Vellum/internal/metadata/googlebooks.go
mithral df740d3e1a Phase 5: job queue and metadata providers
- jobs: a table-backed queue in the same SQLite file. No Redis, no second
  process, included in the same backup. claim() is a single UPDATE...RETURNING
  so a job cannot run twice even with several workers. Failures back off
  exponentially; a missing handler fails permanently rather than retrying a
  bug.
- metadata: Provider interface plus Open Library and Google Books (both
  keyless). The enricher tries providers in registration order, falls back on
  empty, and continues past a provider error.
- migration 0004: metadata_fetch records the attempt, not just the match, so a
  rescan does not re-hammer a rate-limited API for an item that will never
  match. Errors are always retried; ok/notfound are cached for 30 days.
- enrichment writes provider_ids, updates title/year, links authors through
  people/item_people, and downloads the cover as an asset. The cover download
  runs outside the transaction: a slow image host must not hold a write lock.
- endpoints: queue enrichment per library, and inspect an item's matches.
- web: Enrich button per library.

Verified live against Open Library: "The Hobbit" matched /works/OL27482W,
title and year 1937 written, a 301x500 JPEG cover downloaded and served.
2026-10-09 21:16:07 -04:00

130 lines
3.2 KiB
Go

package metadata
import (
"context"
"encoding/json"
"fmt"
"net/http"
"net/url"
"strconv"
"strings"
"time"
)
// GoogleBooks is a fallback catalogue for books. No API key for low volume.
type GoogleBooks struct {
Client *http.Client
}
// NewGoogleBooks builds the provider with a bounded HTTP client.
func NewGoogleBooks() *GoogleBooks {
return &GoogleBooks{Client: &http.Client{Timeout: 10 * time.Second}}
}
func (p *GoogleBooks) Name() string { return "googlebooks" }
func (p *GoogleBooks) Kinds() []string { return []string{"ebooks"} }
type gbResponse struct {
Items []struct {
ID string `json:"id"`
VolumeInfo struct {
Title string `json:"title"`
Authors []string `json:"authors"`
Publisher string `json:"publisher"`
Language string `json:"language"`
Description string `json:"description"`
PublishedDate string `json:"publishedDate"`
ImageLinks struct {
Thumbnail string `json:"thumbnail"`
} `json:"imageLinks"`
IndustryIdentifiers []struct {
Type string `json:"type"`
Identifier string `json:"identifier"`
} `json:"industryIdentifiers"`
} `json:"volumeInfo"`
} `json:"items"`
}
func (p *GoogleBooks) Search(ctx context.Context, q Query) ([]Candidate, error) {
var terms []string
if q.ISBN != "" {
terms = append(terms, "isbn:"+q.ISBN)
} else {
if q.Title != "" {
terms = append(terms, "intitle:"+q.Title)
}
if q.Author != "" {
terms = append(terms, "inauthor:"+q.Author)
}
}
if len(terms) == 0 {
return nil, nil
}
params := url.Values{}
params.Set("q", strings.Join(terms, "+"))
params.Set("maxResults", "5")
params.Set("printType", "books")
endpoint := "https://www.googleapis.com/books/v1/volumes?" + params.Encode()
req, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
if err != nil {
return nil, err
}
resp, err := p.Client.Do(req)
if err != nil {
return nil, fmt.Errorf("googlebooks: %w", err)
}
defer resp.Body.Close()
if resp.StatusCode != http.StatusOK {
return nil, fmt.Errorf("googlebooks: status %d", resp.StatusCode)
}
var parsed gbResponse
if err := json.NewDecoder(resp.Body).Decode(&parsed); err != nil {
return nil, fmt.Errorf("googlebooks: decode: %w", err)
}
out := make([]Candidate, 0, len(parsed.Items))
for _, item := range parsed.Items {
v := item.VolumeInfo
if v.Title == "" {
continue
}
c := Candidate{
Provider: p.Name(),
ExternalID: item.ID,
Title: v.Title,
Authors: v.Authors,
Publisher: v.Publisher,
Language: v.Language,
Description: v.Description,
Year: parseYear(v.PublishedDate),
}
// Google returns http:// thumbnail URLs; https avoids mixed content.
if v.ImageLinks.Thumbnail != "" {
c.CoverURL = strings.Replace(v.ImageLinks.Thumbnail, "http://", "https://", 1)
}
for _, id := range v.IndustryIdentifiers {
if id.Type == "ISBN_13" || c.ISBN == "" {
c.ISBN = id.Identifier
}
}
out = append(out, c)
}
return out, nil
}
// parseYear extracts a leading 4-digit year from dates like "2021-05-04".
func parseYear(date string) int {
if len(date) < 4 {
return 0
}
n, err := strconv.Atoi(date[:4])
if err != nil {
return 0
}
return n
}