// Google Books, for books by ISBN. Asked last, because it answers
     /// anonymous callers only until a daily quota runs out.
@@ -55,14 +56,14 @@ impl Source {
         match kind {
             "doi" => &[Source::Crossref],
             "arxiv" => &[Source::Arxiv],
-            // The index first. Asked for the fields by name it answers with
+            // The index first, for what is true of the work: the title, the
-            // the title, the authors, the publisher, the language, a page
+            // authors by name, the subjects. Then the edition record, for
-            // count and the subjects in one request, which is the whole of
+            // what is true of this edition only: the publisher, the language,
-            // what a catalogue wants; the edition record is then needed only
+            // the year and the length. The index answers about the work, and
-            // for a subtitle or a publisher the index did not give. Asking it
+            // its publishers, languages and years are every edition's at
-            // second cost three requests per book where one usually does, and
+            // once, so they are not asked of it; the lookup goes on to the
-            // at three books in flight that is the difference between two
+            // edition record for them. Google Books last, for whatever the
-            // days and two hours.
+            // edition record does not say.
             "isbn" => &[
                 Source::OpenLibrarySearch,
                 Source::OpenLibrary,
@@ -83,15 +84,16 @@ impl Source {
             Source::OpenLibrary => {
                 format!("https://openlibrary.org/isbn/{}.json", encode(id))
             }
-            // `fields` or the index answers with a handful of defaults and
+            // Only what is true of the work. Not `publisher`, `language`,
-            // keeps the rest, which is how a language it holds went unread.
+            // `first_publish_year` or `number_of_pages_median`: those are every
-            // Not `cover_i`: that is the cover chosen for the whole work, and
+            // edition's at once, and the first of each is usually another
-            // on a work with hundreds of editions it is usually another
+            // edition's (the Penguin *War and Peace* came back Spanish, from
-            // edition's, in another translation or language.
+            // W.W. Norton, in 1845). Not `cover_i`: that is the cover chosen
+            // for the whole work, often another edition's in another
+            // translation or language.
             Source::OpenLibrarySearch => format!(
                 "https://openlibrary.org/search.json?q=isbn:{}\
-&fields=title,subtitle,author_name,first_publish_year,publisher,language,subject,\
+&fields=title,subtitle,author_name,subject&limit=1",
-number_of_pages_median&limit=1",
                 encode(id)
             ),
             Source::GoogleBooks => format!(
@@ -295,6 +297,8 @@ struct SearchReply {
     docs: Vec<SearchDoc>,
 }
 
+/// What the index says about a work. Only the fields true of every edition
+/// are read, so an answer that carries the others anyway cannot leak them.
 #[derive(Deserialize)]
 struct SearchDoc {
     #[serde(default)]
@@ -304,15 +308,7 @@ struct SearchDoc {
     #[serde(default)]
     author_name: Vec<String>,
     #[serde(default)]
-    first_publish_year: Option<i64>,
-    #[serde(default)]
-    publisher: Vec<String>,
-    #[serde(default)]
-    language: Vec<String>,
-    #[serde(default)]
     subject: Vec<String>,
-    #[serde(rename = "number_of_pages_median", default)]
-    pages: Option<u32>,
 }
 
 /// How many of a work's subject headings are worth carrying.
@@ -324,6 +320,11 @@ pub(crate) const SUBJECT_LIMIT: usize = 12;
 
 /// A search that matched nothing answers with no documents rather than a
 /// status, so an empty reply is the absence and not a failure.
+///
+/// The record says what is true of the work and nothing that belongs to one
+/// edition: no publisher, language, year or page count. Those come from the
+/// edition record, which [`crate::ask::lookup`] asks next because a record
+/// without them is never complete.
 fn open_library_search(id: &str, kind: &str, body: &str) -> Result<Record, Error> {
     let reply: SearchReply = serde_json::from_str(body).map_err(|e| Error::Shape(e.to_string()))?;
     let Some(doc) = reply.docs.into_iter().next() else {
@@ -336,14 +337,10 @@ fn open_library_search(id: &str, kind: &str, body: &str) -> Result<Record, Error
         (title, _) => title,
     };
     record.authors = doc.author_name;
-    record.year = doc.first_publish_year;
-    record.container = doc.publisher.into_iter().next();
-    record.language = doc.language.into_iter().next();
     // The index lists every subject any edition of the work carries, which
     // runs to hundreds on a well-known book. A shelf needs a handful.
     record.subjects = doc.subject;
     record.subjects.truncate(SUBJECT_LIMIT);
-    record.pages = doc.pages;
     Ok(record)
 }
 
