defmodule LiveBookWeb.SessionLive do
  use LiveBookWeb, :live_view

  alias LiveBook.{SessionSupervisor, Session, Delta, Notebook, Runtime}

  @impl true
  def mount(%{"id" => session_id}, _session, socket) do
    if SessionSupervisor.session_exists?(session_id) do
      data =
        if connected?(socket) do
          data = Session.register_client(session_id, self())
          Phoenix.PubSub.subscribe(LiveBook.PubSub, "sessions:#{session_id}")

          data
        else
          Session.get_data(session_id)
        end

      platform = platform_from_socket(socket)

      {:ok, assign(socket, initial_assigns(session_id, data, platform))}
    else
      {:ok, redirect(socket, to: Routes.home_path(socket, :page))}
    end
  end

  defp platform_from_socket(socket) do
    with connect_info when connect_info != nil <- get_connect_info(socket),
         {:ok, user_agent} <- Map.fetch(connect_info, :user_agent) do
      platform_from_user_agent(user_agent)
    else
      _ -> nil
    end
  end

  defp initial_assigns(session_id, data, platform) do
    first_section_id =
      case data.notebook.sections do
        [section | _] -> section.id
        [] -> nil
      end

    %{
      platform: platform,
      session_id: session_id,
      data: data,
      selected_section_id: first_section_id,
      focused_cell_id: nil,
      focused_cell_type: nil,
      insert_mode: false
    }
  end

  @impl true
  def render(assigns) do
    ~L"""
    <%= if @live_action == :file do %>
      <%= live_modal @socket, LiveBookWeb.SessionLive.PersistenceComponent,
            id: :file_modal,
            return_to: Routes.session_path(@socket, :page, @session_id),
            session_id: @session_id,
            path: @data.path %>
    <% end %>

    <%= if @live_action == :runtime do %>
      <%= live_modal @socket, LiveBookWeb.SessionLive.RuntimeComponent,
            id: :runtime_modal,
            return_to: Routes.session_path(@socket, :page, @session_id),
            session_id: @session_id,
            runtime: @data.runtime %>
    <% end %>

    <%= if @live_action == :shortcuts do %>
      <%= live_modal @socket, LiveBookWeb.SessionLive.ShortcutsComponent,
            id: :shortcuts_modal,
            platform: @platform,
            return_to: Routes.session_path(@socket, :page, @session_id) %>
    <% end %>

    <div class="flex flex-grow h-full"
      id="session"
      phx-hook="Session"
      data-insert-mode="<%= @insert_mode %>"
      data-focused-cell-id="<%= @focused_cell_id %>"
      data-focused-cell-type="<%= @focused_cell_type %>">
      <div class="flex flex-col w-1/5 bg-gray-100 border-r border-gray-200">
        <h1 class="m-6 py-1 text-2xl border-b-2 border-transparent hover:border-blue-100 focus:border-blue-300"
          id="notebook-name"
          contenteditable
          spellcheck="false"
          phx-blur="set_notebook_name"
          phx-hook="ContentEditable"
          data-update-attribute="phx-value-name"><%= @data.notebook.name %></h1>

