feat: issue #25 implemented - cli

lib/bds/cli/install.ex

@@ -0,0 +1,57 @@
+defmodule BDS.CLI.Install do
+  @moduledoc """
+  Installs the `bds-cli` launcher into `~/.local/bin` (issue #25), used by
+  the install buttons in the GUI and TUI settings.
+
+  The installed file is a two-line shim exec'ing the release's
+  `cli/bin/bds-cli` launcher (shipped via `rel/overlays`), so the CLI always
+  runs the same release — and therefore the same settings and cache
+  database — as the installed application.
+  """
+
+  @launcher_name "bds-cli"
+
+  @doc """
+  Writes the `~/.local/bin/bds-cli` shim. Returns `{:ok, installed_path}`,
+  or `{:error, :no_release}` when not running from a packaged release (dev
+  runs have no launcher to point at).
+  """
+  @spec install(keyword()) :: {:ok, Path.t()} | {:error, :no_release | File.posix()}
+  def install(opts \\ []) do
+    bin_dir = Keyword.get(opts, :bin_dir, Path.expand("~/.local/bin"))
+
+    with {:ok, launcher} <- launcher_path(Keyword.get(opts, :release_root)) do
+      installed = Path.join(bin_dir, @launcher_name)
+
+      with :ok <- File.mkdir_p(bin_dir),
+           :ok <- File.write(installed, shim_script(launcher)),
+           :ok <- File.chmod(installed, 0o755) do
+        {:ok, installed}
+      end
+    end
+  end
+
+  @doc """
+  The release's CLI launcher script, resolved from `RELEASE_ROOT` (set by
+  release scripts) or the code root dir (the release root when running a
+  release). `{:error, :no_release}` when neither contains the launcher.
+  """
+  @spec launcher_path(Path.t() | nil) :: {:ok, Path.t()} | {:error, :no_release}
+  def launcher_path(release_root \\ nil) do
+    [release_root, System.get_env("RELEASE_ROOT"), to_string(:code.root_dir())]
+    |> Enum.reject(&(&1 in [nil, ""]))
+    |> Enum.map(&Path.join([&1, "cli", "bin", @launcher_name]))
+    |> Enum.find(&File.regular?/1)
+    |> case do
+      nil -> {:error, :no_release}
+      path -> {:ok, path}
+    end
+  end
+
+  defp shim_script(launcher) do
+    """
+    #!/bin/sh
+    exec "#{launcher}" "$@"
+    """
+  end
+end