defmodule Ash.Query do
  @moduledoc """
  Utilties around constructing/manipulating ash queries.

  Ash queries are used for read actions and side loads, and ultimately
  map to queries to a resource's data layer.
  """
  defstruct [
    :api,
    :resource,
    :filter,
    :data_layer_query,
    side_load: [],
    sort: [],
    limit: nil,
    offset: 0,
    errors: [],
    valid?: true
  ]

  @type t :: %__MODULE__{}

  defimpl Inspect do
    import Inspect.Algebra

    def inspect(query, opts) do
      opts = %{
        opts
        | syntax_colors: [
            atom: :yellow,
            binary: :green,
            boolean: :magenta,
            list: :cyan,
            map: :magenta,
            number: :red,
            regex: :violet,
            tuple: :white
          ]
      }

      error_doc =
        if Enum.empty?(query.errors) do
          empty()
        else
          concat("errors: ", to_doc(query.errors, opts))
        end

      container_doc(
        "#Ash.Query<",
        [
          concat("resource: ", inspect(query.resource)),
          concat("filter: ", to_doc(query.filter, opts)),
          concat("sort: ", to_doc(query.sort, opts)),
          concat("limit: ", to_doc(query.limit, opts)),
          concat("offset: ", to_doc(query.offset, opts)),
          concat("side_load: ", to_doc(query.side_load, opts)),
          error_doc
        ],
        ">",
        opts,
        fn str, _ -> str end
      )
    end
  end

  alias Ash.Actions.Sort
  alias Ash.Error.Query.{InvalidLimit, InvalidOffset}
  alias Ash.Error.SideLoad.{InvalidQuery, NoSuchRelationship}

  @doc "Create a new query."
  def new(resource, api \\ nil) when is_atom(resource) do
    %__MODULE__{
      api: api,
      filter: nil,
      resource: resource
    }
    |> set_data_layer_query()
  end

  @doc "Set the query's api, and any side loaded query's api"
  def set_api(query, api) do
    query = to_query(query)
    %{query | api: api, side_load: set_side_load_api(query.side_load, api)}
  end

  @doc "Limit the results returned from the query"
  def limit(query, nil), do: query

  def limit(query, limit) when is_integer(limit) do
    query
    |> to_query()
    |> Map.put(:limit, max(0, limit))
    |> set_data_layer_query()
  end

  def limit(query, limit) do
    add_error(query, :offset, InvalidLimit.exception(limit: limit))
  end

  @doc "Skip the first n records"
  def offset(query, nil), do: query

  def offset(query, offset) when is_integer(offset) do
    query
    |> to_query()
    |> Map.put(:offset, max(0, offset))
    |> set_data_layer_query()
  end

  def offset(query, offset) do
    query
    |> to_query()
    |> add_error(:offset, InvalidOffset.exception(offset: offset))
  end

  @doc "Side loads related entities"
  def side_load(query, statement) do
    query = to_query(query)

    with sanitized_statement <- List.wrap(sanitize_side_loads(statement)),
         :ok <- validate_side_load(query.resource, sanitized_statement),
         new_side_loads <- merge_side_load(query.side_load, sanitized_statement) do
      %{query | side_load: new_side_loads}
    else
      {:error, errors} ->
        Enum.reduce(errors, query, &add_error(&2, :side_load, &1))
    end
  end

  def validate_side_load(resource, side_loads, path \\ []) do
    case do_validate_side_load(resource, side_loads, path) do
      [] -> :ok
      errors -> {:error, errors}
    end
  end

  def do_validate_side_load(_resource, %Ash.Query{} = query, path) do
    if query.limit || (query.offset && query.offset != 0) do
      [{:error, InvalidQuery.exception(query: query, side_load_path: Enum.reverse(path))}]
    else
      case query.errors do
        [] ->
          []

        _errors ->
          [
            {:error,
             InvalidQuery.exception(
               query: query,
               side_load_path: Enum.reverse(path)
             )}
          ]
      end
    end
  end

  def do_validate_side_load(resource, {atom, _} = tuple, path) when is_atom(atom) do
    do_validate_side_load(resource, [tuple], path)
  end

  def do_validate_side_load(resource, side_loads, path) when is_list(side_loads) do
    side_loads
    |> List.wrap()
    |> Enum.flat_map(fn
      {_key, %Ash.Query{}} ->
        []

      {key, value} ->
        case Ash.Resource.relationship(resource, key) do
          nil ->
            [
              {:error,
               NoSuchRelationship.exception(
                 resource: resource,
                 relationship: key,
                 side_load_path: Enum.reverse(path)
               )}
            ]

          relationship ->
            validate_matching_query_and_continue(value, resource, key, path, relationship)
        end
    end)
  end

  def filter(query, nil), do: query

  def filter(query, %Ash.Filter{} = filter) do
    query = to_query(query)

    new_filter =
      case query.filter do
        nil ->
          {:ok, filter}

        existing_filter ->
          Ash.Filter.add_to_filter(existing_filter, filter)
      end

    case new_filter do
      {:ok, filter} ->
        set_data_layer_query(%{query | filter: filter})

      {:error, error} ->
        add_error(query, :filter, error)
    end
  end

  def filter(query, statement) do
    query = to_query(query)

    filter =
      if query.filter do
        Ash.Filter.add_to_filter(query.filter, statement)
      else
        Ash.Filter.parse(query.resource, statement)
      end

    case filter do
      {:ok, filter} ->
        query
        |> Map.put(:filter, filter)
        |> set_data_layer_query()

