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

  Countdown-only leading-zero collapse (hide unused day/hour columns) is **on by default** when `countdown` is true. Override with `collapse_leading_zeros={false}` or with fixed `segments`.

  ## Examples

  ### Basic

  ```heex
  <.timer id="t" start_ms={60_000} class="timer">
    <:start_trigger><.heroicon name="hero-play" class="icon" /></:start_trigger>
    <:pause_trigger><.heroicon name="hero-pause" class="icon" /></:pause_trigger>
    <:resume_trigger><.heroicon name="hero-play" class="icon" /></:resume_trigger>
    <:reset_trigger><.heroicon name="hero-arrow-path" class="icon" /></:reset_trigger>
  </.timer>
  ```

  ### Countdown

  ```heex
  <.timer id="t" countdown start_ms={90_000} target_ms={0} class="timer">
    <:start_trigger><.heroicon name="hero-play" class="icon" /></:start_trigger>
    <:pause_trigger><.heroicon name="hero-pause" class="icon" /></:pause_trigger>
    <:resume_trigger><.heroicon name="hero-play" class="icon" /></:resume_trigger>
    <:reset_trigger><.heroicon name="hero-arrow-path" class="icon" /></:reset_trigger>
  </.timer>
  ```

  ### Fixed segments (always four columns)

  ```heex
  <.timer id="t" countdown start_ms={@ms} segments={[:days, :hours, :minutes, :seconds]} class="timer" />
  ```

  ### Separator slot

  Omit `:separator` to render nothing between digit columns. Pass it to supply markup (for example `:` or `·`) between segments.

  ```heex
  <.timer id="t" start_ms={60_000} class="timer">
    <:separator>·</:separator>
  </.timer>
  ```

  ### Region label (a11y)

  ```heex
  <.timer id="t" translation={%Corex.Timer.Translation{area_label: "Countdown"}} class="timer" />
  ```

  ### Unit labels (optional)

  Per-column caption under each digit cell (stacked column). Omit a slot to hide that unit’s label.

  ```heex
  <.timer id="t" countdown start_ms={@ms} target_ms={0} class="timer">
    <:day_label>Days</:day_label>
    <:hour_label>Hours</:hour_label>
    <:minute_label>Minutes</:minute_label>
    <:second_label>Seconds</:second_label>
  </.timer>
  ```

  Action slots (`:start_trigger`, `:pause_trigger`, `:resume_trigger`, `:reset_trigger`) are optional.

  ## Styling

  ```css
  [data-scope="timer"][data-part="root"] {}
  [data-scope="timer"][data-part="area"] {}
  [data-scope="timer"][data-part="item-label"] {}
  [data-scope="timer"][data-part="item"] {}
  [data-scope="timer"][data-part="separator"] {}
  [data-scope="timer"][data-part="control"] {}
  [data-scope="timer"][data-part="action-trigger"] {}
  ```

  ```css
  @import "../corex/components/timer.css";
  ```

  ```heex
  <.timer class="timer timer--accent timer--lg">
  </.timer>
  ```

  '''

  @doc type: :component
  use Phoenix.Component

  alias Corex.Timer.Anatomy.{
    ActionTrigger,
    Area,
    Control,
    Item,
    ItemLabel,
    Props,
    Root,
    Segment,
    Separator
  }

  alias Corex.Timer.Connect
  alias Corex.Timer.Translation, as: TimerTranslation

  @parts [:days, :hours, :minutes, :seconds]

  attr(:id, :string, required: false)
  attr(:countdown, :boolean, default: false)
  attr(:start_ms, :integer, default: 0)
  attr(:target_ms, :integer, default: nil)
  attr(:auto_start, :boolean, default: true)
  attr(:interval, :integer, default: 1000)
  attr(:on_tick, :string, default: nil)
  attr(:on_tick_client, :string, default: nil)
  attr(:on_complete, :string, default: nil)
  attr(:on_complete_client, :string, default: nil)

  attr(:collapse_leading_zeros, :boolean,
    default: nil,
    doc:
      "When nil and countdown without fixed segments, leading zero units are hidden (minimum minutes and seconds visible)."
  )

