defmodule PhoenixKit.Modules.Emails.Web.Templates do
  @moduledoc """
  LiveView for displaying and managing email templates in PhoenixKit admin panel.

  Provides comprehensive template management interface with filtering, searching,
  creation, editing, and analytics for email templates.

  ## Features

  - **Real-time Template List**: Live updates of templates
  - **Advanced Filtering**: By category, status, system vs custom
  - **Search Functionality**: Search across template names, descriptions
  - **Template Management**: Create, edit, clone, archive templates
  - **Usage Analytics**: View template usage statistics
  - **Test Send**: Send test emails using templates
  - **System Templates**: Manage core system templates

  ## Route

  This LiveView is mounted at `{prefix}/admin/emails/templates` and requires
  appropriate admin permissions.

  Note: `{prefix}` is your configured PhoenixKit URL prefix (default: `/phoenix_kit`).

  The route is auto-generated by PhoenixKit from `admin_tabs/0` at compile time and
  injected into `live_session :phoenix_kit_admin`. Do not declare this route in your
  parent app's `router.ex`. See `phoenix_kit/guides/custom-admin-pages.md`.

  ## Permissions

  Access is restricted to users with admin or owner roles in PhoenixKit.
  """

  use PhoenixKitWeb, :live_view
  use Gettext, backend: PhoenixKit.Modules.Emails.Gettext
  import PhoenixKitWeb.Components.Core.Icon
  import PhoenixKitWeb.Components.Core.TableDefault
  import PhoenixKitWeb.Components.Core.Badge
  import PhoenixKitWeb.Components.Core.Pagination

  alias PhoenixKit.Modules.Emails.Template
  alias PhoenixKit.Modules.Emails.Templates
  alias PhoenixKit.Settings
  alias PhoenixKit.Utils.Date, as: UtilsDate
  alias PhoenixKit.Utils.Routes

  @default_per_page 25
  @max_per_page 100

  ## --- Lifecycle Callbacks ---

  @impl true
  def mount(_params, _session, socket) do
    # Get project title from settings

    socket =
      socket
      |> assign(:page_title, gettext("Email Templates"))
      |> assign(:page_subtitle, gettext("Manage and organize your email templates"))
      |> assign(:templates, [])
      |> assign(:total_count, 0)
      |> assign(:stats, %{})
      |> assign(:loading, true)
      |> assign(:show_clone_modal, false)
      |> assign(:clone_template, nil)
      |> assign(:clone_form, %{name: "", display_name: "", errors: %{}})
      |> assign(:confirmation_modal, %{show: false})
      |> assign(:display_locale, Settings.get_content_language() || "en")
      |> assign(:sort_by, :inserted_at)
      |> assign(:sort_dir, :desc)
      |> assign_filter_defaults()
      |> assign_pagination_defaults()

    {:ok, socket}
  end

  @impl true
  def handle_params(params, _url, socket) do
    socket =
      socket
      |> apply_params(params)
      |> load_templates()
      |> load_stats()

    {:noreply, socket}
  end

  ## --- Event Handlers ---

  @impl true
  def handle_event("filter", params, socket) do
    # Handle both search and filter parameters
    combined_params = %{}

    # Extract search parameters
    combined_params =
      case Map.get(params, "search") do
        %{"query" => query} -> Map.put(combined_params, "search", String.trim(query || ""))
        _ -> combined_params
      end

    # Extract filter parameters
    combined_params =
      case Map.get(params, "filter") do
        filter_params when is_map(filter_params) -> Map.merge(combined_params, filter_params)
        _ -> combined_params
      end

    # Reset to first page when filtering
    combined_params = Map.put(combined_params, "page", "1")

    # Build new URL parameters
    new_params = build_url_params(socket.assigns, combined_params)

    {:noreply,
     socket
     |> push_patch(to: Routes.path("/admin/emails/templates?#{new_params}"))}
  end

  @impl true
  def handle_event("clear_filters", _params, socket) do
    {:noreply,
     socket
     |> push_patch(to: Routes.path("/admin/emails/templates"))}
  end

  @impl true
  def handle_event("clear_search", _params, socket) do
    # Clear only the search term (the × inside the search box); keep the other
    # filters and reset to page 1.
    new_params = build_url_params(socket.assigns, %{"search" => "", "page" => "1"})

