accounted/extensions/general/enable-banking/lib/api-client.ts

/**
 * Enable Banking API integration for PSD2 bank connections
 *
 * Documentation: https://enablebanking.com/docs/api/reference/
 *
 * Flow:
 * 1. POST /auth → { url, authorization_id }
 * 2. User redirects to URL, authenticates with bank
 * 3. Callback receives ?code=XXX&state=YYY
 * 4. POST /sessions { code } → { session_id, accounts }
 * 5. GET /accounts/{uid}/balances
 * 6. GET /accounts/{uid}/transactions
 */

import { getAuthorizationHeader } from './jwt'
import { deriveTransactionLabel } from './transaction-label'
import { FALLBACK_DESCRIPTION } from '@/lib/transactions/external-id'
import { bankConnectorMode, CONNECTOR_COMPANY_HEADER } from '@/lib/connect/instance/upstreams'

// Prefer _PRODUCTION variant; sandbox uses api.tilisy.com, production uses api.enablebanking.com
const ENABLE_BANKING_API_URL =
  process.env.ENABLE_BANKING_API_URL_PRODUCTION ||
  process.env.ENABLE_BANKING_API_URL ||
  'https://api.enablebanking.com'

// Types

export interface ASPSP {
  name: string
  country: string
  logo?: string
  bic?: string
  beta?: boolean
  max_consent_validity?: number
  // Enable Banking returns this field as `auth_methods` on the ASPSP object.
  auth_methods?: AuthMethod[]
}

export interface AuthMethod {
  name: string
  title?: string
  // How the SCA is performed. Mobile BankID at several Swedish banks is a
  // DECOUPLED method; the visible default is often a REDIRECT method.
  approach?: 'REDIRECT' | 'DECOUPLED' | 'EMBEDDED'
  // When true, Enable Banking only uses this method if it is requested
  // explicitly via auth_method (it is not the implicit default).
  hidden_method?: boolean
  psu_types?: ('personal' | 'business')[]
}

export interface AuthResponse {
  url: string
  authorization_id: string
}

export interface SessionResponse {
  session_id: string
  access: {
    valid_until: string
  }
  accounts: AccountInfo[]
  aspsp: {
    name: string
    country: string
  }
  psu_type: string
  /**
   * Lifecycle state of the PSD2 session as Enable Banking sees it. Present on
   * GET /sessions/{id}; used by probeSessionHealth to detect a consent that
   * died bank-side without us attempting a transaction fetch.
   */
  status?: string
}

export interface AccountInfo {
  uid: string
  account_id?: {
    iban?: string
    bban?: string
    other?: string
  }
  name?: string
  product?: string
  currency: string
  identification_hash?: string
}

export interface Balance {
  balance_amount: {
    amount: string
    currency: string
  }
  balance_type: string
  reference_date?: string
  last_change_date_time?: string
}

export interface BalanceResponse {
  balances: Balance[]
}

export interface Transaction {
  entry_reference?: string
  transaction_id?: string
  booking_date?: string
  value_date?: string
  transaction_amount: {
    amount: string
    currency: string
  }
  credit_debit_indicator?: 'CRDT' | 'DBIT'  // CRDT = credit (income), DBIT = debit (expense)
  creditor_name?: string
  creditor_account?: {
    iban?: string
    bban?: string
  }
  creditor?: {
    name?: string
  }
  debtor_name?: string
  debtor_account?: {
    iban?: string
    bban?: string
  }
  debtor?: {
    name?: string
  }
  remittance_information?: string[]
  merchant_category_code?: string
  bank_transaction_code?: string
  proprietary_bank_transaction_code?: string
}

export interface TransactionsResponse {
  transactions: Transaction[]
  continuation_key?: string
}

/**
 * Strategy for how Enable Banking fetches transactions from the upstream ASPSP.
 * - 'default': fast path, may return only the most recent window even if date_from is older
 * - 'longest': fetch the longest available history (up to PSD2 90-day max), slower
 *
 * When omitted, Enable Banking applies its default strategy.
 */
export type TransactionsFetchStrategy = 'default' | 'longest'

export interface BankTransaction {
  id: string
  date: string
  booking_date: string
  amount: number
  currency: string
  description: string
  counterparty_name?: string
  counterparty_account?: string
  reference?: string
  merchant_category_code?: string
  // ISO 20022 / proprietary transaction codes: carried through so the
  // description fallback can derive a meaningful Swedish label when remittance
  // text and a counterparty name are both absent. See deriveTransactionLabel.
  bank_transaction_code?: string
  proprietary_bank_transaction_code?: string
}

