feat: add membership fee types admin interface

- Add list view showing name, amount, interval, member count
- Add create/edit forms for membership fee types
- Gray out interval field on edit (immutable)
- Show warning on amount change with impact information
- Prevent deletion if type is in use

lib/mv_web/live/membership_fee_type_live/form.ex

@@ -0,0 +1,331 @@
+defmodule MvWeb.MembershipFeeTypeLive.Form do
+  @moduledoc """
+  LiveView form for creating and editing membership fee types (Admin).
+
+  ## Features
+  - Create new membership fee types
+  - Edit existing membership fee types (name, amount, description - NOT interval)
+  - Amount change warning modal (shows impact on members)
+  - Interval field grayed out on edit
+
+  ## Permissions
+  - Admin only
+  """
+  use MvWeb, :live_view
+
+  require Ash.Query
+
+  alias Mv.MembershipFees
+  alias Mv.MembershipFees.MembershipFeeType
+  alias Mv.Membership.Member
+  alias MvWeb.Helpers.MembershipFeeHelpers
+
+  @impl true
+  def render(assigns) do
+    ~H"""
+    <Layouts.app flash={@flash} current_user={@current_user}>
+      <.header>
+        {@page_title}
+        <:subtitle>
+          {gettext("Use this form to manage membership fee types in your database.")}
+        </:subtitle>
+      </.header>
+
+      <.form
+        class="max-w-xl"
+        for={@form}
+        id="membership-fee-type-form"
+        phx-change="validate"
+        phx-submit="save"
+      >
+        <.input field={@form[:name]} type="text" label={gettext("Name")} required />
+
+        <.input
+          field={@form[:amount]}
+          type="number"
+          label={gettext("Amount")}
+          step="0.01"
+          min="0"
+          required
+        />
+
+        <div class="form-control">
+          <label class="label">
+            <span class="label-text font-semibold">{gettext("Interval")}</span>
+          </label>
+          <select
+            class="select select-bordered w-full"
+            disabled={!is_nil(@membership_fee_type)}
+            name="interval"
+            value={@form[:interval].value || ""}
+          >
+            <option value="">{gettext("Select interval")}</option>
+            <option value="monthly" selected={@form[:interval].value == :monthly}>
+              {gettext("Monthly")}
+            </option>
+            <option value="quarterly" selected={@form[:interval].value == :quarterly}>
+              {gettext("Quarterly")}
+            </option>
+            <option value="half_yearly" selected={@form[:interval].value == :half_yearly}>
+              {gettext("Half-yearly")}
+            </option>
+            <option value="yearly" selected={@form[:interval].value == :yearly}>
+              {gettext("Yearly")}
+            </option>
+          </select>
+          <%= if !is_nil(@membership_fee_type) do %>
+            <label class="label">
+              <span class="label-text-alt text-base-content/60">
+                {gettext("Interval cannot be changed after creation.")}
+              </span>
+            </label>
+          <% end %>
+        </div>
+
+        <.input
+          field={@form[:description]}
+          type="textarea"
+          label={gettext("Description")}
+          rows="3"
+        />
+
+        <div class="mt-4">
+          <.button phx-disable-with={gettext("Saving...")} variant="primary" type="submit">
+            {gettext("Save Membership Fee Type")}
+          </.button>
+          <.button navigate={return_path(@return_to, @membership_fee_type)} type="button">
+            {gettext("Cancel")}
+          </.button>
+        </div>
+      </.form>
+
+      <%!-- Amount Change Warning Modal --%>
+      <%= if @show_amount_warning do %>
+        <dialog id="amount-warning-modal" class="modal modal-open">
+          <div class="modal-box">
+            <h3 class="text-lg font-bold">{gettext("Change Amount?")}</h3>
+            <div class="py-4 space-y-4">
+              <div class="alert alert-warning">
+                <.icon name="hero-exclamation-triangle" class="size-5" />
+                <div>
+                  <p class="font-semibold">
+                    {gettext("Changing the amount will affect %{count} member(s).",
+                      count: @affected_member_count
+                    )}
+                  </p>
+                  <p class="mt-2 text-sm">
