feat(agent): toml config loader with defaults and validation

agent/lib/proxmox_agent/config.ex

@@ -0,0 +1,77 @@
+defmodule ProxmoxAgent.Config do
+  @moduledoc "Loads and validates the TOML agent config."
+
+  defstruct [
+    :server_url,
+    :token,
+    :host_id,
+    fast_seconds: 30,
+    medium_seconds: 300,
+    slow_seconds: 1800
+  ]
+
+  @type t :: %__MODULE__{
+          server_url: String.t(),
+          token: String.t(),
+          host_id: String.t(),
+          fast_seconds: pos_integer(),
+          medium_seconds: pos_integer(),
+          slow_seconds: pos_integer()
+        }
+
+  @required ~w(server_url token)a
+
+  @spec load(Path.t()) ::
+          {:ok, t()}
+          | {:error, {:file_read, term()} | {:parse, term()} | {:missing_key, atom()}}
+  def load(path) do
+    with {:ok, body} <- read_file(path),
+         {:ok, parsed} <- parse_toml(body),
+         :ok <- validate_required(parsed) do
+      {:ok, build(parsed)}
+    end
+  end
+
+  defp read_file(path) do
+    case File.read(path) do
+      {:ok, body} -> {:ok, body}
+      {:error, reason} -> {:error, {:file_read, reason}}
+    end
+  end
+
+  defp parse_toml(body) do
+    case Toml.decode(body) do
+      {:ok, map} -> {:ok, map}
+      {:error, reason} -> {:error, {:parse, reason}}
+    end
+  end
+
+  defp validate_required(map) do
+    Enum.find_value(@required, :ok, fn key ->
+      case Map.get(map, Atom.to_string(key)) do
+        v when is_binary(v) and v != "" -> nil
+        _ -> {:error, {:missing_key, key}}
+      end
+    end)
+  end
+
+  defp build(map) do
+    intervals = Map.get(map, "intervals", %{})
+
+    %__MODULE__{
+      server_url: map["server_url"],
+      token: map["token"],
+      host_id: map["host_id"] || hostname(),
+      fast_seconds: Map.get(intervals, "fast_seconds", 30),
+      medium_seconds: Map.get(intervals, "medium_seconds", 300),
+      slow_seconds: Map.get(intervals, "slow_seconds", 1800)
+    }
+  end
+
+  defp hostname do
+    case :inet.gethostname() do
+      {:ok, name} -> List.to_string(name)
+      _ -> "unknown-host"
+    end
+  end
+end