defmodule RustQ.Reach.Smells.RawRustEscape do
  @moduledoc """
  Detects large raw Rust escape hatches in RustQ generator code.

  Tiny local escapes remain acceptable for macro invocations and parser gaps, but
  multiline or long raw snippets should usually become Rusty-Elixir, RustQ AST,
  source metadata, or a focused `defrustmacro`.
  """

  use Reach.Smell.Check.AST

  alias Reach.Smell.Finding

  @kind :rustq_large_raw_rust_escape
  @max_inline_chars 100

  @impl true
  def kinds, do: [@kind]

  defp scan_ast(ast, file) do
    {_ast, findings} =
      Macro.prewalk(ast, [], fn node, findings ->
        {node, raw_escape_findings(node, file) ++ findings}
      end)

    Enum.reverse(findings)
  end

  defp raw_escape_findings(node, file) do
    with {:ok, meta, source} <- raw_escape(node),
         true <- large_escape?(source) do
      [
        Finding.new(
          kind: @kind,
          message:
            "large raw Rust escape; prefer defrust, RustQ AST/builders, metadata, or a small defrustmacro",
          location: location(file, meta),
          evidence: String.slice(source, 0, 120)
        )
      ]
    else
      _not_raw_or_small -> []
    end
  end

  defp raw_escape({name, meta, [source]})
       when name in [:raw_expr!, :raw_pat!, :raw_stmt!, :raw_arm!] do
    with {:ok, source} <- string_literal(source), do: {:ok, meta, source}
  end

  defp raw_escape({{:., meta, [_receiver, function]}, _call_meta, [source]})
       when function in [:raw, :item, :impl_item, :stmt, :expr, :arm, :macro_item] do
    with {:ok, source} <- string_literal(source), do: {:ok, meta, source}
  end

  defp raw_escape(_node), do: :error

  defp string_literal(source) when is_binary(source), do: {:ok, source}
  defp string_literal({:__block__, _meta, [source]}) when is_binary(source), do: {:ok, source}
  defp string_literal(_source), do: :error

  defp large_escape?(source) do
    String.contains?(source, "\n") or String.length(source) > @max_inline_chars
  end

  defp location(file, meta), do: "#{file}:#{meta[:line] || 0}"
end