defmodule ExForce do
  @moduledoc """
  Simple wrapper for Salesforce REST API.

  ## Usage

  ```elixir
  {:ok, %{instance_url: instance_url} = oauth_response} =
    ExForce.OAuth.get_token(
      "https://login.salesforce.com",
      grant_type: "password",
      client_id: "client_id",
      client_secret: "client_secret",
      username: "username",
      password: "password"
    )

  {:ok, version_maps} = ExForce.versions(instance_url)
  latest_version = version_maps |> Enum.map(&Map.fetch!(&1, "version")) |> List.last()

  client = ExForce.build_client(oauth_response, api_version: latest_version)

  names =
    ExForce.query_stream(client, "SELECT Name FROM Account")
    |> Stream.map(&Map.fetch!(&1.data, "Name"))
    |> Stream.take(50)
    |> Enum.to_list()
  ```
  """

  alias ExForce.{QueryResult, SObject}

  import ExForce.Client, only: [request: 2]

  @type client :: ExForce.Client.t()
  @type sobject_id :: String.t()
  @type sobject_name :: String.t()
  @type field_name :: String.t()
  @type soql :: String.t()
  @type query_id :: String.t()

  @default_api_version "42.0"
  @default_user_agent "ex_force"

  @doc """
  Lists available REST API versions at an instance.

  See [Versions](https://developer.salesforce.com/docs/atlas.en-us.api_rest.meta/api_rest/resources_versions.htm)
  """
  @spec versions(String.t()) :: {:ok, list(map)} | {:error, any}
  def versions(instance_url) do
    case instance_url |> build_client() |> request(method: :get, url: "/services/data") do
      {:ok, %Tesla.Env{status: 200, body: body}} when is_list(body) -> {:ok, body}
      {:ok, %Tesla.Env{body: body}} -> {:error, body}
      {:error, _} = other -> other
    end
  end

  @doc """
  Lists available resources for the specific API version.

  See [Resources by Version](https://developer.salesforce.com/docs/atlas.en-us.api_rest.meta/api_rest/resources_discoveryresource.htm)
  """
  @spec resources(client, String.t()) :: {:ok, map} | {:error, any}
  def resources(client, version) do
    case request(client, method: :get, url: "/services/data/v#{version}") do
      {:ok, %Tesla.Env{status: 200, body: body}} -> {:ok, body}
      {:ok, %Tesla.Env{body: body}} -> {:error, body}
      {:error, _} = other -> other
    end
  end

  @doc """

  Options

  - `:headers`: set additional headers; default: `[{"user-agent", "#{@default_user_agent}"}]`
  - `:api_version`: use the given api_version; default: `"#{@default_api_version}"`
  """
  def build_client(instance_url_or_map, opts \\ [headers: [{"user-agent", @default_user_agent}]])

  def build_client(%{instance_url: instance_url, access_token: access_token}, opts) do
    with headers <- Keyword.get(opts, :headers, []),
         new_headers <- [{"authorization", "Bearer " <> access_token} | headers],
         new_opts <- Keyword.put(opts, :headers, new_headers) do
      build_client(instance_url, new_opts)
    end
  end

  def build_client(instance_url, opts) when is_binary(instance_url) do
    Tesla.client([
      {ExForce.TeslaMiddleware,
       {instance_url, Keyword.get(opts, :api_version, @default_api_version)}},
      {Tesla.Middleware.Compression, format: "gzip"},
      {Tesla.Middleware.JSON, engine: Jason},
      {Tesla.Middleware.Headers, Keyword.get(opts, :headers, [])}
    ])
  end

  @doc """
  Lists the available objects.

  See [Describe Global](https://developer.salesforce.com/docs/atlas.en-us.api_rest.meta/api_rest/resources_describeGlobal.htm)
  """
  @spec describe_global(client) :: {:ok, map} | {:error, any}
  def describe_global(client) do
    case request(client, method: :get, url: "sobjects") do
      {:ok, %Tesla.Env{status: 200, body: body}} -> {:ok, body}
      {:ok, %Tesla.Env{body: body}} -> {:error, body}
      {:error, _} = other -> other
    end
  end

  @doc """
  Retrieves extended metadata for the specified SObject.

  See [SObject Describe](https://developer.salesforce.com/docs/atlas.en-us.api_rest.meta/api_rest/resources_sobject_describe.htm)
  """
  @spec describe_sobject(client, sobject_name) :: {:ok, map} | {:error, any}
  def describe_sobject(client, name) do
    case request(client, method: :get, url: "sobjects/#{name}/describe") do
      {:ok, %Tesla.Env{status: 200, body: body}} -> {:ok, body}
      {:ok, %Tesla.Env{body: body}} -> {:error, body}
      {:error, _} = other -> other
    end
  end

  @doc """
  Retrieves basic metadata for the specific SObject.

