README.md

JaSerializer
============

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jsonapi.org formatting of Elixir data structures suitable for serialization by
libraries such as Poison.

## Usage

See [documentation](http://hexdocs.pm/ja_serializer/) on hexdoc for full
serialization and usage details.

## Installation
Add JaSerializer to your application

mix.deps

```elixir
defp deps do
  [
    # ...
      {:ja_serializer, "~> x.x.x"}
    # ...
  ]
end
```

## Serializer Behaviour and DSL

```elixir
defmodule MyApp.ArticleSerializer do
  use JaSerializer

  location "/articles/:id"
  attributes [:title, :tags, :body, :excerpt]

  has_one :author,
    serializer: PersonSerializer,
    include: true,
    field: :authored_by

  has_many :comments,
    links: [
      related: "/articles/:id/comments",
      self: "/articles/:id/relationships/comments"
    ]

  def comments(article, _conn) do
    Comment.for_article(article)
  end

  def excerpt(article, _conn) do
    [first | _ ] = String.split(article.body, ".")
    first
  end
end
```

### Attributes

Attributes are defined as a list in the serializer module.
The serializer will use the given atom as the key by default.
You can also specify a custom method of attribute retrieval by defining a
<attribute_name>/2 method. The method will be passed the struct
and the connection.

### Relationships

Valid relationships are: `has_one`, `has_many`.
Use `has_one` for `belongs_to` type of relationships.
For each relationship, you can define the name and a variety of options.
Just like attributes, the serializer will use the given atom
to look up the relationship, unless you specify a custom retrieval method
OR provide a `field` option

#### Relationship options

* serializer - The serializer to use when serializing this resource
* include - boolean - true to always side-load this relationship
* field - custom field to use for relationship retrieval
* links - custom links to use in the `relationships` hash

### Direct Usage of Serializer

```elixir
MyApp.ArticleSerializer
|> JaSerializer.format(struct, conn)
|> Poison.encode!
```

### Formatting options

The `format/4` method is able to take in options that can customize the
serialized payload.

#### Include

By specifying the `include` option, the serializer will only side-load
the relationships specified. This option should be a comma separated
list of relationships. Each relationship should be a dot separated path.

Example: `include: "author,comments.author"`

The format of this string should exactly match the one specified by the
[JSON-API spec](http://jsonapi.org/format/#fetching-includes)

Note: If specifying the `include` option, all "default" includes will
be ignored, and only the specified relationships included, per spec.

#### Fields

The `fields` option satisfies the [sparse fieldset](http://jsonapi.org/format/#fetching-sparse-fieldsets) portion of the spec. This options should
be a map of resource types whose value is a comma separated list of fields
to include.

Example: `fields: %{"articles" => "title,body", "comments" => "body"}`

If you're using Plug, you should be able to call `fetch_query_params(conn)`
and pass the result of `conn.query_params["fields"]` as this option.

## Phoenix Usage

For an example of starting with Phoenix's JSON generator and updating
to work with JaSerializer, see [Getting Started with Phoenix](https://github.com/vt-elixir/ja_serializer/wiki/Getting-Started-with-Phoenix).

Simply `use JaSerializer.PhoenixView` in your view (or in the Web module) and
define your serializer as above.

The `render("index.json-api", data)` and `render("show.json-api", data)` are defined
for you. You can just call render as normal from your controller.

By specifying `include`s when calling the render function, you can override
the `include: false` in the ArticleView.

```elixir
defmodule PhoenixExample.ArticlesController do
  use PhoenixExample.Web, :controller

  def index(conn, _params) do
    render conn, "index.json-api", data: Repo.all(Article)
  end

  def show(conn, %{"id" => id}) do
    article = Repo.get(Article, id) |> Repo.preload([:comments])
    render conn, "show.json-api", data: article,
      opts: [include: "comments"]
  end

  def create(conn, %{"data" => data}) do
    attrs = JaSerializer.Params.to_attributes(data)
    changeset = Article.changeset(%Article{}, attrs)
    case Repo.insert(changeset) do
      {:ok, article} ->
        conn
        |> put_status(201)
        |> render("show.json-api", data: article)
      {:error, changeset} ->
        conn
        |> put_status(422)
        |> render(:errors, data: changeset)
    end
  end
end

defmodule PhoenixExample.ArticlesView do
  use PhoenixExample.Web, :view
  use JaSerializer.PhoenixView # Or use in web/web.ex

  attributes [:title]

  has_many :comments,
    serializer: PhoenixExample.CommentsView,
    include: false,
    identifiers: :when_included
  #has_many, etc.
end
```

## Configuration

To use the Phoenix `accepts` plug you must configure Plug to handle the
"application/vnd.api+json" mime type and Phoenix to serialize json-api with
Poison.

Depending on your version of Plug add the following to `config.exs`:

Plug ~> "1.2.0"
```elixir
config :phoenix, :format_encoders,
  "json-api": Poison

config :mime, :types, %{
  "application/vnd.api+json" => ["json-api"]
}
```

And then re-compile mime: (per: https://hexdocs.pm/mime/MIME.html)

```shell
mix deps.clean mime --build
mix deps.get
```

Plug < "1.2.0"
```elixir
config :phoenix, :format_encoders,
  "json-api": Poison

config :plug, :mimes, %{
  "application/vnd.api+json" => ["json-api"]
}
```

And then re-compile plug: (per: https://hexdocs.pm/plug/1.1.3/Plug.MIME.html)

```shell
mix deps.clean plug --build
mix deps.get
```

And then add json api to your plug pipeline.

```elixir
pipeline :api do
  plug :accepts, ["json-api"]
end
```

For strict content-type/accept enforcement and to auto add the proper
content-type to responses add the JaSerializer.ContentTypeNegotiation plug.

