defmodule AI.Completion do
  @moduledoc """
  This module sends a request to the model and handles the response. It is able
  to handle tool calls and responses.
  """
  defstruct [
    :ai,
    :opts,
    :max_tokens,
    :model,
    :use_planner,
    :tools,
    :log_msgs,
    :log_tool_calls,
    :log_tool_call_results,
    :messages,
    :tool_call_requests,
    :response
  ]

  @type t :: %__MODULE__{
          ai: AI.t(),
          opts: Keyword.t(),
          max_tokens: non_neg_integer(),
          model: String.t(),
          use_planner: boolean(),
          tools: list(),
          log_msgs: boolean(),
          log_tool_calls: boolean(),
          log_tool_call_results: boolean(),
          messages: list(),
          tool_call_requests: list(),
          response: String.t() | nil
        }

  @type success :: {:ok, t}
  @type error :: {:error, String.t()}
  @type response :: success | error

  @spec get(AI.t(), Keyword.t()) :: response
  def get(ai, opts) do
    with {:ok, max_tokens} <- Keyword.fetch(opts, :max_tokens),
         {:ok, model} <- Keyword.fetch(opts, :model),
         {:ok, messages} <- Keyword.fetch(opts, :messages) do
      tools = Keyword.get(opts, :tools, nil)
      use_planner = Keyword.get(opts, :use_planner, false)
      log_msgs = Keyword.get(opts, :log_msgs, false)

      quiet? = Application.get_env(:fnord, :quiet)
      log_tool_calls = Keyword.get(opts, :log_tool_calls, !quiet?)
      log_tool_call_results = Keyword.get(opts, :log_tool_call_results, !quiet?)

      state = %__MODULE__{
        ai: ai,
        opts: Enum.into(opts, %{}),
        max_tokens: max_tokens,
        model: model,
        use_planner: use_planner,
        tools: tools,
        log_msgs: log_msgs,
        log_tool_calls: log_tool_calls,
        log_tool_call_results: log_tool_call_results,
        messages: messages,
        tool_call_requests: [],
        response: nil
      }

      state
      |> replay_conversation()
      |> send_request()
      |> maybe_finish_planner()
      |> then(&{:ok, &1})
    end
  end

  def context_window_usage(%{model: model, messages: msgs, max_tokens: max_tokens}) do
    tokens = msgs |> inspect() |> AI.Tokenizer.encode(model) |> length()
    pct = tokens / max_tokens * 100.0
    pct_str = Number.Percentage.number_to_percentage(pct, precision: 2)
    tokens_str = Number.Delimit.number_to_delimited(tokens, precision: 0)
    max_tokens_str = Number.Delimit.number_to_delimited(max_tokens, precision: 0)
    {"Context window usage", "#{pct_str} | #{tokens_str} / #{max_tokens_str}"}
  end

  # -----------------------------------------------------------------------------
  # Completion handling
  # -----------------------------------------------------------------------------
  defp send_request(state) do
    state
    |> maybe_use_planner()
    |> get_completion()
    |> handle_response()
  end

  def get_completion(state) do
    response = AI.get_completion(state.ai, state.model, state.messages, state.tools)
    {response, state}
  end

  defp handle_response({{:ok, :msg, response}, state}) do
    %{
      state
      | messages: state.messages ++ [AI.Util.assistant_msg(response)],
        response: response
    }
  end

  defp handle_response({{:ok, :tool, tool_calls}, state}) do
    %{state | tool_call_requests: tool_calls}
    |> handle_tool_calls()
    |> send_request()
  end

  defp handle_response({{:error, reason}, state}) do
    reason =
      if is_binary(reason) do
        reason
      else
        inspect(reason)
      end

    conversation = Jason.encode!(state.messages, pretty: true)

    error_msg = """
    I encountered an error while processing your request.
    The error message was:

    #{reason}

    Here is the conversation that led to the error:
    #{conversation}
    """

    IO.puts(:stderr, error_msg)

    %{state | response: error_msg}
  end

  # -----------------------------------------------------------------------------
  # Planner
  # -----------------------------------------------------------------------------
  defp maybe_use_planner(%{use_planner: false} = state) do
    state
  end

  defp maybe_use_planner(%{ai: ai, use_planner: true, messages: msgs, tools: tools} = state) do
    on_event(state, :tool_call, {"planner", %{}})

    case AI.Agent.Planner.get_response(ai, %{msgs: msgs, tools: tools}) do
      {:ok, response} ->
        on_event(state, :tool_call_result, {"planner", %{}, {:ok, response}})
        planner_msg = AI.Util.user_msg("From the Planner Agent: #{response}")
        %__MODULE__{state | messages: state.messages ++ [planner_msg]}