  See [SObject Basic Information](https://developer.salesforce.com/docs/atlas.en-us.api_rest.meta/api_rest/resources_sobject_basic_info.htm)
  """
  @spec basic_info(client, sobject_name) :: {:ok, map} | {:error, any}
  def basic_info(client, name) do
    case request(client, method: :get, url: "sobjects/#{name}") do
      {:ok, %Tesla.Env{status: 200, body: %{"recentItems" => recent_items} = body}} ->
        {:ok, Map.put(body, "recentItems", Enum.map(recent_items, &SObject.build/1))}

      {:ok, %Tesla.Env{body: body}} ->
        {:error, body}

      {:error, _} = other ->
        other
    end
  end

  @doc """
  Retrieves a SObject by ID.

  See [SObject Rows](https://developer.salesforce.com/docs/atlas.en-us.api_rest.meta/api_rest/resources_sobject_retrieve.htm)
  """
  @spec get_sobject(client, sobject_id, sobject_name, list) :: {:ok, SObject.t()} | {:error, any}
  def get_sobject(client, id, name, fields),
    do: do_get_sobject(client, "sobjects/#{name}/#{id}", fields)

  @doc """
  Retrieves a SObject based on the value of a specified extneral ID field.

  See [SObject Rows by External ID](https://developer.salesforce.com/docs/atlas.en-us.api_rest.meta/api_rest/resources_sobject_upsert.htm)
  """
  @spec get_sobject_by_external_id(client, any, field_name, sobject_name) ::
          {:ok, SObject.t()} | {:error, any}
  def get_sobject_by_external_id(client, field_value, field_name, sobject_name),
    do:
      do_get_sobject(client, "sobjects/#{sobject_name}/#{field_name}/#{URI.encode(field_value)}")

  @doc """
  Retrieves a SObject by relationship field.

  See [SObject Relationships](https://developer.salesforce.com/docs/atlas.en-us.api_rest.meta/api_rest/resources_sobject_relationships.htm)
  """
  @spec get_sobject_by_relationship(
          client,
          sobject_id,
          sobject_name,
          field_name,
          list(field_name)
        ) :: {:ok, SObject.t() | QueryResult.t()} | {:error, any}
  def get_sobject_by_relationship(client, id, sobject_name, field_name, fields) do
    path = "sobjects/#{sobject_name}/#{id}/#{field_name}"
    case request(client, method: :get, url: path, query: build_fields_query(fields)) do
      {:ok, %Tesla.Env{status: 200, body: %{"attributes" => _} = body}} -> {:ok, SObject.build(body)}
      {:ok, %Tesla.Env{status: 200, body: %{"records" => _} = body}} -> {:ok, build_result_set(body)}
      {:ok, %Tesla.Env{body: body}} -> {:error, body}
      {:error, _} = other -> other
    end
  end

  defp do_get_sobject(client, path, fields \\ []) do
    case request(client, method: :get, url: path, query: build_fields_query(fields)) do
      {:ok, %Tesla.Env{status: 200, body: body}} -> {:ok, SObject.build(body)}
      {:ok, %Tesla.Env{body: body}} -> {:error, body}
      {:error, _} = other -> other
    end
  end

  defp build_fields_query([]), do: []
  defp build_fields_query(fields), do: [fields: Enum.join(fields, ",")]

  @doc """
  Updates a SObject.

  See [SObject Rows](https://developer.salesforce.com/docs/atlas.en-us.api_rest.meta/api_rest/resources_sobject_retrieve.htm)
  """
  @spec update_sobject(client, sobject_id, sobject_name, map) :: :ok | {:error, any}
  def update_sobject(client, id, name, attrs) do
    case request(client, method: :patch, url: "sobjects/#{name}/#{id}", body: attrs) do
      {:ok, %Tesla.Env{status: 204, body: ""}} -> :ok
      {:ok, %Tesla.Env{body: body}} -> {:error, body}
      {:error, _} = other -> other
    end
  end

  @doc """
  Creates a SObject.

  See [SObject Rows](https://developer.salesforce.com/docs/atlas.en-us.api_rest.meta/api_rest/resources_sobject_basic_info.htm)
  """
  @spec create_sobject(client, sobject_name, map) :: {:ok, sobject_id} | {:error, any}
  def create_sobject(client, name, attrs) do
    case request(client, method: :post, url: "sobjects/#{name}/", body: attrs) do
      {:ok, %Tesla.Env{status: 201, body: %{"id" => id, "success" => true}}} -> {:ok, id}
      {:ok, %Tesla.Env{body: body}} -> {:error, body}
      {:error, _} = other -> other
    end
  end

  @doc """
  Deletes a SObject.

