defmodule YapilyClient do
  @moduledoc """
  Official Elixir client for the Yapily Open Banking API v12.

  Connect to 2,000+ banks across the UK and Europe through a single integration.

  ## Installation

  ```elixir
  # mix.exs
  {:yapily_client, "~> 1.0"}
  ```

  Set credentials at runtime (never hard-code them):

  ```elixir
  # config/runtime.exs
  config :yapily_client,
    app_key: System.fetch_env!("YAPILY_APP_KEY"),
    app_secret: System.fetch_env!("YAPILY_APP_SECRET")
  ```

  ## Quick start

      config = YapilyClient.Config.new!(
        app_key: System.fetch_env!("YAPILY_APP_KEY"),
        app_secret: System.fetch_env!("YAPILY_APP_SECRET")
      )

      # List banks
      {:ok, institutions} = YapilyClient.Institutions.list(config)

      # Start account authorisation
      {:ok, auth} = YapilyClient.Authorisations.create_account(config, %{
        institution_id: "monzo",
        application_user_id: "user-123",
        callback: "https://myapp.com/callback",
        feature_scope_list: ["ACCOUNTS", "TRANSACTIONS"],
        one_time_token: true
      })
      # Redirect user to: auth.authorisation_url

      # Exchange token after callback
      {:ok, consent} = YapilyClient.Consents.exchange_one_time_token(config, token)

      # Read accounts
      {:ok, accounts} = YapilyClient.Accounts.list(config, consent.id)

      # Stream transactions
      YapilyClient.Transactions.stream(config, consent.id, account_id)
      |> Stream.filter(&(&1.currency == "GBP"))
      |> Enum.take(100)

      # Make a payment
      {:ok, payment} = YapilyClient.Payments.create(config, consent_token, %{
        type: YapilyClient.payment_type(:domestic),
        payment_idempotency_id: YapilyClient.idempotency_key(),
        amount: 100.00,
        currency: "GBP",
        recipient: %{
          name: "Jane Smith",
          account_identifications: [
            %{type: "SORT_CODE", identification: "200000"},
            %{type: "ACCOUNT_NUMBER", identification: "55779911"}
          ]
        },
        reference: "Invoice-001"
      })

  ## Services

  | Module | Description |
  |--------|-------------|
  | `YapilyClient.Institutions` | List and inspect supported banks |
  | `YapilyClient.Accounts` | Account list and detail |
  | `YapilyClient.Transactions` | History — `list/4`, `list_all/4`, `stream/4` |
  | `YapilyClient.Payments` | Domestic, scheduled, periodic, international |
  | `YapilyClient.BulkPayments` | Batch payment initiation |
  | `YapilyClient.Consents` | Lifecycle — exchange, extend, delete |
  | `YapilyClient.Authorisations` | 14 flows — redirect, embedded, pre-auth |
  | `YapilyClient.FinancialData` | Balances, direct debits, statements, identity |
  | `YapilyClient.Users` | PSU management |
  | `YapilyClient.VRP` | Variable Recurring Payments |
  | `YapilyClient.Notifications` | Event subscriptions |
  | `YapilyClient.DataPlus` | Transaction enrichment |
  | `YapilyClient.HostedPages` | Yapily-hosted UIs |
  | `YapilyClient.Constraints` | Per-institution rules |
  | `YapilyClient.ApplicationManagement` | App and sub-app management |
  | `YapilyClient.Webhooks` | Registration and secret rotation |
  | `YapilyClient.Beneficiaries` | App + user beneficiaries (VoP) |
  | `YapilyClient.Validate` | Account ownership verification |
  | `YapilyClient.ConsentPoller` | Fibonacci back-off polling |
  | `YapilyClient.Webhook` | HMAC-SHA256 signature verification |

  ## Error handling

      case YapilyClient.Accounts.list(config, token) do
        {:ok, accounts} ->
          accounts

        {:error, err} when YapilyClient.Error.not_found?(err) ->
          handle_not_found()

        {:error, err} when YapilyClient.Error.vop_rejected?(err) ->
          handle_vop_failure()

        {:error, %YapilyClient.Error.APIError{status: s, trace_id: t}} ->
          Logger.error("API \#{s} trace=\#{t}")

        {:error, %YapilyClient.Error.EnhancedAPIError{issues: issues}} ->
          Enum.each(issues, &Logger.error("[code \#{&1.code}] \#{&1.message}"))

        {:error, %YapilyClient.Error.ValidationError{field: f, message: m}} ->
          {:error, "\#{f}: \#{m}"}
      end

  ## Consent polling

      case YapilyClient.ConsentPoller.wait_for_authorisation(config, consent_id) do
        {:ok, %{status: "AUTHORIZED"} = consent} -> proceed(consent)
        {:ok, %{status: status}} -> handle_failure(status)
        {:error, :timed_out} -> show_timeout()
      end

  ## Webhook verification

      case YapilyClient.Webhook.verify(raw_body, secret, signature_header) do
        :ok -> process_event(event)
        {:error, :invalid_signature} -> send_resp(conn, 401, "unauthorized")
        {:error, :missing_signature} -> send_resp(conn, 400, "missing signature")
      end
  """

  @version "1.0.0"

  @doc "Returns the SDK version."
  @spec version() :: String.t()
  def version, do: @version

  @doc "Returns the Yapily API version this SDK targets."
  @spec api_version() :: String.t()
  def api_version, do: "12.0.0"

  @doc """
  Returns `key` if non-empty, otherwise generates a unique idempotency key.

