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atomsync/README.md
2026-04-16 20:18:45 +02:00

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# Atomsync
A Clojure-native synced atom. Offline-first key-value store with an `atom` interface that syncs to a SQLite-backed server over Transit.
```clojure
(def conn (<! (atomsync/open "my-app")))
(def todos (atomsync/synced-atom conn "todo" {:server "http://localhost:8090/sync"}))
(swap! todos assoc "todo:1" {:text "Buy milk" :tags #{:groceries}})
@todos ;=> {"todo:1" {:text "Buy milk" :tags #{:groceries}}}
```
## What it does
- **Preserves Clojure types**: keywords, sets, UUIDs, instants — no lossy JSON
- **Works offline**: reads/writes hit IndexedDB immediately, syncs when online
- **Atom interface**: `swap!`, `deref`, `add-watch` — works with Reagent, Rum, or raw CLJS
- **~500 lines**: client (~300) + server (~200), no opaque dependencies
## Quick start
### Server
```bash
clj -M:server
# or: clj -M:server 8090 my-data.db
```
Starts on `http://localhost:8090` with a SQLite file at `atomsync.db`.
### Client (CLJS)
```clojure
(ns my-app.core
(:require [atomsync.core :as pb]
[cljs.core.async :refer [go <!]]))
(go
(let [conn (<! (pb/open "my-app"))
todos (pb/synced-atom conn "todo"
{:server "http://localhost:8090/sync"})]
(<! (pb/ready? todos))
(swap! todos assoc "todo:1" {:text "Buy milk" :done false})
(add-watch todos :log (fn [_ _ _ new] (println (count new) "todos")))))
```
## Architecture
```
Browser Server
┌─────────────┐ ┌──────────────┐
│ SyncedAtom │ ── Transit/HTTP ──▶ │ http-kit │
│ ↕ atom │ │ ↕ Transit │
│ ↕ IndexedDB│ ◀── Transit/HTTP ── │ ↕ Nippy │
│ (Transit) │ │ ↕ SQLite │
└─────────────┘ └──────────────┘
```
## Sync protocol
- **Pull**: `GET /sync?group=todo&since=<epoch-ms>` — returns changed docs
- **Push**: `POST /sync` — sends local changes with version numbers
- **Conflicts**: server rejects stale writes, client accepts server value
## Auth
Optional token-based auth:
```clojure
(server/start! {:port 8090
:users {"alice" {:token "abc123" :groups #{"todo" "settings"}}
"bob" {:token "def456" :groups #{"todo"}}}})
```
Client passes token:
```clojure
(pb/synced-atom conn "todo" {:server "http://localhost:8090/sync"
:token "abc123"})
```
## Dependencies
| Layer | Library | Purpose |
|--------|---------|---------|
| Server | next.jdbc + sqlite-jdbc | SQLite storage |
| Server | nippy | Binary serialization |
| Server | transit-clj | Wire format |
| Server | http-kit | HTTP server |
| Client | transit-cljs | Serialization (IDB + wire) |
| Client | core.async | Sync coordination |
## Tests
```bash
# All server tests
clj -M:dev -e '(require (quote atomsync.db-test) (quote atomsync.transit-test) (quote atomsync.server-test) (quote atomsync.auth-test)) (clojure.test/run-all-tests #"atomsync\..*")'
```
## License
MIT