defmodule ExAws.SNS do
  @moduledoc """
  Operations on AWS Simple Notification Service (SNS).

  See http://docs.aws.amazon.com/sns/latest/api/API_Operations.html for details.
  """

  import ExAws.Utils, only: [camelize_key: 1, camelize_keys: 1]

  ## Topics
  ######################

  @type topic_name :: binary
  @type topic_arn :: binary
  @type topic_attribute_name ::
          :policy
          | :display_name
          | :delivery_policy

  @type topic_attributes :: [
          {atom, binary}
          | {atom, boolean}
          | {atom, integer}
        ]

  @doc "List topics"
  @spec list_topics() :: ExAws.Operation.Query.t()
  @spec list_topics(opts :: [next_token: binary]) :: ExAws.Operation.Query.t()
  def list_topics(opts \\ []) do
    opts =
      opts
      |> Map.new()
      |> camelize_keys

    request(:list_topics, opts)
  end

  @doc "Create topic."
  @spec create_topic(topic_name :: topic_name) :: ExAws.Operation.Query.t()
  @spec create_topic(topic_name :: topic_name, attributes :: topic_attributes) ::
          ExAws.Operation.Query.t()
  def create_topic(topic_name, attributes \\ []) do
    params =
      attributes
      |> build_attrs()
      |> Map.put("Name", topic_name)

    request(:create_topic, params)
  end

  @doc "Get topic attributes."
  @spec get_topic_attributes(topic_arn :: topic_arn) :: ExAws.Operation.Query.t()
  def get_topic_attributes(topic_arn) do
    request(:get_topic_attributes, %{"TopicArn" => topic_arn})
  end

  @doc "Set topic attributes."
  @spec set_topic_attributes(
          attribute_name :: topic_attribute_name,
          attribute_value :: binary,
          topic_arn :: topic_arn
        ) :: ExAws.Operation.Query.t()
  def set_topic_attributes(attribute_name, attribute_value, topic_arn) do
    request(:set_topic_attributes, %{
      "AttributeName" => attribute_name |> camelize_key,
      "AttributeValue" => attribute_value,
      "TopicArn" => topic_arn
    })
  end

  @doc "Delete topic."
  @spec delete_topic(topic_arn :: topic_arn) :: ExAws.Operation.Query.t()
  def delete_topic(topic_arn) do
    request(:delete_topic, %{"TopicArn" => topic_arn})
  end

  @type message_attribute :: %{
          :name => binary,
          :data_type => :string | :number | :binary,
          :value => {:string, binary} | {:binary, binary}
        }
  @type publish_opts :: [
          {:message_attributes, [message_attribute]}
          | {:message_structure, :json}
          | {:subject, binary}
          | {:phone_number, binary}
          | {:target_arn, binary}
          | {:topic_arn, binary}
        ]

  @doc """
  Publish message to a target/topic ARN.

  You must set either `:phone_number`, `:target_arn` or `:topic_arn` but only one,
  via the options argument.

  Do NOT assume that because your message is a JSON blob that you should set
  `:message_structure` to `:json`. This has a very specific meaning, see
  http://docs.aws.amazon.com/sns/latest/api/API_Publish.html for details.
  """
  @spec publish(message :: binary, opts :: publish_opts) :: ExAws.Operation.Query.t()
  def publish(message, opts) do
    opts = opts |> Map.new()

    message_attrs =
      opts
      |> Map.get(:message_attributes, [])
      |> build_message_attributes

    params =
      opts
      |> Map.drop([:message_attributes])
      |> camelize_keys
      |> Map.put("Message", message)
      |> Map.merge(message_attrs)

    request(:publish, params)
  end

  defp build_message_attributes(attrs) do
    attrs
    |> Stream.with_index()
    |> Enum.reduce(%{}, &build_message_attribute/2)
  end

  def build_message_attribute(
        {%{name: name, data_type: data_type, value: {value_type, value}}, i},
        params
      ) do
    param_root = "MessageAttributes.entry.#{i + 1}"
    value_type = value_type |> to_string |> String.capitalize()

    params
    |> Map.put(param_root <> ".Name", name)
    |> Map.put(param_root <> ".Value.#{value_type}Value", value)
    |> Map.put(param_root <> ".Value.DataType", data_type |> to_string |> String.capitalize())
  end