// Constants
const FETCH_TIMEOUT_MS = 15_000
const MAX_RETRIES = 2
const RETRY_DELAY_MS = 1000
const MAX_PAGINATION_PAGES = 100
const DEFAULT_PAGE_SIZE = 500

/**
 * Thrown by getAccountTransactions on a non-OK response. Carries the HTTP
 * status and raw body so the pagination caller (getAllTransactions) can run the
 * same first-page strategy/window fallbacks as getAllTransactionsWithRaw. The
 * message is identical to the previous plain Error for back-compat.
 */
class TransactionsFetchError extends Error {
  constructor(
    readonly status: number,
    readonly body: string
  ) {
    super(`Failed to get transactions (${status}): ${body}`)
    this.name = 'TransactionsFetchError'
  }
}

/**
 * Normalized signatures (uppercase, non-alphanumerics stripped) of the
 * responses Enable Banking (or the upstream ASPSP via Enable Banking's
 * envelope) returns when the PSD2 session can no longer be used: the consent
 * was closed, expired, or invalidated bank-side. Spelling and casing vary by
 * bank (CLOSED_SESSION, EXPIRED_SESSION, SESSION_EXPIRED / session_expired,
 * INVALID_SESSION, SESSION_NOT_FOUND, WRONG_SESSION_STATUS, and the plain
 * "Session is closed" message), so we match the whole family. A dead session
 * is unrecoverable by retrying: the user must re-authorize.
 */
const SESSION_DEAD_NEEDLES = [
  'CLOSEDSESSION', // CLOSED_SESSION
  'SESSIONCLOSED', // "session closed"
  'SESSIONISCLOSED', // "Session is closed"
  'SESSIONEXPIRED', // SESSION_EXPIRED / session_expired
  'EXPIREDSESSION', // EXPIRED_SESSION
  'INVALIDSESSION', // INVALID_SESSION
  'SESSIONNOTFOUND', // SESSION_NOT_FOUND
  'WRONGSESSIONSTATUS', // WRONG_SESSION_STATUS
] as const

/**
 * Whether a failed transactions response signals a dead PSD2 session (vs. a
 * transient error or a config-level auth failure). Only 401/403 with a
 * session-expiry signal in the body counts: a bare 401 "Unauthorized" is an
 * app-credential problem, not a closed consent, and must NOT be misread as
 * "reconnect the bank". The match is deterministic: normalize the body and
 * test for any known session-dead needle.
 */
export function isSessionExpiredResponse(status: number, body: string): boolean {
  if (status !== 401 && status !== 403) return false
  const normalized = body.toUpperCase().replace(/[^A-Z0-9]/g, '')
  return SESSION_DEAD_NEEDLES.some(needle => normalized.includes(needle))
}

/**
 * User-facing (Swedish) messages persisted to bank_connections.error_message
 * and returned to the settings UI. error_message is a literal string in the
 * DB, not an i18n key, matching the extension's other user-facing strings.
 * Raw Enable Banking error bodies are English JSON envelopes and must never
 * land here: they belong in server logs only.
 */
export const REAUTH_REQUIRED_MESSAGE =
  'Bankanslutningen har löpt ut. Förnya anslutningen för att fortsätta synka.'
export const SYNC_FAILED_MESSAGE =
  'Banksynkningen misslyckades. Försök igen, eller förnya anslutningen om felet kvarstår.'

/**
 * Thrown when a transactions fetch fails because the PSD2 session is dead
 * (closed/expired/invalid). Distinct from TransactionsFetchError so the sync
 * handler can flip the connection to 'expired' and prompt re-authorization
 * instead of surfacing a raw error the user can't act on. Carries the status
 * and raw body for logging. See isSessionExpiredResponse for the codes covered.
 */
export class SessionExpiredError extends Error {
  constructor(
    readonly status: number,
    readonly body: string
  ) {
    super(`Bank session expired (${status}): ${body}`)
    this.name = 'SessionExpiredError'
  }
}

// API Helper

async function authenticatedFetch(
  endpoint: string,
  options: RequestInit = {}
): Promise<Response> {
  // Connector mode: a self-host with a connector key and no own Enable Banking
  // credentials routes every upstream call through the hosted bank proxy. The
  // proxy holds the real EB credentials and mints the JWT on its side, so the
  // instance sends the connector key as a Bearer token and NEVER calls
  // getAuthorizationHeader() (there is no private key to sign with here). When
  // this instance has its own EB credentials, or on hosted, bankConnectorMode()
  // returns null and the direct path below is byte-identical to before.
  const connector = bankConnectorMode()
  const url = connector ? `${connector.baseUrl}${endpoint}` : `${ENABLE_BANKING_API_URL}${endpoint}`
  const authorization = connector ? `Bearer ${connector.key}` : getAuthorizationHeader()
  const controller = new AbortController()
  const timeout = setTimeout(() => controller.abort(), FETCH_TIMEOUT_MS)