  attr(:segments, :list,
    default: nil,
    doc:
      "Fixed subset of [:days, :hours, :minutes, :seconds] in natural order; disables collapse when set."
  )

  attr(:translation, TimerTranslation,
    default: nil,
    doc: "Zag timer translations; supports area_label for the timer region aria-label."
  )

  attr(:dir, :string,
    default: nil,
    values: [nil, "ltr", "rtl"],
    doc: "Text direction for styling; nil follows the document."
  )

  attr(:orientation, :string,
    default: "horizontal",
    values: ["horizontal", "vertical"],
    doc: "Layout orientation for CSS."
  )

  attr(:rest, :global)

  slot(:separator, required: false)

  slot(:day_label, required: false)
  slot(:hour_label, required: false)
  slot(:minute_label, required: false)
  slot(:second_label, required: false)

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

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

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

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

  def timer(assigns) do
    assigns = assign_new(assigns, :id, fn -> "timer-#{System.unique_integer([:positive])}" end)
    segments = normalize_segments(assigns.segments)
    time_values = time_values(assigns.start_ms)

    visibility_hidden =
      visibility_hidden(
        assigns.countdown,
        assigns.collapse_leading_zeros,
        segments,
        time_values
      )

    assigns =
      assigns
      |> assign(:time_values, time_values)
      |> assign(:running, assigns.auto_start)
      |> assign(:paused, false)
      |> assign(:segments, segments)
      |> assign(
        :has_timer_controls?,
        assigns.start_trigger != [] or assigns.pause_trigger != [] or assigns.resume_trigger != [] or
          assigns.reset_trigger != []
      )
      |> assign(:visibility_hidden, visibility_hidden)
      |> assign(:props_struct, props_struct(assigns, segments))

    ~H"""
    <div
      id={@id}
      phx-hook="Timer"
      {@rest}
      {Connect.props(@props_struct)}
    >
      <div phx-mounted={Connect.ignore_root(%Root{id: @id, dir: @dir, orientation: @orientation})} {Connect.root(%Root{id: @id, dir: @dir, orientation: @orientation})}>
        <div phx-mounted={Connect.ignore_area(%Area{id: @id, dir: @dir, orientation: @orientation})} {Connect.area(%Area{id: @id, dir: @dir, orientation: @orientation})}>
          <%= for {part, i} <- Enum.with_index([:days, :hours, :minutes, :seconds]) do %>
            <% hv = Enum.at(@visibility_hidden, i) %>
            <% ls = label_slot(assigns, part) %>
            <div
              phx-mounted={Connect.ignore_segment(%Segment{id: @id, type: to_string(part), hidden: hv})}
              {Connect.segment(%Segment{id: @id, type: to_string(part), hidden: hv})}
            >
              <div
                phx-mounted={Connect.ignore_item(%Item{id: @id, type: to_string(part), value: Map.fetch!(@time_values, part), dir: @dir, orientation: @orientation, hidden: hv})}
                {Connect.item(%Item{id: @id, type: to_string(part), value: Map.fetch!(@time_values, part), dir: @dir, orientation: @orientation, hidden: hv})}
              >
              </div>
              <%= if ls != [] do %>
                <span
                  phx-mounted={Connect.ignore_item_label(%ItemLabel{id: @id, type: to_string(part), dir: @dir, orientation: @orientation})}
                  {Connect.item_label(%ItemLabel{id: @id, type: to_string(part), dir: @dir, orientation: @orientation})}
                >
                  {render_slot(ls)}
                </span>
              <% end %>
            </div>
            <%= if i < 3 and @separator != [] do %>
              <% sh = Enum.at(@visibility_hidden, i) %>
              <div
                phx-mounted={
                  Connect.ignore_separator(%Separator{
                    id: "timer:#{@id}:sep:#{i}",
                    dir: @dir,
                    orientation: @orientation,
                    hidden: sh
                  })
                }
                {Connect.separator(%Separator{
                  id: "timer:#{@id}:sep:#{i}",
                  dir: @dir,
                  orientation: @orientation,
                  hidden: sh
                })}
              >
                {render_slot(@separator)}
              </div>
            <% end %>
          <% end %>
        </div>
        <div
          :if={@has_timer_controls?}
          phx-mounted={Connect.ignore_control(%Control{id: @id, dir: @dir, orientation: @orientation})}
          {Connect.control(%Control{id: @id, dir: @dir, orientation: @orientation})}
        >
          <button
            :if={@start_trigger != []}
            type="button"
            phx-mounted={Connect.ignore_action_trigger(%ActionTrigger{id: @id, action: "start", hidden: @running or @paused, dir: @dir, orientation: @orientation})}
            {Connect.action_trigger(%ActionTrigger{id: @id, action: "start", hidden: @running or @paused, dir: @dir, orientation: @orientation})}
          >
            {render_slot(@start_trigger)}
          </button>
          <button
            :if={@pause_trigger != []}
            type="button"
            phx-mounted={Connect.ignore_action_trigger(%ActionTrigger{id: @id, action: "pause", hidden: not @running, dir: @dir, orientation: @orientation})}
            {Connect.action_trigger(%ActionTrigger{id: @id, action: "pause", hidden: not @running, dir: @dir, orientation: @orientation})}
          >
            {render_slot(@pause_trigger)}
          </button>
          <button
            :if={@resume_trigger != []}
            type="button"
            phx-mounted={Connect.ignore_action_trigger(%ActionTrigger{id: @id, action: "resume", hidden: not @paused, dir: @dir, orientation: @orientation})}
            {Connect.action_trigger(%ActionTrigger{id: @id, action: "resume", hidden: not @paused, dir: @dir, orientation: @orientation})}
          >
            {render_slot(@resume_trigger)}
          </button>
          <button
            :if={@reset_trigger != []}
            type="button"
            phx-mounted={Connect.ignore_action_trigger(%ActionTrigger{id: @id, action: "reset", hidden: not @running and not @paused, dir: @dir, orientation: @orientation})}
            {Connect.action_trigger(%ActionTrigger{id: @id, action: "reset", hidden: not @running and not @paused, dir: @dir, orientation: @orientation})}
          >
            {render_slot(@reset_trigger)}
          </button>
        </div>
      </div>
    </div>
    """
  end

