# 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