feat: adds field visibility dropdown live component

lib/mv_web/components/core_components.ex

@@ -111,6 +111,126 @@ defmodule MvWeb.CoreComponents do
     end
   end
 
+  @doc """
+  Renders a dropdown menu.
+
+  ## Examples
+
+      <.dropdown_menu items={@items} open={@open} phx-target={@myself} />
+  """
+  attr :id, :string, default: "dropdown-menu"
+  attr :items, :list, required: true, doc: "List of %{label: string, value: any} maps"
+  attr :button_label, :string, default: "Dropdown"
+  attr :icon, :string, default: nil
+  attr :checkboxes, :boolean, default: false
+  attr :selected, :map, default: %{}
+  attr :open, :boolean, default: false, doc: "Whether the dropdown is open"
+  attr :show_select_buttons, :boolean, default: false, doc: "Show select all/none buttons"
+  attr :phx_target, :any, default: nil
+
+  def dropdown_menu(assigns) do
+    unless Map.has_key?(assigns, :phx_target) do
+      raise ArgumentError, ":phx_target is required in dropdown_menu/1"
+    end
+
+    assigns =
+      assign_new(assigns, :items, fn -> [] end)
+      |> assign_new(:button_label, fn -> "Dropdown" end)
+      |> assign_new(:icon, fn -> nil end)
+      |> assign_new(:checkboxes, fn -> false end)
+      |> assign_new(:selected, fn -> %{} end)
+      |> assign_new(:open, fn -> false end)
+      |> assign_new(:show_select_buttons, fn -> false end)
+      |> assign(:phx_target, assigns.phx_target)
+      |> assign_new(:id, fn -> "dropdown-menu" end)
+
+    ~H"""
+    <div class="relative" phx-click-away="close_dropdown" phx-target={@phx_target}>
+      <button
+        type="button"
+        tabindex="0"
+        role="button"
+        aria-haspopup="menu"
+        aria-expanded={@open}
+        aria-controls={@id}
+        class="btn btn-ghost"
+        phx-click="toggle_dropdown"
+        phx-target={@phx_target}
+      >
+        <%= if @icon do %><.icon name={@icon} /><% end %>
+        <span><%= @button_label %></span>
+      </button>
+
+      <ul
+        :if={@open}
+        id={@id}
+        role="menu"
+        class="absolute right-0 mt-2 bg-base-100 z-[100] p-2 shadow-lg rounded-box w-64 max-h-96 overflow-y-auto border border-base-300"
+        tabindex="0"
+        phx-window-keydown="close_dropdown"
+        phx-key="Escape"
+        phx-target={@phx_target}
+      >
+        <li :if={@show_select_buttons} role="none">
+          <div class="flex justify-between items-center mb-2 px-2">
+            <span class="font-semibold">{gettext("Options")}</span>
+            <div class="flex gap-1">
+              <button
+                type="button"
+                role="menuitem"
+                aria-label={gettext("Select all")}
+                phx-click="select_all"
+                phx-target={@phx_target}
+                class="btn btn-xs btn-ghost"
+              >
+                {gettext("All")}
+              </button>
+              <button
+                type="button"
+                role="menuitem"
+                aria-label={gettext("Select none")}
+                phx-click="select_none"
+                phx-target={@phx_target}
+                class="btn btn-xs btn-ghost"
+              >
+                {gettext("None")}
+              </button>
+            </div>
+          </div>
+        </li>
+
+        <li :if={@show_select_buttons} role="separator" class="divider my-1"></li>
+
+        <%= for item <- @items do %>
+          <li role="none">
+            <label
+              role={if @checkboxes, do: "menuitemcheckbox", else: "menuitem"}
+              aria-checked={@checkboxes && Map.get(@selected, item.value, true)}
+              tabindex="0"
+              class="flex items-center gap-2 px-2 py-1 rounded cursor-pointer hover:bg-base-200"
+              phx-click="select_item"
+              phx-value-item={item.value}
+              phx-target={@phx_target}
+            >
+              <%= if @checkboxes do %>
+                <input
+                  type="checkbox"
+                  class="checkbox checkbox-sm"
+                  checked={Map.get(@selected, item.value, true)}
+                  tabindex="-1"
+                  aria-hidden="true"
+                  readonly
+                />
+              <% end %>
+              <span><%= item.label %></span>
+            </label>
+          </li>
+        <% end %>
+      </ul>
+    </div>
+    """
+  end
+
   @doc """
   Renders an input with label and error messages.
 

