defmodule Mix.Tasks.Log.Stats do
  @moduledoc """
  Show summary statistics for log files.

  ## Usage

      mix log.stats <path> [options]

  ## Options

      --top    Number of top items to show per category (default: 5)

  ## Examples

      mix log.stats logs/app.log
      mix log.stats logs/ --top 10
  """
  @shortdoc "Show log file statistics"

  use Mix.Task

  alias TelemetryData.FileReader

  @impl Mix.Task
  def run(args) do
    {opts, positional, _} = OptionParser.parse(args, strict: [top: :integer])

    path = List.first(positional) || "logs/"
    top_n = Keyword.get(opts, :top, 5)

    entries = load_entries(path)
    total = length(entries)

    if total == 0 do
      Mix.shell().info("No log entries found.")
    else
      Mix.shell().info("\n#{IO.ANSI.bright()}Log Statistics#{IO.ANSI.reset()} (#{total} entries)\n")
      print_section("By Level", count_by(entries, :level), total)
      print_section("By Format", count_by(entries, :format), total)
      print_top_section("Top Sources", top_by(entries, :source, top_n))
      print_top_section("Top Error Messages", top_errors(entries, top_n))
    end
  end

  defp load_entries(path) do
    if File.dir?(path) do
      case FileReader.read_dir(path) do
        {:ok, entries} -> entries
        {:error, reason} -> Mix.raise("Failed to read directory #{path}: #{reason}")
      end
    else
      case FileReader.read_file(path) do
        {:ok, entries} -> entries
        {:error, reason} -> Mix.raise("Failed to read file #{path}: #{reason}")
      end
    end
  end

  defp count_by(entries, field) do
    entries
    |> Enum.group_by(&Map.get(&1, field))
    |> Enum.map(fn {key, items} -> {key, length(items)} end)
    |> Enum.sort_by(fn {_, count} -> -count end)
  end

  defp top_by(entries, field, n) do
    entries
    |> Enum.filter(&(Map.get(&1, field) != nil))
    |> Enum.group_by(&Map.get(&1, field))
    |> Enum.map(fn {key, items} -> {key, length(items)} end)
    |> Enum.sort_by(fn {_, count} -> -count end)
    |> Enum.take(n)
  end

  defp top_errors(entries, n) do
    entries
    |> Enum.filter(&(&1.level in ["error", "warn", "warning"]))
    |> Enum.group_by(& &1.message)
    |> Enum.map(fn {msg, items} -> {msg, length(items)} end)
    |> Enum.sort_by(fn {_, count} -> -count end)
    |> Enum.take(n)
  end

  defp print_section(title, counts, total) do
    Mix.shell().info("  #{IO.ANSI.bright()}#{title}#{IO.ANSI.reset()}")

    Enum.each(counts, fn {key, count} ->
      pct = Float.round(count / total * 100, 1)
      bar = String.duplicate("█", round(pct / 2))
      Mix.shell().info("    #{pad(to_string(key), 12)} #{pad_num(count, 4)}  #{bar} #{pct}%")
    end)

    Mix.shell().info("")
  end

  defp print_top_section(title, counts) do
    if counts == [] do
      :ok
    else
      Mix.shell().info("  #{IO.ANSI.bright()}#{title}#{IO.ANSI.reset()}")

      Enum.each(counts, fn {key, count} ->
        label = String.slice(to_string(key), 0, 60)
        Mix.shell().info("    #{pad_num(count, 4)}x  #{label}")
      end)

      Mix.shell().info("")
    end
  end

  defp pad(str, width) do
    String.pad_trailing(str, width)
  end

  defp pad_num(num, width) do
    num |> to_string() |> String.pad_leading(width)
  end
end