defmodule Untangle do
  @moduledoc """
  Logging and debug printing that include location information
  """

  defmacro __using__(_) do
    quote do
      import Untangle
      require Logger
      use Untangle.Time
    end
  end

  @doc "IO.inspect but outputs to Logger with position information, an optional label and configured not to truncate output too much."
  defmacro dump(thing, label \\ "") do
    pre = format_label(__CALLER__)

    quote do
      # unquote(__MODULE__).__dbg__(
      #   "#{unquote(pre)} #{unquote(label)}",
      #   unquote(thing)
      # )

      require Logger

      {formatted, result} =
        unquote(__MODULE__).__prepare_dbg__(
          "#{unquote(pre)} #{unquote(label)}",
          unquote(thing),
          pretty: true,
          limit: :infinity,
          printable_limit: :infinity
        )

      Logger.info(formatted)
      result
    end
  end

  @doc "Like `dump`, but for logging at debug level"
  defmacro debug(thing, label \\ "") do
    pre = format_label(__CALLER__)

    quote do
      if Untangle.log_level?(:debug) do
        require Logger

        {formatted, result} =
          unquote(__MODULE__).__prepare_dbg__(
            "#{unquote(pre)} #{unquote(label)}",
            unquote(thing),
            pretty: true,
            limit: 10000,
            printable_limit: 10000
          )

        Logger.debug(formatted)
        result
      else
        unquote(thing)
      end
    end
  end

  @doc "Like `dump`, but for logging at info level"
  defmacro info(thing, label \\ "") do
    pre = format_label(__CALLER__)
    # thang = Macro.var(:thing, __MODULE__)

    quote do
      if Untangle.log_level?(:info) do
        require Logger

        # {:current_stacktrace, stacktrace} = :erlang.process_info(self(), :current_stacktrace)

        {formatted, result} =
          unquote(__MODULE__).__prepare_dbg__(
            "#{unquote(pre)} #{unquote(label)}",
            unquote(thing),
            # stacktrace: Untangle.format_stacktrace_sliced(stacktrace, 1, 2),
            pretty: true,
            limit: 10000,
            printable_limit: 10000
          )

        Logger.info(formatted)
        result
      else
        unquote(thing)
      end
    end
  end

  @doc "Like `dump`, but for logging at warn level"
  defmacro warn(thing, label \\ "") do
    # pre = format_label(__CALLER__)
    # thang = Macro.var(:thing, __MODULE__)

    quote do
      if Untangle.log_level?(:warning) do
        require Logger

        {:current_stacktrace, stacktrace} = :erlang.process_info(self(), :current_stacktrace)

        {formatted, result} =
          unquote(__MODULE__).__prepare_dbg__(
            "#{unquote(label)}",
            unquote(thing),
            stacktrace: Untangle.format_stacktrace_sliced(stacktrace, 0, 5),
            pretty: true,
            limit: 10000,
            printable_limit: 10000
          )

        Logger.warning(formatted)
        result
      else
        unquote(thing)
      end
    end
  end

  @doc """
  Similar to `dump`, but for logging at error level, and returns an error tuple:
  - an error tuple with the label, if any
  - an error tuple with the passed value otherwise

  iex> error(:value)
  ### [error] :value
  {:error, :value}

  iex> error({:error, :value})
  ### [error] :value
  {:error, :value}

  iex> error(:value, "with label")
  ### [error] with label: :value
  {:error, "with label"}

  iex> error({:error, :value}, "with label")
  ### [error] with label: :value
  {:error, "with label"}

  """
  defmacro error(thing, label \\ "") do
    # pre = format_label(__CALLER__)
    # stacktrace = Macro.Env.stacktrace(__CALLER__) 

    quote do
      if Untangle.log_level?(:error) do
        require Logger

        {:current_stacktrace, stacktrace} = :erlang.process_info(self(), :current_stacktrace)

        {formatted, result} =
          unquote(__MODULE__).__prepare_dbg__(
            "#{unquote(label)}",
            Untangle.__naked_error__(unquote(thing)),
            stacktrace: Untangle.format_stacktrace_sliced(stacktrace, 0, 8),
            pretty: true,
            limit: 10000,
            printable_limit: 10000
          )

