defmodule Absinthe.Pipeline do
  @moduledoc """
  Execute a pipeline of phases.

  A pipeline is merely a list of phases. This module contains functions for building,
  modifying, and executing pipelines of phases.

  Pipelines are used to build, validate and manipulate GraphQL documents or schema's.

  * See [`Absinthe.Plug`](https://hexdocs.pm/absinthe_plug/Absinthe.Plug.html) on adjusting the document pipeline for GraphQL over http requests.
  * See [`Absinthe.Phoenix`](https://hexdocs.pm/absinthe_phoenix/) on adjusting the document pipeline for GraphQL over Phoenix channels.
  * See `Absinthe.Schema` on adjusting the schema pipeline for schema manipulation.
  """

  alias Absinthe.Phase

  @type data_t :: any

  @type phase_config_t :: Phase.t() | {Phase.t(), Keyword.t()}

  @type t :: [phase_config_t | [phase_config_t]]

  @spec run(data_t, t) :: {:ok, data_t, [Phase.t()]} | {:error, String.t(), [Phase.t()]}
  def run(input, pipeline) do
    pipeline
    |> List.flatten()
    |> run_phase(input)
  end

  @defaults [
    adapter: Absinthe.Adapter.LanguageConventions,
    operation_name: nil,
    variables: %{},
    context: %{},
    root_value: %{},
    validation_result_phase: Phase.Document.Validation.Result,
    result_phase: Phase.Document.Result,
    jump_phases: true
  ]

  def options(overrides \\ []) do
    Keyword.merge(@defaults, overrides)
  end

  @spec for_document(Absinthe.Schema.t()) :: t
  @spec for_document(Absinthe.Schema.t(), Keyword.t()) :: t
  @doc """
  The default document pipeline
  """
  def for_document(schema, options \\ []) do
    options = options(Keyword.put(options, :schema, schema))

    [
      Phase.Init,
      {Phase.Telemetry, Keyword.put(options, :event, [:execute, :operation, :start])},
      # Parse Document
      {Phase.Parse, options},
      # Convert to Blueprint
      {Phase.Blueprint, options},
      # Find Current Operation (if any)
      {Phase.Document.Validation.ProvidedAnOperation, options},
      {Phase.Document.CurrentOperation, options},
      # Mark Fragment/Variable Usage
      Phase.Document.Uses,
      # Validate Document Structure
      {Phase.Document.Validation.NoFragmentCycles, options},
      Phase.Document.Validation.LoneAnonymousOperation,
      {Phase.Document.Validation.SelectedCurrentOperation, options},
      Phase.Document.Validation.KnownFragmentNames,
      Phase.Document.Validation.NoUndefinedVariables,
      Phase.Document.Validation.NoUnusedVariables,
      Phase.Document.Validation.NoUnusedFragments,
      Phase.Document.Validation.UniqueFragmentNames,
      Phase.Document.Validation.UniqueOperationNames,
      Phase.Document.Validation.UniqueVariableNames,
      # Apply Input
      {Phase.Document.Context, options},
      {Phase.Document.Variables, options},
      Phase.Document.Validation.ProvidedNonNullVariables,
      Phase.Document.Arguments.Normalize,
      # Map to Schema
      {Phase.Schema, options},
      # Ensure Types
      Phase.Validation.KnownTypeNames,
      Phase.Document.Arguments.VariableTypesMatch,
      # Process Arguments
      Phase.Document.Arguments.CoerceEnums,
      Phase.Document.Arguments.CoerceLists,
      {Phase.Document.Arguments.Parse, options},
      Phase.Document.MissingVariables,
      Phase.Document.MissingLiterals,
      Phase.Document.Arguments.FlagInvalid,
      # Validate Full Document
      Phase.Document.Validation.KnownDirectives,
      Phase.Document.Validation.RepeatableDirectives,
      Phase.Document.Validation.ScalarLeafs,
      Phase.Document.Validation.VariablesAreInputTypes,
      Phase.Document.Validation.ArgumentsOfCorrectType,
      Phase.Document.Validation.KnownArgumentNames,
      Phase.Document.Validation.ProvidedNonNullArguments,
      Phase.Document.Validation.UniqueArgumentNames,
      Phase.Document.Validation.UniqueInputFieldNames,
      Phase.Document.Validation.FieldsOnCorrectType,
      Phase.Document.Validation.OnlyOneSubscription,
      # Check Validation
      {Phase.Document.Validation.Result, options},
      # Prepare for Execution
      Phase.Document.Arguments.Data,
      # Apply Directives
      Phase.Document.Directives,
      # Analyse Complexity
      {Phase.Document.Complexity.Analysis, options},
      {Phase.Document.Complexity.Result, options},
      # Execution
      {Phase.Subscription.SubscribeSelf, options},
      {Phase.Document.Execution.Resolution, options},
      # Format Result
      Phase.Document.Result,
      {Phase.Telemetry, Keyword.put(options, :event, [:execute, :operation, :stop])}
    ]
  end

