### Implement Custom Pagination with AshJsonApiWrapper Paginator

Source: https://context7.com/ash-project/ash_json_api_wrapper/llms.txt

Demonstrates how to implement custom pagination schemes by defining a module that adheres to the `AshJsonApiWrapper.Paginator` behavior. Includes an example of a cursor-based paginator and how to apply it globally or per-endpoint.

```elixir
defmodule MyApp.CursorPaginator do
  use AshJsonApiWrapper.Paginator

  @impl true
  def start(_opts) do
    {:ok, %{params: %{"page" => 1}}}
  end

  @impl true
  def continue(_response, [], _opts) do
    :halt  # No more entities, stop paginating
  end

  def continue(response, _entities, opts) do
    case ExJSONPath.eval(response, "$.meta.next_cursor") do
      {:ok, [cursor | _]} when not is_nil(cursor) ->
        {:ok, %{params: %{"cursor" => cursor}}}

      _ ->
        :halt
    end
  end
end

defmodule MyApp.Article do
  use Ash.Resource,
    domain: MyApp.Domain,
    data_layer: AshJsonApiWrapper.DataLayer

  json_api_wrapper do
    # Base paginator applies to all endpoints
    base_paginator {MyApp.CursorPaginator, []}

    endpoints do
      base "https://api.example.com"

      endpoint :read do
        path "/articles"
        entity_path "$.articles"
        # Or use built-in continuation_property paginator
        paginator continuation_property("$.next_page_token", param: "page_token")
      end
    end
  end

  attributes do
    attribute :id, :integer, primary_key?: true, allow_nil?: false
    attribute :title, :string
  end

  actions do
    defaults [:read]
  end
end

# Pagination is automatic - all pages are fetched
MyApp.Article |> Ash.read!()

```

--------------------------------

### Integrate with Hacker News API for Stories and Authors

Source: https://context7.com/ash-project/ash_json_api_wrapper/llms.txt

Provides a comprehensive example of integrating with the Hacker News API. It defines resources for stories and top stories, demonstrating how to fetch data from different endpoints, handle nested data, define relationships (e.g., story to author), and perform calculations on retrieved data. The example also shows how to query and transform the data.

```elixir
defmodule HackerNews.Story do
  use Ash.Resource,
    domain: HackerNews.Domain,
    data_layer: AshJsonApiWrapper.DataLayer

  json_api_wrapper do
    endpoints do
      base "https://hacker-news.firebaseio.com/v0/"

      get_endpoint :read, :id do
        path "item/:id.json"
      end
    end
  end

  attributes do
    attribute :id, :integer, primary_key?: true, allow_nil?: false
    attribute :by, :string, allow_nil?: false
    attribute :score, :integer, allow_nil?: false
    attribute :title, :string
    attribute :url, :string
    attribute :time, :integer
  end

  calculations do
    calculate :short_url, :string, expr(
      fragment("REPLACE(REPLACE(?, 'https://', ''), 'http://', '')", url)
    )
  end

  relationships do
    has_one :author, HackerNews.User do
      source_attribute :by
      destination_attribute :id
    end
  end

  actions do
    defaults [:read]
  end
end

defmodule HackerNews.TopStories do
  use Ash.Resource,
    domain: HackerNews.Domain,
    data_layer: AshJsonApiWrapper.DataLayer

  json_api_wrapper do
    endpoints do
      base "https://hacker-news.firebaseio.com/v0/"

      endpoint :read do
        path "topstories.json"
        limit_with {:param, "limitToFirst"}
      end
    end

    fields do
      field :id do
        path ""  # Each item in response IS the id
      end
    end
  end

  attributes do
    attribute :id, :integer, primary_key?: true, allow_nil?: false
  end

  relationships do
    has_one :story, HackerNews.Story do
      source_attribute :id
      destination_attribute :id
    end
  end

  actions do
    defaults [:read]
  end
end

# Fetch top stories with full story details and author
HackerNews.TopStories
|> Ash.Query.limit(5)
|> Ash.Query.load(story: :author)
|> Ash.read!()
|> Enum.map(fn top ->
  %{ 
    title: top.story.title,
    score: top.story.score,
    author: top.story.author.id,
    url: top.story.url
  }
end)
```

--------------------------------

### Install AshJsonApiWrapper in Mix Project (Elixir)

Source: https://github.com/ash-project/ash_json_api_wrapper/blob/main/README.md

This code snippet shows how to add the AshJsonApiWrapper dependency to your Elixir project's `mix.exs` file. Ensure you are using a compatible version of Elixir and Ash.

```elixir
def deps do
  [
    {:ash_json_api_wrapper, "~> 0.1.0"}
  ]
end
```