+                    {gettext("Future unpaid cycles will be regenerated with the new amount.")}
+                  </p>
+                  <p class="mt-2 text-sm">
+                    {gettext("Already paid cycles will remain with the old amount.")}
+                  </p>
+                </div>
+              </div>
+
+              <div class="space-y-2">
+                <div class="flex justify-between">
+                  <span class="text-base-content/70">{gettext("Current amount")}:</span>
+                  <span class="font-mono font-semibold">
+                    {MembershipFeeHelpers.format_currency(@old_amount)}
+                  </span>
+                </div>
+                <div class="flex justify-between">
+                  <span class="text-base-content/70">{gettext("New amount")}:</span>
+                  <span class="font-mono font-semibold text-primary">
+                    {MembershipFeeHelpers.format_currency(@new_amount)}
+                  </span>
+                </div>
+              </div>
+            </div>
+
+            <div class="modal-action">
+              <button
+                type="button"
+                phx-click="cancel_amount_change"
+                class="btn"
+              >
+                {gettext("Cancel")}
+              </button>
+              <button
+                type="button"
+                phx-click="confirm_amount_change"
+                class="btn btn-primary"
+              >
+                {gettext("Confirm Change")}
+              </button>
+            </div>
+          </div>
+        </dialog>
+      <% end %>
+    </Layouts.app>
+    """
+  end
+
+  @impl true
+  def mount(params, _session, socket) do
+    membership_fee_type =
+      case params["id"] do
+        nil -> nil
+        id -> Ash.get!(MembershipFeeType, id, domain: MembershipFees)
+      end
+
+    page_title =
+      if is_nil(membership_fee_type),
+        do: gettext("New Membership Fee Type"),
+        else: gettext("Edit Membership Fee Type")
+
+    {:ok,
+     socket
+     |> assign(:return_to, return_to(params["return_to"]))
+     |> assign(:membership_fee_type, membership_fee_type)
+     |> assign(:page_title, page_title)
+     |> assign(:show_amount_warning, false)
+     |> assign(:old_amount, nil)
+     |> assign(:new_amount, nil)
+     |> assign(:affected_member_count, 0)
+     |> assign(:pending_amount, nil)
+     |> assign_form()}
+  end
+
+  defp return_to("index"), do: "index"
+  defp return_to(_), do: "index"
+
+  @impl true
+  def handle_event("validate", %{"membership_fee_type" => params}, socket) do
+    validated_form = AshPhoenix.Form.validate(socket.assigns.form, params)
+
+    # Check if amount changed on edit
+    socket =
+      if socket.assigns.membership_fee_type && Map.has_key?(params, "amount") do
+        new_amount_str = params["amount"]
+        old_amount = socket.assigns.membership_fee_type.amount
+
+        case Decimal.parse(new_amount_str) do
+          {new_amount, _} when is_struct(new_amount, Decimal) ->
+            if Decimal.compare(new_amount, old_amount) != :eq do
+              # Amount changed - show warning
+              affected_count = get_affected_member_count(socket.assigns.membership_fee_type.id)
+
+              socket
+              |> assign(:show_amount_warning, true)
+              |> assign(:old_amount, old_amount)
+              |> assign(:new_amount, new_amount)
+              |> assign(:affected_member_count, affected_count)
+              |> assign(:pending_amount, new_amount_str)
+            else
+              # Amount unchanged - hide warning
+              socket
+              |> assign(:show_amount_warning, false)
+              |> assign(:pending_amount, nil)
+            end
+
+          :error ->
+            socket
+        end
+      else
+        socket
+      end
+
+    {:noreply, assign(socket, form: validated_form)}
+  end
+
+  def handle_event("cancel_amount_change", _params, socket) do
+    # Reset form to original amount
+    form = socket.assigns.form
+
+    original_amount =
+      if socket.assigns.membership_fee_type do
+        socket.assigns.membership_fee_type.amount
+      else
+        Decimal.new("0")
+      end
+
+    # Update form with original amount
+    updated_form =
+      AshPhoenix.Form.validate(form, %{
+        "amount" => Decimal.to_string(original_amount)