        <div class="flex-grow flex flex-col space-y-2 pl-4">
          <%= for section <- @data.notebook.sections do %>
            <div phx-click="select_section"
                 phx-value-section_id="<%= section.id %>"
                 class="py-2 px-4 rounded-l-md cursor-pointer hover:text-current border border-r-0 <%= if(section.id == @selected_section_id, do: "bg-white border-gray-200", else: "text-gray-500 border-transparent") %>">
              <span>
                <%= section.name %>
              </span>
            </div>
          <% end %>
          <button phx-click="add_section" class="py-2 px-4 rounded-l-md cursor-pointer text-gray-300 hover:text-gray-400">
            <div class="flex items-center space-x-2">
              <%= Icons.svg(:plus, class: "h-6") %>
              <span>New section</span>
            </div>
          </button>
        </div>
        <%= live_patch to: Routes.session_path(@socket, :runtime, @session_id) do %>
          <div class="text-sm text-gray-500 text-medium px-4 py-2 border-b border-gray-200 flex space-x-2 items-center hover:bg-gray-200">
            <%= Icons.svg(:chip, class: "h-5 text-gray-400") %>
            <span><%= runtime_description(@data.runtime) %></span>
          </div>
        <% end %>
        <%= live_patch to: Routes.session_path(@socket, :file, @session_id) do %>
          <div class="text-sm text-gray-500 text-medium px-4 py-2 border-b border-gray-200 flex space-x-2 items-center hover:bg-gray-200">
            <%= if @data.path do %>
              <%= if @data.dirty do %>
                <%= Icons.svg(:dots_circle_horizontal, class: "h-5 text-blue-400") %>
              <% else %>
                <%= Icons.svg(:check_circle, class: "h-5 text-green-400") %>
              <% end %>
              <span>
                <%= Path.basename(@data.path) %>
              </span>
            <% else %>
              <%= Icons.svg(:document_text, class: "h-5 text-gray-400") %>
              <span>
                No file choosen
              </span>
            <% end %>
          </div>
        <% end %>
        <div class="p-4 flex space-x-2">
          <%= live_patch to: Routes.home_path(@socket, :page) do %>
            <%= Icons.svg(:home, class: "h-6 w-6 text-gray-600 hover:text-current") %>
          <% end %>
          <%= live_patch to: Routes.session_path(@socket, :shortcuts, @session_id) do %>
            <%= Icons.svg(:question_mark_circle, class: "h-6 w-6 text-gray-600 hover:text-current") %>
          <% end %>
        </div>
      </div>
      <div class="flex-grow px-6 py-8 flex overflow-y-auto">
        <div class="max-w-screen-lg w-full mx-auto">
          <%= for section <- @data.notebook.sections do %>
            <%= live_component @socket, LiveBookWeb.SectionComponent,
                  id: section.id,
                  section: section,
                  selected: section.id == @selected_section_id,
                  cell_infos: @data.cell_infos,
                  focused_cell_id: @focused_cell_id,
                  insert_mode: @insert_mode %>
          <% end %>
        </div>
      </div>
    </div>

    <%= if @insert_mode do %>
      <%# Show a tiny insert indicator for clarity %>
      <div class="fixed right-5 bottom-1 text-gray-500 text-semibold text-sm">
        insert
      </div>
    <% end %>
    """
  end

  @impl true
  def handle_params(_params, _url, socket) do
    {:noreply, socket}
  end

  @impl true
  def handle_event("cell_init", %{"cell_id" => cell_id}, socket) do
    data = socket.assigns.data

    case Notebook.fetch_cell_and_section(data.notebook, cell_id) do
      {:ok, cell, _section} ->
        payload = %{
          source: cell.source,
          revision: data.cell_infos[cell.id].revision
        }

        {:reply, payload, socket}

      :error ->
        {:noreply, socket}
    end
  end

  def handle_event("add_section", _params, socket) do
    end_index = length(socket.assigns.data.notebook.sections)
    Session.insert_section(socket.assigns.session_id, end_index)

    {:noreply, socket}
  end

  def handle_event("delete_section", %{"section_id" => section_id}, socket) do
    Session.delete_section(socket.assigns.session_id, section_id)

    {:noreply, socket}
  end

  def handle_event("select_section", %{"section_id" => section_id}, socket) do
    {:noreply, assign(socket, selected_section_id: section_id)}
  end

  def handle_event(
        "insert_cell",
        %{"section_id" => section_id, "index" => index, "type" => type},
        socket
      ) do
    index = String.to_integer(index) |> max(0)
    type = String.to_atom(type)
    Session.insert_cell(socket.assigns.session_id, section_id, index, type)

    {:noreply, socket}
  end

  def handle_event("insert_cell_below_focused", %{"type" => type}, socket) do
    type = String.to_atom(type)
    insert_cell_next_to_focused(socket.assigns, type, idx_offset: 1)

    {:noreply, socket}
  end

  def handle_event("insert_cell_above_focused", %{"type" => type}, socket) do
    type = String.to_atom(type)
    insert_cell_next_to_focused(socket.assigns, type, idx_offset: 0)

    {:noreply, socket}
  end

  def handle_event("delete_focused_cell", %{}, socket) do
    if socket.assigns.focused_cell_id do
      Session.delete_cell(socket.assigns.session_id, socket.assigns.focused_cell_id)
    end

    {:noreply, socket}
  end

  def handle_event("set_notebook_name", %{"name" => name}, socket) do
    name = normalize_name(name)
    Session.set_notebook_name(socket.assigns.session_id, name)

    {:noreply, socket}
  end

  def handle_event("set_section_name", %{"section_id" => section_id, "name" => name}, socket) do
    name = normalize_name(name)
    Session.set_section_name(socket.assigns.session_id, section_id, name)