--------------------------------

### Define Basic Resource with AshJsonApiWrapper

Source: https://context7.com/ash-project/ash_json_api_wrapper/llms.txt

Demonstrates how to define a basic Ash resource using AshJsonApiWrapper. This involves configuring the `json_api_wrapper` section with endpoint and field mappings. The data layer handles HTTP requests and transforms JSON responses into Ash records. It shows how to map JSON fields using JSONPath and enable filtering.

```elixir
defmodule MyApp.Pet do
  use Ash.Resource,
    domain: MyApp.Domain,
    data_layer: AshJsonApiWrapper.DataLayer

  json_api_wrapper do
    tesla MyApp.CustomTesla  # Optional custom Tesla client

    endpoints do
      base "https://petstore.example.com/api/v3"

      endpoint :list_pets do
        path "/pets"
        entity_path "$.data"  # JSONPath to extract entities from response
        runtime_sort? true
      end

      get_endpoint :get_pet, :id do
        path "/pets/:id"
      end
    end

    fields do
      field :name do
        path "$.name"  # JSONPath within each entity
      end

      field :status do
        filter_handler :simple  # Enable filtering on this field
      end
    end
  end

  attributes do
    attribute :id, :integer do
      primary_key? true
      allow_nil? false
    end

    attribute :name, :string
    attribute :status, :atom, constraints: [one_of: [:available, :pending, :sold]]
  end

  actions do
    read :list_pets
    read :get_pet
  end
end

# Usage
MyApp.Pet
|> Ash.Query.for_read(:list_pets)
|> Ash.Query.filter(status == :available)
|> Ash.Query.limit(10)
|> Ash.read!()

```

--------------------------------

### Configure Endpoints for AshJsonApiWrapper Resources

Source: https://context7.com/ash-project/ash_json_api_wrapper/llms.txt

Illustrates how to configure endpoints for Ash resources using AshJsonApiWrapper. It shows mapping resource actions to specific API endpoints, including standard list operations (`endpoint`) and fetching single records by ID (`get_endpoint`). It also demonstrates configuring query parameters for limits and handling multiple actions with a single endpoint configuration.

```elixir
defmodule MyApp.Story do
  use Ash.Resource,
    domain: MyApp.Domain,
    data_layer: AshJsonApiWrapper.DataLayer

  json_api_wrapper do
    endpoints do
      base "https://api.example.com/v1"

      # Standard endpoint for listing
      endpoint :read do
        path "/stories"
        entity_path "$.stories"
        limit_with {:param, "limit"}  # Pass limit as query param
        runtime_sort? true
      end

      # Get endpoint for fetching by ID
      get_endpoint :read, :id do
        path "/stories/:id"  # :id is replaced with filter value
      end

      # Endpoint for multiple actions
      endpoint [:search, :filter_by_author] do
        path "/stories/search"
        entity_path "$.results"
      end
    end
  end

  attributes do
    attribute :id, :integer, primary_key?: true, allow_nil?: false
    attribute :title, :string
    attribute :author, :string
  end

  actions do
    read :read
    read :search
    read :filter_by_author
  end
end

# Fetch by ID - uses get_endpoint
MyApp.Story
|> Ash.Query.filter(id == 123)
|> Ash.read_one!()

# Fetch multiple IDs in parallel
MyApp.Story
|> Ash.Query.filter(id in [1, 2, 3])
|> Ash.read!()

```

--------------------------------

### Configure Record Creation with Custom Request Body

Source: https://context7.com/ash-project/ash_json_api_wrapper/llms.txt

Illustrates how to configure Ash resources for creating records via API endpoints. It shows how to specify the request body structure using `fields_in` and `write_entity_path`, and how to customize the write path for individual fields. It also demonstrates creating records via query parameters.

```elixir
defmodule MyApp.Post do
  use Ash.Resource,
    domain: MyApp.Domain,
    data_layer: AshJsonApiWrapper.DataLayer

  json_api_wrapper do
    endpoints do
      base "https://api.example.com"

      endpoint :create do
        path "/posts"
        fields_in :body  # Put fields in request body (default)
        write_entity_path ["post"]  # Nest fields under "post" key
        entity_path "$.post"  # Extract created entity from response
      end

      endpoint :create_via_params do
        path "/posts/quick"
        fields_in :params  # Put fields in query params instead
      end
    end

    fields do
      field :title do
        write_path ["post", "title"]  # Override write location
      end
    end
  end

  attributes do
    attribute :id, :integer, primary_key?: true, allow_nil?: false
    attribute :title, :string
    attribute :body, :string
    attribute :published, :boolean
  end

  actions do
    create :create do
      accept [:title, :body, :published]
    end

    create :create_via_params do
      accept [:title]
    end
  end
end

# Create sends POST with body: {"post": {"title": "...", "body": "...", "published": true}}
MyApp.Post
|> Ash.Changeset.for_create(:create, %{
  title: "Hello World",
  body: "My first post",
  published: true
})
|> Ash.create!()
```