        Logger.error(formatted)
        Untangle.__return_error__(unquote(label), result)
      else
        Untangle.__return_error__(unquote(label), unquote(thing))
      end
    end
  end

  def log_level?(level) do
    min_level =
      if env_level = Application.get_env(:logger, :level) do
        env_level
      else
        :debug
      end

    if Logger.compare_levels(level, min_level) != :lt do
      true
    end
  end

  @doc "Like `debug`, but will do nothing unless the `:debug` option is truthy"
  defmacro maybe_dbg(thing, label \\ "", options) do
    opts = Macro.var(:opts, __MODULE__)

    quote do
      unquote(opts) = unquote(options)

      if unquote(opts)[:debug] do
        debug(unquote(thing), unquote(label))
      else
        unquote(thing)
      end
    end
  end

  @doc "Like `maybe_dbg`, but requires the `:verbose` option to be set. Intended for large outputs."
  defmacro maybe_info(thing, label \\ "", options) do
    opts = Macro.var(:opts, __MODULE__)

    quote do
      unquote(opts) = unquote(options)

      if unquote(opts)[:verbose] do
        info(unquote(thing), unquote(label))
      else
        unquote(thing)
      end
    end
  end

  @doc """
  Tries to 'do what i mean'. Requires the `debug` option to be set regardless. If `verbose` is also
  set, will inspect else will attempt to print some (hopefully smaller) type-dependent summary of
  the data (list length, map keys).
  """
  defmacro smart(thing, label \\ "", options) do
    pre = format_label(__CALLER__)
    opts = Macro.var(:opts, __MODULE__)
    thang = Macro.var(:thing, __MODULE__)

    quote do
      require Logger
      unquote(opts) = unquote(options)
      unquote(thang) = unquote(thing)

      cond do
        !unquote(opts)[:debug] ->
          nil

        unquote(opts)[:verbose] ->
          Logger.debug(
            "#{unquote(pre)} #{unquote(label)}: #{inspect(unquote(thang), pretty: true, limit: 10000, printable_limit: 10000)}"
          )

        is_list(unquote(thang)) ->
          Logger.debug(
            "#{unquote(pre)} #{unquote(label)} (length): #{Enum.count(unquote(thang))}"
          )

        is_struct(unquote(thang)) ->
          Logger.debug("#{unquote(pre)} #{unquote(label)}: %#{unquote(thang).__struct__}{}")

        is_map(unquote(thang)) and not is_struct(unquote(thang)) ->
          Logger.debug(
            "#{unquote(pre)} #{unquote(label)} (keys): #{inspect(Map.keys(unquote(thang)))}"
          )

        true ->
          Logger.debug(
            "#{unquote(pre)} #{unquote(label)} (inspect elided, pass `:verbose` to see)"
          )
      end

      unquote(thang)
    end
  end

  @doc """
  Custom backend for `Kernel.dbg/2`.
  This function provides a backend for `Kernel.dbg/2`.
  This function:
    * may log or print information about the given `env`
    * may log or print information about `code` and its returned value (using `opts` to inspect terms)
    * returns the value returned by evaluating `code`
  """
  def custom_dbg(code, options, %Macro.Env{} = env) do
    header = "#{format_label(env)} #{options[:label]}:"

    quote do
      unquote(__MODULE__).__dbg__(
        unquote(header),
        unquote(dbg_ast_to_debuggable(code)),
        unquote(options)
      )
    end
  end

  if not macro_exported?(Kernel, :dbg, 2) do
    @doc """
    Polyfill for `dbg/2` if running Elixir pre 1.14
    """
    defmacro dbg(code \\ quote(do: binding()), options \\ []) do
      custom_dbg(code, options, __CALLER__)
    end
  end

  # Pipelines - copied from `Macro.dbg/2`
  defp dbg_ast_to_debuggable({:|>, _meta, _args} = pipe_ast) do
    value_var = Macro.unique_var(:value, __MODULE__)
    values_acc_var = Macro.unique_var(:values, __MODULE__)

    [start_ast | rest_asts] = asts = for {ast, 0} <- Macro.unpipe(pipe_ast), do: ast

    rest_asts = Enum.map(rest_asts, &Macro.pipe(value_var, &1, 0))

    string_asts = Enum.map(asts, &to_string/1)

    initial_acc =
      quote do
        unquote(value_var) = unquote(start_ast)
        unquote(values_acc_var) = [unquote(value_var)]
      end

    values_ast =
      for step_ast <- rest_asts, reduce: initial_acc do
        ast_acc ->
          quote do
            unquote(ast_acc)
            unquote(value_var) = unquote(step_ast)

            unquote(values_acc_var) = [
              unquote(value_var) | unquote(values_acc_var)
            ]
          end
      end

    quote do
      unquote(values_ast)
      {:pipe, unquote(string_asts), Enum.reverse(unquote(values_acc_var))}
    end
  end

  defp dbg_ast_to_debuggable({:value, _, _} = value_ast) do
    value_ast
  end

  # Any other AST
  defp dbg_ast_to_debuggable(ast) do
    quote do: {:value, unquote(to_string(ast)), unquote(ast)}
  end

  # Made public to be called from Macro.dbg/3, so that we generate as little code
  # as possible and call out into a function as soon as we can.
  # Copied from `Macro.dbg/2`
  @doc false
  def __dbg__(header_string, to_debug, options \\ []) do
    {formatted, result} = __prepare_dbg__(header_string, to_debug, options)