To normalize attributes to underscores include the JaSerializer.Deserializer
plug.

```elixir
pipeline :api do
  plug :accepts, ["json-api"]
  plug JaSerializer.ContentTypeNegotiation
  plug JaSerializer.Deserializer
end
```

If you're rendering JSON API errors, like `404.json-api`, then you _must_ add `json-api`
to the `accepts` of your `render_errors` within your existing configuration in `config.exs`, like so:

```elixir
config :phoenix, PhoenixExample.Endpoint,
  render_errors: [view: PhoenixExample.ErrorView, accepts: ~w(html json json-api)]
```

If you're rendering both JSON-API and HTML, you need to include the `html` option in the config:

```elixir
config :phoenix, :format_encoders,
  html: Phoenix.Template.HTML,
  "json-api": Poison
```

## Testing controllers

Set the right headers in `setup` and when passing parameters to put and post requests,
you should pass them as a binary. That is because for map and list parameters,
the content-type will be automatically changed to multipart.

```elixir
defmodule Sample.SomeControllerTest do
  use Sample.ConnCase

  setup %{conn: conn} do
    conn =
      conn
      |> put_req_header("accept", "application/vnd.api+json")
      |> put_req_header("content-type", "application/vnd.api+json")

    {:ok, conn: conn}
  end

  test "create action", %{conn: conn} do
    params = Poison.encode!(%{data: %{attributes: @valid_attrs}})
    conn = post conn, "/some_resource", params

    ...
  end

  ...
end
```

## Pagination

JaSerializer provides page based pagination integration with
[Scrivener](https://github.com/drewolson/scrivener) or custom pagination
by passing your owns links in.

### Custom

JaSerializer allows custom pagination via the `page` option. The `page` option
expects to receive a `Map` with URL values for `first`, `next`, `prev`,
and `last`.

For example:

```elixir
page = %{
  first: "http://example.com/api/v1/posts?page[cursor]=1&page[per]=20",
  prev: nil
  next: "http://example.com/api/v1/posts?page[cursor]=20&page[per]=20",
  last: "http://example.com/api/v1/posts?page[cursor]=60&page[per]=20"
}

# Direct call
JaSerializer.format(MySerializer, collection, conn, page: page)

# In Phoenix Controller
render conn, "index.json-api", data: collection, opts: [page: page]
```

#### Builder

You can build the pagination links with
`JaSerializer.Builder.PaginationLinks.build/2`

Simply pass in the following:

```elixir
links =
  JaSerializer.Builder.PaginationLinks.build(
    %{
      number: 2,
      size: 10,
      total: 20
    },
    conn
  )
```

See `JaSerializer.Builder.PaginationLinks` for how to customize.

### Scrivener Integration

If you are using Scrivener for pagination, all you need to do is pass the
results of `paginate/2` to your serializer.

```elixir
page = MyRepo.paginate(MyModel, params.page)

# Direct call
JaSerializer.format(MySerializer, page, conn, [])

# In Phoenix controller
render conn, "index.json-api", data: page
```

When integrating with Scrivener, the URLs generated will be based on the
`Plug.Conn`'s path. This can be overridden by passing in the `page[:base_url]`
option.

```elixir
render conn, "index.json-api", data: page, opts: [base_url: "http://example.com/foos"]
```

You can also configure `ja_serializer` to use a global default URL
base for all links.

```elixir
config :ja_serializer,
  page_base_url: "http://example.com:4000/v1/"
```

*Note*: The resulting URLs will use the JSON-API recommended `page` query
param.

Example URL:
`http://example.com:4000/v1/posts?page[page]=2&page[page-size]=50`

### Meta Data

JaSerializer allows adding top level meta information via the `meta` option. The `meta` option
expects to receive a `Map` containing the data which will be rendered under the top level meta key.

```elixir
meta_data = %{
  "key" => "value"
}

# Direct call
JaSerializer.format(MySerializer, data, conn, meta: meta_data)

# In Phoenix controller
render conn, "index.json-api", data: data, opts: [meta: meta_data]
```

## Customization

### Key Format (for Attribute, Relationship and Query Param)

By default keys are `dash-erized` as per the JSON:API 1.0 recommendation, but keys can be customized via config.

In your `config.exs` file you can use `camel_cased` recommended by upcoming JSON:API 1.1:

```elixir
config :ja_serializer,
  key_format: :camel_cased
```

Or `underscored`:

```elixir
config :ja_serializer,
  key_format: :underscored
```

You may also pass custom function for serialization and a second optional one for deserialization. Both accept a single binary argument:

```elixir
defmodule MyStringModule do
  def camelize(key), do: key #...
  def underscore(key), do: key #...
end

config :ja_serializer,
  key_format: {:custom, MyStringModule, :camelize, :underscore}
```

### Custom Attribute Value Formatters

When serializing attribute values more complex than string, numbers, atoms or
list of those things it is recommended to implement a custom formatter.

To implement a custom formatter:

```elixir
defimpl JaSerializer.Formatter, for: [MyStruct] do
  def format(struct), do: struct
end
```

### Pluralizing All Types By Default

You can opt-in to pluralizing all types for default:

```elixir
config :ja_serializer,
  pluralize_types: true
```


## Complimentary Libraries

* [JaResource](https://github.com/vt-elixir/ja_resource) - WIP behaviour for creating JSON-API controllers in Phoenix.
* [voorhees](https://github.com/danmcclain/voorhees) - Testing tool for JSON API responses
* [inquisitor](https://github.com/DockYard/inquisitor) - Composable query builder for Ecto
* [scrivener](https://github.com/drewolson/scrivener) - Ecto pagination

## License

JaSerializer source code is released under Apache 2 License. Check LICENSE
file for more information.