Add Statistics module for member and cycle aggregates

- first_join_year, active/inactive counts, joins/exits by year
- cycle_totals_by_year, open_amount_total
- Unit tests for Statistics

lib/mv/statistics.ex

@@ -0,0 +1,180 @@
+defmodule Mv.Statistics do
+  @moduledoc """
+  Aggregated statistics for members and membership fee cycles.
+
+  Used by the statistics LiveView to display counts and sums. All functions
+  accept an `opts` keyword list and pass `:actor` (and `:domain` where needed)
+  to Ash reads so that policies are enforced.
+  """
+
+  require Ash.Query
+  import Ash.Expr
+
+  alias Mv.Membership.Member
+  alias Mv.MembershipFees
+  alias Mv.MembershipFees.MembershipFeeCycle
+
+  @doc """
+  Returns the earliest year in which any member has a join_date.
+
+  Used to determine the start of the "relevant" year range for statistics
+  (from first membership to current year). Returns `nil` if no member has
+  a join_date.
+  """
+  @spec first_join_year(keyword()) :: non_neg_integer() | nil
+  def first_join_year(opts) do
+    query =
+      Member
+      |> Ash.Query.filter(expr(not is_nil(join_date)))
+      |> Ash.Query.sort(join_date: :asc)
+      |> Ash.Query.limit(1)
+
+    case Ash.read_one(query, opts) do
+      {:ok, nil} -> nil
+      {:ok, member} -> member.join_date.year
+      {:error, _} -> nil
+    end
+  end
+
+  @doc """
+  Returns the count of active members (exit_date is nil).
+  """
+  @spec active_member_count(keyword()) :: non_neg_integer()
+  def active_member_count(opts) do
+    query =
+      Member
+      |> Ash.Query.filter(expr(is_nil(exit_date)))
+
+    case Ash.count(query, opts) do
+      {:ok, count} -> count
+      {:error, _} -> 0
+    end
+  end
+
+  @doc """
+  Returns the count of inactive members (exit_date is not nil).
+  """
+  @spec inactive_member_count(keyword()) :: non_neg_integer()
+  def inactive_member_count(opts) do
+    query =
+      Member
+      |> Ash.Query.filter(expr(not is_nil(exit_date)))
+
+    case Ash.count(query, opts) do
+      {:ok, count} -> count
+      {:error, _} -> 0
+    end
+  end
+
+  @doc """
+  Returns the count of members who joined in the given year (join_date in that year).
+  """
+  @spec joins_by_year(integer(), keyword()) :: non_neg_integer()
+  def joins_by_year(year, opts) do
+    first_day = Date.new!(year, 1, 1)
+    last_day = Date.new!(year, 12, 31)
+
+    query =
+      Member
+      |> Ash.Query.filter(expr(join_date >= ^first_day and join_date <= ^last_day))
+
+    case Ash.count(query, opts) do
+      {:ok, count} -> count
+      {:error, _} -> 0
+    end
+  end
+
+  @doc """
+  Returns the count of members who exited in the given year (exit_date in that year).
+  """
+  @spec exits_by_year(integer(), keyword()) :: non_neg_integer()
+  def exits_by_year(year, opts) do
+    first_day = Date.new!(year, 1, 1)
+    last_day = Date.new!(year, 12, 31)
+
+    query =
+      Member
+      |> Ash.Query.filter(expr(exit_date >= ^first_day and exit_date <= ^last_day))
+
+    case Ash.count(query, opts) do
+      {:ok, count} -> count
+      {:error, _} -> 0
+    end
+  end
+
+  @doc """
+  Returns totals for membership fee cycles whose cycle_start falls in the given year.
+
+  Returns a map with keys: `:total`, `:paid`, `:unpaid`, `:suspended` (each a Decimal sum).
+  """
+  @spec cycle_totals_by_year(integer(), keyword()) :: %{
+          total: Decimal.t(),
+          paid: Decimal.t(),
+          unpaid: Decimal.t(),
+          suspended: Decimal.t()
+        }
+  def cycle_totals_by_year(year, opts) do
+    first_day = Date.new!(year, 1, 1)
+    last_day = Date.new!(year, 12, 31)
+
+    query =
+      MembershipFeeCycle
+      |> Ash.Query.filter(expr(cycle_start >= ^first_day and cycle_start <= ^last_day))
+
+    opts_with_domain = Keyword.put(opts, :domain, MembershipFees)
+
+    case Ash.read(query, opts_with_domain) do
+      {:ok, cycles} -> cycle_totals_from_cycles(cycles)
+      {:error, _} -> zero_cycle_totals()
+    end
+  end
+
+  defp cycle_totals_from_cycles(cycles) do
+    by_status = Enum.group_by(cycles, & &1.status)
+    sum = fn status -> sum_amounts(by_status[status] || []) end
+
+    total =
+      [:paid, :unpaid, :suspended]
+      |> Enum.map(&sum.(&1))
+      |> Enum.reduce(Decimal.new(0), &Decimal.add/2)
+
+    %{
+      total: total,
+      paid: sum.(:paid),
+      unpaid: sum.(:unpaid),
+      suspended: sum.(:suspended)
+    }
+  end
+
+  defp sum_amounts(cycles),
+    do: Enum.reduce(cycles, Decimal.new(0), fn c, acc -> Decimal.add(acc, c.amount) end)
+
+  defp zero_cycle_totals do
+    %{
+      total: Decimal.new(0),
+      paid: Decimal.new(0),
+      unpaid: Decimal.new(0),
+      suspended: Decimal.new(0)
+    }
+  end
+
+  @doc """
+  Returns the sum of amount for all cycles with status :unpaid.
+  """
+  @spec open_amount_total(keyword()) :: Decimal.t()
+  def open_amount_total(opts) do
+    query =
+      MembershipFeeCycle
+      |> Ash.Query.filter(expr(status == :unpaid))
+
+    opts_with_domain = Keyword.put(opts, :domain, MembershipFees)
+
+    case Ash.read(query, opts_with_domain) do
+      {:ok, cycles} ->
+        Enum.reduce(cycles, Decimal.new(0), fn c, acc -> Decimal.add(acc, c.amount) end)
+
+      {:error, _} ->
+        Decimal.new(0)
+    end
+  end
+end