defmodule Codex.Voice.Models.OpenAISTT do
  @moduledoc """
  OpenAI speech-to-text model implementation.

  This module implements the `Codex.Voice.Model.STTModel` behaviour using
  OpenAI's audio transcription API. It supports both single-shot transcription
  and streaming transcription sessions via WebSocket.

  ## Default Model

  The default model is `gpt-4o-transcribe`, which provides high-quality
  transcriptions with support for multiple languages.

  ## Example

      model = OpenAISTT.new()
      audio = AudioInput.new(wav_data)
      settings = STTSettings.new(language: "en")

      {:ok, text} = OpenAISTT.transcribe(model, audio, settings, true, false)
  """

  @behaviour Codex.Voice.Model.STTModel

  alias Codex.Auth
  alias Codex.Config.Defaults
  alias Codex.Voice.Config.STTSettings
  alias Codex.Voice.Input.AudioInput
  alias Codex.Voice.Input.StreamedAudioInput
  alias Codex.Voice.Models.OpenAISTTSession

  defstruct [:model, :client, :api_key, :base_url]

  @type t :: %__MODULE__{
          model: String.t(),
          client: term(),
          api_key: String.t() | nil,
          base_url: String.t()
        }

  @default_model Defaults.stt_model()
  @default_base_url Defaults.openai_api_base_url()

  @doc """
  Create a new OpenAI STT model.

  ## Options

  - `:client` - Optional HTTP client (for testing)
  - `:api_key` - API key (defaults to OPENAI_API_KEY env var)
  - `:base_url` - API base URL (defaults to OpenAI)

  ## Examples

      iex> model = Codex.Voice.Models.OpenAISTT.new()
      iex> model.model
      "gpt-4o-transcribe"

      iex> model = Codex.Voice.Models.OpenAISTT.new("whisper-1")
      iex> model.model
      "whisper-1"
  """
  @spec new(String.t() | nil, keyword()) :: t()
  def new(model \\ nil, opts \\ []) do
    %__MODULE__{
      model: model || @default_model,
      client: Keyword.get(opts, :client),
      api_key: Keyword.get(opts, :api_key),
      base_url: Keyword.get(opts, :base_url, @default_base_url)
    }
  end

  @impl true
  def model_name, do: @default_model

  @doc """
  Transcribe audio input to text.

  Makes a POST request to OpenAI's audio transcriptions endpoint with
  the audio data in WAV format.

  ## Parameters

  - `model` - The OpenAISTT model struct
  - `input` - AudioInput with the audio data
  - `settings` - STTSettings with transcription options
  - `_trace_include_sensitive_data` - Whether to include text in traces (unused)
  - `_trace_include_sensitive_audio_data` - Whether to include audio in traces (unused)

  ## Returns

  - `{:ok, text}` - The transcribed text
  - `{:error, reason}` - If the request fails
  """
  @spec transcribe(
          t(),
          AudioInput.t(),
          STTSettings.t(),
          boolean(),
          boolean()
        ) :: {:ok, String.t()} | {:error, term()}
  def transcribe(
        %__MODULE__{} = model,
        %AudioInput{} = input,
        %STTSettings{} = settings,
        _trace_include_sensitive_data,
        _trace_include_sensitive_audio_data
      ) do
    api_key = model.api_key || Auth.direct_api_key()

    {filename, wav_data, content_type} = AudioInput.to_audio_file(input)

    # Build multipart form for Req library
    # Req expects: {name, {value, options}} where options is a keyword list
    # Options can include :filename, :content_type, :size
    multipart =
      [
        {:file, {wav_data, filename: filename, content_type: content_type}},
        {:model, model.model}
      ]
      |> maybe_add_param(:prompt, settings.prompt)
      |> maybe_add_param(:language, settings.language)
      |> maybe_add_param(:temperature, format_temperature(settings.temperature))

    case Req.post("#{model.base_url}/audio/transcriptions",
           headers: [{"Authorization", "Bearer #{api_key}"}],
           form_multipart: multipart
         ) do
      {:ok, %{status: 200, body: %{"text" => text}}} ->
        {:ok, text}

      {:ok, %{status: status, body: body}} ->
        {:error, {:api_error, status, body}}

      {:error, reason} ->
        {:error, reason}
    end
  end

  @impl true
  def create_session(
        %StreamedAudioInput{} = input,
        %STTSettings{} = settings,
        trace_include_sensitive_data,
        trace_include_sensitive_audio_data
      ) do
    OpenAISTTSession.start_link(
      input: input,
      settings: settings,
      model: @default_model,
      trace_include_sensitive_data: trace_include_sensitive_data,
      trace_include_sensitive_audio_data: trace_include_sensitive_audio_data
    )
  end

  defp maybe_add_param(list, _key, nil), do: list
  defp maybe_add_param(list, key, value) when is_atom(key), do: list ++ [{key, to_string(value)}]

  @spec format_temperature(float() | nil) :: String.t() | nil
  defp format_temperature(nil), do: nil
  defp format_temperature(temp), do: Float.to_string(temp)
end

defmodule Codex.Voice.Models.OpenAISTTSession do
  @moduledoc """
  Streaming transcription session using WebSocket.

  This GenServer manages a WebSocket connection to OpenAI's realtime
  transcription API. It receives audio input from a `StreamedAudioInput`
  and produces text transcriptions for each detected turn.

