# Magpie 🐦

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Elixir client for the [Dropbox API v2](https://www.dropbox.com/developers/documentation/http/documentation), built on [Req](https://hexdocs.pm/req).

Like the bird, Magpie collects and stashes your things — in your Dropbox.

## Installation

Add `magpie` to your dependencies in `mix.exs`:

```elixir
def deps do
  [
    {:magpie, "~> 0.3"}
  ]
end
```

No configuration is required. The Dropbox endpoints can be overridden (rarely needed), and extra `Req` options can be merged into every request:

```elixir
config :magpie,
  base_url: "https://api.dropboxapi.com/2",
  upload_url: "https://content.dropboxapi.com/2/",
  req_options: []
```

## Usage

```elixir
# A static access token — fine for scripts, but Dropbox expires it in ~4h
client = Magpie.Client.new("DROPBOX_ACCESS_TOKEN")

# A refresh token — Magpie mints access tokens as needed, so this client
# keeps working forever (see the OAuth guide)
client =
  Magpie.Client.new(
    refresh_token: System.fetch_env!("DROPBOX_REFRESH_TOKEN"),
    app_key: System.fetch_env!("DROPBOX_APP_KEY"),
    app_secret: System.fetch_env!("DROPBOX_APP_SECRET")
  )

# Who am I?
Magpie.Users.current_account(client)

# List a folder
{:ok, %{"entries" => entries}} = Magpie.Files.ListFolder.list_folder(client, "/Photos")

# Create a folder
{:ok, %{"metadata" => folder}} = Magpie.Files.create_folder(client, "/Backup")

# Upload a file
Magpie.Files.upload(client, "/Backup/report.pdf", "priv/report.pdf")

# Download a file
{:ok, %{body: contents}} = Magpie.Files.download(client, "/Backup/report.pdf")
```

Every call returns `{:ok, result}` on success or `{:error, %Magpie.Error{}}` on API errors — with the HTTP `status`, Dropbox's `error_summary` and the full error `body`.

## OAuth 2 & token refresh

Dropbox stopped issuing long-lived access tokens: they expire after about four hours. Magpie handles the whole OAuth 2 flow and keeps tokens fresh on its own — proactively before they expire, and by replaying the request if Dropbox rejects one anyway. Concurrent requests never trigger parallel refreshes.

```elixir
# Build the authorization URL (PKCE optional, offline access by default)
{verifier, challenge} = Magpie.Auth.pkce_pair()
Magpie.Auth.authorize_url(app_key, redirect_uri: callback_url, code_challenge: challenge)

# Exchange the code Dropbox sent back for a refresh token
{:ok, token} = Magpie.Auth.exchange_code(app_key, code, code_verifier: verifier)

# Keep a supervised token holder, and build clients from it
children = [
  {Magpie.Auth.TokenServer,
   name: MyApp.DropboxToken,
   app_key: app_key,
   app_secret: app_secret,
   refresh_token: token.refresh_token}
]

client = Magpie.Client.new(token_provider: {Magpie.Auth.TokenServer, MyApp.DropboxToken})
```

Tokens can live wherever you want — implement `Magpie.Auth.TokenProvider` and pass `token_provider: {MyProvider, arg}`. See the [OAuth guide](https://magpie.hexdocs.pm/oauth.html).

## High-level flows

Magpie automates the multi-endpoint dances the Dropbox API expects from you
(see the [Examples guide](https://magpie.hexdocs.pm/examples.html) for more):

```elixir
# Smart upload: single request for small files, chunked upload session for
# big ones — streaming from disk, picked automatically
{:ok, _} = Magpie.Files.upload_file(client, "/Backup/db.dump", "priv/db.dump")

# Lazy pagination: cursors and /continue calls hidden behind a Stream
client
|> Magpie.Files.ListFolder.stream("/Photos")
|> Stream.filter(&(&1[".tag"] == "file"))
|> Enum.take(100)

# Async batch jobs: polling with exponential backoff
{:ok, launch} = Magpie.Files.MoveBatch.move_batch(client, entries)
{:ok, result} = Magpie.Async.await(client, launch, &Magpie.Files.MoveBatch.check/2)
```

## Phoenix & LiveView

LiveView already owns the upload experience — `allow_upload/3`, drag & drop,
progress, validation. Magpie doesn't try to replace any of it; it only fills
the gap a Dropbox backend creates.