lib/mv_web/components/field_visibility_dropdown_component.ex

@@ -0,0 +1,172 @@
+defmodule MvWeb.Components.FieldVisibilityDropdownComponent do
+  @moduledoc """
+  LiveComponent for managing field visibility in the member overview.
+
+  Provides an accessible dropdown menu where users can select/deselect
+  which member fields and custom fields are visible in the table.
+
+  ## Props
+    - `:all_fields` - List of all available fields
+    - `:custom_fields` - List of CustomField resources
+    - `:selected_fields` - Map field_name → boolean
+    - `:id` - Component ID
+
+  ## Events sent to parent:
+    - `{:field_toggled, field, value}`
+    - `{:fields_selected, map}`
+  """
+
+  use MvWeb, :live_component
+
+  # ---------------------------------------------------------------------------
+  # UPDATE
+  # ---------------------------------------------------------------------------
+
+  @impl true
+  def update(assigns, socket) do
+    socket =
+      socket
+      |> assign(assigns)
+      |> assign_new(:open, fn -> false end)
+      |> assign_new(:all_fields, fn -> [] end)
+      |> assign_new(:custom_fields, fn -> [] end)
+      |> assign_new(:selected_fields, fn -> %{} end)
+
+    {:ok, socket}
+  end
+
+  # ---------------------------------------------------------------------------
+  # RENDER
+  # ---------------------------------------------------------------------------
+
+  @impl true
+  def render(assigns) do
+    all_fields = assigns.all_fields || []
+    custom_fields = assigns.custom_fields || []
+
+    all_items =
+      Enum.map(member_fields(all_fields), fn field ->
+        %{
+          value: field_to_string(field),
+          label: format_field_label(field)
+        }
+      end) ++
+        Enum.map(custom_fields(all_fields), fn field ->
+          %{
+            value: field,
+            label: format_custom_field_label(field, custom_fields)
+          }
+        end)
+
+    assigns = assign(assigns, :all_items, all_items)
+
+    # LiveComponents require a static HTML element as root, not a function component
+    ~H"""
+    <div>
+      <.dropdown_menu
+        id="field-visibility-menu"
+        icon="hero-adjustments-horizontal"
+        button_label={gettext("Columns")}
+        items={@all_items}
+        checkboxes={true}
+        selected={@selected_fields}
+        open={@open}
+        show_select_buttons={true}
+        phx_target={@myself}
+      />
+    </div>
+    """
+  end
+
+  # ---------------------------------------------------------------------------
+  # EVENTS (matching the Core Component API)
+  # ---------------------------------------------------------------------------
+
+  @impl true
+  def handle_event("toggle_dropdown", _params, socket) do
+    {:noreply, assign(socket, :open, !socket.assigns.open)}
+  end
+
+  def handle_event("close_dropdown", _params, socket) do
+    {:noreply, assign(socket, :open, false)}
+  end
+
+  # toggle single item
+  def handle_event("select_item", %{"item" => item}, socket) do
+    current = Map.get(socket.assigns.selected_fields, item, true)
+    updated = Map.put(socket.assigns.selected_fields, item, !current)
+
+    send(self(), {:field_toggled, item, !current})
+    {:noreply, assign(socket, :selected_fields, updated)}
+  end
+
+  # select all
+  def handle_event("select_all", _params, socket) do
+    all =
+      socket.assigns.all_fields
+      |> Enum.map(&field_to_string/1)
+      |> Enum.map(&{&1, true})
+      |> Enum.into(%{})
+
+    send(self(), {:fields_selected, all})
+    {:noreply, assign(socket, :selected_fields, all)}
+  end
+
+  # select none
+  def handle_event("select_none", _params, socket) do
+    none =
+      socket.assigns.all_fields
+      |> Enum.map(&field_to_string/1)
+      |> Enum.map(&{&1, false})
+      |> Enum.into(%{})
+
+    send(self(), {:fields_selected, none})
+    {:noreply, assign(socket, :selected_fields, none)}
+  end
+
+  # ---------------------------------------------------------------------------
+  # HELPERS (with defensive nil guards)
+  # ---------------------------------------------------------------------------
+
+  defp member_fields(nil), do: []
+
+  defp member_fields(fields) do
+    Enum.filter(fields, fn field ->
+      is_atom(field) ||
+        (is_binary(field) && not String.starts_with?(field, "custom_field_"))
+    end)
+  end
+
+  defp custom_fields(nil), do: []
+
+  defp custom_fields(fields) do
+    Enum.filter(fields, fn field ->
+      is_binary(field) && String.starts_with?(field, "custom_field_")
+    end)
+  end
+
+  defp field_to_string(field) when is_atom(field), do: Atom.to_string(field)
+  defp field_to_string(field) when is_binary(field), do: field
+
+  defp format_field_label(field) do
+    field
+    |> field_to_string()
+    |> String.replace("_", " ")
+    |> String.split()
+    |> Enum.map(&String.capitalize/1)
+    |> Enum.join(" ")
+  end
+
+  defp format_custom_field_label(field_string, custom_fields) do
+    case String.trim_leading(field_string, "custom_field_") do
+      "" ->
+        field_string
+
+      id ->
+        case Enum.find(custom_fields, fn cf -> to_string(cf.id) == id end) do
+          nil -> gettext("Custom Field %{id}", id: id)
+          custom_field -> custom_field.name
+        end
+    end
+  end
+end

lib/mv_web/live/member_live/index.ex

@@ -31,6 +31,8 @@ defmodule MvWeb.MemberLive.Index do
 
   alias Mv.Membership
   alias MvWeb.MemberLive.Index.Formatter
+  alias MvWeb.MemberLive.Index.FieldSelection
+  alias MvWeb.MemberLive.Index.FieldVisibility
 