  defp label_slot(assigns, :days), do: assigns.day_label
  defp label_slot(assigns, :hours), do: assigns.hour_label
  defp label_slot(assigns, :minutes), do: assigns.minute_label
  defp label_slot(assigns, :seconds), do: assigns.second_label

  defp props_struct(assigns, segments) do
    %Props{
      id: assigns.id,
      countdown: assigns.countdown,
      start_ms: assigns.start_ms,
      target_ms: assigns.target_ms,
      auto_start: assigns.auto_start,
      interval: assigns.interval,
      on_tick: assigns.on_tick,
      on_tick_client: assigns.on_tick_client,
      on_complete: assigns.on_complete,
      on_complete_client: assigns.on_complete_client,
      dir: assigns.dir,
      orientation: assigns.orientation,
      collapse_leading_zeros: assigns.collapse_leading_zeros,
      segments: segments,
      translation: assigns.translation
    }
  end

  defp normalize_segments(nil), do: nil

  defp normalize_segments([]) do
    raise ArgumentError, "Corex.Timer: segments must not be empty when provided"
  end

  defp normalize_segments(list) when is_list(list) do
    allowed = MapSet.new(@parts)

    unless MapSet.subset?(MapSet.new(list), allowed) do
      raise ArgumentError, "Corex.Timer: segments must be a subset of #{inspect(@parts)}"
    end

    idx = fn atom -> Enum.find_index(@parts, &(&1 == atom)) end

    indexes =
      list
      |> Enum.map(fn a ->
        case idx.(a) do
          nil -> raise ArgumentError, "Corex.Timer: invalid segment #{inspect(a)}"
          i -> i
        end
      end)

    unless indexes == Enum.sort(indexes) do
      raise ArgumentError, "Corex.Timer: segments must follow order #{inspect(@parts)}"
    end