  ## Turn Detection

  The session uses semantic VAD (Voice Activity Detection) by default
  to detect turn boundaries in the audio stream.
  """

  use GenServer

  alias Codex.Auth
  alias Codex.Config.Defaults
  alias Codex.Voice.Config.STTSettings
  alias Codex.Voice.Input.StreamedAudioInput

  @behaviour Codex.Voice.Model.StreamedTranscriptionSession

  defstruct [
    :input,
    :settings,
    :model,
    :api_key,
    :trace_include_sensitive_data,
    :trace_include_sensitive_audio_data,
    :websocket,
    :listener_task,
    :stream_task,
    transcripts: [],
    waiters: []
  ]

  @type t :: %__MODULE__{
          input: StreamedAudioInput.t(),
          settings: STTSettings.t(),
          model: String.t(),
          api_key: String.t() | nil,
          trace_include_sensitive_data: boolean(),
          trace_include_sensitive_audio_data: boolean(),
          websocket: pid() | nil,
          listener_task: Task.t() | nil,
          stream_task: Task.t() | nil,
          transcripts: [String.t()],
          waiters: [{GenServer.from(), reference()}]
        }

  @default_turn_detection Defaults.stt_default_turn_detection()

  @doc """
  Start a new streaming transcription session.

  ## Options

  - `:input` - StreamedAudioInput to read audio from (required)
  - `:settings` - STTSettings for transcription options (required)
  - `:model` - Model name to use
  - `:api_key` - API key (defaults to OPENAI_API_KEY env var)
  - `:trace_include_sensitive_data` - Whether to include text in traces
  - `:trace_include_sensitive_audio_data` - Whether to include audio in traces
  """
  @spec start_link(keyword()) :: GenServer.on_start()
  def start_link(opts) do
    GenServer.start_link(__MODULE__, opts)
  end

  @impl Codex.Voice.Model.StreamedTranscriptionSession
  def transcribe_turns(session) do
    Stream.resource(
      fn -> session end,
      fn session ->
        case GenServer.call(session, :get_transcript, :infinity) do
          {:ok, text} -> {[text], session}
          :done -> {:halt, session}
          {:error, reason} -> raise "Transcription error: #{inspect(reason)}"
        end
      end,
      fn _ -> :ok end
    )
  end

  @impl Codex.Voice.Model.StreamedTranscriptionSession
  def close(session) do
    GenServer.stop(session, :normal)
    :ok
  end

  @impl GenServer
  def init(opts) do
    input = Keyword.fetch!(opts, :input)
    settings = Keyword.fetch!(opts, :settings)

    state = %__MODULE__{
      input: input,
      settings: settings,
      model: Keyword.get(opts, :model, "gpt-4o-transcribe"),
      api_key: Keyword.get(opts, :api_key, Auth.direct_api_key()),
      trace_include_sensitive_data: Keyword.get(opts, :trace_include_sensitive_data, true),
      trace_include_sensitive_audio_data:
        Keyword.get(opts, :trace_include_sensitive_audio_data, false)
    }

    # Connection will be established when transcribe_turns is first called
    {:ok, state}
  end

  @impl GenServer
  def handle_call(:get_transcript, from, state) do
    case state.transcripts do
      [text | rest] ->
        {:reply, {:ok, text}, %{state | transcripts: rest}}

      [] ->
        # No transcripts available, add to waiters
        monitor_ref = monitor_waiter(from)
        {:noreply, %{state | waiters: state.waiters ++ [{from, monitor_ref}]}}
    end
  end

  @impl GenServer
  def handle_info({:transcript, text}, state) do
    case state.waiters do
      [{waiter, monitor_ref} | rest] ->
        Process.demonitor(monitor_ref, [:flush])
        GenServer.reply(waiter, {:ok, text})
        {:noreply, %{state | waiters: rest}}

      [] ->
        {:noreply, %{state | transcripts: state.transcripts ++ [text]}}
    end
  end

  @impl GenServer
  def handle_info({:DOWN, ref, :process, _pid, _reason}, state) do
    waiters =
      Enum.reject(state.waiters, fn {_waiter, monitor_ref} ->
        monitor_ref == ref
      end)

    {:noreply, %{state | waiters: waiters}}
  end

  @impl GenServer
  def handle_info(:session_complete, state) do
    # Notify all waiters that we're done
    for {waiter, monitor_ref} <- state.waiters do
      Process.demonitor(monitor_ref, [:flush])
      GenServer.reply(waiter, :done)
    end

    {:noreply, %{state | waiters: []}}
  end

  @impl GenServer
  def handle_info({:error, reason}, state) do
    # Notify all waiters of the error
    for {waiter, monitor_ref} <- state.waiters do
      Process.demonitor(monitor_ref, [:flush])
      GenServer.reply(waiter, {:error, reason})
    end

    {:noreply, %{state | waiters: []}}
  end

  @impl GenServer
  def terminate(_reason, state) do
    Enum.each(state.waiters, fn {waiter, monitor_ref} ->
      Process.demonitor(monitor_ref, [:flush])
      GenServer.reply(waiter, {:error, :closed})
    end)

    close_websocket(state.websocket)
    shutdown_task(state.listener_task)
    shutdown_task(state.stream_task)

    :ok
  end

  @doc false
  def default_turn_detection, do: @default_turn_detection

  defp close_websocket(pid) when is_pid(pid) do
    if Process.alive?(pid) do
      Process.exit(pid, :shutdown)
    end
  rescue
    _ -> :ok
  catch
    :exit, _ -> :ok
  end

  defp close_websocket(_), do: :ok

  defp shutdown_task(%Task{} = task) do
    case task.pid do
      pid when is_pid(pid) ->
        if Process.alive?(pid) do
          Process.exit(pid, :kill)
        end

        :ok

      _ ->
        :ok
    end
  rescue
    _ -> :ok
  catch
    :exit, _ -> :ok
  end

  defp shutdown_task(_), do: :ok

  defp monitor_waiter({pid, _tag}) when is_pid(pid) do
    Process.monitor(pid)
  end
end