defmodule AI.Tools.Tasks.PushTask do
  @moduledoc """
  Tool to push a new task to the front of a Services.Task list.
  """

  @behaviour AI.Tools

  @impl AI.Tools
  def async?, do: false

  @impl AI.Tools
  def is_available?, do: true

  @impl AI.Tools
  def read_args(args) when is_map(args) do
    with {:ok, list_id} <- AI.Tools.get_arg(args, "list_id"),
         true <- is_integer(list_id) or {:error, :invalid_argument, "list_id must be an integer"} do
      case Map.fetch(args, "tasks") do
        {:ok, tasks} ->
          with {:ok, normalized} <- validate_and_normalize_tasks(tasks) do
            {:ok, %{"list_id" => list_id, "tasks" => normalized}}
          end

        :error ->
          # legacy single-task args: return task_id and data directly for backward compatibility
          with {:ok, task_id} <- AI.Tools.get_arg(args, "task_id"),
               true <-
                 is_binary(task_id) or {:error, :invalid_argument, "task_id must be a string"},
               {:ok, data} <- AI.Tools.get_arg(args, "data"),
               true <- is_binary(data) or {:error, :invalid_argument, "data must be a string"} do
            {:ok, %{"list_id" => list_id, "task_id" => task_id, "data" => data}}
          end
      end
    end
  end

  @impl AI.Tools
  def ui_note_on_request(%{"tasks" => [%{"task_id" => task_id, "data" => data}]}) do
    {task_id, data}
  end

  @impl AI.Tools
  def ui_note_on_request(%{"tasks" => tasks}) when is_list(tasks) do
    count = length(tasks)
    ids = Enum.map(tasks, & &1["task_id"])
    preview = ids |> Enum.take(3) |> Enum.join(", ")
    {"Pushing #{count} tasks", preview}
  end

  @impl AI.Tools
  def ui_note_on_request(%{"task_id" => task_id, "data" => data}) do
    {task_id, data}
  end

  @impl AI.Tools
  def ui_note_on_result(%{"tasks" => tasks}, _result) when is_list(tasks) do
    count = length(tasks)
    "Pushed #{count} task(s)"
  end

  @impl AI.Tools
  def ui_note_on_result(%{"task_id" => _task_id}, _result) do
    "Pushed 1 task"
  end

  @impl AI.Tools
  def ui_note_on_result(_args, _result), do: nil

  @impl AI.Tools
  def spec do
    %{
      type: "function",
      function: %{
        name: "tasks_push_task",
        description: """
        Push a new task to the front of an existing task list. The task is
        identified by a unique task_id that should be a short label, describing
        the task at a glance (e.g. "Add some_function/3 to Some.Module") Note
        that this is NOT a "slug" - it's a human-readable label. The data field
        is a free-form string that can contain any details or payload for the
        task.

        Tasks are intended to help you retain state between interactions, even
        if your context window is full. Ensure that the data field includes
        enough context for you to understand and complete the task later, even
        if you have forgotten the details you had in mind when creating it.

        Tasks are added IN STACK ORDER - the last task you push will be the
        next task to be completed.
        """,
        parameters: %{
          type: "object",
          additionalProperties: false,
          required: ["list_id"],
          properties: %{
            "list_id" => %{
              type: :integer,
              description: "The ID of the task list."
            },
            "task_id" => %{
              type: "string",
              description: """
              A short task label that describes the task. This doubles as the
              unique identifier for the task. Examples:
              - "Add some_function/3 to Some.Module"
              - "Write tests for Another.Module"
              - "Identify stale documentation in Some.Module"
              """
            },
            "data" => %{
              type: "string",
              description: "Free-form detail or payload for the task."
            },
            "tasks" => %{
              type: "array",
              description: "A list of tasks to add, each with a task_id and data.",
              items: %{
                type: "object",
                additionalProperties: false,
                required: ["task_id", "data"],
                properties: %{
                  "task_id" => %{
                    type: "string",
                    description: """
                    A short task label that describes the task. This doubles as the
                    unique identifier for the task. Examples:
                    - "Add some_function/3 to Some.Module"
                    - "Write tests for Another.Module"
                    - "Identify stale documentation in Some.Module"
                    """
                  },
                  "data" => %{
                    type: "string",
                    description: "The detail or payload for the task."
                  }
                }
              }
            }
          }
        }
      }
    }
  end

  @impl AI.Tools
  def call(%{"list_id" => list_id, "tasks" => tasks}) when is_list(tasks) do
    tasks
    |> Enum.reverse()
    |> Enum.each(fn %{"task_id" => task_id, "data" => data} ->
      Services.Task.push_task(list_id, task_id, data)
    end)

    {:ok, Services.Task.as_string(list_id)}
  end

  @impl AI.Tools
  def call(%{"list_id" => list_id, "task_id" => task_id, "data" => data}) do
    Services.Task.push_task(list_id, task_id, data)
    {:ok, Services.Task.as_string(list_id)}
  end

  # Validate and normalize a list of tasks into the required format or return an error tuple.
  defp validate_and_normalize_tasks(tasks) do
    cond do
      not is_list(tasks) ->
        {:error, :invalid_argument, "tasks must be a list of task objects"}

      tasks == [] ->
        {:error, :invalid_argument, "tasks list cannot be empty"}

      true ->
        tasks
        |> Enum.reduce_while({:ok, []}, fn
          %{"task_id" => task_id, "data" => data}, {:ok, acc}
          when is_binary(task_id) and is_binary(data) ->
            {:cont, {:ok, [%{"task_id" => task_id, "data" => data} | acc]}}

          %{"task_id" => _, "data" => _}, _ ->
            {:halt, {:error, :invalid_argument, "each task must have string task_id and data"}}

          _, _ ->
            {:halt,
             {:error, :invalid_argument,
              "tasks must be list of %{\"task_id\" => string, \"data\" => string}"}}
        end)
        |> case do
          {:ok, list} -> {:ok, Enum.reverse(list)}
          error -> error
        end
    end
  end
end