--------------------------------

### Configure Custom Tesla Client with Middleware

Source: https://context7.com/ash-project/ash_json_api_wrapper/llms.txt

Demonstrates how to configure a custom Tesla client within an Ash resource. This includes setting a base URL, adding authentication headers, enabling JSON parsing, configuring retry logic, and adding logging and redirects. The client is then used by the Ash resource for API interactions.

```elixir
defmodule MyApp.AuthenticatedTesla do
  use Tesla

  plug Tesla.Middleware.BaseUrl, "https://api.example.com"

  plug Tesla.Middleware.Headers, [
    {"Authorization", "Bearer #{System.get_env("API_TOKEN")}"},
    {"Accept", "application/json"}
  ]

  plug Tesla.Middleware.JSON

  plug Tesla.Middleware.Retry,
    delay: 1000,
    max_retries: 3,
    max_delay: 4000,
    should_retry: fn
      {:ok, %{status: status}} when status in [429, 500, 502, 503] -> true
      {:ok, _} -> false
      {:error, _} -> true
    end

  plug Tesla.Middleware.Logger
  plug Tesla.Middleware.FollowRedirects
end

defmodule MyApp.ProtectedResource do
  use Ash.Resource,
    domain: MyApp.Domain,
    data_layer: AshJsonApiWrapper.DataLayer

  json_api_wrapper do
    tesla MyApp.AuthenticatedTesla

    endpoints do
      base "/v1"  # Combined with Tesla BaseUrl

      endpoint :read do
        path "/protected"
        entity_path "$.data"
      end
    end
  end

  attributes do
    attribute :id, :integer, primary_key?: true, allow_nil?: false
    attribute :name, :string
  end

  actions do
    defaults [:read]
  end
end
```

--------------------------------

### Configure API Fields and Filters with AshJsonApiWrapper

Source: https://context7.com/ash-project/ash_json_api_wrapper/llms.txt

Defines how API response paths are mapped to resource attributes and how filters are handled. Supports simple filters, custom query parameter paths, list filtering, and CSV list filtering. Endpoint-specific field overrides are also supported.

```elixir
defmodule MyApp.User do
  use Ash.Resource,
    domain: MyApp.Domain,
    data_layer: AshJsonApiWrapper.DataLayer

  json_api_wrapper do
    endpoints do
      base "https://api.example.com"

      endpoint :read do
        path "/users"
        entity_path "$.users"

        # Endpoint-specific field override
        field :email do
          path "$.contact.email"
        end
      end
    end

    fields do
      # Map nested JSON path to attribute
      field :id do
        path "$.user_id"
      end

      # Configure write path for create/update
      field :name do
        path "$.profile.name"
        write_path ["user", "profile", "name"]
      end

      # Simple filter - adds field directly to query params
      field :status do
        filter_handler :simple
      end

      # Filter with custom query param path
      field :category do
        filter_handler {:simple, ["filters", "category"]}
      end

      # Place multiple filter values in a list
      field :tags do
        filter_handler {:place_in_list, ["filter", "tags"]}
      end

      # Place filter values as CSV
      field :ids do
        filter_handler {:place_in_csv_list, ["ids"]}
      end
    end
  end

  attributes do
    attribute :id, :string, primary_key?: true, allow_nil?: false
    attribute :name, :string
    attribute :email, :string
    attribute :status, :string
    attribute :category, :string
    attribute :tags, {:array, :string}
  end

  actions do
    defaults [:read]
  end
end

# Filter converts to query params based on filter_handler
MyApp.User
|> Ash.Query.filter(status == "active" and category == "premium")
|> Ash.read!()
# Results in: GET /users?status=active&filters[category]=premium

```

--------------------------------

### Dynamically Set Query Parameters and Body with AshJsonApiWrapper

Source: https://context7.com/ash-project/ash_json_api_wrapper/llms.txt

Provides functions to dynamically inject parameters into API requests. `set_query_params/2` sets all query parameters, `merge_query_params/2` adds or updates existing parameters, and `set_body_param/3` is used for setting body parameters, typically for POST requests.

```elixir
defmodule MyApp.Search do
  use Ash.Resource,
    domain: MyApp.Domain,
    data_layer: AshJsonApiWrapper.DataLayer

  json_api_wrapper do
    endpoints do
      base "https://api.example.com"

      endpoint :search do
        path "/search"
        entity_path "$.results"
      end
    end
  end

  attributes do
    attribute :id, :string, primary_key?: true, allow_nil?: false
    attribute :title, :string
    attribute :score, :float
  end

  actions do
    read :search
  end
end

# Set query parameters dynamically
MyApp.Search
|> Ash.Query.for_read(:search)
|> AshJsonApiWrapper.set_query_params(%{
  "q" => "elixir",
  "sort" => "relevance",
  "filters" => %{"type" => "article"}
})
|> Ash.read!()

# Merge additional params (preserves existing)
MyApp.Search
|> Ash.Query.for_read(:search)
|> AshJsonApiWrapper.merge_query_params(%{"q" => "elixir"})
|> AshJsonApiWrapper.merge_query_params(%{"limit" => 50})
|> Ash.read!()

# Set body parameters for POST endpoints
changeset
|> AshJsonApiWrapper.set_body_param("api_key", "secret123")
|> AshJsonApiWrapper.set_body_param("options", %{"notify" => true})

```

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