defmodule NextLSPrivate.Tracer do
  @moduledoc false
  def trace(:start, _env) do
    :ok
  end

  def trace({:alias_reference, meta, module}, env) do
    parent = parent_pid()

    alias_map = Map.new(env.aliases, fn {alias, mod} -> {mod, alias} end)

    Process.send(
      parent,
      {{:tracer, :reference},
       %{
         meta: meta,
         identifier: Map.get(alias_map, module, module),
         file: env.file,
         type: :alias,
         module: module
       }},
      []
    )

    :ok
  end

  def trace({type, meta, module, func, arity}, env)
      when type in [:remote_function, :remote_macro, :imported_macro] and
             module not in [:elixir_def, :elixir_utils, Kernel, Enum] do
    parent = parent_pid()

    if type == :remote_macro && meta[:closing][:line] != meta[:line] do
      # this is the case that a macro is getting expanded from inside
      # another macro expansion
      :noop
    else
      Process.send(
        parent,
        {{:tracer, :reference},
         %{
           meta: meta,
           identifier: func,
           arity: arity,
           file: env.file,
           type: :function,
           module: module
         }},
        []
      )
    end

    :ok
  end

  def trace({type, meta, func, arity}, env) when type in [:local_function, :local_macro] do
    parent = parent_pid()

    Process.send(
      parent,
      {{:tracer, :reference},
       %{
         meta: meta,
         identifier: func,
         arity: arity,
         file: env.file,
         type: :function,
         module: env.module
       }},
      []
    )

    :ok
  end

  def trace({:on_module, bytecode, _}, env) do
    parent = parent_pid()

    defs = Module.definitions_in(env.module)

    defs =
      for {name, arity} = _def <- defs do
        {name, Module.get_definition(env.module, {name, arity})}
      end

    {:ok, {_, [{~c"Dbgi", bin}]}} = :beam_lib.chunks(bytecode, [~c"Dbgi"])

    {:debug_info_v1, _, {_, %{line: line, struct: struct}, _}} = :erlang.binary_to_term(bin)

    Process.send(
      parent,
      {:tracer,
       %{
         file: env.file,
         module: env.module,
         module_line: line,
         struct: struct,
         defs: defs
       }},
      []
    )

    :ok
  end

  def trace(_event, _env) do
    :ok
  end

  defp parent_pid do
    "NEXTLS_PARENT_PID" |> System.get_env() |> Base.decode64!() |> :erlang.binary_to_term()
  end
end

defmodule :_next_ls_private_compiler do
  @moduledoc false

  def compile do
    # keep stdout on this node
    Process.group_leader(self(), Process.whereis(:user))

    Mix.Task.clear()

    # load the paths for deps and compile them
    # will noop if they are already compiled
    # The mix cli basically runs this before any mix task
    # we have to rerun because we already ran a mix task
    # (mix run), which called this, but we also passed
    # --no-compile, so nothing was compiled, but the
    # task was not re-enabled it seems
    Mix.Task.rerun("deps.loadpaths")
    Mix.Task.rerun("compile", ["--no-protocol-consolidation", "--return-errors", "--tracer", "NextLSPrivate.Tracer"])
  rescue
    e -> {:error, e}
  end
end