defmodule Mix.Tasks.Snakepit.ProfileInspector do
  @moduledoc """
  Inspect Snakepit pool profiles and worker statistics.

  This task provides detailed information about pool configurations,
  worker profiles (process vs thread), capacity utilization, memory usage,
  and performance recommendations. It also surfaces how many times pools
  recycled BEAM gRPC workers because `memory_threshold_mb` was exceeded
  (the `Memory Recycles` field in the output), so operators know when
  BEAM-side memory pressure is triggering restarts.

  ## Usage

      # Inspect all pools
      mix snakepit.profile_inspector

      # Inspect a specific pool
      mix snakepit.profile_inspector --pool default

      # Show detailed per-worker information
      mix snakepit.profile_inspector --detailed

      # Export to JSON format
      mix snakepit.profile_inspector --format json

  ## Options

    * `--pool` - Specific pool to inspect (default: all pools)
    * `--detailed` - Show detailed per-worker statistics
    * `--format` - Output format: text (default) or json
    * `--recommendations` - Show optimization recommendations

  ## Examples

      # Basic inspection
      mix snakepit.profile_inspector

      # Detailed inspection of HPC pool
      mix snakepit.profile_inspector --pool hpc --detailed

      # Get recommendations
      mix snakepit.profile_inspector --recommendations
  """

  use Mix.Task
  require Logger

  alias Snakepit.Diagnostics.ProfileInspector
  alias Snakepit.Config

  @shortdoc "Inspect pool profiles and worker statistics"

  @impl Mix.Task
  def run(args) do
    {opts, _, _} =
      OptionParser.parse(args,
        strict: [
          pool: :string,
          detailed: :boolean,
          format: :string,
          recommendations: :boolean
        ]
      )

    # Start the application
    Mix.Task.run("app.start")

    format = Keyword.get(opts, :format, "text")
    pool_name = parse_pool_name(Keyword.get(opts, :pool))
    detailed? = Keyword.get(opts, :detailed, false)
    show_recommendations? = Keyword.get(opts, :recommendations, false)

    case format do
      "json" ->
        run_json_format(pool_name)

      "text" ->
        run_text_format(pool_name, detailed?, show_recommendations?)

      invalid ->
        IO.puts("Error: Invalid format '#{invalid}'. Use 'text' or 'json'.")
        System.halt(1)
    end
  end

  # Private functions

  defp parse_pool_name(nil), do: nil

  defp parse_pool_name(name) when is_binary(name) do
    String.to_atom(name)
  end

  defp run_text_format(nil, detailed?, show_recommendations?) do
    # Inspect all pools
    print_header()

    case Config.get_pool_configs() do
      {:ok, configs} ->
        Enum.each(configs, fn config ->
          pool_name = Map.fetch!(config, :name)
          inspect_pool_text(pool_name, config, detailed?)

          if show_recommendations? do
            print_recommendations(pool_name)
          end
        end)

      {:error, reason} ->
        IO.puts("\n❌ Error: Failed to get pool configurations: #{inspect(reason)}")
        System.halt(1)
    end

    print_footer()
  end

  defp run_text_format(pool_name, detailed?, show_recommendations?) do
    print_header()

    case Config.get_pool_config(pool_name) do
      {:ok, config} ->
        inspect_pool_text(pool_name, config, detailed?)

        if show_recommendations? do
          print_recommendations(pool_name)
        end

      {:error, :pool_not_found} ->
        IO.puts("\n❌ Error: Pool '#{pool_name}' not found")
        System.halt(1)

      {:error, reason} ->
        IO.puts("\n❌ Error: #{inspect(reason)}")
        System.halt(1)
    end

    print_footer()
  end

  defp run_json_format(nil) do
    # Export all pools as JSON
    case ProfileInspector.get_comprehensive_report() do
      {:ok, report} ->
        json = Jason.encode!(report, pretty: true)
        IO.puts(json)

      {:error, reason} ->
        error = %{error: inspect(reason)}
        json = Jason.encode!(error, pretty: true)
        IO.puts(json)
        System.halt(1)
    end
  end

  defp run_json_format(pool_name) do
    # Export specific pool as JSON
    case ProfileInspector.get_pool_stats(pool_name) do
      {:ok, stats} ->
        json = Jason.encode!(stats, pretty: true)
        IO.puts(json)

      {:error, reason} ->
        error = %{error: inspect(reason)}
        json = Jason.encode!(error, pretty: true)
        IO.puts(json)
        System.halt(1)
    end
  end

  defp print_header do
    IO.puts("\n" <> String.duplicate("=", 80))
    IO.puts("🔍 SNAKEPIT PROFILE INSPECTOR")
    IO.puts(String.duplicate("=", 80) <> "\n")
  end

  defp print_footer do
    IO.puts("\n" <> String.duplicate("=", 80))
    IO.puts("✅ INSPECTION COMPLETE")
    IO.puts(String.duplicate("=", 80) <> "\n")
  end

  defp inspect_pool_text(pool_name, config, detailed?) do
    IO.puts("📊 Pool: #{pool_name}")
    IO.puts(String.duplicate("-", 80))

    # Show configuration
    print_configuration(config)

    # Get and display statistics
    case ProfileInspector.get_pool_stats(pool_name) do
      {:ok, stats} ->
        print_statistics(stats)
        print_capacity_info(stats)
        print_memory_info(pool_name)

        if detailed? do
          print_worker_details(stats.workers)
        end

      {:error, :pool_not_running} ->
        IO.puts("⚠️  Pool is not currently running")

      {:error, reason} ->
        IO.puts("❌ Error getting pool stats: #{inspect(reason)}")
    end