  ## Platform
  ######################

  @type platform_application_arn :: binary

  @doc "Create plaform application."
  @spec create_platform_application(
          name :: binary,
          platform :: binary,
          attributes :: %{String.t() => String.t()}
        ) :: ExAws.Operation.Query.t()
  def create_platform_application(name, platform, attributes) do
    attributes =
      attributes
      |> build_kv_attrs
      |> Map.merge(%{
        "Name" => name,
        "Platform" => platform
      })

    request(:create_platform_application, attributes)
  end

  @doc "Delete platform application."
  @spec delete_platform_application(platform_application_arn :: platform_application_arn) ::
          ExAws.Operation.Query.t()
  def delete_platform_application(platform_application_arn) do
    request(:delete_platform_application, %{
      "PlatformApplicationArn" => platform_application_arn
    })
  end

  @doc "List platform applications."
  @spec list_platform_applications() :: ExAws.Operation.Query.t()
  def list_platform_applications() do
    request(:list_platform_applications, %{})
  end

  @spec list_platform_applications(next_token :: binary) :: ExAws.Operation.Query.t()
  def list_platform_applications(next_token) do
    request(:list_platform_applications, %{"NextToken" => next_token})
  end

  @doc "Create platform endpoint."
  @spec create_platform_endpoint(
          platform_application_arn :: platform_application_arn,
          token :: binary
        ) :: ExAws.Operation.Query.t()
  @spec create_platform_endpoint(
          platform_application_arn :: platform_application_arn,
          token :: binary,
          custom_user_data :: binary | nil
        ) :: ExAws.Operation.Query.t()
  def create_platform_endpoint(platform_application_arn, token, custom_user_data \\ nil) do
    attrs = %{
      "PlatformApplicationArn" => platform_application_arn,
      "Token" => token
    }

    attrs =
      if custom_user_data do
        Map.put(attrs, "CustomUserData", custom_user_data)
      else
        attrs
      end

    request(:create_platform_endpoint, attrs)
  end

  @doc "Get platform application attributes."
  @spec get_platform_application_attributes(platform_application_arn :: platform_application_arn) ::
          ExAws.Operation.Query.t()
  def get_platform_application_attributes(platform_application_arn) do
    request(:get_platform_application_attributes, %{
      "PlatformApplicationArn" => platform_application_arn
    })
  end

  ## Subscriptions
  ######################

  @type subscription_attribute_name :: :delivery_policy | :filter_policy | :raw_message_delivery
  @type subscribe_opt :: {:return_subscription_arn, boolean}

  @doc "Create Subscription."
  @spec subscribe(topic_arn :: binary, protocol :: binary, endpoint :: binary, [subscribe_opt]) ::
          ExAws.Operation.Query.t()
  def subscribe(topic_arn, protocol, endpoint, opts \\ []) do
    params = %{
      "TopicArn" => topic_arn,
      "Protocol" => protocol,
      "Endpoint" => endpoint,
      "ReturnSubscriptionArn" => opts[:return_subscription_arn] || false
    }

    request(:subscribe, params)
  end

  @doc "Confirm Subscription."
  @spec confirm_subscription(
          topic_arn :: binary,
          token :: binary,
          authenticate_on_unsubscribe :: boolean
        ) :: ExAws.Operation.Query.t()
  def confirm_subscription(topic_arn, token, authenticate_on_unsubscribe \\ false) do
    request(:confirm_subscription, %{
      "TopicArn" => topic_arn,
      "Token" => token,
      "AuthenticateOnUnsubscribe" => to_string(authenticate_on_unsubscribe)
    })
  end

  @doc "List Subscriptions."
  @spec list_subscriptions() :: ExAws.Operation.Query.t()
  def list_subscriptions() do
    request(:list_subscriptions, %{})
  end

  @spec list_subscriptions(next_token :: binary) :: ExAws.Operation.Query.t()
  def list_subscriptions(next_token) do
    request(:list_subscriptions, %{"NextToken" => next_token})
  end

  @type list_subscriptions_by_topic_opt :: {:next_token, binary}

  @doc "List Subscriptions by Topic."
  @spec list_subscriptions_by_topic(topic_arn :: topic_arn) :: ExAws.Operation.Query.t()
  @spec list_subscriptions_by_topic(topic_arn :: topic_arn, [list_subscriptions_by_topic_opt]) ::
          ExAws.Operation.Query.t()
  def list_subscriptions_by_topic(topic_arn, opts \\ []) do
    params =
      case opts do
        [next_token: next_token] ->
          %{"TopicArn" => topic_arn, "NextToken" => next_token}