  @default_prototype_schema Absinthe.Schema.Prototype

  @spec for_schema(nil | Absinthe.Schema.t()) :: t
  @spec for_schema(nil | Absinthe.Schema.t(), Keyword.t()) :: t
  @doc """
  The default schema pipeline
  """
  def for_schema(schema, options \\ []) do
    options =
      options
      |> Enum.reject(fn {_, v} -> is_nil(v) end)
      |> Keyword.put(:schema, schema)
      |> Keyword.put_new(:prototype_schema, @default_prototype_schema)

    [
      Phase.Schema.TypeImports,
      Phase.Schema.DeprecatedDirectiveFields,
      Phase.Schema.ApplyDeclaration,
      Phase.Schema.Introspection,
      {Phase.Schema.Hydrate, options},
      Phase.Schema.Arguments.Normalize,
      {Phase.Schema, options},
      Phase.Schema.Validation.TypeNamesAreUnique,
      Phase.Schema.Validation.TypeReferencesExist,
      Phase.Schema.Validation.TypeNamesAreReserved,
      # This phase is run once now because a lot of other
      # validations aren't possible if type references are invalid.
      Phase.Schema.Validation.NoCircularFieldImports,
      {Phase.Schema.Validation.Result, pass: :initial},
      Phase.Schema.FieldImports,
      Phase.Schema.Validation.KnownDirectives,
      Phase.Document.Validation.KnownArgumentNames,
      {Phase.Schema.Arguments.Parse, options},
      Phase.Schema.Arguments.Data,
      Phase.Schema.Directives,
      Phase.Schema.Validation.DefaultEnumValuePresent,
      Phase.Schema.Validation.DirectivesMustBeValid,
      Phase.Schema.Validation.InputOutputTypesCorrectlyPlaced,
      Phase.Schema.Validation.InterfacesMustResolveTypes,
      Phase.Schema.Validation.ObjectInterfacesMustBeValid,
      Phase.Schema.Validation.ObjectMustImplementInterfaces,
      Phase.Schema.Validation.NoInterfaceCyles,
      Phase.Schema.Validation.QueryTypeMustBeObject,
      Phase.Schema.Validation.NamesMustBeValid,
      Phase.Schema.Validation.UniqueFieldNames,
      Phase.Schema.RegisterTriggers,
      Phase.Schema.MarkReferenced,
      Phase.Schema.ReformatDescriptions,
      # This phase is run again now after additional validations
      {Phase.Schema.Validation.Result, pass: :final},
      Phase.Schema.Build,
      Phase.Schema.InlineFunctions,
      {Phase.Schema.Compile, options}
    ]
  end

  @doc """
  Return the part of a pipeline before a specific phase.

  ## Examples

      iex> Pipeline.before([A, B, C], B)
      [A]
  """
  @spec before(t, phase_config_t) :: t
  def before(pipeline, phase) do
    result =
      List.flatten(pipeline)
      |> Enum.take_while(&(!match_phase?(phase, &1)))

    case result do
      ^pipeline ->
        raise RuntimeError, "Could not find phase #{phase}"

      _ ->
        result
    end
  end

  @doc """
  Return the part of a pipeline after (and including) a specific phase.

  ## Examples

      iex> Pipeline.from([A, B, C], B)
      [B, C]
  """
  @spec from(t, atom) :: t
  def from(pipeline, phase) do
    result =
      List.flatten(pipeline)
      |> Enum.drop_while(&(!match_phase?(phase, &1)))

    case result do
      [] ->
        raise RuntimeError, "Could not find phase #{phase}"

      _ ->
        result
    end
  end

  @doc """
  Replace a phase in a pipeline with another, supporting reusing the same
  options.

  ## Examples

  Replace a simple phase (without options):

      iex> Pipeline.replace([A, B, C], B, X)
      [A, X, C]

  Replace a phase with options, retaining them:

      iex> Pipeline.replace([A, {B, [name: "Thing"]}, C], B, X)
      [A, {X, [name: "Thing"]}, C]

  Replace a phase with options, overriding them:

      iex> Pipeline.replace([A, {B, [name: "Thing"]}, C], B, {X, [name: "Nope"]})
      [A, {X, [name: "Nope"]}, C]

  """
  @spec replace(t, Phase.t(), phase_config_t) :: t
  def replace(pipeline, phase, replacement) do
    Enum.map(pipeline, fn candidate ->
      case match_phase?(phase, candidate) do
        true ->
          case phase_invocation(candidate) do
            {_, []} ->
              replacement

            {_, opts} ->
              if is_atom(replacement) do
                {replacement, opts}
              else
                replacement
              end
          end

        false ->
          candidate
      end
    end)
  end

  # Whether a phase configuration is for a given phase
  @spec match_phase?(Phase.t(), phase_config_t) :: boolean
  defp match_phase?(phase, phase), do: true
  defp match_phase?(phase, {phase, _}) when is_atom(phase), do: true
  defp match_phase?(_, _), do: false

  @doc """
  Return the part of a pipeline up to and including a specific phase.