   # Prefix used in sort field names for custom fields (e.g., "custom_field_<id>")
   @custom_field_prefix "custom_field_"
@@ -48,8 +50,8 @@ defmodule MvWeb.MemberLive.Index do
   and member selection. Actual data loading happens in `handle_params/3`.
   """
   @impl true
-  def mount(_params, _session, socket) do
+  def mount(_params, session, socket) do
-    # Load custom fields that should be shown in overview
+    # Load custom fields that should be shown in overview (for display)
     # Note: Using Ash.read! (bang version) - errors will be handled by Phoenix LiveView
     # and result in a 500 error page. This is appropriate for LiveViews where errors
     # should be visible to the user rather than silently failing.
@@ -59,6 +61,12 @@ defmodule MvWeb.MemberLive.Index do
       |> Ash.Query.sort(name: :asc)
       |> Ash.read!()
 
+    # Load ALL custom fields for the dropdown (to show all available fields)
+    all_custom_fields =
+      Mv.Membership.CustomField
+      |> Ash.Query.sort(name: :asc)
+      |> Ash.read!()
+
     # Load settings once to avoid N+1 queries
     settings =
       case Membership.get_settings() do
@@ -67,6 +75,20 @@ defmodule MvWeb.MemberLive.Index do
         {:error, _} -> %{member_field_visibility: %{}}
       end
 
+    # Load user field selection from session
+    session_selection = FieldSelection.get_from_session(session)
+
+    # Get all available fields (for dropdown - includes ALL custom fields)
+    all_available_fields = FieldVisibility.get_all_available_fields(all_custom_fields)
+
+    # Merge session selection with global settings for initial state (use all_custom_fields)
+    initial_selection =
+      FieldVisibility.merge_with_global_settings(
+        session_selection,
+        settings,
+        all_custom_fields
+      )
+
     socket =
       socket
       |> assign(:page_title, gettext("Members"))
@@ -76,8 +98,14 @@ defmodule MvWeb.MemberLive.Index do
       |> assign(:selected_members, [])
       |> assign(:settings, settings)
       |> assign(:custom_fields_visible, custom_fields_visible)
+      |> assign(:all_custom_fields, all_custom_fields)
+      |> assign(:all_available_fields, all_available_fields)
+      |> assign(:user_field_selection, initial_selection)
       |> assign(:member_field_configurations, get_member_field_configurations(settings))
-      |> assign(:member_fields_visible, get_visible_member_fields(settings))
+      |> assign(
+        :member_fields_visible,
+        FieldVisibility.get_visible_member_fields(initial_selection)
+      )
 
     # We call handle params to use the query from the URL
     {:ok, socket}
@@ -144,6 +172,8 @@ defmodule MvWeb.MemberLive.Index do
   ## Supported messages:
   - `{:sort, field}` - Sort event from SortHeaderComponent. Updates sort field/order and syncs URL
   - `{:search_changed, query}` - Search event from SearchBarComponent. Filters members and syncs URL
+  - `{:field_toggled, field, visible}` - Field toggle event from FieldVisibilityDropdownComponent
+  - `{:fields_selected, selection}` - Select all/deselect all event from FieldVisibilityDropdownComponent
   """
   @impl true
   def handle_info({:sort, field_str}, socket) do
@@ -170,11 +200,12 @@ defmodule MvWeb.MemberLive.Index do
     existing_sort_query = socket.assigns.sort_order
 
     # Build the URL with queries
-    query_params = %{
+    query_params =
-      "query" => q,
+      build_query_params(socket, %{
-      "sort_field" => existing_field_query,
+        "query" => q,
-      "sort_order" => existing_sort_query
+        "sort_field" => existing_field_query,
-    }
+        "sort_order" => existing_sort_query
+      })
 
     # Set the new path with params
     new_path = ~p"/members?#{query_params}"
@@ -187,22 +218,109 @@ defmodule MvWeb.MemberLive.Index do
      )}
   end
 
