defmodule Corex.Select do
  @moduledoc ~S'''
  Phoenix implementation of [Zag.js Select](https://zagjs.com/components/react/select).

  ## Examples
  <!-- tabs-open -->

  ### Minimal

  This example assumes the import of `.icon` from `Core Components`, you are free to replace it

  ```heex
  <.select
    id="my-select"
    class="select"
    placeholder="Select a country"
    collection={[
      %{label: "France", id: "fra", disabled: true},
      %{label: "Belgium", id: "bel"},
      %{label: "Germany", id: "deu"},
      %{label: "Netherlands", id: "nld"},
      %{label: "Switzerland", id: "che"},
      %{label: "Austria", id: "aut"}
    ]}
  >
    <:trigger>
      <.icon name="hero-chevron-down" />
    </:trigger>
  </.select>
  ```

  ### Grouped

  This example assumes the import of `.icon` from `Core Components`, you are free to replace it

  ```heex
  <.select
    class="select"
    placeholder="Select a country"
    collection={[
      %{label: "France", id: "fra", group: "Europe"},
      %{label: "Belgium", id: "bel", group: "Europe"},
      %{label: "Germany", id: "deu", group: "Europe"},
      %{label: "Netherlands", id: "nld", group: "Europe"},
      %{label: "Switzerland", id: "che", group: "Europe"},
      %{label: "Austria", id: "aut", group: "Europe"},
      %{label: "Japan", id: "jpn", group: "Asia"},
      %{label: "China", id: "chn", group: "Asia"},
      %{label: "South Korea", id: "kor", group: "Asia"},
      %{label: "Thailand", id: "tha", group: "Asia"},
      %{label: "USA", id: "usa", group: "North America"},
      %{label: "Canada", id: "can", group: "North America"},
      %{label: "Mexico", id: "mex", group: "North America"}
    ]}
  >
    <:trigger>
      <.icon name="hero-chevron-down" />
    </:trigger>
  </.select>
  ```

    ### Custom

  This example requires the installation of [Flagpack](https://hex.pm/packages/flagpack) to display the use of custom item rendering.
  This example assumes the import of `.icon` from `Core Components`, you are free to replace it

  ```heex
  <.select
    class="select"
    placeholder="Select a country"
    collection={[
      %{label: "France", id: "fra"},
      %{label: "Belgium", id: "bel"},
      %{label: "Germany", id: "deu"},
      %{label: "Netherlands", id: "nld"},
      %{label: "Switzerland", id: "che"},
      %{label: "Austria", id: "aut"}
    ]}
  >
    <:label>
      Country of residence
    </:label>
    <:item :let={item}>
      <Flagpack.flag name={String.to_atom(item.id)} />
      {item.label}
    </:item>
    <:trigger>
      <.icon name="hero-chevron-down" />
    </:trigger>
    <:item_indicator>
      <.icon name="hero-check" />
    </:item_indicator>
  </.select>
  ```

  ### Custom Grouped

  This example requires the installation of [Flagpack](https://hex.pm/packages/flagpack) to display the use of custom item rendering.
  This example assumes the import of `.icon` from `Core Components`, you are free to replace it

  ```heex
  <.select
    class="select"
    placeholder="Select a country"
    collection={[
      %{label: "France", id: "fra", group: "Europe"},
      %{label: "Belgium", id: "bel", group: "Europe"},
      %{label: "Germany", id: "deu", group: "Europe"},
      %{label: "Japan", id: "jpn", group: "Asia"},
      %{label: "China", id: "chn", group: "Asia"},
      %{label: "South Korea", id: "kor", group: "Asia"}
    ]}
  >
    <:item :let={item}>
      <Flagpack.flag name={String.to_atom(item.id)} />
      {item.label}
    </:item>
    <:trigger>
      <.icon name="hero-chevron-down" />
    </:trigger>
    <:item_indicator>
      <.icon name="hero-check" />
    </:item_indicator>
  </.select>
  ```

  <!-- tabs-close -->

  ## Phoenix Form Integration

  When using with Phoenix forms, you must add an id to the form using the `Corex.Form.get_form_id/1` function.