      {:error, reason} ->
        on_event(state, :tool_call_error, {"planner", %{}, reason})
        state
    end
  end

  defp maybe_finish_planner(%{use_planner: false} = state) do
    state
  end

  defp maybe_finish_planner(%{ai: ai, use_planner: true, messages: msgs, tools: tools} = state) do
    on_event(state, :tool_call, {"feedback", %{}})

    msgs =
      msgs ++
        [
          AI.Util.system_msg("""
          NOTE TO PLANNER: The orchestrating AI has completed its work. This is
          your opportunity to evaluate the results, create or update research
          strategies, and save your notes to improve future performance using
          your tools.
          """)
        ]

    case AI.Agent.Planner.get_response(ai, %{msgs: msgs, tools: tools}) do
      {:ok, response} when is_binary(response) ->
        on_event(state, :tool_call_result, {"planner", %{}, response})
        planner_msg = AI.Util.system_msg(response)
        %__MODULE__{state | messages: state.messages ++ [planner_msg]}

      {:ok, response} ->
        on_event(state, :tool_call_result, {"planner", %{}, Jason.encode!(response)})
        planner_msg = AI.Util.system_msg(response)
        %__MODULE__{state | messages: state.messages ++ [planner_msg]}

      {:error, reason} ->
        on_event(state, :tool_call_error, {"planner", %{}, reason})
        state
    end
  end

  # -----------------------------------------------------------------------------
  # Tool calls
  # -----------------------------------------------------------------------------
  defp handle_tool_calls(%{tool_call_requests: tool_calls} = state) do
    {:ok, queue} = Queue.start_link(&handle_tool_call(state, &1))

    outputs =
      tool_calls
      |> Queue.map(queue)
      |> Enum.flat_map(fn {:ok, msgs} -> msgs end)

    Queue.shutdown(queue)
    Queue.join(queue)

    %__MODULE__{
      state
      | tool_call_requests: [],
        messages: state.messages ++ outputs
    }
  end

  def handle_tool_call(state, %{id: id, function: %{name: func, arguments: args_json}}) do
    request = AI.Util.assistant_tool_msg(id, func, args_json)

    UI.debug("Tool call", "#{func} -> #{args_json}")

    with {:ok, output} <- perform_tool_call(state, func, args_json) do
      response = AI.Util.tool_msg(id, func, output)
      {:ok, [request, response]}
    else
      :error ->
        on_event(state, :tool_call_error, {func, args_json, :error})
        msg = "An error occurred (most likely incorrect arguments)"
        response = AI.Util.tool_msg(id, func, msg)
        {:ok, [request, response]}

      {:error, reason} ->
        on_event(state, :tool_call_error, {func, args_json, {:error, reason}})
        response = AI.Util.tool_msg(id, func, reason)
        {:ok, [request, response]}

      {:error, :unknown_tool, tool} ->
        on_event(state, :tool_call_error, {func, args_json, {:error, "Unknown tool: #{tool}"}})

        error = """
        Your attempt to call #{func} failed because the tool '#{tool}' is unknown.
        Your tool call request supplied the following arguments: #{args_json}.
        Please consult the specifications for your available tools and use only the tools that are listed.
        """

        response = AI.Util.tool_msg(id, func, error)
        {:ok, [request, response]}

      {:error, :missing_argument, key} ->
        on_event(
          state,
          :tool_call_error,
          {func, args_json, {:error, "Missing required argument: #{key}"}}
        )

        spec =
          with {:ok, spec} <- AI.Tools.tool_spec(func),
               {:ok, json} <- Jason.encode(spec) do
            json
          else
            error -> "Error retrieving specification: #{inspect(error)}"
          end

        error = """
        Your attempt to call #{func} failed because it was missing a required argument, '#{key}'.
        Your tool call request supplied the following arguments: #{args_json}.
        The parameter `#{key}` must be included and cannot be `null` or an empty string.
        The correct specification for the tool call is: #{spec}
        """

        response = AI.Util.tool_msg(id, func, error)
        {:ok, [request, response]}
    end
  end

  defp perform_tool_call(state, func, args_json) when is_binary(args_json) do
    with {:ok, args} <- Jason.decode(args_json) do
      on_event(state, :tool_call, {func, args})

      result =
        AI.Tools.perform_tool_call(state, func, args)
        |> case do
          {:ok, response} when is_binary(response) -> {:ok, response}
          {:ok, response} -> Jason.encode(response)
          :ok -> {:ok, "#{func} completed successfully"}
          other -> other
        end

      on_event(state, :tool_call_result, {func, args, result})
      result
    end
  end

