From 687fc170828814d2e44a3d5d464ccc14a7006e2c Mon Sep 17 00:00:00 2001
From: Carsten <carsten@ravensburg.it>
Date: Tue, 21 Apr 2026 22:27:20 +0200
Subject: [PATCH] feat(server): metrics schema + context with
 record/latest/prune

---
 server/lib/server/metrics.ex                  | 48 ++++++++++++++
 server/lib/server/schema/metric.ex            | 22 +++++++
 .../20260421202512_create_metrics.exs         | 17 +++++
 server/test/server/metrics_test.exs           | 66 +++++++++++++++++++
 4 files changed, 153 insertions(+)
 create mode 100644 server/lib/server/metrics.ex
 create mode 100644 server/lib/server/schema/metric.ex
 create mode 100644 server/priv/repo/migrations/20260421202512_create_metrics.exs
 create mode 100644 server/test/server/metrics_test.exs

diff --git a/server/lib/server/metrics.ex b/server/lib/server/metrics.ex
new file mode 100644
index 0000000..928fb1b
--- /dev/null
+++ b/server/lib/server/metrics.ex
@@ -0,0 +1,48 @@
+defmodule Server.Metrics do
+  @moduledoc "Metric sample storage and retrieval."
+
+  import Ecto.Query
+
+  alias Server.Repo
+  alias Server.Schema.Metric
+
+  @spec record_sample(integer(), String.t(), DateTime.t(), map()) ::
+          {:ok, Metric.t()} | {:error, Ecto.Changeset.t()}
+  def record_sample(host_id, interval_type, collected_at, payload) do
+    changeset =
+      Metric.changeset(%Metric{}, %{
+        host_id: host_id,
+        interval_type: interval_type,
+        collected_at: collected_at,
+        payload: payload
+      })
+
+    with %Ecto.Changeset{valid?: true} = cs <- changeset,
+         true <- host_exists?(host_id) || {:host_missing, cs} do
+      Repo.insert(cs)
+    else
+      %Ecto.Changeset{} = cs -> {:error, cs}
+      {:host_missing, cs} -> {:error, Ecto.Changeset.add_error(cs, :host, "does not exist")}
+    end
+  end
+
+  defp host_exists?(host_id) do
+    Repo.exists?(from(h in Server.Schema.Host, where: h.id == ^host_id))
+  end
+
+  @spec latest_sample(integer(), String.t()) :: Metric.t() | nil
+  def latest_sample(host_id, interval_type) do
+    from(m in Metric,
+      where: m.host_id == ^host_id and m.interval_type == ^interval_type,
+      order_by: [desc: m.collected_at],
+      limit: 1
+    )
+    |> Repo.one()
+  end
+
+  @spec delete_older_than(DateTime.t()) :: {non_neg_integer(), nil}
+  def delete_older_than(%DateTime{} = cutoff) do
+    from(m in Metric, where: m.collected_at < ^cutoff)
+    |> Repo.delete_all()
+  end
+end
diff --git a/server/lib/server/schema/metric.ex b/server/lib/server/schema/metric.ex
new file mode 100644
index 0000000..5466a06
--- /dev/null
+++ b/server/lib/server/schema/metric.ex
@@ -0,0 +1,22 @@
+defmodule Server.Schema.Metric do
+  use Ecto.Schema
+  import Ecto.Changeset
+
+  @intervals ~w(fast medium slow)
+
+  schema "metrics" do
+    belongs_to :host, Server.Schema.Host
+    field :collected_at, :utc_datetime_usec
+    field :interval_type, :string
+    field :payload, :map
+
+    timestamps(type: :utc_datetime_usec, updated_at: false)
+  end
+
+  def changeset(metric, attrs) do
+    metric
+    |> cast(attrs, [:host_id, :collected_at, :interval_type, :payload])
+    |> validate_required([:host_id, :collected_at, :interval_type, :payload])
+    |> validate_inclusion(:interval_type, @intervals)
+  end
+end