  Always provide an idempotency key when creating payments to prevent duplicate
  submissions on network retry.

  ## Examples

      YapilyClient.idempotency_key("order-123")   # => "order-123"
      YapilyClient.idempotency_key()              # => "idem-<monotonic-int>"
      YapilyClient.idempotency_key("")            # => "idem-<monotonic-int>"
  """
  @spec idempotency_key(String.t()) :: String.t()
  def idempotency_key(key \\ "") do
    if key != "" and String.trim(key) != "",
      do: key,
      else: "idem-#{System.unique_integer([:positive, :monotonic])}"
  end

  @doc """
  Returns the Yapily API payment type string for the given atom.

  | Atom | String |
  |------|--------|
  | `:domestic` | `"DOMESTIC_PAYMENT"` |
  | `:domestic_scheduled` | `"DOMESTIC_SCHEDULED_PAYMENT"` |
  | `:domestic_periodic` | `"DOMESTIC_PERIODIC_PAYMENT"` |
  | `:international` | `"INTERNATIONAL_PAYMENT"` |
  | `:international_scheduled` | `"INTERNATIONAL_SCHEDULED_PAYMENT"` |
  | `:international_periodic` | `"INTERNATIONAL_PERIODIC_PAYMENT"` |
  """
  @spec payment_type(
          :domestic
          | :domestic_scheduled
          | :domestic_periodic
          | :international
          | :international_scheduled
          | :international_periodic
        ) ::
          String.t()
  def payment_type(:domestic), do: "DOMESTIC_PAYMENT"
  def payment_type(:domestic_scheduled), do: "DOMESTIC_SCHEDULED_PAYMENT"
  def payment_type(:domestic_periodic), do: "DOMESTIC_PERIODIC_PAYMENT"
  def payment_type(:international), do: "INTERNATIONAL_PAYMENT"
  def payment_type(:international_scheduled), do: "INTERNATIONAL_SCHEDULED_PAYMENT"
  def payment_type(:international_periodic), do: "INTERNATIONAL_PERIODIC_PAYMENT"

  @doc """
  Returns the Yapily frequency string for a periodic payment.

  | Atom | String |
  |------|--------|
  | `:daily` | `"DAILY"` |
  | `:every_working_day` | `"EVERY_WORKING_DAY"` |
  | `:calendar_day` | `"CALENDAR_DAY"` |
  | `:weekly` | `"WEEKLY"` |
  | `:every_two_weeks` | `"EVERY_TWO_WEEKS"` |
  | `:monthly` | `"MONTHLY"` |
  | `:every_two_months` | `"EVERY_TWO_MONTHS"` |
  | `:quarterly` | `"QUARTERLY"` |
  | `:semi_annual` | `"SEMIANNUAL"` |
  | `:annual` | `"ANNUAL"` |
  """
  @spec frequency(
          :daily
          | :every_working_day
          | :calendar_day
          | :weekly
          | :every_two_weeks
          | :monthly
          | :every_two_months
          | :quarterly
          | :semi_annual
          | :annual
        ) ::
          String.t()
  def frequency(:daily), do: "DAILY"
  def frequency(:every_working_day), do: "EVERY_WORKING_DAY"
  def frequency(:calendar_day), do: "CALENDAR_DAY"
  def frequency(:weekly), do: "WEEKLY"
  def frequency(:every_two_weeks), do: "EVERY_TWO_WEEKS"
  def frequency(:monthly), do: "MONTHLY"
  def frequency(:every_two_months), do: "EVERY_TWO_MONTHS"
  def frequency(:quarterly), do: "QUARTERLY"
  def frequency(:semi_annual), do: "SEMIANNUAL"
  def frequency(:annual), do: "ANNUAL"

  @doc "Returns the Yapily consent status string for the given atom."
  @spec consent_status(:awaiting | :authorized | :rejected | :revoked | :failed | :expired) ::
          String.t()
  def consent_status(:awaiting), do: "AWAITING_AUTHORIZATION"
  def consent_status(:authorized), do: "AUTHORIZED"
  def consent_status(:rejected), do: "REJECTED"
  def consent_status(:revoked), do: "REVOKED"
  def consent_status(:failed), do: "FAILED"
  def consent_status(:expired), do: "EXPIRED"
end