    {:noreply, push_patch(socket, to: Routes.path("/admin/emails/templates?#{new_params}"))}
  end

  @impl true
  def handle_event("set_filter", %{"field" => field, "value" => value}, socket) do
    # Dropdown filter selection (category/status/is_system): set the chosen
    # filter, reset to page 1, and patch. Empty value clears that filter.
    new_params = build_url_params(socket.assigns, %{field => value, "page" => "1"})

    {:noreply, push_patch(socket, to: Routes.path("/admin/emails/templates?#{new_params}"))}
  end

  @impl true
  def handle_event("toggle_sort", %{"by" => by}, socket) do
    # Clicking a sortable column header: validate the field, then toggle the
    # direction if it's already the active sort, otherwise switch to that field
    # ascending. Resets to page 1 and patches.
    field = validate_sort_by(by)

    sort_dir =
      if field == socket.assigns.sort_by do
        if socket.assigns.sort_dir == :asc, do: :desc, else: :asc
      else
        :asc
      end

    new_params =
      build_url_params(socket.assigns, %{
        "sort_by" => to_string(field),
        "sort_dir" => to_string(sort_dir),
        "page" => "1"
      })

    {:noreply, push_patch(socket, to: Routes.path("/admin/emails/templates?#{new_params}"))}
  end

  @impl true
  def handle_event("refresh", _params, socket) do
    {:noreply,
     socket
     |> assign(:loading, true)
     |> load_templates()
     |> load_stats()}
  end

  @impl true
  def handle_event("show_clone_modal", %{"uuid" => template_uuid}, socket) do
    case Templates.get_template(template_uuid) do
      nil ->
        {:noreply,
         socket
         |> put_flash(:error, gettext("Template not found"))}

      template ->
        {:noreply,
         socket
         |> assign(:show_clone_modal, true)
         |> assign(:clone_template, template)
         |> assign(:clone_form, %{
           name: "#{template.name}_copy",
           display_name: "#{Template.get_translation(template.display_name, "en")} (Copy)",
           errors: %{}
         })}
    end
  end

  @impl true
  def handle_event("hide_clone_modal", _params, socket) do
    {:noreply,
     socket
     |> assign(:show_clone_modal, false)
     |> assign(:clone_template, nil)
     |> assign(:clone_form, %{name: "", display_name: "", errors: %{}})}
  end

  @impl true
  def handle_event("validate_clone", %{"clone" => clone_params}, socket) do
    errors = validate_clone_form(clone_params)

    form = %{
      name: clone_params["name"] || "",
      display_name: clone_params["display_name"] || "",
      errors: errors
    }

    {:noreply, assign(socket, :clone_form, form)}
  end

  @impl true
  def handle_event("clone_template", %{"clone" => clone_params}, socket) do
    errors = validate_clone_form(clone_params)

    if map_size(errors) == 0 and socket.assigns.clone_template do
      case Templates.clone_template(
             socket.assigns.clone_template,
             String.trim(clone_params["name"]),
             %{display_name: clone_params["display_name"]}
           ) do
        {:ok, new_template} ->
          {:noreply,
           socket
           |> assign(:show_clone_modal, false)
           |> assign(:clone_template, nil)
           |> put_flash(
             :info,
             gettext("Template cloned successfully as '%{name}'", name: new_template.name)
           )
           |> push_navigate(to: Routes.path("/admin/emails/templates/#{new_template.uuid}/edit"))}

        {:error, _changeset} ->
          {:noreply,
           socket
           |> put_flash(:error, gettext("Failed to clone template"))}
      end
    else
      # Show validation errors
      form = %{
        name: clone_params["name"] || "",
        display_name: clone_params["display_name"] || "",
        errors: errors
      }

      {:noreply, assign(socket, :clone_form, form)}
    end
  end

  @impl true
  def handle_event("edit_template", %{"uuid" => template_uuid}, socket) do
    {:noreply,
     socket
     |> push_navigate(to: Routes.path("/admin/emails/templates/#{template_uuid}/edit"))}
  end

  @impl true
  def handle_event("archive_template", %{"uuid" => template_uuid}, socket) do
    case Templates.get_template(template_uuid) do
      nil ->
        {:noreply,
         socket
         |> put_flash(:error, gettext("Template not found"))}