    {:noreply, socket}
  end

  def handle_event(
        "apply_cell_delta",
        %{"cell_id" => cell_id, "delta" => delta, "revision" => revision},
        socket
      ) do
    delta = Delta.from_compressed(delta)
    Session.apply_cell_delta(socket.assigns.session_id, self(), cell_id, delta, revision)

    {:noreply, socket}
  end

  def handle_event(
        "report_cell_revision",
        %{"cell_id" => cell_id, "revision" => revision},
        socket
      ) do
    Session.report_cell_revision(socket.assigns.session_id, self(), cell_id, revision)

    {:noreply, socket}
  end

  def handle_event("focus_cell", %{"cell_id" => nil}, socket) do
    {:noreply, focus_cell(socket, nil)}
  end

  def handle_event("focus_cell", %{"cell_id" => cell_id}, socket) do
    case Notebook.fetch_cell_and_section(socket.assigns.data.notebook, cell_id) do
      {:ok, cell, _section} ->
        {:noreply, focus_cell(socket, cell)}

      :error ->
        {:noreply, socket}
    end
  end

  def handle_event("move_cell_focus", %{"offset" => offset}, socket) do
    case new_focused_cell_from_offset(socket.assigns, offset) do
      {:ok, cell} ->
        {:noreply, focus_cell(socket, cell)}

      :error ->
        {:noreply, socket}
    end
  end

  def handle_event("move_cell", %{"offset" => offset}, socket) do
    if socket.assigns.focused_cell_id do
      Session.move_cell(socket.assigns.session_id, socket.assigns.focused_cell_id, offset)
    end

    {:noreply, socket}
  end

  def handle_event("set_insert_mode", %{"enabled" => enabled}, socket) do
    if socket.assigns.focused_cell_id do
      {:noreply, assign(socket, insert_mode: enabled)}
    else
      {:noreply, socket}
    end
  end

  def handle_event("enable_insert_mode", %{}, socket) do
    if socket.assigns.focused_cell_id do
      {:noreply, assign(socket, insert_mode: true)}
    else
      {:noreply, socket}
    end
  end

  def handle_event("queue_focused_cell_evaluation", %{}, socket) do
    if socket.assigns.focused_cell_id do
      Session.queue_cell_evaluation(socket.assigns.session_id, socket.assigns.focused_cell_id)
    end

    {:noreply, socket}
  end

  def handle_event("queue_section_cells_evaluation", %{}, socket) do
    if socket.assigns.selected_section_id do
      {:ok, section} =
        Notebook.fetch_section(
          socket.assigns.data.notebook,
          socket.assigns.selected_section_id
        )

      for cell <- section.cells, cell.type == :elixir do
        Session.queue_cell_evaluation(socket.assigns.session_id, cell.id)
      end
    end

    {:noreply, socket}
  end

  def handle_event("queue_child_cells_evaluation", %{}, socket) do
    if socket.assigns.focused_cell_id do
      {:ok, cell, _section} =
        Notebook.fetch_cell_and_section(
          socket.assigns.data.notebook,
          socket.assigns.focused_cell_id
        )

      cells = Notebook.child_cells(socket.assigns.data.notebook, cell.id)

      for cell <- cells, cell.type == :elixir do
        Session.queue_cell_evaluation(socket.assigns.session_id, cell.id)
      end
    end

    {:noreply, socket}
  end

  def handle_event("cancel_focused_cell_evaluation", %{}, socket) do
    if socket.assigns.focused_cell_id do
      Session.cancel_cell_evaluation(socket.assigns.session_id, socket.assigns.focused_cell_id)
    end

    {:noreply, socket}
  end

  def handle_event("show_shortcuts", %{}, socket) do
    {:noreply,
     push_patch(socket, to: Routes.session_path(socket, :shortcuts, socket.assigns.session_id))}
  end

  @impl true
  def handle_info({:operation, operation}, socket) do
    case Session.Data.apply_operation(socket.assigns.data, operation) do
      {:ok, data, actions} ->
        new_socket =
          socket
          |> assign(data: data)
          |> after_operation(socket, operation)
          |> handle_actions(actions)

        {:noreply, new_socket}

      :error ->
        {:noreply, socket}
    end
  end

  def handle_info({:error, error}, socket) do
    message = error |> to_string() |> String.capitalize()

    {:noreply, put_flash(socket, :error, message)}
  end

  def handle_info({:info, info}, socket) do
    message = info |> to_string() |> String.capitalize()