  ## Examples

      iex> Pipeline.upto([A, B, C], B)
      [A, B]
  """
  @spec upto(t, phase_config_t) :: t
  def upto(pipeline, phase) do
    beginning = before(pipeline, phase)
    item = get_in(pipeline, [Access.at(length(beginning))])
    beginning ++ [item]
  end

  @doc """
  Return the pipeline with the supplied phase removed.

  ## Examples

      iex> Pipeline.without([A, B, C], B)
      [A, C]
  """
  @spec without(t, Phase.t()) :: t
  def without(pipeline, phase) do
    pipeline
    |> Enum.filter(&(not match_phase?(phase, &1)))
  end

  @doc """
  Return the pipeline with the phase/list of phases inserted before
  the supplied phase.

  ## Examples

  Add one phase before another:

      iex> Pipeline.insert_before([A, C, D], C, B)
      [A, B, C, D]

  Add list of phase before another:

      iex> Pipeline.insert_before([A, D, E], D, [B, C])
      [A, B, C, D, E]

  """
  @spec insert_before(t, Phase.t(), phase_config_t | [phase_config_t]) :: t
  def insert_before(pipeline, phase, additional) do
    beginning = before(pipeline, phase)
    beginning ++ List.wrap(additional) ++ (pipeline -- beginning)
  end

  @doc """
  Return the pipeline with the phase/list of phases inserted after
  the supplied phase.

  ## Examples

  Add one phase after another:

      iex> Pipeline.insert_after([A, C, D], A, B)
      [A, B, C, D]

  Add list of phases after another:

      iex> Pipeline.insert_after([A, D, E], A, [B, C])
      [A, B, C, D, E]

  """
  @spec insert_after(t, Phase.t(), phase_config_t | [phase_config_t]) :: t
  def insert_after(pipeline, phase, additional) do
    beginning = upto(pipeline, phase)
    beginning ++ List.wrap(additional) ++ (pipeline -- beginning)
  end

  @doc """
  Return the pipeline with the phases matching the regex removed.

  ## Examples

      iex> Pipeline.reject([A, B, C], ~r/A|B/)
      [C]
  """
  @spec reject(t, Regex.t() | (module -> boolean)) :: t
  def reject(pipeline, %Regex{} = pattern) do
    reject(pipeline, fn phase ->
      Regex.match?(pattern, Atom.to_string(phase))
    end)
  end

  def reject(pipeline, fun) do
    Enum.reject(pipeline, fn
      {phase, _} -> fun.(phase)
      phase -> fun.(phase)
    end)
  end

  @spec run_phase(t, data_t, [Phase.t()]) ::
          {:ok, data_t, [Phase.t()]} | {:error, String.t(), [Phase.t()]}
  def run_phase(pipeline, input, done \\ [])

  def run_phase([], input, done) do
    {:ok, input, done}
  end

  def run_phase([phase_config | todo] = all_phases, input, done) do
    {phase, options} = phase_invocation(phase_config)

    case phase.run(input, options) do
      {:record_phases, result, fun} ->
        result = fun.(result, all_phases)
        run_phase(todo, result, [phase | done])

      {:ok, result} ->
        run_phase(todo, result, [phase | done])

      {:jump, result, destination_phase} when is_atom(destination_phase) ->
        run_phase(from(todo, destination_phase), result, [phase | done])

      {:insert, result, extra_pipeline} ->
        run_phase(List.wrap(extra_pipeline) ++ todo, result, [phase | done])

      {:swap, result, target, replacements} ->
        todo
        |> replace(target, replacements)
        |> run_phase(result, [phase | done])

      {:replace, result, final_pipeline} ->
        run_phase(List.wrap(final_pipeline), result, [phase | done])

      {:error, message} ->
        {:error, message, [phase | done]}

      _ ->
        {:error, "Last phase did not return a valid result tuple.", [phase | done]}
    end
  end

  @spec phase_invocation(phase_config_t) :: {Phase.t(), list}
  defp phase_invocation({phase, options}) when is_list(options) do
    {phase, options}
  end

  defp phase_invocation(phase) do
    {phase, []}
  end
end