@@ -475,9 +472,8 @@ mod tests {
     fn each_kind_goes_to_the_body_that_assigns_it() {
         assert_eq!(Source::for_kind("doi"), Some(Source::Crossref));
         assert_eq!(Source::for_kind("arxiv"), Some(Source::Arxiv));
-        // The index, not the edition record: it answers with the whole of
+        // The index first, for the authors by name; the edition record names
-        // what a catalogue wants in one request, where the edition record
+        // them by key, and is asked next for what only the edition knows.
-        // takes up to twenty-eight seconds and names its authors by key.
         assert_eq!(Source::for_kind("isbn"), Some(Source::OpenLibrarySearch));
         // No register answers about an ISSN without a key.
         assert_eq!(Source::for_kind("issn"), None);
@@ -599,6 +595,96 @@ mod tests {
         assert!(!Source::OpenLibrarySearch.url("1").contains("cover_i"));
     }
 
+    /// What the index said for ISBN 9780140447934, the Penguin Classics *War
+    /// and Peace*, on 2026-11-13, asked for the fields the lookup asked for
+    /// before #6: the publishers, languages and first year of every edition
+    /// of the work.
+    const WAR_AND_PEACE_INDEX: &str = r#"{"docs":[{"title":"War and Peace",
+        "author_name":["Leo Tolstoy"],"first_publish_year":1845,
+        "publisher":["W.W. Norton","IndyPublish.com","Canterbury Classics"],
+        "language":["spa","gre","dut","eng"],"subject":["Fiction"],
+        "number_of_pages_median":1296}]}"#;
+
+    /// The edition record for the same ISBN, `/isbn/9780140447934.json`, with
+    /// the English language its `languages` field should name.
+    const WAR_AND_PEACE_EDITION: &str = r#"{"title":"War and Peace (Penguin Classics)",
+        "publishers":["Penguin Books"],"publish_date":"September 27, 2007",
+        "languages":[{"key":"/languages/eng"}],"number_of_pages":1440}"#;
+
+    /// Index first, then the edition record, merged as `ask::lookup` merges.
+    fn looked_up(edition: &str) -> Record {
+        let mut kept =
+            open_library_search("9780140447934", "isbn", WAR_AND_PEACE_INDEX).expect("a record");
+        kept.fill_from(open_library("9780140447934", "isbn", edition).expect("a record"));
+        kept
+    }
+
+    #[test]
+    fn the_index_says_nothing_only_an_edition_can() {
+        let record =
+            open_library_search("9780140447934", "isbn", WAR_AND_PEACE_INDEX).expect("a record");
+        // What is true of the work is kept.
+        assert_eq!(record.title.as_deref(), Some("War and Peace"));
+        assert_eq!(record.authors, ["Leo Tolstoy"]);
+        // What belongs to one edition is not taken from all of them.
+        assert_eq!(record.language, None);
+        assert_eq!(record.container, None);
+        assert_eq!(record.year, None);
+        assert_eq!(record.pages, None);
+    }
+
+    #[test]
+    fn a_lookup_by_isbn_gives_the_editions_language_publisher_and_year() {
+        let record = looked_up(WAR_AND_PEACE_EDITION);
+        assert_eq!(record.language.as_deref(), Some("eng"));
+        assert_eq!(record.container.as_deref(), Some("Penguin Books"));
+        assert_eq!(record.year, Some(2007));
+        assert_eq!(record.pages, Some(1440));
+        assert_eq!(record.authors, ["Leo Tolstoy"]);
+    }
+
+    #[test]
+    fn what_the_edition_does_not_say_is_missing_rather_than_the_works() {
+        // The real edition record today names no language at all.
+        let record = looked_up(
+            r#"{"title":"War and Peace (Penguin Classics)","publishers":["Penguin Books"],
+            "publish_date":"September 27, 2007","number_of_pages":1440}"#,
+        );
+        assert_eq!(record.language, None);
+        assert_eq!(record.container.as_deref(), Some("Penguin Books"));
+        assert_eq!(record.year, Some(2007));
+        // Nor a date: the work's first year is not this edition's.
+        let record = looked_up(r#"{"title":"War and Peace (Penguin Classics)"}"#);
+        assert_eq!(record.year, None);
+        assert_eq!(record.container, None);
+        assert_eq!(record.pages, None);
+    }
+
+    #[test]
+    fn the_index_alone_never_ends_a_lookup() {
+        // `lookup` stops at the first complete record; the index must not be
+        // one, or the edition record is never asked.
+        let record =
+            open_library_search("9780140447934", "isbn", WAR_AND_PEACE_INDEX).expect("a record");
+        assert!(!record.complete());
+    }
+
+    #[test]
+    fn the_index_is_not_asked_for_what_its_editions_differ_in() {
+        let url = Source::OpenLibrarySearch.url("9780140447934");
+        for field in [
+            "publisher",
+            "language",
+            "first_publish_year",
+            "number_of_pages_median",
+        ] {
+            assert!(
+                !url.split(['=', ',', '&']).any(|f| f == field),
+                "{field} in {url}"
+            );
+        }
+    }
+
     #[test]
     fn an_answer_that_is_not_what_it_should_be_says_so() {
         assert!(matches!(