        _ ->
          %{"TopicArn" => topic_arn}
      end

    request(:list_subscriptions_by_topic, params)
  end

  @doc "Unsubscribe."
  @spec unsubscribe(subscription_arn :: binary) :: ExAws.Operation.Query.t()
  def unsubscribe(subscription_arn) do
    request(:unsubscribe, %{
      "SubscriptionArn" => subscription_arn
    })
  end

  @doc "Get subscription attributes."
  @spec get_subscription_attributes(subscription_arn :: binary) :: ExAws.Operation.Query.t()
  def get_subscription_attributes(subscription_arn) do
    request(:get_subscription_attributes, %{
      "SubscriptionArn" => subscription_arn
    })
  end

  @doc "Set subscription attributes."
  @spec set_subscription_attributes(
          attribute_name :: subscription_attribute_name,
          attribute_value :: binary,
          subscription_arn :: binary
        ) :: ExAws.Operation.Query.t()
  def set_subscription_attributes(attribute_name, attribute_value, subscription_arn) do
    request(:set_subscription_attributes, %{
      "AttributeName" => attribute_name |> camelize_key,
      "AttributeValue" => attribute_value,
      "SubscriptionArn" => subscription_arn
    })
  end

  @doc "List phone numbers opted out."
  @spec list_phone_numbers_opted_out() :: ExAws.Operation.Query.t()
  def list_phone_numbers_opted_out() do
    request(:list_phone_numbers_opted_out, %{})
  end

  @spec list_phone_numbers_opted_out(next_token :: binary) :: ExAws.Operation.Query.t()
  def list_phone_numbers_opted_out(next_token) do
    request(:list_phone_numbers_opted_out, %{"nextToken" => next_token})
  end

  @doc "Opt in phone number."
  @spec opt_in_phone_number(phone_number :: binary) :: ExAws.Operation.Query.t()
  def opt_in_phone_number(phone_number) do
    request(:opt_in_phone_number, %{"phoneNumber" => phone_number})
  end

  ## Endpoints
  ######################

  @type endpoint_arn :: binary

  @type endpoint_attributes :: [
          {:token, binary}
          | {:enabled, boolean}
          | {:custom_user_data, binary}
        ]

  @doc "Get endpoint attributes."
  @spec get_endpoint_attributes(endpoint_arn :: endpoint_arn) :: ExAws.Operation.Query.t()
  def get_endpoint_attributes(endpoint_arn) do
    request(:get_endpoint_attributes, %{"EndpointArn" => endpoint_arn})
  end

  @doc "Set endpoint attributes."
  @spec set_endpoint_attributes(endpoint_arn :: endpoint_arn, attributes :: endpoint_attributes) ::
          ExAws.Operation.Query.t()
  def set_endpoint_attributes(endpoint_arn, attributes) do
    params =
      attributes
      |> build_attrs

    request(:set_endpoint_attributes, Map.put(params, "EndpointArn", endpoint_arn))
  end

  @doc "Delete endpoint."
  @spec delete_endpoint(endpoint_arn :: endpoint_arn) :: ExAws.Operation.Query.t()
  def delete_endpoint(endpoint_arn) do
    request(:delete_endpoint, %{
      "EndpointArn" => endpoint_arn
    })
  end

  @type list_endpoints_by_platform_application_opt :: {:next_token, binary}

  @doc "List endpoints and endpoint attributes for devices in a supported push notification service."
  @spec list_endpoints_by_platform_application(topic_arn :: topic_arn) ::
          ExAws.Operation.Query.t()
  @spec list_endpoints_by_platform_application(topic_arn :: topic_arn, [
          list_endpoints_by_platform_application_opt
        ]) :: ExAws.Operation.Query.t()
  def list_endpoints_by_platform_application(platform_application_arn, opts \\ []) do
    params =
      case opts do
        [next_token: next_token] ->
          %{"PlatformApplicationArn" => platform_application_arn, "NextToken" => next_token}