+  @impl true
+  def handle_info({:field_toggled, field_string, visible}, socket) do
+    # Update user field selection
+    new_selection = Map.put(socket.assigns.user_field_selection, field_string, visible)
+
+    # Save to session (cookie will be saved on next page load via handle_params)
+    socket = update_session_field_selection(socket, new_selection)
+
+    # Merge with global settings
+    final_selection =
+      FieldVisibility.merge_with_global_settings(
+        new_selection,
+        socket.assigns.settings,
+        socket.assigns.custom_fields_visible
+      )
+
+    # Get visible fields
+    visible_member_fields = FieldVisibility.get_visible_member_fields(final_selection)
+    visible_custom_fields = FieldVisibility.get_visible_custom_fields(final_selection)
+
+    socket =
+      socket
+      |> assign(:user_field_selection, final_selection)
+      |> assign(:member_fields_visible, visible_member_fields)
+      |> assign(:visible_custom_field_ids, extract_custom_field_ids(visible_custom_fields))
+      |> load_members(socket.assigns.query)
+      |> prepare_dynamic_cols()
+      |> push_field_selection_url()
+
+    {:noreply, socket}
+  end
+
+  @impl true
+  def handle_info({:fields_selected, selection}, socket) do
+    # Save to session
+    socket = update_session_field_selection(socket, selection)
+
+    # Merge with global settings (use all_custom_fields for merging)
+    final_selection =
+      FieldVisibility.merge_with_global_settings(
+        selection,
+        socket.assigns.settings,
+        socket.assigns.all_custom_fields
+      )
+
+    # Get visible fields
+    visible_member_fields = FieldVisibility.get_visible_member_fields(final_selection)
+    visible_custom_fields = FieldVisibility.get_visible_custom_fields(final_selection)
+
+    socket =
+      socket
+      |> assign(:user_field_selection, final_selection)
+      |> assign(:member_fields_visible, visible_member_fields)
+      |> assign(:visible_custom_field_ids, extract_custom_field_ids(visible_custom_fields))
+      |> load_members(socket.assigns.query)
+      |> prepare_dynamic_cols()
+      |> push_field_selection_url()
+
+    {:noreply, socket}
+  end
+
   # -----------------------------------------------------------------
   # Handle Params from the URL
   # -----------------------------------------------------------------
   @doc """
   Handles URL parameter changes.
 
-  Parses query parameters for search query, sort field, and sort order,
+  Parses query parameters for search query, sort field, sort order, and field selection,
   then loads members accordingly. This enables bookmarkable URLs and
   browser back/forward navigation.
   """
   @impl true
   def handle_params(params, _url, socket) do
+    # Parse field selection from URL
+    url_selection = FieldSelection.parse_from_url(params)
+
+    # Merge with session selection (URL has priority)
+    merged_selection =
+      FieldSelection.merge_sources(
+        url_selection,
+        socket.assigns.user_field_selection,
+        %{}
+      )
+
+    # Merge with global settings (use all_custom_fields for merging)
+    final_selection =
+      FieldVisibility.merge_with_global_settings(
+        merged_selection,
+        socket.assigns.settings,
+        socket.assigns.all_custom_fields
+      )
+
+    # Get visible fields
+    visible_member_fields = FieldVisibility.get_visible_member_fields(final_selection)
+    visible_custom_fields = FieldVisibility.get_visible_custom_fields(final_selection)
+
     socket =
       socket
       |> maybe_update_search(params)
       |> maybe_update_sort(params)
+      |> assign(:user_field_selection, final_selection)
+      |> assign(:member_fields_visible, visible_member_fields)
+      |> assign(:visible_custom_field_ids, extract_custom_field_ids(visible_custom_fields))
       |> load_members(params["query"])
       |> prepare_dynamic_cols()
 
@@ -215,10 +333,16 @@ defmodule MvWeb.MemberLive.Index do
   # - `:custom_field` - The CustomField resource
   # - `:render` - A function that formats the custom field value for a given member
   #
+  # Only includes custom fields that are visible according to user field selection.
+  #
   # Returns the socket with `:dynamic_cols` assigned.
   defp prepare_dynamic_cols(socket) do
+    visible_custom_field_ids = socket.assigns[:visible_custom_field_ids] || []
+
     dynamic_cols =
-      Enum.map(socket.assigns.custom_fields_visible, fn custom_field ->
+      socket.assigns.custom_fields_visible
+      |> Enum.filter(fn custom_field -> custom_field.id in visible_custom_field_ids end)
+      |> Enum.map(fn custom_field ->
         %{
           custom_field: custom_field,
           render: fn member ->
@@ -294,11 +418,11 @@ defmodule MvWeb.MemberLive.Index do
         field
       end
 
-    query_params = %{
+    query_params =
-      "query" => socket.assigns.query,
+      build_query_params(socket, %{
-      "sort_field" => field_str,
+        "sort_field" => field_str,
-      "sort_order" => Atom.to_string(order)
+        "sort_order" => Atom.to_string(order)
-    }
+      })
 
     new_path = ~p"/members?#{query_params}"
 