From a controller there is nothing to learn: `Plug.Upload` hands you a path and
`upload_file/4` takes it from there (single request or upload session, decided
by size).

```elixir
def create(conn, %{"file" => %Plug.Upload{} = upload}) do
  {:ok, metadata} =
    Magpie.Files.upload_file(client, "/Uploads/" <> upload.filename, upload.path)
end
```

In LiveView the same one-liner works inside `consume_uploaded_entry/3`, but the
entry is spooled to a temporary file first — a 500 MB upload hits your disk in
full before a single byte reaches Dropbox. `Magpie.LiveView.UploadWriter`
removes that round trip, appending to an upload session as the chunks arrive:

```elixir
allow_upload(socket, :report,
  accept: ~w(.pdf),
  max_file_size: 500_000_000,
  writer: fn _name, entry, _socket ->
    {Magpie.LiveView.UploadWriter, client: client, path: "/Reports/" <> entry.client_name}
  end
)

# The file is already committed — `meta/1` carries the Dropbox metadata
consume_uploaded_entries(socket, :report, fn %{metadata: metadata}, _entry ->
  {:ok, metadata}
end)
```

To take your server out of the path completely, `Magpie.LiveView.presign_upload/4`
mints a one-time upload link and the browser posts the bytes straight to
Dropbox (`content.dropboxapi.com` allows the cross-origin request):

```elixir
allow_upload(socket, :avatar, accept: ~w(.jpg .png), external: &presign/2)

defp presign(entry, socket) do
  Magpie.LiveView.presign_upload(client, entry, socket, path: "/Avatars/" <> entry.client_name)
end
```

```javascript
// assets/js/app.js
import Uploaders from "../../deps/magpie/priv/static/magpie_uploader"

let liveSocket = new LiveSocket("/live", Socket, {uploaders: Uploaders, params: {...}})
```

The destination path is baked into the link, so the browser cannot redirect
the upload elsewhere. Dropbox caps these links at 150 MB — larger entries are
rejected at presign time, and belong on the `UploadWriter` path.

Magpie does not depend on `:phoenix_live_view` — the writer's callbacks are a
plain behaviour and the presign function only reads `client_name`/`client_size`
off the entry. Requiring the dependency would drag Phoenix into every project
that only wants a Dropbox client.

## Covered endpoints

Magpie covers **all current user-scoped routes** of the Dropbox API v2 (132 routes as of August 2026), verified against the official [dropbox-api-spec](https://github.com/dropbox/dropbox-api-spec):

- **files** — upload (single and sessions, incl. batch), download, download_zip, export, copy/move/delete (incl. batches), list_folder (+ continue, cursor, longpoll), metadata, search, thumbnails, previews, temporary links and upload links, save_url, tags, locks, Paper-as-files
- **sharing** — shared links (create/modify/revoke/list/download), file members, folder members, full shared-folder lifecycle
- **file_properties** — property groups and templates (user- and team-owned)
- **file_requests** — create, get, update, list, count, delete
- **users** / **account** / **auth** / **check** / **contacts** / **openid**
- **paper** — legacy `/paper/docs/*` kept for compatibility (deprecated by Dropbox — prefer `Magpie.Files.Paper`)

Dropbox Business (`/team/*`) routes are out of scope.