+      })
+
+    {:noreply,
+     socket
+     |> assign(:form, updated_form)
+     |> assign(:show_amount_warning, false)
+     |> assign(:pending_amount, nil)}
+  end
+
+  def handle_event("confirm_amount_change", _params, socket) do
+    # Update form with pending amount and hide warning
+    form = socket.assigns.form
+
+    updated_form =
+      if socket.assigns.pending_amount do
+        AshPhoenix.Form.validate(form, %{"amount" => socket.assigns.pending_amount})
+      else
+        form
+      end
+
+    {:noreply,
+     socket
+     |> assign(:form, updated_form)
+     |> assign(:show_amount_warning, false)
+     |> assign(:pending_amount, nil)}
+  end
+
+  def handle_event("save", %{"membership_fee_type" => params}, socket) do
+    # If amount warning was shown but not confirmed, don't save
+    if socket.assigns.show_amount_warning do
+      {:noreply, put_flash(socket, :error, gettext("Please confirm the amount change first"))}
+    else
+      case AshPhoenix.Form.submit(socket.assigns.form, params: params) do
+        {:ok, membership_fee_type} ->
+          notify_parent({:saved, membership_fee_type})
+
+          socket =
+            socket
+            |> put_flash(:info, gettext("Membership fee type saved successfully"))
+            |> push_navigate(to: return_path(socket.assigns.return_to, membership_fee_type))
+
+          {:noreply, socket}
+
+        {:error, form} ->
+          {:noreply, assign(socket, form: form)}
+      end
+    end
+  end
+
+  @spec notify_parent(any()) :: any()
+  defp notify_parent(msg), do: send(self(), {__MODULE__, msg})
+
+  @spec assign_form(Phoenix.LiveView.Socket.t()) :: Phoenix.LiveView.Socket.t()
+  defp assign_form(%{assigns: %{membership_fee_type: membership_fee_type}} = socket) do
+    form =
+      if membership_fee_type do
+        AshPhoenix.Form.for_update(
+          membership_fee_type,
+          :update,
+          domain: MembershipFees,
+          as: "membership_fee_type"
+        )
+      else
+        AshPhoenix.Form.for_create(
+          MembershipFeeType,
+          :create,
+          domain: MembershipFees,
+          as: "membership_fee_type"
+        )
+      end
+
+    assign(socket, form: to_form(form))
+  end
+
+  @spec return_path(String.t(), MembershipFeeType.t() | nil) :: String.t()
+  defp return_path("index", _membership_fee_type), do: ~p"/membership_fee_types"
+
+  @spec get_affected_member_count(String.t()) :: non_neg_integer()
+  defp get_affected_member_count(fee_type_id) do
+    case Ash.count(Member |> Ash.Query.filter(membership_fee_type_id == ^fee_type_id)) do
+      {:ok, count} -> count
+      _ -> 0
+    end
+  end
+end

lib/mv_web/live/membership_fee_type_live/index.ex

@@ -0,0 +1,185 @@
+defmodule MvWeb.MembershipFeeTypeLive.Index do
+  @moduledoc """
+  LiveView for managing membership fee types (Admin).
+
+  ## Features
+  - List all membership fee types
+  - Display: Name, Amount, Interval, Member count
+  - Create new membership fee types
+  - Edit existing membership fee types (name, amount, description - NOT interval)
+  - Delete membership fee types (if no members assigned)
+
+  ## Permissions
+  - Admin only
+  """
+  use MvWeb, :live_view
+
+  require Ash.Query
+
+  alias Mv.MembershipFees
+  alias Mv.MembershipFees.MembershipFeeType
+  alias Mv.Membership.Member
+  alias MvWeb.Helpers.MembershipFeeHelpers
+
+  @impl true
+  def mount(_params, _session, socket) do
+    {:ok,
+     socket
+     |> assign(:page_title, gettext("Membership Fee Types"))
+     |> assign(:membership_fee_types, load_membership_fee_types())}
+  end
+
+  @impl true
+  def render(assigns) do
+    ~H"""
+    <Layouts.app flash={@flash} current_user={@current_user}>
+      <.header>
+        {gettext("Membership Fee Types")}
+        <:subtitle>
+          {gettext("Manage membership fee types for membership fees.")}
+        </:subtitle>
+        <:actions>
+          <.button variant="primary" navigate={~p"/membership_fee_types/new"}>
+            <.icon name="hero-plus" /> {gettext("New Membership Fee Type")}
+          </.button>
+        </:actions>
+      </.header>
+
+      <.table
+        id="membership_fee_types"
+        rows={@membership_fee_types}
+        row_id={fn mft -> "mft-#{mft.id}" end}
+      >
+        <:col :let={mft} label={gettext("Name")}>