@@ -309,6 +433,47 @@ defmodule MvWeb.MemberLive.Index do
      )}
   end
 
+  # Builds query parameters including field selection
+  defp build_query_params(socket, base_params) do
+    base_params
+    |> Map.put("query", socket.assigns.query || "")
+    |> maybe_add_field_selection(socket.assigns[:user_field_selection])
+  end
+
+  # Adds field selection to query params if present
+  defp maybe_add_field_selection(params, nil), do: params
+
+  defp maybe_add_field_selection(params, selection) when is_map(selection) do
+    fields_param = FieldSelection.to_url_param(selection)
+    if fields_param != "", do: Map.put(params, "fields", fields_param), else: params
+  end
+
+  defp maybe_add_field_selection(params, _), do: params
+
+  # Pushes URL with updated field selection
+  defp push_field_selection_url(socket) do
+    query_params =
+      build_query_params(socket, %{
+        "sort_field" => field_to_string(socket.assigns.sort_field),
+        "sort_order" => Atom.to_string(socket.assigns.sort_order)
+      })
+
+    new_path = ~p"/members?#{query_params}"
+
+    push_patch(socket, to: new_path, replace: true)
+  end
+
+  # Converts field to string
+  defp field_to_string(field) when is_atom(field), do: Atom.to_string(field)
+  defp field_to_string(field) when is_binary(field), do: field
+
+  # Updates session field selection (stored in socket for now, actual session update via controller)
+  defp update_session_field_selection(socket, selection) do
+    # Store in socket for now - actual session persistence would require a controller
+    # This is a placeholder for future session persistence
+    assign(socket, :user_field_selection, selection)
+  end
+
   # Loads members from the database with custom field values and applies search/sort filters.
   #
   # Process:
@@ -333,9 +498,9 @@ defmodule MvWeb.MemberLive.Index do
       |> Ash.Query.new()
       |> Ash.Query.select(@overview_fields)
 
-    # Load custom field values for visible custom fields
+    # Load custom field values for visible custom fields (based on user selection)
-    custom_field_ids_list = Enum.map(socket.assigns.custom_fields_visible, & &1.id)
+    visible_custom_field_ids = socket.assigns[:visible_custom_field_ids] || []
-    query = load_custom_field_values(query, custom_field_ids_list)
+    query = load_custom_field_values(query, visible_custom_field_ids)
 
     # Apply the search filter first
     query = apply_search_filter(query, search_query)
@@ -770,20 +935,6 @@ defmodule MvWeb.MemberLive.Index do
     end)
   end
 
-  # Gets the list of member fields that should be visible in the overview.
-  #
-  # Filters the member field configurations to return only fields with show_in_overview: true.
-  #
-  # Parameters:
-  #   - `settings` - The settings struct loaded from the database
-  #
-  # Returns a list of atoms representing visible member field names.
-  @spec get_visible_member_fields(map()) :: [atom()]
-  defp get_visible_member_fields(settings) do
-    get_member_field_configurations(settings)
-    |> Enum.filter(fn {_field, show_in_overview} -> show_in_overview end)
-    |> Enum.map(fn {field, _show_in_overview} -> field end)
-  end
 
   # Normalizes visibility config map keys from strings to atoms.
   # JSONB in PostgreSQL converts atom keys to string keys when storing.
@@ -808,4 +959,16 @@ defmodule MvWeb.MemberLive.Index do
   end
 
   defp normalize_visibility_config(_), do: %{}
+
+  # Extracts custom field IDs from visible custom field strings
+  # Format: "custom_field_<id>" -> <id>
+  defp extract_custom_field_ids(visible_custom_fields) do
+    Enum.map(visible_custom_fields, fn field_string ->
+      case String.split(field_string, "custom_field_") do
+        ["", id] -> id
+        _ -> nil
+      end
+    end)
+    |> Enum.filter(&(&1 != nil))
+  end
 end

lib/mv_web/live/member_live/index.html.heex

@@ -2,6 +2,13 @@
   <.header>
     {gettext("Members")}
     <:actions>
+      <.live_component
+        module={MvWeb.Components.FieldVisibilityDropdownComponent}
+        id="field-visibility-dropdown"
+        all_fields={@all_available_fields}
+        custom_fields={@all_custom_fields}
+        selected_fields={@user_field_selection}
+      />
       <.button variant="primary" navigate={~p"/members/new"}>
         <.icon name="hero-plus" /> {gettext("New Member")}
       </.button>
@@ -54,6 +61,7 @@
     </:col>
     <:col
       :let={member}
+      :if={:first_name in @member_fields_visible}
       label={
         ~H"""
         <.live_component
@@ -67,7 +75,25 @@
         """
       }
     >
-      {member.first_name} {member.last_name}
+      {member.first_name}
+    </:col>
+    <:col
+      :let={member}
+      :if={:last_name in @member_fields_visible}
+      label={
+        ~H"""
+        <.live_component
+          module={MvWeb.Components.SortHeaderComponent}
+          id={:sort_last_name}
+          field={:last_name}
+          label={gettext("Last name")}
+          sort_field={@sort_field}
+          sort_order={@sort_order}
+        />
+        """
+      }
+    >
+      {member.last_name}
     </:col>
     <:col
       :let={member}