      %Template{is_system: true} ->
        {:noreply,
         socket
         |> put_flash(:error, gettext("System templates cannot be archived"))}

      template ->
        case Templates.archive_template(template) do
          {:ok, _archived_template} ->
            {:noreply,
             socket
             |> put_flash(
               :info,
               gettext("Template '%{name}' archived successfully", name: template.name)
             )
             |> load_templates()
             |> load_stats()}

          {:error, _changeset} ->
            {:noreply,
             socket
             |> put_flash(:error, gettext("Failed to archive template"))}
        end
    end
  end

  @impl true
  def handle_event("activate_template", %{"uuid" => template_uuid}, socket) do
    case Templates.get_template(template_uuid) do
      nil ->
        {:noreply,
         socket
         |> put_flash(:error, gettext("Template not found"))}

      template ->
        case Templates.activate_template(template) do
          {:ok, _activated_template} ->
            {:noreply,
             socket
             |> put_flash(
               :info,
               gettext("Template '%{name}' activated successfully", name: template.name)
             )
             |> load_templates()
             |> load_stats()}

          {:error, _changeset} ->
            {:noreply,
             socket
             |> put_flash(:error, gettext("Failed to activate template"))}
        end
    end
  end

  @impl true
  def handle_event("request_delete", %{"uuid" => uuid, "name" => name}, socket) do
    modal = %{
      show: true,
      title: "Confirm Delete",
      message:
        "Are you sure you want to delete template '#{name}'? This action cannot be undone.",
      button_text: "Delete Template",
      action: "delete_template",
      uuid: uuid
    }

    {:noreply, assign(socket, :confirmation_modal, modal)}
  end

  @impl true
  def handle_event("cancel_confirmation", _params, socket) do
    {:noreply, assign(socket, :confirmation_modal, %{show: false})}
  end

  @impl true
  def handle_event("confirm_action", %{"action" => "delete_template", "uuid" => uuid}, socket) do
    socket = assign(socket, :confirmation_modal, %{show: false})
    handle_event("delete_template", %{"uuid" => uuid}, socket)
  end

  @impl true
  def handle_event("delete_template", %{"uuid" => template_uuid}, socket) do
    case Templates.get_template(template_uuid) do
      nil ->
        {:noreply,
         socket
         |> put_flash(:error, gettext("Template not found"))}

      %Template{is_system: true} ->
        {:noreply,
         socket
         |> put_flash(:error, gettext("System templates cannot be deleted"))}

      template ->
        case Templates.delete_template(template) do
          {:ok, _deleted_template} ->
            {:noreply,
             socket
             |> put_flash(
               :info,
               gettext("Template '%{name}' deleted successfully", name: template.name)
             )
             |> load_templates()
             |> load_stats()}

          {:error, :system_template_protected} ->
            {:noreply,
             socket
             |> put_flash(:error, gettext("System templates cannot be deleted"))}

          {:error, _changeset} ->
            {:noreply,
             socket
             |> put_flash(:error, gettext("Failed to delete template"))}
        end
    end
  end

  ## --- Template ---

  ## --- Private Helper Functions ---

  # Apply default filter values
  defp assign_filter_defaults(socket) do
    filters = %{
      search: "",
      category: "",
      status: "",
      is_system: ""
    }

    assign(socket, :filters, filters)
  end

  # Apply default pagination values
  defp assign_pagination_defaults(socket) do
    socket
    |> assign(:page, 1)
    |> assign(:per_page, @default_per_page)
    |> assign(:total_pages, 0)
  end

  # Apply URL parameters to socket assigns
  defp apply_params(socket, params) do
    filters = %{
      search: params["search"] || "",
      category: params["category"] || "",
      status: params["status"] || "",
      is_system: params["is_system"] || ""
    }

    page = String.to_integer(params["page"] || "1")
    per_page = min(String.to_integer(params["per_page"] || "#{@default_per_page}"), @max_per_page)

    sort_by = validate_sort_by(params["sort_by"])
    sort_dir = validate_sort_dir(params["sort_dir"])

    socket
    |> assign(:filters, filters)
    |> assign(:page, page)
    |> assign(:per_page, per_page)
    |> assign(:sort_by, sort_by)
    |> assign(:sort_dir, sort_dir)
  end