  ### Controller

  ```elixir
  defmodule MyAppWeb.PageController do
    use MyAppWeb, :controller

    def home(conn, params) do
      form = Phoenix.Component.to_form(Map.get(params, "user", %{}), as: :user)
      render(conn, :home, form: form)
    end
  end
  ```

  ```heex
  <.form :let={f} as={:user} for={@form} id={get_form_id(@form)} method="get">
    <.select
      field={f[:country]}
      class="select"
      placeholder="Select a country"
      collection={[
        %{label: "France", id: "fra", disabled: true},
        %{label: "Belgium", id: "bel"},
        %{label: "Germany", id: "deu"},
        %{label: "Netherlands", id: "nld"},
        %{label: "Switzerland", id: "che"},
        %{label: "Austria", id: "aut"}
      ]}
    >
      <:label>Your country of residence</:label>
      <:trigger>
        <.icon name="hero-chevron-down" />
      </:trigger>
      <:error :let={msg}>
        <.icon name="hero-exclamation-circle" class="icon" />
        {msg}
      </:error>
    </.select>
    <button type="submit">Submit</button>
  </.form>
  ```

  ### Live View

  When using Phoenix form in a Live view you must also add controlled mode. This allows the Live view to be the source of truth and the component to be in sync accordingly.

  ```elixir
  defmodule MyAppWeb.SelectLive do
    use MyAppWeb, :live_view

    def mount(_params, _session, socket) do
      form = to_form(%{"country" => nil}, as: :user)
      {:ok, assign(socket, :form, form)}
    end

    def render(assigns) do
      ~H"""
      <.form as={:user} for={@form} id={get_form_id(@form)}>
        <.select
          field={@form[:country]}
          class="select"
          controlled
          placeholder="Select a country"
          collection={[
            %{label: "France", id: "fra", disabled: true},
            %{label: "Belgium", id: "bel"},
            %{label: "Germany", id: "deu"},
            %{label: "Netherlands", id: "nld"},
            %{label: "Switzerland", id: "che"},
            %{label: "Austria", id: "aut"}
          ]}
        >
          <:label>Your country of residence</:label>
          <:trigger>
            <.icon name="hero-chevron-down" />
          </:trigger>
          <:error :let={msg}>
            <.icon name="hero-exclamation-circle" class="icon" />
            {msg}
          </:error>
        </.select>
        <button type="submit">Submit</button>
      </.form>
      """
    end
  end
  ```

  ### With Ecto changeset

  When using Ecto changeset for validation and inside a Live view you must enable the controlled mode.

  This allows the Live View to be the source of truth and the component to be in sync accordingly.

  First create your schema and changeset:

  ```elixir
  defmodule MyApp.Accounts.User do
    use Ecto.Schema
    import Ecto.Changeset

    schema "users" do
      field :name, :string
      field :country, :string
      timestamps(type: :utc_datetime)
    end

    def changeset(user, attrs) do
      user
      |> cast(attrs, [:name, :country])
      |> validate_required([:name, :country])
    end
  end
  ```

  ```elixir
  defmodule MyAppWeb.UserLive do
    use MyAppWeb, :live_view
    alias MyApp.Accounts.User

    def mount(_params, _session, socket) do
      {:ok, assign(socket, :form, to_form(User.changeset(%User{}, %{})))}
    end

    def handle_event("validate", %{"user" => user_params}, socket) do
      changeset = User.changeset(%User{}, user_params)
      {:noreply, assign(socket, form: to_form(changeset, action: :validate))}
    end

    def render(assigns) do
      ~H"""
      <.form for={@form} id={get_form_id(@form)} phx-change="validate">
        <.select
          field={@form[:country]}
          class="select"
          controlled
          placeholder="Select a country"
          collection={[
            %{label: "France", id: "fra"},
            %{label: "Belgium", id: "bel"},
            %{label: "Germany", id: "deu"}
          ]}
        >
          <:label>Your country of residence</:label>
          <:trigger>
            <.icon name="hero-chevron-down" />
          </:trigger>
          <:error :let={msg}>
            <.icon name="hero-exclamation-circle" class="icon" />
            {msg}
          </:error>
        </.select>
      </.form>
      """
    end
  end
  ```