diff --git a/server/priv/repo/migrations/20260421202512_create_metrics.exs b/server/priv/repo/migrations/20260421202512_create_metrics.exs
new file mode 100644
index 0000000..4081951
--- /dev/null
+++ b/server/priv/repo/migrations/20260421202512_create_metrics.exs
@@ -0,0 +1,17 @@
+defmodule Server.Repo.Migrations.CreateMetrics do
+  use Ecto.Migration
+
+  def change do
+    create table(:metrics) do
+      add :host_id, references(:hosts, on_delete: :delete_all), null: false
+      add :collected_at, :utc_datetime_usec, null: false
+      add :interval_type, :string, null: false
+      add :payload, :string, null: false
+
+      timestamps(type: :utc_datetime_usec, updated_at: false)
+    end
+
+    create index(:metrics, [:host_id, :collected_at])
+    create index(:metrics, [:collected_at])
+  end
+end
diff --git a/server/test/server/metrics_test.exs b/server/test/server/metrics_test.exs
new file mode 100644
index 0000000..de6de14
--- /dev/null
+++ b/server/test/server/metrics_test.exs
@@ -0,0 +1,66 @@
+defmodule Server.MetricsTest do
+  use Server.DataCase, async: true
+
+  alias Server.Metrics
+  alias Server.Hosts
+
+  setup do
+    {:ok, {host, _token}} = Hosts.create_host("pve-01")
+    %{host: host}
+  end
+
+  describe "record_sample/4" do
+    test "inserts a metric row with the given payload", %{host: host} do
+      ts = DateTime.utc_now()
+      payload = %{"host" => %{"load1" => 0.5}}
+
+      assert {:ok, metric} = Metrics.record_sample(host.id, "fast", ts, payload)
+      assert metric.host_id == host.id
+      assert metric.interval_type == "fast"
+      assert metric.payload == payload
+      assert metric.collected_at == ts
+    end
+
+    test "rejects unknown interval_type", %{host: host} do
+      ts = DateTime.utc_now()
+      assert {:error, cs} = Metrics.record_sample(host.id, "nope", ts, %{})
+      assert %{interval_type: ["is invalid"]} = errors_on(cs)
+    end
+
+    test "rejects unknown host_id" do
+      ts = DateTime.utc_now()
+      assert {:error, cs} = Metrics.record_sample(999_999, "fast", ts, %{})
+      assert %{host: ["does not exist"]} = errors_on(cs)
+    end
+  end
+
+  describe "latest_sample/2" do
+    test "returns most recent sample for a host and interval", %{host: host} do
+      {:ok, _} = Metrics.record_sample(host.id, "fast", dt(-60), %{"v" => 1})
+      {:ok, _} = Metrics.record_sample(host.id, "fast", dt(-30), %{"v" => 2})
+      {:ok, _} = Metrics.record_sample(host.id, "fast", dt(-10), %{"v" => 3})
+
+      assert %{payload: %{"v" => 3}} = Metrics.latest_sample(host.id, "fast")
+    end
+
+    test "returns nil when no samples exist", %{host: host} do
+      assert Metrics.latest_sample(host.id, "fast") == nil
+    end
+  end
+
+  describe "delete_older_than/1" do
+    test "deletes samples with collected_at before the cutoff", %{host: host} do
+      {:ok, _} = Metrics.record_sample(host.id, "fast", dt(-3600 * 50), %{"v" => "old"})
+      {:ok, keep} = Metrics.record_sample(host.id, "fast", dt(-60), %{"v" => "fresh"})
+
+      cutoff = DateTime.add(DateTime.utc_now(), -48 * 3600, :second)
+      assert {1, nil} = Metrics.delete_older_than(cutoff)
+
+      remaining = Server.Repo.all(Server.Schema.Metric)
+      assert length(remaining) == 1
+      assert hd(remaining).id == keep.id
+    end
+  end
+
+  defp dt(offset_seconds), do: DateTime.add(DateTime.utc_now(), offset_seconds, :second)
+end