lib/mv_web/live/member_live/index/field_selection.ex

@@ -0,0 +1,232 @@
+defmodule MvWeb.MemberLive.Index.FieldSelection do
+  @moduledoc """
+  Handles user-specific field selection persistence and URL parameter parsing.
+
+  This module manages:
+  - Reading/writing field selection from cookies (persistent storage)
+  - Reading/writing field selection from session (temporary storage)
+  - Parsing field selection from URL parameters
+  - Merging multiple sources with priority: URL > Session > Cookie
+
+  ## Data Format
+
+  Field selection is stored as a map:
+  ```elixir
+  %{
+    "first_name" => true,
+    "email" => true,
+    "street" => false,
+    "custom_field_abc-123" => true
+  }
+  ```
+
+  ## Cookie/Session Format
+
+  Stored as JSON string: `{"first_name":true,"email":true}`
+
+  ## URL Format
+
+  Comma-separated list: `?fields=first_name,email,custom_field_abc-123`
+  """
+
+  @cookie_name "member_field_selection"
+  @cookie_max_age 365 * 24 * 60 * 60
+  @session_key "member_field_selection"
+
+  @doc """
+  Reads field selection from session.
+
+  Returns a map of field names (strings) to boolean visibility values.
+  Returns empty map if no selection is stored.
+  """
+  @spec get_from_session(map()) :: %{String.t() => boolean()}
+  def get_from_session(session) when is_map(session) do
+    case Map.get(session, @session_key) do
+      nil -> %{}
+      json_string when is_binary(json_string) -> parse_json(json_string)
+      _ -> %{}
+    end
+  end
+
+  def get_from_session(_), do: %{}
+
+  @doc """
+  Saves field selection to session.
+
+  Converts the map to JSON string and stores it in the session.
+  """
+  @spec save_to_session(map(), %{String.t() => boolean()}) :: map()
+  def save_to_session(session, selection) when is_map(selection) do
+    json_string = Jason.encode!(selection)
+    Map.put(session, @session_key, json_string)
+  end
+
+  def save_to_session(session, _), do: session
+
+  @doc """
+  Reads field selection from cookie.
+
+  Returns a map of field names (strings) to boolean visibility values.
+  Returns empty map if no cookie is present.
+
+  Note: This function requires the connection to have cookies parsed.
+  In LiveView, cookies are typically accessed via get_connect_info.
+  """
+  @spec get_from_cookie(Plug.Conn.t()) :: %{String.t() => boolean()}
+  def get_from_cookie(conn) do
+    case Plug.Conn.get_req_header(conn, "cookie") do
+      nil ->
+        %{}
+
+      cookie_header ->
+        # Parse cookies manually from header
+        cookies = parse_cookie_header(cookie_header)
+
+        case Map.get(cookies, @cookie_name) do
+          nil -> %{}
+          json_string when is_binary(json_string) -> parse_json(json_string)
+          _ -> %{}
+        end
+    end
+  end
+
+  # Parses cookie header string into a map
+  defp parse_cookie_header(cookie_header) when is_binary(cookie_header) do
+    cookie_header
+    |> String.split(";")
+    |> Enum.map(&String.trim/1)
+    |> Enum.map(&String.split(&1, "=", parts: 2))
+    |> Enum.reduce(%{}, fn
+      [key, value], acc -> Map.put(acc, key, URI.decode(value))
+      [key], acc -> Map.put(acc, key, "")
+      _, acc -> acc
+    end)
+  end
+
+  defp parse_cookie_header(_), do: %{}
+
+  @doc """
+  Saves field selection to cookie.
+
+  Sets a persistent cookie with the field selection as JSON.
+  """
+  @spec save_to_cookie(Plug.Conn.t(), %{String.t() => boolean()}) :: Plug.Conn.t()
+  def save_to_cookie(conn, selection) when is_map(selection) do
+    json_string = Jason.encode!(selection)
+    secure = Application.get_env(:mv, :use_secure_cookies, false)
+
+    Plug.Conn.put_resp_cookie(conn, @cookie_name, json_string,
+      max_age: @cookie_max_age,
+      same_site: "Lax",
+      http_only: true,
+      secure: secure
+    )
+  end
+
+  def save_to_cookie(conn, _), do: conn
+
+  @doc """
+  Parses field selection from URL parameters.
+
+  Expects a comma-separated list of field names in the `fields` parameter.
+  All fields in the list are set to `true` (visible).
+
+  ## Examples
+
+      iex> parse_from_url(%{"fields" => "first_name,email"})
+      %{"first_name" => true, "email" => true}
+
+      iex> parse_from_url(%{"fields" => "custom_field_abc-123"})
+      %{"custom_field_abc-123" => true}
+
+      iex> parse_from_url(%{})
+      %{}
+  """
+  @spec parse_from_url(map()) :: %{String.t() => boolean()}
+  def parse_from_url(params) when is_map(params) do
+    case Map.get(params, "fields") do
+      nil -> %{}
+      "" -> %{}
+      fields_string when is_binary(fields_string) -> parse_fields_string(fields_string)
+      _ -> %{}
+    end
+  end
+
+  def parse_from_url(_), do: %{}
+
+  @doc """
+  Merges multiple field selection sources with priority.
+
+  Priority order (highest to lowest):
+  1. URL parameters
+  2. Session
+  3. Cookie
+
+  Later sources override earlier ones for the same field.
+
+  ## Examples
+
+      iex> merge_sources(%{"first_name" => true}, %{"email" => true}, %{"street" => true})
+      %{"first_name" => true, "email" => true, "street" => true}
+
+      iex> merge_sources(%{"first_name" => false}, %{"first_name" => true}, %{})
+      %{"first_name" => false}  # URL has priority
+  """
+  @spec merge_sources(
+          %{String.t() => boolean()},
+          %{String.t() => boolean()},
+          %{String.t() => boolean()}
+        ) :: %{String.t() => boolean()}
+  def merge_sources(url_selection, session_selection, cookie_selection) do
+    %{}
+    |> Map.merge(cookie_selection)
+    |> Map.merge(session_selection)
+    |> Map.merge(url_selection)
+  end
+
+  @doc """
+  Converts field selection map to URL parameter string.
+
+  Returns a comma-separated string of visible fields (where value is `true`).
+
+  ## Examples
+
+      iex> to_url_param(%{"first_name" => true, "email" => true, "street" => false})
+      "first_name,email"
+  """
+  @spec to_url_param(%{String.t() => boolean()}) :: String.t()
+  def to_url_param(selection) when is_map(selection) do
+    selection
+    |> Enum.filter(fn {_field, visible} -> visible end)
+    |> Enum.map(fn {field, _visible} -> field end)
+    |> Enum.join(",")
+  end
+
+  def to_url_param(_), do: ""
+
+  # Parses a JSON string into a map, handling errors gracefully
+  defp parse_json(json_string) when is_binary(json_string) do
+    case Jason.decode(json_string) do
+      {:ok, decoded} when is_map(decoded) ->
+        # Ensure all values are booleans
+        Enum.reduce(decoded, %{}, fn
+          {key, value} when is_boolean(value) -> {key, value}
+          {key, _value} -> {key, true}
+        end)
+
+      _ ->
+        %{}
+    end
+  end
+
+  defp parse_json(_), do: %{}
+
+  # Parses a comma-separated string of field names
+  defp parse_fields_string(fields_string) do
+    fields_string
+    |> String.split(",")
+    |> Enum.map(&String.trim/1)
+    |> Enum.filter(&(&1 != ""))
+    |> Enum.reduce(%{}, fn field, acc -> Map.put(acc, field, true) end)
+  end
+end