  ## API Control

  ```heex
  # Client-side
  <button phx-click={Corex.Select.set_value("my-select", "fra")}>
    Check
  </button>

  <button phx-click={Corex.Select.toggle_value("my-select")}>
    Toggle
  </button>

  # Server-side
  def handle_event("set_value", _, socket) do
    {:noreply, Corex.Select.set_value(socket, "my-select", "fra")}
  end
  ```

  ## Styling

  Use data attributes to target elements:
  - `[data-scope="select"][data-part="root"]` - Label wrapper
  - `[data-scope="select"][data-part="control"]` - Select control
  - `[data-scope="select"][data-part="label"]` - Label text
  - `[data-scope="select"][data-part="input"]` - Hidden input
  - `[data-scope="select"][data-part="error"]` - Error message

  State-specific styling:
  - `[data-state="open"]` - When select is open
  - `[data-state="closed"]` - When select is closed
  - `[data-disabled]` - When select is disabled
  - `[data-readonly]` - When select is read-only
  - `[data-invalid]` - When select has validation errors

  If you wish to use the default Corex styling, you can use the class `select` on the component.
  This requires to install mix corex.design first and import the component css file.

  ```css
  @import "../corex/main.css";
  @import "../corex/tokens/themes/neo/light.css";
  @import "../corex/components/select.css";
  ```

  You can then use modifiers

  ```heex
  <.select class="select select--accent select--lg">
  ```

  Learn more about modifiers and [Corex Design](https://corex-ui.com/components/select#modifiers)

  '''

  use Phoenix.Component
  alias Corex.Select.Connect
  alias Corex.Select.Anatomy.{Props, Root, Label, Control, Positioner, Content}

  attr(:id, :string, required: false)
  attr(:collection, :list, default: [])
  attr(:controlled, :boolean, default: false, doc: "Whether the select is controlled")
  attr(:placeholder, :string, default: nil, doc: "The placeholder of the select")
  attr(:value, :list, default: [], doc: "The value of the select")
  attr(:disabled, :boolean, default: false, doc: "Whether the select is disabled")
  attr(:close_on_select, :boolean, default: true, doc: "Whether to close the select on select")
  attr(:dir, :string, default: "ltr", doc: "The direction of the select")
  attr(:loop_focus, :boolean, default: false, doc: "Whether to loop focus the select")
  attr(:multiple, :boolean, default: false, doc: "Whether to allow multiple selection")
  attr(:invalid, :boolean, default: false, doc: "Whether the select is invalid")
  attr(:name, :string, doc: "The name of the select")
  attr(:form, :string, doc: "The id of the form of the select")
  attr(:read_only, :boolean, default: false, doc: "Whether the select is read only")
  attr(:required, :boolean, default: false, doc: "Whether the select is required")
  attr(:prompt, :string, default: nil, doc: "the prompt for select inputs")

  attr(:on_value_change, :string,
    default: nil,
    doc: "The server event name to trigger on value change"
  )

  attr(:on_value_change_client, :string,
    default: nil,
    doc: "The client event name to trigger on value change"
  )

  attr(:bubble, :boolean, default: false, doc: "Whether the client events are bubbled")

  attr(:positioning, Corex.Positioning,
    default: %Corex.Positioning{},
    doc: "Positioning options for the dropdown"
  )

  attr(:rest, :global)

  slot(:label, required: false, doc: "The label content")
  slot(:trigger, required: true, doc: "The trigger button content")
  slot(:item_indicator, required: false, doc: "Optional indicator for selected items")

