Library management system

Catalogue books, issue and return copies, charge for overdue ones. The classic final-year project, and the one that teaches the two modelling decisions people most often get wrong.

Read lost and found first if you have not — it explains the conventions these pages share.

The two decisions

A book is not a copy. The library owns three copies of one title. A loan is of a copy, a reservation is of a title, and the catalogue searches titles. Collapse the two and you cannot answer “is it available?” without a bug. So: Book for the bibliographic record, Copy for the physical thing on the shelf with its own barcode.

A book has many authors, and an author has many books. Flare has no many-to-many field, deliberately — that relationship always grows a column eventually (billing order, “with contributions by”), and a junction you cannot add a column to has to be rebuilt the day it does. So you write the junction yourself, as an ordinary resource with two belongsTo fields. It is three more words on the command line and it never needs undoing.

Resource	What it holds
Shelf	Where in the building
Author	A person who wrote things
Book	The title: ISBN, publisher, cover
BookAuthor	The junction, one row per pairing
Copy	One physical book, with a barcode and a condition
Loan	A copy, out with somebody, due back
Fine	What they owe, and whether it is paid

1. The app

Next.js

pnpm create flare-framework library
cd library
docker compose up -d

Cloudflare

pnpm create flare-framework library --stack cloudflare
cd library

2. The catalogue

npx flare gen resource Shelf --icon library --group Catalogue \
  --fields 'name:string!'

npx flare gen resource Author --icon user-pen --group Catalogue \
  --fields 'name:string!, bio:text?'

npx flare gen resource Book --icon book --group Catalogue \
  --fields 'isbn:string!, title:string, publisher:string?, year:int?, description:markdown?, cover:file:[image]:2mb?, shelf:belongsTo(Shelf)?'

isbn:string! is unique, which is the whole of “do not catalogue the same title twice” — enforced by the database rather than by whoever is typing.

description:markdown? gives a Markdown editor in the form and renders the result on the detail page. A blurb wants a paragraph break and the odd italic; a plain text? would show them as literal asterisks.

3. The junction

npx flare gen resource BookAuthor --icon link --group Catalogue \
  --fields 'book:belongsTo(Book), author:belongsTo(Author)'

That is the many-to-many. Both sides get a searchable picker, both foreign keys get an index, and when you later need role:enum(author,editor,translator) on it, you add a field to a table that already exists.

Keep it out of the librarian’s sidebar

A junction is rarely something anyone browses. The sidebar lists only the resources the signed-in person may read, so a policy is enough:

npx flare gen policy BookAuthor --roles admin

A librarian no longer sees it; an admin still can. The list is built by visibleResources() in app/dashboard/layout.tsx — your file, if you want a different rule.

4. Circulation

npx flare gen resource Copy --icon copy --group Circulation \
  --fields 'barcode:string!, shelfMark:string?, condition:enum(new,good,worn,damaged), status:enum(available,onLoan,reserved,lost), book:belongsTo(Book)'

npx flare gen resource Loan --icon arrow-right-left --group Circulation \
  --fields 'issuedAt:date, dueDate:date, returnedAt:date?, renewals:int, borrowerId:string, copy:belongsTo(Copy)'

barcode:string! is what the scanner types. Unique, because two copies with the same barcode is the one failure a scanner cannot recover from.

returnedAt:date? nullable is the open-loan flag. Resist adding isReturned:boolean beside it — two columns that must agree will one day disagree, and then you have to decide which is telling the truth.

borrowerId:string is the account id, as on every page here. See lost and found for why it is not a relation.

5. Fines, and the thing to get right about money

npx flare gen resource Fine --icon banknote --group Circulation \
  --fields 'amount:money, reason:enum(overdue,damage,loss), paid:boolean, paidAt:datetime?, loan:belongsTo(Loan)'

money is not a float. It is stored as whole minor units — 1500 for UGX 1,500, 250 for $2.50 — because 0.1 + 0.2 is not 0.3 in binary, and a fines ledger that drifts by a cent a row is a fines ledger nobody trusts. The form shows and accepts the amount the way a person writes it; the column holds an integer.

The exponent comes from the currency, so a zero-decimal currency like UGX or JPY stores the whole number and a two-decimal one stores cents. You do not configure that.

6. Run it

npx flare migrate
npx flare seed:resource Shelf 6
npx flare seed:resource Author 20
npx flare seed:resource Book 60
npx flare seed:resource Copy 120
npx flare seed:resource Loan 50
npx flare seed:resource Fine 20
npx flare dev

Parents before children, or the command tells you which table is empty.

What you still owe

• The fine calculation. Days overdue times a rate, capped, waived for some member types. A hook on Loan update, or a scheduled job. This is your algorithm and the thing to write about.
• Availability. “Is this title on the shelf” is a count of its copies with status = available. A computed field on Book, or a view.
• Reservations and renewals, with their own rules: how many, how long, who jumps the queue.
• The barcode scanner. A scanner is a keyboard; the work is a form that listens for a fast burst of keystrokes ending in Enter.
• Search. The generated table filters and sorts. Real catalogue search across title, author and ISBN wants an index built for it — Postgres full-text on the Next.js stack, FTS5 on Cloudflare.

Make it yours

• Members see only their own loans. npx flare gen policy Loan --roles '*' --own borrowerId --own-except librarian,admin
• E-books. Add file:file:[pdf]:50mb? to Book, or a separate Ebook resource if a title can have several formats.
• Never lose a withdrawn title. Generate Book with --soft-delete and a removed record goes to a Trash view instead of away.