phia_ui

defmodule PhiaUi.Components.ThemeProvider do
  @moduledoc """
  Runtime theme provider component.

  Sets the `data-phia-theme` attribute on a wrapper div, activating the
  corresponding CSS custom property overrides from the static `phia-themes.css`
  file generated by `mix phia.theme install`.

  CSS custom properties cascade naturally: any `bg-primary` inside the wrapper
  will use the theme's primary color automatically.

  ## Usage

      <.theme_provider theme={:blue}>
        <section class="p-4">
          <.button>Blue button</.button>
        </section>
      </.theme_provider>

      <%!-- Custom theme from struct --%>
      <.theme_provider theme={@org_theme}>
        <%= render_slot(@inner_block) %>
      </.theme_provider>

  ## Setup

  Import `phia-themes.css` in your `app.css`:

      @import "./phia-themes.css";

  Or generate it with:

      mix phia.theme install

  ## Theme values

  - Atom (`:zinc`, `:blue`, `:slate`, etc.) — resolves to the theme name string
  - `%PhiaUi.Theme{}` struct — uses `theme.name` directly
  - `nil` — renders the slot without any `data-phia-theme` attribute (no-op)
  """

  use Phoenix.Component
  import PhiaUi.ClassMerger, only: [cn: 1]
  alias PhiaUi.Theme

  attr(:theme, :any,
    default: nil,
    doc: "Theme key (atom), %PhiaUi.Theme{} struct, or nil for no override"
  )

  attr(:class, :string, default: nil, doc: "Additional CSS classes for the wrapper div")
  attr(:rest, :global, doc: "HTML attributes forwarded to the wrapper div")

  slot(:inner_block, required: true, doc: "Content rendered inside the themed wrapper")

  @doc """
  Wraps content in a scoped theme context.

  When `theme` is given, sets `data-phia-theme` on the wrapper div so that
  CSS custom properties from `phia-themes.css` cascade into all children.
  """
  def theme_provider(assigns) do
    assigns = assign(assigns, :theme_name, resolve_name(assigns.theme))

    ~H"""
    <div data-phia-theme={@theme_name} class={cn([@class])} {@rest}>
      <%= render_slot(@inner_block) %>
    </div>
    """
  end

  # ---------------------------------------------------------------------------
  # Private helpers
  # ---------------------------------------------------------------------------

  defp resolve_name(nil), do: nil

  defp resolve_name(%Theme{name: name}), do: name

  defp resolve_name(key) when is_atom(key) do
    case Theme.get(key) do
      {:ok, theme} -> theme.name
      {:error, :not_found} -> nil
    end
  end
end