  slot :error, required: false do
    attr(:class, :string, required: false)
  end

  slot(:item,
    required: false,
    doc: "Custom content for each item. Receives the item as :let binding"
  )

  attr(:field, Phoenix.HTML.FormField,
    doc:
      "A form field struct retrieved from the form, for example: @form[:country]. Automatically sets id, name, value, and errors from the form field"
  )

  attr(:errors, :list,
    default: [],
    doc: "List of error messages to display"
  )

  def select(%{field: %Phoenix.HTML.FormField{} = field} = assigns) do
    errors = if Phoenix.Component.used_input?(field), do: field.errors, else: []
    value = get_value(field.value)
    selected_label = get_selected_label(assigns.collection, value)

    assigns
    |> assign(field: nil)
    |> assign(:errors, Enum.map(errors, &Corex.Gettext.translate_error(&1)))
    |> assign_new(:id, fn -> field.id end)
    |> assign_new(:form, fn -> field.form.id end)
    |> assign_new(:name, fn -> field.name end)
    |> assign(:value, value)
    |> assign(:selected_label, selected_label)
    |> select()
  end

  def select(assigns) do
    assigns =
      assigns
      |> assign_new(:id, fn -> "select-#{System.unique_integer([:positive])}" end)
      |> assign_new(:name, fn -> "name-#{System.unique_integer([:positive])}" end)
      |> assign_new(:form, fn -> nil end)

    value = Map.get(assigns, :value, [])

    value_list = get_value(value)
    selected_label = get_selected_label(assigns.collection, value_list)

    assigns = assign(assigns, :selected_label, selected_label)

    options = transform_collection_to_options(assigns.collection)

    grouped_items = Enum.group_by(assigns.collection, &Map.get(&1, :group))

    has_groups =
      grouped_items
      |> Map.keys()
      |> Enum.any?(& &1)

    selected_for_options =
      if assigns.multiple do
        value_list
      else
        if value_list == [], do: "", else: List.first(value_list)
      end

    options_with_prompt = [{"", ""} | options]

    assigns =
      assigns
      |> assign(:grouped_items, grouped_items)
      |> assign(:has_groups, has_groups)
      |> assign(:options, options)
      |> assign(:options_with_prompt, options_with_prompt)
      |> assign(:selected_for_options, selected_for_options)
      |> assign(:disabled_values, get_disabled_values(assigns.collection))
      |> assign(:value_for_hidden_input, value_for_hidden_input(value_list, assigns.multiple))

    ~H"""
    <div id={@id} phx-hook="Select" {@rest} {Connect.props(%Props{
      id: @id, collection: @collection, controlled: @controlled, placeholder: @placeholder, value: @value,
      disabled: @disabled, close_on_select: @close_on_select, dir: @dir, loop_focus: @loop_focus,
      multiple: @multiple, invalid: @invalid, name: @name, form: @form, read_only: @read_only,
      required: @required, on_value_change: @on_value_change, on_value_change_client: @on_value_change_client,
      bubble: @bubble, positioning: @positioning
    })}>
      <div {Connect.root(%Root{id: @id, changed: if(@__changed__, do: true, else: false), invalid: @invalid, read_only: @read_only})}>

      <input type="hidden" name={@name} form={@form} id={"#{@id}-value"} data-scope="select" data-part="value-input" value={@value_for_hidden_input} />

      <select multiple={@multiple} data-scope="select" data-part="hidden-select" aria-hidden="true" tabindex="-1" style="border:0;clip:rect(0 0 0 0);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px;white-space:nowrap;word-wrap:normal;">
        <%= Phoenix.HTML.Form.options_for_select(
          @options_with_prompt,
          @selected_for_options,
          disabled: @disabled_values
        ) %>
      </select>