        _ ->
          %{"PlatformApplicationArn" => platform_application_arn}
      end

    request(:list_endpoints_by_platform_application, params)
  end

  ## Messages
  ######################

  @notification_params ["Message", "MessageId", "Subject", "Timestamp", "TopicArn", "Type"]
  @optional_notification_params ["Subject"]
  @confirmation_params [
    "Message",
    "MessageId",
    "SubscribeURL",
    "Timestamp",
    "Token",
    "TopicArn",
    "Type"
  ]
  @signature_params ["SignatureVersion", "Signature", "SigningCertURL"]
  @message_types ["SubscriptionConfirmation", "UnsubscribeConfirmation", "Notification"]

  @doc "Verify message signature."
  @spec verify_message(message_params :: %{String.t() => String.t()}) ::
          :ok | {:error, String.t()}
  def verify_message(message_params) do
    with :ok <- validate_message_params(message_params),
         :ok <- validate_signature_version(message_params["SignatureVersion"]),
         {:ok, public_key} <- ExAws.SNS.PublicKeyCache.get(message_params["SigningCertURL"]) do
      message_params
      |> get_string_to_sign
      |> verify(message_params["Signature"], public_key)
    end
  end

  defp validate_message_params(message_params) do
    with {:ok, required_params} <- get_required_params(message_params["Type"]) do
      case required_params -- Map.keys(message_params) do
        [] ->
          :ok

        missing_params ->
          {:error, "The following parameters are missing: #{inspect(missing_params)}"}
      end
    end
  end

  defp get_required_params(message_type) do
    case message_type do
      "Notification" ->
        {:ok, (@notification_params -- @optional_notification_params) ++ @signature_params}

      "SubscriptionConfirmation" ->
        {:ok, @confirmation_params ++ @signature_params}

      "UnsubscribeConfirmation" ->
        {:ok, @confirmation_params ++ @signature_params}

      type when is_binary(type) ->
        {:error, "Invalid Type, expected one of #{inspect(@message_types)}"}

      type when is_nil(type) ->
        {:error, "Missing message type parameter (Type)"}

      type ->
        {:error, "Invalid message type's type, expected a String, got #{inspect(type)}"}
    end
  end

  defp validate_signature_version(version) do
    case version do
      "1" ->
        :ok

      val when is_binary(val) ->
        {:error, "Unsupported SignatureVersion, expected \"1\", got #{version}"}

      _ ->
        {:error, "Invalid SignatureVersion format, expected a String, got #{version}"}
    end
  end

  defp get_string_to_sign(message_params) do
    message_params
    |> Map.take(get_params_to_sign(message_params["Type"]))
    |> Enum.map(fn {key, value} -> [to_string(key), "\n", to_string(value), "\n"] end)
    |> IO.iodata_to_binary()
  end

  defp get_params_to_sign(message_type) do
    case message_type do
      "Notification" -> @notification_params
      "SubscriptionConfirmation" -> @confirmation_params
      "UnsubscribeConfirmation" -> @confirmation_params
    end
  end

  defp verify(message, signature, public_key) do
    case :public_key.verify(message, :sha, Base.decode64!(signature), public_key) do
      true -> :ok
      false -> {:error, "Signature is invalid"}
    end
  end

  ## Request
  ######################

  defp request(action, params) do
    action_string = action |> Atom.to_string() |> Macro.camelize()

    %ExAws.Operation.Query{
      path: "/",
      params: params |> Map.put("Action", action_string),
      service: :sns,
      action: action,
      parser: &ExAws.SNS.Parsers.parse/2
    }
  end

  defp build_attrs(attrs) do
    attrs
    |> Enum.with_index(1)
    |> Enum.map(&build_attr/1)
    |> Enum.reduce(%{}, &Map.merge(&1, &2))
  end

  defp build_attr({{name, value}, index}) do
    prefix = "Attributes.entry.#{index}."

    %{}
    |> Map.put(prefix <> "name", format_param_key(name))
    |> Map.put(prefix <> "value", value)
  end

  defp build_kv_attrs(attrs) do
    attrs
    |> Enum.with_index(1)
    |> Enum.map(&build_kv_attr/1)
    |> Enum.reduce(%{}, &Map.merge(&1, &2))
  end

  defp build_kv_attr({{key, value}, index}) do
    prefix = "Attributes.entry.#{index}."

    %{}
    |> Map.put(prefix <> "key", key)
    |> Map.put(prefix <> "value", value)
  end

  defp format_param_key("*"), do: "*"

  defp format_param_key(key) do
    key
    |> Atom.to_string()
    |> ExAws.Utils.camelize()
  end
end