# `GraphApi.Delta`
[🔗](https://github.com/keenmate/microsoft_graph/blob/v1.0.0-rc.1/lib/graph_api/delta.ex#L1)

Delta query support for tracking incremental changes.

Delta queries return changes since the last sync point. The first call returns
the full dataset plus a `deltaLink`. Subsequent calls with the `deltaLink`
return only items that changed (created, updated, or deleted).

## How it works

1. Initial sync: `Delta.query("/users/delta", client: client)`
   Returns all current items + a `delta_link` for future syncs.

2. Incremental sync: `Delta.query(delta_link, client: client)`
   Returns only changes since the last sync. Deleted items have an `@removed` property.

## Examples

    # Initial sync
    {:ok, page} = Delta.query("/users/delta", client: client)
    # page.items => [all current users]
    # page.delta_link => "https://graph...?$deltatoken=..."

    # Store delta_link, then later:
    {:ok, changes} = Delta.query(page.delta_link, client: client)
    # changes.items => only what changed

    # Collect all pages at once
    {:ok, result} = Delta.collect_all("/users/delta", client: client)

## Supported resources

- `/users/delta`
- `/groups/delta`
- `/groups/{id}/members/delta`
- `/me/messages/delta` or `/users/{id}/messages/delta`
- `/me/mailFolders/{id}/messages/delta`
- `/me/events/delta` or `/users/{id}/events/delta`
- `/drives/{id}/root/delta`

# `delta_page`

```elixir
@type delta_page() :: %{
  items: [map()],
  delta_link: String.t() | nil,
  next_link: String.t() | nil
}
```

# `collect_all`

```elixir
@spec collect_all(
  String.t(),
  keyword()
) :: {:ok, delta_page()} | {:error, term()}
```

Collects all pages of a delta query into a single result.

Follows `@odata.nextLink` pages until a `deltaLink` is received.
Returns all accumulated items plus the final `delta_link`.

## Examples

    {:ok, result} = Delta.collect_all("/users/delta", client: client)
    # result.items => all items across all pages
    # result.delta_link => "https://...?$deltatoken=..."

# `query`

```elixir
@spec query(
  String.t(),
  keyword()
) :: {:ok, delta_page()} | {:error, term()}
```

Performs a delta query and returns a single page of results.

Accepts either a relative path (e.g., `"/users/delta"`) for initial sync,
or a full deltaLink/nextLink URL for subsequent pages.

## Options

Same as other resource functions: `:client`, `:query`, `:access_token`, `:api_version`, `:as`

## Examples

    # Initial sync
    {:ok, page} = Delta.query("/users/delta", client: client)

    # Follow deltaLink for changes
    {:ok, changes} = Delta.query(page.delta_link, client: client)

    # With OData query
    query = OData.new() |> OData.select(["id", "displayName"]) |> OData.top(100)
    {:ok, page} = Delta.query("/users/delta", client: client, query: query)

# `stream`

```elixir
@spec stream(
  delta_page(),
  keyword()
) :: Enumerable.t()
```

Creates a lazy `Stream` that yields items from all pages of a delta query.

The stream follows `@odata.nextLink` pages automatically. After the stream
is consumed, use `collect_all/2` if you need the `delta_link`.

## Examples

    {:ok, first_page} = Delta.query("/users/delta", client: client)

    first_page
    |> Delta.stream(client: client)
    |> Stream.filter(fn item -> item["@removed"] == nil end)
    |> Enum.to_list()

---

*Consult [api-reference.md](api-reference.md) for complete listing*