## Testing

The test suite runs entirely offline using [`Req.Test`](https://hexdocs.pm/req/Req.Test.html) stubs — every endpoint wrapper is verified against the exact route it must hit, and the high-level flows are tested end-to-end:

```sh
mix test            # run the suite
mix coveralls       # run with coverage report (currently ~94% line coverage)
```

## Roadmap

Magpie already covers every user-scoped route of the Dropbox API v2. The focus
now is on the client-side ergonomics that real applications need — including a
few things the official SDKs never shipped.

### 0.2.0 — OAuth 2 & token refresh ✅

- [x] `Magpie.Auth` — authorization URL builder, PKCE helpers, code-for-token exchange
- [x] Automatic access-token refresh (proactive, with margin, and reactive on
      `expired_access_token`) with single-flight guarantees
- [x] `Magpie.Auth.TokenProvider` behaviour + supervised `TokenServer`, so apps
      can plug their own token persistence
- [x] OAuth guide (Dropbox deprecated long-lived tokens — this makes Magpie
      production-ready for 24/7 applications)

### 0.2.1 — TokenServer ergonomics ✅

- [x] `TokenServer` can start without a refresh token and receive one at runtime
      (`set_refresh_token/3`) — plain static supervision trees, no DynamicSupervisor
      dance for apps that obtain tokens via OAuth callback
- [x] `authorize_url/2` `extra_params:` passthrough (`force_reapprove`, `locale`, …)

### 0.3.0 — Phoenix uploads ✅

- [x] `Magpie.LiveView.UploadWriter` — stream a LiveView upload straight into a
      Dropbox upload session, without spooling it to the server's disk
- [x] `Magpie.LiveView.presign_upload/4` — direct browser → Dropbox uploads via
      `get_temporary_upload_link/3`, so the bytes bypass your server entirely,
      with the JS uploader entry shipped in `priv/static`

### 0.4.0 — Typed metadata

- [ ] Decode API responses into structs (`Magpie.FileMetadata`,
      `Magpie.FolderMetadata`, `Magpie.DeletedMetadata`) with proper types —
      `DateTime` timestamps, first-class `content_hash` — instead of raw maps
      with `".tag"` keys

### 0.5.0 — Reacting to changes

- [ ] `Magpie.Webhook` — what the official SDKs never shipped: verification
      challenge handling, constant-time `X-Dropbox-Signature` HMAC validation,
      notification payload parsing, and a drop-in `Magpie.Webhook.Plug` for
      Phoenix (raw-body aware)
- [ ] `Magpie.Watcher` — supervised process wrapping `list_folder/longpoll`
      (cursor management, backoff, reconnection) that delivers folder change
      events as messages — "when a file lands in `/Inbox`, trigger a pipeline"
- [ ] Webhook → Watcher integration: use webhook notifications as the wake-up
      signal and `list_folder/continue` to fetch what actually changed

### Backlog

- [ ] Streaming download to disk (`download_file/3` mirroring `upload_file/4`,
      without loading the file into memory)
- [ ] Dropbox `content_hash` helper — verify integrity after transfers and skip
      uploads of unchanged files (`verify: true` / `skip_unchanged: true`)
- [ ] Rate-limit aware retries — honor `Retry-After` on 429/503 out of the box
- [ ] `:telemetry` events for every request
- [ ] `Dropbox-API-Path-Root` support — access team space namespaces, not just
      the member folder
- [ ] `upload_many/3` — concurrent multi-file upload via upload session batches

Magpie is a client library — application-level workflows (retention policies,
deduplication, sync) are intentionally out of scope, though the guides include
recipes for building them on top. 

Suggestions and PRs are welcome — open an [issue](https://github.com/alexcassol/magpie/issues).

## Origin

Magpie started as a fork of [sger/elixir_dropbox](https://hex.pm/packages/elixir_dropbox), which is no longer maintained (its GitHub repository has been deleted). The code has since been modernized: HTTPoison/Poison were replaced with Req/Jason, and the test suite was rewritten with Req.Test. Credit and thanks to the original Elixir Dropbox contributors.

## License

MIT — see [LICENSE](LICENSE).