  [SObject Rows](https://developer.salesforce.com/docs/atlas.en-us.api_rest.meta/api_rest/resources_sobject_retrieve.htm)
  """
  @spec delete_sobject(client, sobject_id, sobject_name) :: :ok | {:error, any}
  def delete_sobject(client, id, name) do
    case request(client, method: :delete, url: "sobjects/#{name}/#{id}") do
      {:ok, %Tesla.Env{status: 204, body: ""}} -> :ok
      {:ok, %Tesla.Env{status: 404, body: body}} -> {:error, body}
      {:error, _} = other -> other
    end
  end

  @doc """
  Excute the SOQL query and get the result of it.

  [Query](https://developer.salesforce.com/docs/atlas.en-us.api_rest.meta/api_rest/resources_query.htm)
  """
  @spec query(client, soql) :: {:ok, QueryResult.t()} | {:error, any}
  def query(client, soql) do
    case request(client, method: :get, url: "query", query: [q: soql]) do
      {:ok, %Tesla.Env{status: 200, body: body}} -> {:ok, build_result_set(body)}
      {:ok, %Tesla.Env{body: body}} -> {:error, body}
      {:error, _} = other -> other
    end
  end

  @spec query_stream(client, soql) :: Enumerable.t()
  def query_stream(client, soql), do: start_query_stream(client, &query/2, soql)

  @doc """
  Retrieve additional query results for the specified query ID.

  [Query](https://developer.salesforce.com/docs/atlas.en-us.api_rest.meta/api_rest/resources_query.htm)
  """
  @spec query_retrieve(client, query_id | String.t()) :: {:ok, QueryResult.t()} | {:error, any}
  def query_retrieve(client, query_id_or_url) do
    path =
      if full_path?(query_id_or_url) do
        query_id_or_url
      else
        "query/#{query_id_or_url}"
      end

    case request(client, method: :get, url: path) do
      {:ok, %Tesla.Env{status: 200, body: body}} -> {:ok, build_result_set(body)}
      {:ok, %Tesla.Env{body: body}} -> {:error, body}
      {:error, _} = other -> other
    end
  end

  @doc """
  Excute the SOQL query and get the result of it, including deleted or archived objects.

  [QueryAll](https://developer.salesforce.com/docs/atlas.en-us.api_rest.meta/api_rest/resources_queryall.htm)
  """
  @spec query_all(client, soql) :: {:ok, QueryResult.t()} | {:error, any}
  def query_all(client, soql) do
    case request(client, method: :get, url: "queryAll", query: [q: soql]) do
      {:ok, %Tesla.Env{status: 200, body: body}} -> {:ok, build_result_set(body)}
      {:ok, %Tesla.Env{body: body}} -> {:error, body}
      {:error, _} = other -> other
    end
  end

  @spec query_all_stream(client, soql) :: Enumerable.t()
  def query_all_stream(client, soql), do: start_query_stream(client, &query_all/2, soql)

  defp build_result_set(%{"records" => records, "totalSize" => total_size} = resp) do
    case resp do
      %{"done" => true} ->
        %QueryResult{
          done: true,
          total_size: total_size,
          records: records |> Enum.map(&SObject.build/1)
        }

      %{"done" => false, "nextRecordsUrl" => next_records_url} ->
        %QueryResult{
          done: false,
          next_records_url: next_records_url,
          total_size: total_size,
          records: records |> Enum.map(&SObject.build/1)
        }
    end
  end

  @spec start_query_stream(
          client,
          (client, soql -> {:ok, QueryResult.t()} | any),
          soql
        ) :: Enumerable.t()
  defp start_query_stream(client, func, soql) do
    {:ok, qr} = func.(client, soql)
    stream_query_result(client, qr)
  end

  @doc """
  Returns `Enumerable.t` from the `QueryResult`.
  """
  @spec stream_query_result(client, QueryResult.t()) :: Enumerable.t()
  def stream_query_result(client, %QueryResult{} = qr) do
    Stream.unfold({client, qr}, &stream_unfold/1)
  end

  defp stream_unfold({client, %QueryResult{records: [h | tail]} = qr}),
    do: {h, {client, %QueryResult{qr | records: tail}}}

  defp stream_unfold({
         client,
         %QueryResult{records: [], done: false, next_records_url: next_records_url}
       }) do
    {:ok, %QueryResult{records: [h | tail]} = qr} = query_retrieve(client, next_records_url)
    {h, {client, %QueryResult{qr | records: tail}}}
  end

  defp stream_unfold({_client, %QueryResult{records: [], done: true}}), do: nil

  defp full_path?(path), do: String.starts_with?(path, "/services/data/v")
end