+          <span class="font-medium">{mft.name}</span>
+          <p :if={mft.description} class="text-sm text-base-content/60">{mft.description}</p>
+        </:col>
+
+        <:col :let={mft} label={gettext("Amount")}>
+          <span class="font-mono">{MembershipFeeHelpers.format_currency(mft.amount)}</span>
+        </:col>
+
+        <:col :let={mft} label={gettext("Interval")}>
+          <span class="badge badge-outline">
+            {MembershipFeeHelpers.format_interval(mft.interval)}
+          </span>
+        </:col>
+
+        <:col :let={mft} label={gettext("Members")}>
+          <span class="badge badge-ghost">{get_member_count(mft)}</span>
+        </:col>
+
+        <:action :let={mft}>
+          <.link navigate={~p"/membership_fee_types/#{mft.id}/edit"} class="btn btn-ghost btn-xs">
+            <.icon name="hero-pencil" class="size-4" />
+          </.link>
+        </:action>
+
+        <:action :let={mft}>
+          <button
+            phx-click="delete"
+            phx-value-id={mft.id}
+            data-confirm={gettext("Are you sure?")}
+            class={[
+              "btn btn-ghost btn-xs",
+              if(get_member_count(mft) > 0,
+                do: "text-error opacity-50 cursor-not-allowed",
+                else: "text-error"
+              )
+            ]}
+            title={
+              if get_member_count(mft) > 0,
+                do:
+                  gettext("Cannot delete - %{count} member(s) assigned", count: get_member_count(mft)),
+                else: gettext("Delete")
+            }
+            disabled={get_member_count(mft) > 0}
+          >
+            <.icon name="hero-trash" class="size-4" />
+          </button>
+        </:action>
+      </.table>
+
+      <.info_card />
+    </Layouts.app>
+    """
+  end
+
+  @impl true
+  def handle_event("delete", %{"id" => id}, socket) do
+    fee_type = Ash.get!(MembershipFeeType, id)
+
+    case Ash.destroy(fee_type, domain: MembershipFees) do
+      :ok ->
+        updated_types = Enum.reject(socket.assigns.membership_fee_types, &(&1.id == id))
+
+        {:noreply,
+         socket
+         |> assign(:membership_fee_types, updated_types)
+         |> put_flash(:info, gettext("Membership fee type deleted"))}
+
+      {:error, error} ->
+        {:noreply, put_flash(socket, :error, format_error(error))}
+    end
+  end
+
+  # Helper functions
+
+  defp load_membership_fee_types do
+    MembershipFeeType
+    |> Ash.Query.sort(name: :asc)
+    |> Ash.read!(domain: MembershipFees)
+  end
+
+  defp get_member_count(fee_type) do
+    # Count members with this fee type
+    case Ash.count(Member |> Ash.Query.filter(membership_fee_type_id == ^fee_type.id)) do
+      {:ok, count} -> count
+      _ -> 0
+    end
+  end
+
+  defp format_error(%Ash.Error.Invalid{} = error) do
+    Enum.map_join(error.errors, ", ", fn e -> e.message end)
+  end
+
+  defp format_error(error) when is_binary(error), do: error
+  defp format_error(_error), do: gettext("An error occurred")
+
+  # Info card explaining the membership fee type concept
+  defp info_card(assigns) do
+    ~H"""
+    <div class="card bg-base-200 mt-6">
+      <div class="card-body">
+        <h2 class="card-title">
+          <.icon name="hero-information-circle" class="size-5" />
+          {gettext("About Membership Fee Types")}
+        </h2>
+        <div class="prose prose-sm max-w-none">
+          <p>
+            {gettext(
+              "Membership fee types define different membership fee structures. Each type has a fixed interval (monthly, quarterly, half-yearly, yearly) that cannot be changed after creation."
+            )}
+          </p>
+          <ul>
+            <li>
+              <strong>{gettext("Name & Amount")}</strong>
+              - {gettext("Can be changed at any time. Amount changes affect future periods only.")}
+            </li>
+            <li>
+              <strong>{gettext("Interval")}</strong>
+              - {gettext(
+                "Fixed after creation. Members can only switch between types with the same interval."
+              )}
+            </li>
+            <li>
+              <strong>{gettext("Deletion")}</strong>
+              - {gettext("Only possible if no members are assigned to this type.")}
+            </li>
+          </ul>
+        </div>
+      </div>
+    </div>
+    """
+  end
+end