bibfetch: the books a register has under a title

A book that arrives as a file often has no identifier to ask about, only
a title and perhaps a name. `bibfetch search --title T [--author A]
[--limit N]` asks Open Library's index which books it has under those,
and Google Books only when Open Library has nothing, and prints one
record per candidate in the order the register gave them. From Rust,
`bibfetch::search(&agent, title, author, limit, attempts)`.

Each candidate is one edition. The index answers with works and, asked
for `editions.*`, names the edition of each that best matches; the ISBN,
publisher, language, year and cover come from that edition, the title,
authors, subjects and length from the work. The work's own ISBN list
mixes editions: the first War and Peace work lists four, while the
edition matched is a 1917 printing with none.

`id` is the first ISBN whose check digit agrees, in thirteen digits,
thirteen-digit entries taken first. A candidate with none is named by
the register's key: `olid` (OL…M for the edition, OL…W for the work when
no edition was named) or `googlebooks` (a volume id). Google's `OTHER`
shelfmarks are never read as ISBNs.

`cover_id` keeps the meaning it has in a lookup record: the edition's
own first cover, taken from `editions.cover_i` and only when the record
names that edition. The work's `cover_i` and `cover_edition_key` are not
asked for. A work with no edition named, and every Google Books
candidate, has none.

Open Library having nothing stands when Google Books is down; both down
is exit 69. Exit 0 a candidate, 1 none, 65 an empty title.

The retrying GET that lookups use is now `ask::get`, shared by both, and
no longer sleeps after its last attempt.

crates/bibfetch/README.md

@@ -20,6 +20,8 @@ So this asks, and that is the only thing it does.
 - **Filling in a reference** you have only the identifier for.
 - **Before citing something**, to check the year and the authors are what you
   think they are.
+- **Cataloguing a book that came with no identifier**, to find the editions a
+  register has under its title, and an ISBN to file it by.
 
 ## Install
 
@@ -148,6 +150,77 @@ From Rust, `bibfetch::cover(&agent, isbn, cover_id, size)` returns
 `Ok(None)` when there is no cover, and a [`Cover`](src/cover.rs) with the
 bytes, the media type and the address asked when there is.
 
+## Searching by title
+
+```
+$ bibfetch search --title 'The First World War' --author Howard --limit 2
+{"v":1,"id":"9780192853622","kind":"isbn","found":true,"source":"openlibrary","title":"The First World War","authors":["Michael Eliot Howard"],"year":2002,"container":"Oxford University Press","subjects":["World War, 1914-1918"],"language":"eng","pages":154,"cover_id":1123124}
+{"v":1,"id":"9780199205592","kind":"isbn","found":true,"source":"openlibrary","title":"The First World War: A Very Short Introduction","authors":["Michael Howard"],"year":2007,"container":"Oxford University Press","language":"eng","cover_id":14606475}
+```
+
+A book that arrives as a file often has no identifier to ask about, only a
+title and perhaps a name. This asks which books a register has under those,
+and prints one record per candidate: Open Library's index first, and Google
+Books only when Open Library has nothing.
+
+Each candidate is one edition. Open Library's index answers with works, and
+names the edition of each that best matches the search; what belongs to an
+edition — its ISBN, publisher, language, year and cover — is that edition's,
+and what belongs to the work — the title, the authors, the subjects and the
+length — is the work's. Google Books answers with volumes, which are editions
+already.
+
+| Field | When the candidate has an ISBN | When it has none |
+|---|---|---|
+| `id` | The first ISBN whose check digit agrees, in thirteen digits; one written in thirteen is taken over one written in ten | The register's own key: an Open Library id such as `OL37863121M` for the edition, or `OL267171W` for the work when no edition was named; a Google Books volume id |
+| `kind` | `isbn` | `olid` for Open Library, `googlebooks` for Google Books |
+
+An ISBN whose check digit is wrong is passed over rather than corrected, and
+Google's shelfmarks, typed `OTHER`, are not read as ISBNs even when their
+digits would pass for one. A record of kind `isbn` can be handed straight back
+to `bibfetch` for everything the registers say about that edition; `olid` and
+`googlebooks` are names no lookup here answers about.
+
+`cover_id` is the same thing it is in a lookup record: the first cover in
+Open Library's record of the edition the record names, by that edition's ISBN
+or its key, so `bibfetch cover --cover-id` fetches that edition's cover and no
+other. The cover the index picked for the whole work is never asked for,
+because it is often another edition's. A work the index names no edition of
+gives the first ISBN it lists that reads, which may be any edition's, and no
+cover id; Google Books knows nothing of Open Library's covers and gives none.
+
+The candidates are what the register said, in the order it said them. This
+makes no judgement about which one is the book in hand, and keeps one that is
+plainly another book, because a title is not an identifier: *The Hamlet* comes
+back for *Hamlet*. Deciding whether a candidate is the same work is a
+comparison of titles, and [`bibclean`](../bibclean/README.md)'s `same_work`
+is one.
+
+```sh
+bibfetch search --title 'Anathem' --author Stephenson \
+  | jq -r 'select(.kind == "isbn") | .id' | head -1
+```
+
+Open Library answering that it has nothing is an answer, and it stands when
+Google Books cannot be reached; a register being down is a failure only when
+both are. Each is asked the same way a lookup asks, retried with the same
+waits. Open Library is sent the title and the author as written; Google Books
+is sent each word as its own `intitle:` or `inauthor:` term, so nothing in a
+title is read as search syntax.
+
+| Option | Effect |
+|---|---|
+| `--title <TITLE>` | The title, or as much of it as you have |
+| `--author <AUTHOR>` | An author's name, or part of one |
+| `--limit <COUNT>` | The most candidates to print, `1` to `40`. Default `10` |
+
+Exit `0` at least one candidate was printed, `1` no register has the title,
+`65` the title was empty, `69` no register could be reached, `74` the output
+could not be written.
+
+From Rust, `bibfetch::search(&agent, title, author, limit, attempts)` returns
+the candidates, empty when no register has the title.
+
 ## Reaching the network
 
 This and [`emb`](../emb/README.md) are the only two tools here that do. Both
@@ -156,10 +229,11 @@ something that happens on the way to something else — which is the condition
 under which [the contract](../../docs/contract.md) allows it at all.
 
 Nothing is cached, nothing is stored but a cover you asked to have written,
-and nothing is sent but the identifier and the address you pass to
-`--polite`.
+and nothing is sent but the identifier, or the title and author searched for,
+and the address you pass to `--polite`.
 
 ## See also
 
 - [`idnorm`](../idnorm/README.md) — reading the identifier in the first place.
-- [`bibclean`](../bibclean/README.md) — the rest of a catalogue record.
+- [`bibclean`](../bibclean/README.md) — the rest of a catalogue record, and
+  whether a candidate is the same work.