    IO.write(formatted)

    result
  end

  @doc false
  def __prepare_dbg__(header_string, to_debug, options \\ []) do
    {print_location?, options} = Keyword.pop(options, :print_location, true)

    options =
      Keyword.merge(
        [width: 80, pretty: true, syntax_colors: syntax_colors()],
        options
      )

    {formatted, result} = dbg_format_ast_to_debug(to_debug, options)

    formatted =
      cond do
        print_location? && options[:stacktrace] ->
          [:italic, header_string, :reset, ": ", formatted, :default_color, options[:stacktrace]]

        print_location? ->
          [:italic, header_string, :reset, ": ", formatted]

        true ->
          [formatted]
      end

    ansi_enabled? = options[:syntax_colors] != []

    {IO.ANSI.format(formatted, ansi_enabled?), result}
  end

  # inspect & format output - copied from `Macro.dbg/2`
  defp dbg_format_ast_to_debug({:pipe, code_asts, values}, options) do
    result = List.last(values)
    [{first_ast, first_value} | asts_with_values] = Enum.zip(code_asts, values)

    first_formatted = [
      dbg_format_ast(first_ast),
      " ",
      inspect(first_value, options),
      ?\n
    ]

    rest_formatted =
      Enum.map(asts_with_values, fn {code_ast, value} ->
        [
          :faint,
          "|> ",
          :reset,
          dbg_format_ast(code_ast),
          " ",
          inspect(value, options),
          ?\n
        ]
      end)

    {[first_formatted | rest_formatted], result}
  end

  defp dbg_format_ast_to_debug({:value, code_ast, value}, options) do
    {[dbg_format_ast(code_ast), " ", inspect(value, options), ?\n], value}
  end

  defp dbg_format_ast_to_debug(value, options) when is_binary(value) do
    {[value, ?\n], value}
  end

  defp dbg_format_ast_to_debug(value, options) do
    {[inspect(value, options), ?\n], value}
  end

  defp dbg_format_ast(ast) do
    [ast, :faint, " #=>", :reset]
  end

  defp syntax_colors do
    if IO.ANSI.enabled?() do
      if function_exported?(IO.ANSI, :syntax_colors, 0),
        do: IO.ANSI.syntax_colors(),
        # polyfill for pre-1.14 elixir
        else: [
          {:atom, :cyan},
          {:binary, :default_color},
          {:boolean, :magenta},
          {:charlist, :yellow},
          {:list, :default_color},
          {:map, :default_color},
          {nil, :magenta},
          {:number, :yellow},
          {:string, :green},
          {:tuple, :default_color}
        ]
    else
      []
    end
  end

  defp format_label(caller) do
    app =
      if function_exported?(Mix.Project, :config, 0),
        do: Mix.Project.config()[:app]

    file = Path.relative_to_cwd(caller.file)

    case caller.function do
      {fun, arity} ->
        "[#{app}/#{file}:#{caller.line}@#{module_name(caller.module)}.#{fun}/#{arity}]"

      _ ->
        "[#{app}/#{file}:#{caller.line}]"
    end
  end

  def format_stacktrace_sliced(stacktrace, starts \\ 1, ends \\ 5)

  def format_stacktrace_sliced(stacktrace, starts, ends) when is_list(stacktrace) do
    stacktrace
    |> Enum.slice(starts, ends)
    |> Exception.format_stacktrace()
  end

  def format_stacktrace_sliced(_stacktrace, _, _), do: nil

  defp module_name(name) when is_atom(name),
    do: module_name(Atom.to_string(name))

  defp module_name(name) when is_binary(name),
    do: String.replace_prefix(name, "Elixir.", "")

  @doc false
  def __naked_error__({:error, e}), do: e
  def __naked_error__(object), do: object

  @doc false
  def __return_error__(_label, {:error, _} = tuple), do: tuple

  def __return_error__(label, _object) when is_binary(label) and label != "",
    do: {:error, label}

  def __return_error__(_label, object), do: {:error, object}
end