  # -----------------------------------------------------------------------------
  # Tool call UI integration
  # -----------------------------------------------------------------------------
  defp log_user_msg(state, msg) do
    if state.log_msgs do
      UI.info("You", msg)
    end
  end

  defp log_assistant_msg(state, msg) do
    if state.log_msgs do
      UI.info("Assistant", msg)
    end
  end

  defp log_tool_call(state, step) do
    if state.log_tool_calls do
      UI.info(step)
    end
  end

  defp log_tool_call(state, step, msg) do
    if state.log_tool_calls do
      UI.info(step, msg)
    end
  end

  defp log_tool_call_result(state, step) do
    if state.log_tool_call_results do
      UI.debug(step)
    end
  end

  defp log_tool_call_result(state, step, msg) do
    if state.log_tool_call_results do
      UI.debug(step, msg)
    end
  end

  defp log_tool_call_error(_state, tool, reason) do
    UI.error("Error calling #{tool}", reason)
  end

  # ----------------------------------------------------------------------------
  # Planner
  # ----------------------------------------------------------------------------
  defp on_event(state, :tool_call, {"planner", _}) do
    log_tool_call(state, "Evaluating research and planning next steps")
  end

  defp on_event(state, :tool_call_result, {"planner", _, {:ok, plan}}) do
    log_tool_call_result(state, "Research plan", plan)
  end

  defp on_event(state, :tool_call, {"feedback", _}) do
    log_tool_call(state, "Consolidating lessons learned from this session")
  end

  # -----------------------------------------------------------------------------
  # Tool call logging
  # -----------------------------------------------------------------------------
  defp on_event(state, :tool_call, {tool, args}) do
    AI.Tools.on_tool_request(tool, args)
    |> case do
      nil -> state
      {step, msg} -> log_tool_call(state, step, msg)
      step -> log_tool_call(state, step)
    end
  end

  defp on_event(state, :tool_call_result, {tool, args, {:ok, result}}) do
    AI.Tools.on_tool_result(tool, args, result)
    |> case do
      nil -> state
      {step, msg} -> log_tool_call_result(state, step, msg)
      step -> log_tool_call_result(state, step)
    end
  end

  defp on_event(state, :tool_call_error, {tool, _args_json, {:error, reason}}) do
    log_tool_call_error(state, tool, reason)
  end

  defp on_event(_state, _, _), do: :ok

  # ----------------------------------------------------------------------------
  # Continuing a conversation
  # ----------------------------------------------------------------------------
  defp replay_conversation(state) do
    # Make a lookup for tool call args by id
    tool_call_args =
      state.messages
      |> Enum.reduce(%{}, fn msg, acc ->
        case msg do
          %{role: "assistant", content: nil, tool_calls: tool_calls} ->
            tool_calls
            |> Enum.map(fn %{"id" => id, "function" => %{"arguments" => args}} ->
              {id, args}
            end)
            |> Enum.into(acc)

          _ ->
            acc
        end
      end)

    state.messages
    # Skip the first message, which is the system prompt for the agent
    |> Enum.drop(1)
    |> Enum.each(fn
      %{role: "assistant", content: nil, tool_calls: tool_calls} ->
        tool_calls
        |> Enum.each(fn %{"function" => %{"name" => func, "arguments" => args_json}} ->
          with {:ok, args} <- Jason.decode(args_json) do
            on_event(state, :tool_call, {func, args})
          end
        end)

      %{role: "tool", name: func, tool_call_id: id, content: content} ->
        on_event(state, :tool_call_result, {func, tool_call_args[id], content})

      %{role: "system", content: content} ->
        on_event(state, :tool_call_result, {"planner", %{}, content})

      %{role: "assistant", content: content} ->
        log_assistant_msg(state, content)

      %{role: "user", content: content} ->
        log_user_msg(state, content)
    end)

    state
  end
end