    {:noreply, put_flash(socket, :info, message)}
  end

  def handle_info(:session_closed, socket) do
    {:noreply,
     socket
     |> put_flash(:info, "Session has been closed")
     |> push_redirect(to: Routes.home_path(socket, :page))}
  end

  def handle_info(_message, socket), do: {:noreply, socket}

  defp after_operation(socket, _prev_socket, {:insert_section, _index, section_id}) do
    assign(socket, selected_section_id: section_id)
  end

  defp after_operation(socket, _prev_socket, {:delete_section, _section_id}) do
    assign(socket, selected_section_id: nil)
  end

  defp after_operation(socket, _prev_socket, {:insert_cell, _, _, _, cell_id}) do
    {:ok, cell, _section} = Notebook.fetch_cell_and_section(socket.assigns.data.notebook, cell_id)
    focus_cell(socket, cell, insert_mode: true)
  end

  defp after_operation(socket, prev_socket, {:delete_cell, cell_id}) do
    if cell_id == socket.assigns.focused_cell_id do
      case Notebook.fetch_cell_sibling(prev_socket.assigns.data.notebook, cell_id, 1) do
        {:ok, next_cell} ->
          focus_cell(socket, next_cell)

        :error ->
          case Notebook.fetch_cell_sibling(prev_socket.assigns.data.notebook, cell_id, -1) do
            {:ok, previous_cell} ->
              focus_cell(socket, previous_cell)

            :error ->
              focus_cell(socket, nil)
          end
      end
    else
      socket
    end
  end

  defp after_operation(socket, _prev_socket, _operation), do: socket

  defp handle_actions(socket, actions) do
    Enum.reduce(actions, socket, &handle_action(&2, &1))
  end

  defp handle_action(socket, {:broadcast_delta, from, cell, delta}) do
    if from == self() do
      push_event(socket, "cell_acknowledgement:#{cell.id}", %{})
    else
      push_event(socket, "cell_delta:#{cell.id}", %{delta: Delta.to_compressed(delta)})
    end
  end

  defp handle_action(socket, _action), do: socket

  defp normalize_name(name) do
    name
    |> String.trim()
    |> String.replace(~r/\s+/, " ")
    |> case do
      "" -> "Untitled"
      name -> name
    end
  end

  defp focus_cell(socket, cell, opts \\ [])

  defp focus_cell(socket, nil = _cell, _opts) do
    assign(socket, focused_cell_id: nil, focused_cell_type: nil, insert_mode: false)
  end

  defp focus_cell(socket, cell, opts) do
    insert_mode? = Keyword.get(opts, :insert_mode, false)

    assign(socket,
      focused_cell_id: cell.id,
      focused_cell_type: cell.type,
      insert_mode: insert_mode?
    )
  end

  defp insert_cell_next_to_focused(assigns, type, idx_offset: idx_offset) do
    if assigns.focused_cell_id do
      {:ok, cell, section} =
        Notebook.fetch_cell_and_section(assigns.data.notebook, assigns.focused_cell_id)

      index = Enum.find_index(section.cells, &(&1 == cell))
      Session.insert_cell(assigns.session_id, section.id, index + idx_offset, type)
    else
      append_cell_to_section(assigns, type)
    end
  end

  defp append_cell_to_section(assigns, type) do
    if assigns.selected_section_id do
      {:ok, section} = Notebook.fetch_section(assigns.data.notebook, assigns.selected_section_id)

      end_index = length(section.cells)

      Session.insert_cell(assigns.session_id, section.id, end_index, type)
    end
  end

  defp new_focused_cell_from_offset(assigns, offset) do
    cond do
      assigns.focused_cell_id ->
        # If a cell is focused, look up the appropriate sibling
        Notebook.fetch_cell_sibling(assigns.data.notebook, assigns.focused_cell_id, offset)

      assigns.selected_section_id ->
        # If no cell is focused, focus the first one for easier keyboard navigation.
        {:ok, section} =
          Notebook.fetch_section(assigns.data.notebook, assigns.selected_section_id)

        Enum.fetch(section.cells, 0)

      true ->
        :error
    end
  end

  defp runtime_description(nil), do: "No runtime"
  defp runtime_description(%Runtime.ElixirStandalone{}), do: "Elixir standalone runtime"
  defp runtime_description(%Runtime.MixStandalone{}), do: "Mix standalone runtime"
  defp runtime_description(%Runtime.Attached{}), do: "Attached runtime"
end