# Shelves data model

Replace the TODO-state-based book model with shelf-based organization.
Shelves are top-level Org headings; books are nested underneath them.

## Motivation

Books-as-top-level-headings with TODO states (WANT/READING/READ/ABANDONED)
made the file's structure reflect lifecycle status rather than organizing
concepts. The user wants arbitrary grouping ("shelves") as the primary
organizing axis. TODO states are removed — logbook entries (already present)
record when reading happened.

## Org data model

```org
#+TITLE: Spine

* Fiction
** Piranesi
:PROPERTIES:
:AUTHOR:  Susanna Clarke
:FORMAT:  ebook
:REC_BY:  Alex
:REC_NOTE: Le Guin at her most human
:RATING:
:ADDED:   [2026-04-01]
:LAST_MODIFIED: [2026-04-01]
:ID:      5e8d-pir
:END:
::LOGBOOK:
- State "READ" from "WANT" [2026-01-10]
::END:
- [2025-11-22] The pronoun game is a genuinely fresh take on identity.

* Non-Fiction
** The Checklist Manifesto
...
```

- Shelves are level-1 headlines (`*`)
- Books are level-2 headlines (`**`)
- Books keep their TODO keyword syntax for `org-mode` compatibility,
  but the app ignores it entirely
- The `#+TODO:` line is removed — no TODO states
- Empty shelves (a level-1 headline with no children) are valid and
  appear in the UI
- LOGBOOK drawers remain for historical state-change records but are
  not surfaced by the UI

## Key functions

### `spine-shelves` (new)

Returns an ordered list of shelf names (strings), one per level-1 headline
that is not a COMMENT or archive target. Empty shelves are included.

### `spine-books` (modified)

Walks level-1 headlines as shelves. For each shelf, walks level-2 children
as books. Returns flat plist list; each book plist gains a `:shelf` key
with the parent headline text. No status/TODO filtering.

Places that previously checked Todo state (e.g. `spine-set-status`) are
removed — the only remaining mutable fields are notes, rating, format.

### `spine-index-model` (modified)

Groups books by `:shelf` instead of `:status`. Accepts an optional
`shelf` filter (instead of `read`/`want`/`all`) to show one shelf.
Includes shelf nav items for all shelves (even empty ones, from
`spine-shelves`).

Removes:
- Summary groups (READ/ABANDONED links)
- Concise view truncation
- Status-related book model fields (status_class, status_label)

### `spine-add-book` (modified)

Takes required `:shelf` argument. Inserts the new book heading under
the matching level-1 shelf headline instead of at file end. If the
shelf doesn't exist, signals an error (shelves are created manually).

Removes:
- `org-todo "WANT"` call
- `#+TODO:` file initialization
- Category field logic (replaced by shelf)

### Functions removed

- `spine-set-status` — no status to change. Logbook records history.
- All HTTP endpoints and UI actions that invoke it.

## UI changes

### Index view (`index.mustache`)

- **Titlebar**: `N books · M shelves`
- **Filter bar**: replaced with shelf nav — links for each shelf name
  plus "All" (default). Active shelf highlighted.
- **Groups**: one section per shelf. Each shelf shows its books in the
  existing row format, minus the status pill.
- **Empty shelves**: shown as a group with the shelf name and "(empty)"
  subtext. No expandable books.
- **Minibuffer** (when a book is selected): simplified to two actions —
  **Add note**, **Set rating**. Same for every book.

### Add form (`add.mustache`)

- "Category" free-text field replaced with "Shelf" `<select>` dropdown
  populated from `spine-shelves`.
- Required. No datalist — only existing shelves.
- All other fields unchanged.

## Sample file

`sample-books.org` is restructured to the new shelf layout with
shelves like "Fiction", "Non-Fiction", "Science Fiction".

## Test changes

- `spine-books-parses-sample`: loads restructured sample, asserts flat
  book list with `:shelf` keys.
- `spine-books-first-book-has-all-fields`: adds `:shelf` assertion.
- `spine-books-missing-properties-are-nil`: adds `:shelf` check.
- `spine-index-model-*`: rewritten — tests shelf grouping, shelf
  filtering, empty-shelf inclusion. Status-based tests removed.
- `spine-add-book-*`: tests require `:shelf` arg. Removes status check.
  Tests that books land under the correct shelf heading.
- `spine-edit-*`: keeps note/rating tests. Removes status-change tests.
  Updates model-assertion tests for new minibuffer shape.
- New `spine-shelves` tests: parses shelf names, includes empty shelves.