excessibility

defmodule Excessibility.TelemetryCapture do
  @moduledoc """
  Telemetry-based automatic snapshot capture for LiveView tests.

  Attaches to Phoenix LiveView telemetry events to automatically capture
  snapshots when LiveView events occur, with no test code changes required.
  """

  require Logger

  @doc """
  Attaches telemetry handlers for automatic snapshot capture.

  Call this before running tests to enable auto-capture.
  """
  def attach do
    # Create ETS table for cross-process snapshot storage
    unless :ets.whereis(:excessibility_snapshots) != :undefined do
      :ets.new(:excessibility_snapshots, [:named_table, :public, :bag])
    end

    :telemetry.attach_many(
      "excessibility-capture",
      [
        [:phoenix, :live_view, :mount, :stop],
        [:phoenix, :live_view, :handle_event, :stop],
        [:phoenix, :live_view, :handle_params, :stop]
      ],
      &handle_event/4,
      nil
    )
  end

  @doc """
  Detaches telemetry handlers.
  """
  def detach do
    :telemetry.detach("excessibility-capture")
  end

  @doc """
  Handles telemetry events and captures snapshots.
  """
  def handle_event([:phoenix, :live_view, :mount, :stop], measurements, metadata, _config) do
    IO.puts("📸 Excessibility: Telemetry mount event fired!")
    capture_snapshot("mount", measurements, metadata)
  end

  def handle_event([:phoenix, :live_view, :handle_event, :stop], measurements, metadata, _config) do
    event_name =
      try do
        get_in(metadata, [:params, "event"]) || "event"
      rescue
        _ -> "event"
      end

    capture_snapshot("handle_event:#{event_name}", measurements, metadata)
  end

  def handle_event([:phoenix, :live_view, :handle_params, :stop], measurements, metadata, _config) do
    capture_snapshot("handle_params", measurements, metadata)
  end

  defp capture_snapshot(event_type, _measurements, metadata) do
    socket = metadata[:socket]

    if socket do
      clean_assigns = extract_clean_assigns(socket)
      view_module = extract_view_module(socket, metadata)

      store_snapshot(event_type, clean_assigns, view_module, metadata)
    else
      Logger.debug("Excessibility: No socket in metadata for #{event_type}")
    end
  rescue
    error ->
      Logger.warning("Excessibility: Failed to capture snapshot for #{event_type}: #{inspect(error)}")
  end

  defp extract_clean_assigns(socket) do
    assigns =
      cond do
        is_struct(socket.assigns) -> Map.from_struct(socket.assigns)
        is_map(socket.assigns) -> socket.assigns
        true -> %{}
      end

    assigns
    |> Map.drop([:flash, :__changed__, :__temp__])
    |> Enum.filter(fn {k, _v} -> !String.starts_with?(to_string(k), "_") end)
    |> Map.new()
  end

  defp extract_view_module(socket, metadata) do
    cond do
      is_struct(socket) && Map.has_key?(socket, :view) -> socket.view
      is_map(metadata) && Map.has_key?(metadata, :view) -> metadata[:view]
      true -> :unknown
    end
  end

  defp store_snapshot(event_type, clean_assigns, view_module, metadata) do
    key = {DateTime.utc_now(), :erlang.unique_integer([:monotonic])}

    snapshot = %{
      event_type: event_type,
      assigns: clean_assigns,
      timestamp: DateTime.utc_now(),
      view_module: view_module,
      metadata_keys: Map.keys(metadata)
    }

    :ets.insert(:excessibility_snapshots, {key, snapshot})

    IO.puts("✅ Captured telemetry snapshot for #{event_type}")
    Logger.debug("Excessibility: Captured snapshot for #{event_type} with assigns: #{inspect(Map.keys(clean_assigns))}")
  end

  @doc """
  Retrieves all captured snapshots and clears the table.
  """
  def get_snapshots do
    case :ets.whereis(:excessibility_snapshots) do
      :undefined ->
        []

      _table ->
        snapshots =
          :excessibility_snapshots
          |> :ets.tab2list()
          |> Enum.map(fn {_key, snapshot} -> snapshot end)
          |> Enum.sort_by(& &1.timestamp, DateTime)

        snapshots
    end
  end

  @doc """
  Clears all captured snapshots.
  """
  def clear_snapshots(_test_name \\ nil) do
    case :ets.whereis(:excessibility_snapshots) do
      :undefined ->
        :ok

      _table ->
        :ets.delete_all_objects(:excessibility_snapshots)
    end
  end

  @doc """
  Writes captured snapshots to HTML files.
  """
  def write_snapshots(test_name) do
    snapshots = get_snapshots()
    IO.puts("💾 Excessibility: Writing #{length(snapshots)} telemetry snapshots for test #{inspect(test_name)}")

    if snapshots != [] do
      output_path =
        Application.get_env(
          :excessibility,
          :excessibility_output_path,
          "test/excessibility"
        )

      snapshots_path = Path.join(output_path, "html_snapshots")
      File.mkdir_p!(snapshots_path)

      snapshots
      |> Enum.with_index(1)
      |> Enum.each(fn {snapshot, index} ->
        filename = "#{sanitize_test_name(test_name)}_telemetry_#{index}_#{sanitize_event_type(snapshot.event_type)}.html"
        path = Path.join(snapshots_path, filename)

        html = build_snapshot_html(snapshot, index, test_name)
        File.write!(path, html)

        Logger.info("Wrote telemetry snapshot: #{filename}")
      end)
    end
  end

  defp build_snapshot_html(snapshot, sequence, test_name) do
    """
    <!--
    Excessibility Telemetry Snapshot
    Test: #{test_name}
    Sequence: #{sequence}
    Event: #{snapshot.event_type}
    Timestamp: #{snapshot.timestamp}
    View Module: #{inspect(snapshot.view_module)}
    Assigns: #{inspect(snapshot.assigns, pretty: true)}
    -->

    <html>
      <head>
        <title>Telemetry Snapshot - #{snapshot.event_type}</title>
      </head>
      <body>
        <h1>Telemetry Snapshot: #{snapshot.event_type}</h1>
        <h2>Sequence: #{sequence}</h2>
        <h3>Assigns:</h3>
        <pre>#{inspect(snapshot.assigns, pretty: true)}</pre>
        <p><em>Note: This is a telemetry-captured snapshot. Full HTML rendering requires the LiveView process context.</em></p>
      </body>
    </html>
    """
  end

  defp sanitize_test_name(test_name) when is_atom(test_name) do
    test_name
    |> to_string()
    |> String.replace(" ", "_")
    |> String.replace(~r/[^a-zA-Z0-9_]/, "")
  end

  defp sanitize_test_name(test_name), do: to_string(test_name)

  defp sanitize_event_type(event_type) do
    event_type
    |> to_string()
    |> String.replace(":", "_")
    |> String.replace(" ", "_")
  end
end