    list
  end

  defp visibility_hidden(_countdown, _collapse_opt, segments, _time_values)
       when is_list(segments) do
    Enum.map(@parts, fn atom -> atom not in segments end)
  end

  defp visibility_hidden(countdown, collapse_opt, nil, time_values) do
    vals = Enum.map(@parts, &Map.fetch!(time_values, &1))

    cond do
      collapse_opt == false ->
        [false, false, false, false]

      collapse_opt == true ->
        start_i = collapse_start_index(vals)
        Enum.map(0..3, fn i -> i < start_i end)

      countdown ->
        start_i = collapse_start_index(vals)
        Enum.map(0..3, fn i -> i < start_i end)

      true ->
        [false, false, false, false]
    end
  end

  defp collapse_start_index(vals) do
    collapse_start_index(vals, 0)
  end

  defp collapse_start_index(_vals, idx) when idx > 2 do
    idx
  end

  defp collapse_start_index(vals, idx) do
    rest_after = length(vals) - idx

    if idx < 3 && Enum.at(vals, idx) == 0 && rest_after > 2 do
      collapse_start_index(vals, idx + 1)
    else
      idx
    end
  end

  @doc type: :component
  attr(:id, :string, required: false)
  attr(:rest, :global)

  def timer_skeleton(assigns) do
    assigns = assign_new(assigns, :id, fn -> "timer-#{System.unique_integer([:positive])}" end)

    ~H"""
    <div id={@id} {@rest}>
      <div {Connect.root(%Root{id: @id, dir: "ltr", orientation: "horizontal"})}>
        <div {Connect.area(%Area{id: @id, dir: "ltr", orientation: "horizontal"})}>
          <div {Connect.segment(%Segment{id: @id, type: "days", hidden: false})}>
            <div {Connect.item(%Item{id: @id, type: "days", value: 0, dir: "ltr", orientation: "horizontal", hidden: false})}></div>
          </div>
          <div {Connect.separator(%Separator{id: "timer:#{@id}:sep:0", dir: "ltr", orientation: "horizontal"})}>:</div>
          <div {Connect.segment(%Segment{id: @id, type: "hours", hidden: false})}>
            <div {Connect.item(%Item{id: @id, type: "hours", value: 0, dir: "ltr", orientation: "horizontal", hidden: false})}></div>
          </div>
          <div {Connect.separator(%Separator{id: "timer:#{@id}:sep:1", dir: "ltr", orientation: "horizontal"})}>:</div>
          <div {Connect.segment(%Segment{id: @id, type: "minutes", hidden: false})}>
            <div {Connect.item(%Item{id: @id, type: "minutes", value: 0, dir: "ltr", orientation: "horizontal", hidden: false})}></div>
          </div>
          <div {Connect.separator(%Separator{id: "timer:#{@id}:sep:2", dir: "ltr", orientation: "horizontal"})}>:</div>
          <div {Connect.segment(%Segment{id: @id, type: "seconds", hidden: false})}>
            <div {Connect.item(%Item{id: @id, type: "seconds", value: 0, dir: "ltr", orientation: "horizontal", hidden: false})}></div>
          </div>
        </div>
        <div {Connect.control(%Control{id: @id, dir: "ltr", orientation: "horizontal"})}>
          <div class="timer-skeleton__btn" data-scope="timer" data-part="action-trigger" aria-hidden="true"></div>
          <div class="timer-skeleton__btn" data-scope="timer" data-part="action-trigger" aria-hidden="true"></div>
          <div class="timer-skeleton__btn" data-scope="timer" data-part="action-trigger" aria-hidden="true"></div>
          <div class="timer-skeleton__btn" data-scope="timer" data-part="action-trigger" aria-hidden="true"></div>
        </div>
      </div>
    </div>
    """
  end

  defp time_values(ms) do
    ms = max(0, ms)
    seconds = div(rem(ms, 60_000), 1_000)
    minutes = div(rem(ms, 3_600_000), 60_000)
    hours = div(rem(ms, 86_400_000), 3_600_000)
    days = div(ms, 86_400_000)

    %{days: days, hours: hours, minutes: minutes, seconds: seconds}
  end
end