lib/mv_web/live/member_live/index/field_visibility.ex

@@ -0,0 +1,235 @@
+defmodule MvWeb.MemberLive.Index.FieldVisibility do
+  @moduledoc """
+  Manages field visibility by merging user-specific selection with global settings.
+
+  This module handles:
+  - Getting all available fields (member fields + custom fields)
+  - Merging user selection with global settings (user selection takes priority)
+  - Falling back to global settings when no user selection exists
+  - Converting between different field name formats (atoms vs strings)
+
+  ## Field Naming Convention
+
+  - **Member Fields**: Atoms (e.g., `:first_name`, `:email`)
+  - **Custom Fields**: Strings with format `"custom_field_<id>"` (e.g., `"custom_field_abc-123"`)
+
+  ## Priority Order
+
+  1. User-specific selection (from URL/Session/Cookie)
+  2. Global settings (from database)
+  3. Default (all fields visible)
+  """
+
+  @doc """
+  Gets all available fields for selection.
+
+  Returns a list of field identifiers:
+  - Member fields as atoms (e.g., `:first_name`, `:email`)
+  - Custom fields as strings (e.g., `"custom_field_abc-123"`)
+
+  ## Parameters
+
+    - `custom_fields` - List of CustomField resources that are available
+
+  ## Returns
+
+    List of field identifiers (atoms and strings)
+  """
+  @spec get_all_available_fields([struct()]) :: [atom() | String.t()]
+  def get_all_available_fields(custom_fields) do
+    member_fields = Mv.Constants.member_fields()
+    custom_field_names = Enum.map(custom_fields, &"custom_field_#{&1.id}")
+
+    member_fields ++ custom_field_names
+  end
+
+  @doc """
+  Merges user field selection with global settings.
+
+  User selection takes priority over global settings. If a field is not in the
+  user selection, the global setting is used. If a field is not in global settings,
+  it defaults to `true` (visible).
+
+  ## Parameters
+
+    - `user_selection` - Map of field names (strings) to boolean visibility
+    - `global_settings` - Settings struct with `member_field_visibility` field
+    - `custom_fields` - List of CustomField resources
+
+  ## Returns
+
+    Map of field names (strings) to boolean visibility values
+
+  ## Examples
+
+      iex> user_selection = %{"first_name" => false}
+      iex> settings = %{member_field_visibility: %{first_name: true, email: true}}
+      iex> merge_with_global_settings(user_selection, settings, [])
+      %{"first_name" => false, "email" => true}  # User selection overrides global
+  """
+  @spec merge_with_global_settings(
+          %{String.t() => boolean()},
+          map(),
+          [struct()]
+        ) :: %{String.t() => boolean()}
+  def merge_with_global_settings(user_selection, global_settings, custom_fields) do
+    all_fields = get_all_available_fields(custom_fields)
+    global_visibility = get_global_visibility_map(global_settings, custom_fields)
+
+    Enum.reduce(all_fields, %{}, fn field, acc ->
+      field_string = field_to_string(field)
+
+      visibility =
+        case Map.get(user_selection, field_string) do
+          nil -> Map.get(global_visibility, field_string, true)
+          user_value -> user_value
+        end
+
+      Map.put(acc, field_string, visibility)
+    end)
+  end
+
+  @doc """
+  Gets the list of visible fields from a field selection map.
+
+  Returns only fields where visibility is `true`.
+
+  ## Parameters
+
+    - `field_selection` - Map of field names to boolean visibility
+
+  ## Returns
+
+    List of field identifiers (atoms for member fields, strings for custom fields)
+
+  ## Examples
+
+      iex> selection = %{"first_name" => true, "email" => false, "street" => true}
+      iex> get_visible_fields(selection)
+      [:first_name, :street]
+  """
+  @spec get_visible_fields(%{String.t() => boolean()}) :: [atom() | String.t()]
+  def get_visible_fields(field_selection) when is_map(field_selection) do
+    field_selection
+    |> Enum.filter(fn {_field, visible} -> visible end)
+    |> Enum.map(fn {field_string, _visible} -> to_field_identifier(field_string) end)
+  end