        <div :if={!Enum.empty?(@label)} {Connect.label(%Label{id: @id, changed: if(@__changed__, do: true, else: false), invalid: @invalid, read_only: @read_only, required: @required, disabled: @disabled, dir: @dir})}>
          {render_slot(@label)}
        </div>
        <div {Connect.control(%Control{id: @id, changed: Map.get(assigns, :__changed__, nil) != nil, invalid: @invalid, dir: @dir, disabled: @disabled})}>
          <button :if={!Enum.empty?(@trigger)} data-scope="select" data-part="trigger">
            <span data-scope="select" data-part="item-text">
              {if @selected_label do @selected_label else @placeholder end}
            </span>
            {render_slot(@trigger)}
          </button>
        </div>
        <div :if={!Enum.empty?(@errors)} :for={msg <- @errors} data-scope="select" data-part="error">
          {render_slot(@error, msg)}
        </div>
        <div {Connect.positioner(%Positioner{id: @id, changed: Map.get(assigns, :__changed__, nil) != nil, dir: @dir})}>
          <ul {Connect.content(%Content{id: @id, changed: Map.get(assigns, :__changed__, nil) != nil, dir: @dir})}>
          </ul>

          <div style="display: none;" data-templates="select">
            <div :if={@has_groups} :for={{group, items} <- @grouped_items} data-scope="select" data-part="item-group" data-id={group || "default"} data-template="true">
              <div :if={group} data-scope="select" data-part="item-group-label" data-id={group}>
                {group}
              </div>
              <li :for={item <- items} data-scope="select" data-part="item" data-value={item.id} data-template="true">
                <span :if={!Enum.empty?(@item)} data-scope="select" data-part="item-text">
                  {render_slot(@item, item)}
                </span>
                <span :if={Enum.empty?(@item)} data-scope="select" data-part="item-text">
                  {item.label}
                </span>
                <span :if={!Enum.empty?(@item_indicator)} data-scope="select" data-part="item-indicator">
                  {render_slot(@item_indicator)}
                </span>
              </li>
            </div>

            <li :if={!@has_groups} :for={item <- @collection} data-scope="select" data-part="item" data-value={item.id} data-template="true">
              <span :if={!Enum.empty?(@item)} data-scope="select" data-part="item-text">
                {render_slot(@item, item)}
              </span>
              <span :if={Enum.empty?(@item)} data-scope="select" data-part="item-text">
                {item.label}
              </span>
              <span :if={!Enum.empty?(@item_indicator)} data-scope="select" data-part="item-indicator">
                {render_slot(@item_indicator)}
              </span>
            </li>
          </div>
        </div>
      </div>
    </div>
    """
  end

  defp get_disabled_values(collection) do
    collection
    |> Enum.filter(&Map.get(&1, :disabled, false))
    |> Enum.map(& &1.id)
  end

  defp value_for_hidden_input(value_list, _multiple) when value_list == [], do: ""
  defp value_for_hidden_input(value_list, false), do: List.first(value_list)
  defp value_for_hidden_input(value_list, true), do: Enum.join(value_list, ",")

  defp transform_collection_to_options(collection) do
    grouped = Enum.group_by(collection, &Map.get(&1, :group))

    case Map.keys(grouped) do
      [nil] ->
        Enum.map(collection, &{&1.label, &1.id})

      _ ->
        grouped
        |> Enum.sort_by(fn {group, _} -> group || "" end)
        |> Enum.flat_map(&group_to_options/1)
    end
  end

  defp group_to_options({nil, items}), do: Enum.map(items, &{&1.label, &1.id})
  defp group_to_options({group, items}), do: [{group, Enum.map(items, &{&1.label, &1.id})}]

  defp get_value(field_value) do
    case field_value do
      nil -> []
      [] -> []
      value when is_list(value) -> Enum.map(value, &to_string/1)
      value -> [to_string(value)]
    end
  end

  defp get_selected_label(collection, value) do
    case value do
      [] ->
        nil

      _ ->
        value
        |> Enum.map(fn val ->
          collection
          |> Enum.find(&(&1.id == val))
        end)
        |> Enum.filter(& &1)
        |> Enum.map(& &1.label)
        |> case do
          [] -> nil
          labels -> Enum.join(labels, ", ")
        end
    end
  end
end