      {:error, error} ->
        add_error(query, :filter, error)
    end
  end

  def sort(query, sorts) when is_list(sorts) do
    query = to_query(query)

    sorts
    |> Enum.reduce(query, fn
      {sort, direction}, query ->
        %{query | sort: query.sort ++ [{sort, direction}]}

      sort, query ->
        %{query | sort: query.sort ++ [{sort, :asc}]}
    end)
    |> validate_sort()
    |> set_data_layer_query()
  end

  def unset(query, keys) when is_list(keys) do
    Enum.reduce(keys, query, &unset(&2, &1))
  end

  def unset(query, key) do
    if key in [:api, :resource] do
      query
    else
      query
      |> to_query()
      |> struct([{key, Map.get(%__MODULE__{}, key)}])
    end
  end

  @doc false
  def data_layer_query(%{resource: resource} = ash_query, opts \\ []) do
    query = Ash.DataLayer.resource_to_query(resource)

    with {:ok, query} <- Ash.DataLayer.sort(query, ash_query.sort, resource),
         {:ok, query} <- maybe_filter(query, ash_query, opts) do
      {:ok, query}
    else
      {:error, error} -> {:error, error}
    end
  end

  defp validate_sort(%{resource: resource, sort: sort} = query) do
    case Sort.process(resource, sort) do
      {:ok, new_sort} -> %{query | sort: new_sort}
      {:error, error} -> add_error(query, :sort, error)
    end
  end

  defp add_error(query, key, message) do
    query = to_query(query)

    message =
      if is_binary(message) do
        "#{key}: #{message}"
      else
        message
      end

    %{
      query
      | errors: [Map.put(Ash.Error.to_ash_error(message), :path, key) | query.errors],
        valid?: false
    }
  end

  defp set_data_layer_query(query) do
    case data_layer_query(query) do
      {:ok, data_layer_query} -> %{query | data_layer_query: data_layer_query}
      {:error, error} -> add_error(query, :data_layer_query, error)
    end
  end

  defp validate_matching_query_and_continue(value, resource, key, path, relationship) do
    %{destination: relationship_resource} = relationship

    case value do
      %__MODULE__{resource: query_resource} = destination_query
      when query_resource != relationship_resource ->
        [
          InvalidQuery.exception(
            resource: resource,
            relationship: key,
            query: destination_query,
            side_load_path: Enum.reverse(path)
          )
        ]

      other ->
        do_validate_side_load(relationship.destination, other, [key | path])
    end
  end

  defp maybe_filter(query, %{filter: nil}, _) do
    {:ok, query}
  end

  defp maybe_filter(query, ash_query, opts) do
    case Ash.DataLayer.filter(query, ash_query.filter, ash_query.resource) do
      {:ok, filtered} ->
        if Keyword.get(opts, :only_validate_filter?, true) do
          {:ok, query}
        else
          {:ok, filtered}
        end

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

  defp set_side_load_api(nil, _), do: nil
  defp set_side_load_api([], _), do: []

  defp set_side_load_api(%__MODULE__{} = query, api) do
    set_api(query, api)
  end

  defp set_side_load_api(side_loads, api) do
    Enum.map(side_loads, fn {key, further} ->
      {key, set_side_load_api(further, api)}
    end)
  end

  defp to_query(%__MODULE__{} = query), do: query
  defp to_query(resource), do: new(resource)

  defp merge_side_load([], right), do: sanitize_side_loads(right)
  defp merge_side_load(left, []), do: sanitize_side_loads(left)

  defp merge_side_load(
         %__MODULE__{side_load: left_side_loads},
         %__MODULE__{side_load: right_side_loads} = query
       ) do
    %{query | side_load: merge_side_load(left_side_loads, right_side_loads)}
  end

  defp merge_side_load(%__MODULE__{} = query, right) when is_list(right) do
    Ash.Query.side_load(query, right)
  end

  defp merge_side_load(left, %Ash.Query{} = query) when is_list(left) do
    Ash.Query.side_load(query, left)
  end

  defp merge_side_load(left, right) when is_atom(left), do: merge_side_load([{left, []}], right)
  defp merge_side_load(left, right) when is_atom(right), do: merge_side_load(left, [{right, []}])

  defp merge_side_load(left, right) when is_list(left) and is_list(right) do
    right
    |> sanitize_side_loads()
    |> Enum.reduce(sanitize_side_loads(left), fn {rel, rest}, acc ->
      Keyword.update(acc, rel, rest, &merge_side_load(&1, rest))
    end)
  end

  defp sanitize_side_loads(side_load) when is_atom(side_load), do: {side_load, []}

  defp sanitize_side_loads(%Ash.Query{} = query) do
    Map.update!(query, :side_load, &sanitize_side_loads/1)
  end

  defp sanitize_side_loads(side_loads) do
    side_loads
    |> List.wrap()
    |> Enum.map(fn
      {key, value} ->
        {key, sanitize_side_loads(value)}

      side_load_part ->
        cond do
          is_atom(side_load_part) -> {side_load_part, []}
          is_list(side_load_part) -> sanitize_side_loads(side_load_part)
          true -> side_load_part
        end
    end)
  end
end