    IO.puts("")
  end

  defp print_configuration(config) do
    IO.puts("\n📋 Configuration:")
    profile = Map.get(config, :worker_profile, :process)
    pool_size = Map.get(config, :pool_size, 0)

    IO.puts("  Profile:          #{format_profile(profile)}")
    IO.puts("  Pool Size:        #{pool_size}")

    case profile do
      :thread ->
        threads = Map.get(config, :threads_per_worker, 10)
        total_capacity = pool_size * threads
        IO.puts("  Threads/Worker:   #{threads}")
        IO.puts("  Total Capacity:   #{total_capacity}")

        if Map.get(config, :thread_safety_checks, false) do
          IO.puts("  Safety Checks:    ✓ Enabled")
        end

      :process ->
        IO.puts("  Workers/Capacity: 1:1 (single-threaded)")

        batch_size = Map.get(config, :startup_batch_size, 8)
        IO.puts("  Batch Size:       #{batch_size}")
    end

    # Lifecycle settings
    case Map.get(config, :worker_ttl, :infinity) do
      :infinity -> :ok
      {value, unit} -> IO.puts("  Worker TTL:       #{value} #{unit}")
    end

    case Map.get(config, :worker_max_requests, :infinity) do
      :infinity -> :ok
      count -> IO.puts("  Max Requests:     #{count}")
    end
  end

  defp print_statistics(stats) do
    IO.puts("\n📈 Statistics:")
    IO.puts("  Active Workers:   #{stats.worker_count}")
    IO.puts("  Total Capacity:   #{stats.capacity_total}")
    IO.puts("  Used Capacity:    #{stats.capacity_used}")
    IO.puts("  Available:        #{stats.capacity_available}")
    IO.puts("  Memory Recycles:  #{stats.memory_recycles}")

    # Color-coded utilization
    utilization_str = format_utilization(stats.utilization_percent)
    IO.puts("  Utilization:      #{utilization_str}")
  end

  defp print_capacity_info(stats) do
    case stats.profile do
      :thread ->
        if stats.capacity_total > 0 and stats.worker_count > 0 do
          threads_per_worker = div(stats.capacity_total, stats.worker_count)
          avg_load = div(stats.capacity_used, max(stats.worker_count, 1))

          IO.puts("\n🧵 Thread Profile Details:")
          IO.puts("  Workers:          #{stats.worker_count} processes")
          IO.puts("  Threads/Worker:   #{threads_per_worker}")
          IO.puts("  Total Threads:    #{stats.capacity_total}")
          IO.puts("  Avg Load/Worker:  #{avg_load}/#{threads_per_worker} threads")
        end

      :process ->
        IO.puts("\n⚙️  Process Profile Details:")
        IO.puts("  Mode:             Single-threaded processes")
        IO.puts("  Isolation:        Full process isolation")
        IO.puts("  Concurrency:      #{stats.capacity_total} concurrent requests")
    end
  end

  defp print_memory_info(pool_name) do
    case ProfileInspector.get_memory_stats(pool_name) do
      {:ok, memory} ->
        IO.puts("\n💾 Memory Usage:")
        IO.puts("  Total:            #{memory.total_memory_mb} MB")
        IO.puts("  Average/Worker:   #{memory.avg_memory_per_worker_mb} MB")
        IO.puts("  Max Worker:       #{memory.max_memory_worker_mb} MB")
        IO.puts("  Min Worker:       #{memory.min_memory_worker_mb} MB")

      {:error, _} ->
        :ok
    end
  end

  defp print_worker_details(workers) do
    IO.puts("\n👷 Worker Details:")
    IO.puts(String.duplicate("-", 80))

    IO.puts(
      String.pad_trailing("Worker ID", 30) <>
        String.pad_trailing("Status", 12) <>
        String.pad_trailing("Load/Cap", 12) <>
        String.pad_trailing("Memory", 12) <>
        "PID"
    )

    IO.puts(String.duplicate("-", 80))

    Enum.each(workers, fn worker ->
      worker_id_short = String.slice(worker.worker_id, 0, 28)
      status = format_worker_status(worker.status)
      load_cap = "#{worker.load}/#{worker.capacity}"
      memory = "#{worker.memory_mb} MB"
      pid = inspect(worker.pid)

      IO.puts(
        String.pad_trailing(worker_id_short, 30) <>
          String.pad_trailing(status, 12) <>
          String.pad_trailing(load_cap, 12) <>
          String.pad_trailing(memory, 12) <>
          pid
      )
    end)
  end

  defp print_recommendations(pool_name) do
    case ProfileInspector.get_recommendations(pool_name) do
      {:ok, [_ | _] = recommendations} ->
        IO.puts("\n💡 Recommendations:")

        Enum.each(recommendations, fn rec ->
          IO.puts("  • #{rec}")
        end)

      {:ok, []} ->
        IO.puts("\n✅ No recommendations - pool is operating optimally")

      {:error, _} ->
        :ok
    end
  end

  # Formatting helpers

  defp format_profile(:process), do: "Process (multi-process)"
  defp format_profile(:thread), do: "Thread (multi-threaded)"
  defp format_profile(other), do: to_string(other)

  defp format_utilization(percent) when percent >= 90.0 do
    "#{percent}% 🔴 CRITICAL"
  end

  defp format_utilization(percent) when percent >= 80.0 do
    "#{percent}% 🟡 HIGH"
  end

  defp format_utilization(percent) when percent >= 60.0 do
    "#{percent}% 🟢 GOOD"
  end

  defp format_utilization(percent) do
    "#{percent}% ⚪ LOW"
  end

  defp format_worker_status(:available), do: "✓ Available"
  defp format_worker_status(:busy), do: "● Busy"
  defp format_worker_status(:unknown), do: "? Unknown"
end