+
+  def get_visible_fields(_), do: []
+
+  @doc """
+  Gets visible member fields from field selection.
+
+  Returns only member fields (atoms) that are visible.
+
+  ## Examples
+
+      iex> selection = %{"first_name" => true, "email" => true, "custom_field_123" => true}
+      iex> get_visible_member_fields(selection)
+      [:first_name, :email]
+  """
+  @spec get_visible_member_fields(%{String.t() => boolean()}) :: [atom()]
+  def get_visible_member_fields(field_selection) when is_map(field_selection) do
+    member_fields = Mv.Constants.member_fields()
+
+    field_selection
+    |> Enum.filter(fn {field_string, visible} ->
+      field_atom = to_field_identifier(field_string)
+      visible && field_atom in member_fields
+    end)
+    |> Enum.map(fn {field_string, _visible} -> to_field_identifier(field_string) end)
+  end
+
+  def get_visible_member_fields(_), do: []
+
+  @doc """
+  Gets visible custom fields from field selection.
+
+  Returns only custom field identifiers (strings) that are visible.
+
+  ## Examples
+
+      iex> selection = %{"first_name" => true, "custom_field_123" => true, "custom_field_456" => false}
+      iex> get_visible_custom_fields(selection)
+      ["custom_field_123"]
+  """
+  @spec get_visible_custom_fields(%{String.t() => boolean()}) :: [String.t()]
+  def get_visible_custom_fields(field_selection) when is_map(field_selection) do
+    field_selection
+    |> Enum.filter(fn {field_string, visible} ->
+      visible && String.starts_with?(field_string, "custom_field_")
+    end)
+    |> Enum.map(fn {field_string, _visible} -> field_string end)
+  end
+
+  def get_visible_custom_fields(_), do: []
+
+  # Gets global visibility map from settings
+  defp get_global_visibility_map(settings, custom_fields) do
+    member_visibility = get_member_field_visibility_from_settings(settings)
+    custom_field_visibility = get_custom_field_visibility(custom_fields)
+
+    Map.merge(member_visibility, custom_field_visibility)
+  end
+
+  # Gets member field visibility from settings
+  defp get_member_field_visibility_from_settings(settings) do
+    visibility_config =
+      normalize_visibility_config(Map.get(settings, :member_field_visibility, %{}))
+
+    member_fields = Mv.Constants.member_fields()
+
+    Enum.reduce(member_fields, %{}, fn field, acc ->
+      field_string = Atom.to_string(field)
+      show_in_overview = Map.get(visibility_config, field, true)
+      Map.put(acc, field_string, show_in_overview)
+    end)
+  end
+
+  # Gets custom field visibility (all custom fields with show_in_overview=true are visible)
+  defp get_custom_field_visibility(custom_fields) do
+    Enum.reduce(custom_fields, %{}, fn custom_field, acc ->
+      field_string = "custom_field_#{custom_field.id}"
+      visible = Map.get(custom_field, :show_in_overview, true)
+      Map.put(acc, field_string, visible)
+    end)
+  end
+
+  # Normalizes visibility config map keys from strings to atoms
+  defp normalize_visibility_config(config) when is_map(config) do
+    Enum.reduce(config, %{}, fn
+      {key, value}, acc when is_atom(key) ->
+        Map.put(acc, key, value)
+
+      {key, value}, acc when is_binary(key) ->
+        try do
+          atom_key = String.to_existing_atom(key)
+          Map.put(acc, atom_key, value)
+        rescue
+          ArgumentError -> acc
+        end
+
+      _, acc ->
+        acc
+    end)
+  end
+
+  defp normalize_visibility_config(_), do: %{}
+
+  # Converts field string to atom (for member fields) or keeps as string (for custom fields)
+  defp to_field_identifier(field_string) when is_binary(field_string) do
+    if String.starts_with?(field_string, "custom_field_") do
+      field_string
+    else
+      try do
+        String.to_existing_atom(field_string)
+      rescue
+        ArgumentError -> field_string
+      end
+    end
+  end
+
+  # Converts field identifier to string
+  defp field_to_string(field) when is_atom(field), do: Atom.to_string(field)
+  defp field_to_string(field) when is_binary(field), do: field
+end