  # Load templates based on current filters and pagination
  defp load_templates(socket) do
    %{filters: filters, page: page, per_page: per_page} = socket.assigns

    # Build filters for Templates query, adding sort order (list only — the
    # count query below intentionally drops ordering).
    query_filters =
      build_query_filters(filters, page, per_page)
      |> Map.put(:order_by, socket.assigns.sort_by)
      |> Map.put(:order_direction, socket.assigns.sort_dir)

    templates = Templates.list_templates(query_filters)

    # Get total count for pagination
    total_count = Templates.count_templates(Map.drop(query_filters, [:limit, :offset]))

    total_pages = ceil(total_count / per_page)

    socket
    |> assign(:templates, templates)
    |> assign(:total_count, total_count)
    |> assign(:total_pages, total_pages)
    |> assign(:loading, false)
  end

  # Load template statistics
  defp load_stats(socket) do
    stats = Templates.get_template_stats()
    assign(socket, :stats, stats)
  end

  # Build query filters from form filters
  defp build_query_filters(filters, page, per_page) do
    query_filters = %{
      limit: per_page,
      offset: (page - 1) * per_page,
      order_by: :inserted_at,
      order_direction: :desc
    }

    # Add non-empty filters
    filters
    |> Enum.reduce(query_filters, fn
      {:search, search}, acc when search != "" ->
        Map.put(acc, :search, search)

      {:category, category}, acc when category != "" ->
        Map.put(acc, :category, category)

      {:status, status}, acc when status != "" ->
        Map.put(acc, :status, status)

      {:is_system, is_system}, acc when is_system != "" ->
        Map.put(acc, :is_system, is_system == "true")

      _, acc ->
        acc
    end)
  end

  # Build URL parameters from current state
  defp build_url_params(assigns, additional_params) do
    base_params = %{
      "search" => assigns.filters.search,
      "category" => assigns.filters.category,
      "status" => assigns.filters.status,
      "is_system" => assigns.filters.is_system,
      "sort_by" => to_string(assigns.sort_by),
      "sort_dir" => to_string(assigns.sort_dir),
      "page" => assigns.page,
      "per_page" => assigns.per_page
    }

    Map.merge(base_params, additional_params)
    |> Enum.reject(fn {_key, value} -> value == "" or is_nil(value) end)
    |> Map.new()
    |> URI.encode_query()
  end

  # Whitelist of fields that may be passed to Templates.list_templates/1
  # :order_by. Anything outside this set falls back to the default inserted_at.
  # These are the only DB columns the context's apply_ordering/2 supports.
  # Only Name (the "Template" column) and Usage get clickable sort headers.
  # Category and Status are intentionally not sortable because the context's
  # apply_ordering/2 does not order by them.
  @sort_fields [:name, :usage_count, :last_used_at, :inserted_at]

  defp validate_sort_by(value) when is_atom(value) do
    if value in @sort_fields, do: value, else: :inserted_at
  end

  defp validate_sort_by(value) when is_binary(value) do
    case Enum.find(@sort_fields, fn field -> Atom.to_string(field) == value end) do
      nil -> :inserted_at
      field -> field
    end
  end

  defp validate_sort_by(_), do: :inserted_at

  defp validate_sort_dir(:asc), do: :asc
  defp validate_sort_dir(:desc), do: :desc
  defp validate_sort_dir("asc"), do: :asc
  defp validate_sort_dir("desc"), do: :desc
  defp validate_sort_dir(_), do: :desc

  # Validate clone form
  defp validate_clone_form(params) do
    errors = %{}

    # Validate name
    errors =
      case String.trim(params["name"] || "") do
        "" ->
          Map.put(errors, :name, "Name is required")

        name ->
          if Regex.match?(~r/^[a-z][a-z0-9_]*$/, name) do
            # Check if name already exists
            case Templates.get_template_by_name(name) do
              nil -> errors
              _ -> Map.put(errors, :name, "Name already exists")
            end
          else
            Map.put(
              errors,
              :name,
              "Must start with a letter and contain only lowercase letters, numbers, and underscores"
            )
          end
      end

    # Validate display_name
    errors =
      case String.trim(params["display_name"] || "") do
        "" ->
          Map.put(errors, :display_name, "Display name is required")

        _ ->
          errors
      end

    errors
  end
end