backpex

defmodule Backpex.Filters.Boolean do
  @moduledoc """
  The boolean filter renders one checkbox per given option, hence multiple options can apply at the same time.
  Instead of implementing a `query` callback, you need to define predicates for each option leveraging [`Ecto.Query.dynamic/2`](https://hexdocs.pm/ecto/Ecto.Query.html#dynamic/2).

  > #### Warning {: .warning}
  >
  > Note that only query elements will work as a predicate that also work in an [`Ecto.Query.where/3`](https://hexdocs.pm/ecto/Ecto.Query.html#where/3).

  If none is selected, the filter does not change the query. If multiple options are selected they are logically reduced via `orWhere`.

  See the following example for an implementation of a boolean filter for a published field.

      defmodule MyAppWeb.Filters.EventPublished do
        use Backpex.Filters.Boolean

        @impl Backpex.Filter
        def label, do: "Published?"

        @impl Backpex.Filters.Boolean
        def options do
          [
            %{
              label: "Published",
              key: "published",
              predicate: dynamic([x], x.published)
            },
            %{
              label: "Not published",
              key: "not_published",
              predicate: dynamic([x], not x.published)
            }
          ]
        end
      end

  > #### `use Backpex.Filters.Boolean` {: .info}
  >
  > When you `use Backpex.Filters.Boolean`, the `Backpex.Filters.Boolean` module will set `@behavior Backpex.Filters.Boolean`.
  > In addition it will add a `render` and `render_form` function in order to display the corresponding filter.
  > It will also implement the `Backpex.Filter.query` function to define a boolean query.
  """
  use BackpexWeb, :filter

  @doc """
  The list of options for the select filter.
  """
  @callback options :: [map()]

  defmacro __using__(_opts) do
    quote do
      use BackpexWeb, :filter
      use Backpex.Filter

      alias Backpex.Filters.Boolean, as: BooleanFilter

      @behaviour Backpex.Filters.Boolean

      @impl Backpex.Filter
      def query(query, attribute, value) do
        BooleanFilter.query(query, options(), attribute, value)
      end

      @impl Backpex.Filter
      def render(assigns) do
        assigns = assign(assigns, :options, options())
        BooleanFilter.render(assigns)
      end

      @impl Backpex.Filter
      def render_form(assigns) do
        assigns = assign(assigns, :options, options())
        BooleanFilter.render_form(assigns)
      end

      defoverridable query: 3, render: 1, render_form: 1
    end
  end

  attr :value, :any, required: true
  attr :options, :list, required: true

  def render(assigns) do
    assigns = assign(assigns, :label, option_value_to_label(assigns.options, assigns.value))

    ~H"""
    {@label}
    """
  end

  attr :form, :any, required: true
  attr :field, :atom, required: true
  attr :value, :any, required: true
  attr :options, :list, required: true

  def render_form(assigns) do
    value = if is_nil(assigns.value), do: [], else: assigns.value
    options = Enum.map(assigns.options, fn %{label: l, key: k} -> {l, k} end)

    assigns =
      assigns
      |> assign(:value, value)
      |> assign(:options, options)

    ~H"""
    <div class="mt-2 flex flex-col space-y-2">
      <input type="hidden" name={@form[@field].name} value="" />
      <%= for {label, v} <- @options do %>
        <label class="flex cursor-pointer items-center gap-x-2">
          <input
            id={"#{@form[@field].name}[]-#{v}"}
            type="checkbox"
            name={@form[@field].name <> "[]"}
            class="checkbox checkbox-sm checkbox-primary"
            value={v}
            checked={to_string(v) in @value}
          />
          <span class="label-text">
            {label}
          </span>
        </label>
      <% end %>
    </div>
    """
  end

  def query(query, _options, _attribute, []), do: query

  def query(query, options, _attribute, value) do
    Enum.reduce(value, nil, fn
      v, nil ->
        Map.get(predicates(options), v)

      v, p ->
        dynamic(^p or ^Map.get(predicates(options), v))
    end)
    |> maybe_query(query)
  end

  def maybe_query(nil, query), do: query
  def maybe_query(predicates, query), do: where(query, ^predicates)

  def option_value_to_label(options, values) do
    Enum.map(values, fn key -> find_option_label(options, key) end)
    |> Enum.intersperse(", ")
  end

  def find_option_label(options, key) do
    Enum.find_value(options, fn option ->
      if to_string(option.key) == to_string(key), do: option.label
    end) || ""
  end

  def predicates(options) do
    Enum.map(options, fn %{predicate: p, key: k} -> {k, p} end)
    |> Enum.into(%{})
  end
end