  try {
    const response = await fetch(url, {
      ...options,
      signal: controller.signal,
      headers: {
        'Authorization': authorization,
        'Content-Type': 'application/json',
        ...options.headers,
      },
    })

    return response
  } finally {
    clearTimeout(timeout)
  }
}

/**
 * Retry wrapper for idempotent read operations.
 * Retries on 429, 502, 503, 504, and AbortError (timeout).
 */
async function authenticatedFetchWithRetry(
  endpoint: string,
  options: RequestInit = {}
): Promise<Response> {
  for (let attempt = 0; attempt <= MAX_RETRIES; attempt++) {
    try {
      const response = await authenticatedFetch(endpoint, options)
      if (attempt < MAX_RETRIES && [429, 502, 503, 504].includes(response.status)) {
        // A 429 caused by a DAILY quota cannot clear within the retry window:
        // PSD2 unattended consents allow only a handful of balance calls per
        // day (observed body: "Consent daily limit 4 is exceeded"), so
        // retrying just burns time and duplicates the failure in logs. Read
        // the body from a clone so the returned response stays consumable.
        if (response.status === 429) {
          const body = await response.clone().text().catch(() => '')
          if (/daily limit/i.test(body)) {
            console.warn(`[enable-banking] 429 daily quota exhausted for ${endpoint}: not retrying`, {
              status: response.status,
              body,
            })
            return response
          }
        }
        console.warn(`[enable-banking] Retrying ${endpoint} (attempt ${attempt + 1}/${MAX_RETRIES})`, {
          status: response.status,
          statusText: response.statusText,
        })
        await new Promise(resolve => setTimeout(resolve, RETRY_DELAY_MS * (attempt + 1)))
        continue
      }
      return response
    } catch (error: unknown) {
      const isAbort = error instanceof Error && error.name === 'AbortError'
      if (attempt < MAX_RETRIES && isAbort) {
        console.warn(`[enable-banking] Request timeout, retrying ${endpoint} (attempt ${attempt + 1}/${MAX_RETRIES})`)
        await new Promise(resolve => setTimeout(resolve, RETRY_DELAY_MS * (attempt + 1)))
        continue
      }
      console.error(`[enable-banking] Request failed for ${endpoint}`, {
        attempt,
        error: error instanceof Error ? error.message : String(error),
        name: error instanceof Error ? error.name : undefined,
        isTimeout: isAbort,
      })
      throw error
    }
  }
  // Unreachable, but satisfies TypeScript
  throw new Error('Max retries exceeded')
}

// API Functions

/**
 * Get list of supported banks (ASPSPs) for a country
 */
export async function getASPSPs(country: string = 'SE', psuType?: 'personal' | 'business'): Promise<ASPSP[]> {
  const resolvedPsuType = psuType || process.env.ENABLE_BANKING_PSU_TYPE || 'business'
  const isSandbox = ENABLE_BANKING_API_URL.includes('tilisy')
  const params = new URLSearchParams({
    country,
    sandbox: String(isSandbox),
    psu_type: resolvedPsuType,
  })
  const response = await authenticatedFetchWithRetry(`/aspsps?${params.toString()}`)

  if (!response.ok) {
    const body = await response.text()
    console.error('[enable-banking] getASPSPs failed', {
      status: response.status,
      statusText: response.statusText,
      body,
      country,
      psuType: resolvedPsuType,
      sandbox: isSandbox,
      apiUrl: ENABLE_BANKING_API_URL,
    })
    throw new Error(`Failed to fetch banks (${response.status})`)
  }

  const data = await response.json()
  return data.aspsps || []
}

/**
 * Pick the DECOUPLED auth method worth pinning explicitly, or undefined to let
 * Enable Banking run the ASPSP's default flow.
 *
 * A method is only pinned when pinning is both NECESSARY and APPLICABLE:
 *
 * - hidden_method === true: a hidden method is never used unless requested
 *   explicitly via auth_method, so pinning is the only way to reach it. That
 *   is the Handelsbanken case: its Mobile BankID (DECOUPLED) is hidden, and
 *   without pinning it corporate PSUs fail right after approving in the
 *   BankID app ("fel efter BankID"). A VISIBLE decoupled method is already
 *   part of the bank's own default flow; force-pinning it overrides a working
 *   default. That regression (from PR #854) broke Lunar-class banks: the user
 *   typed their personnummer on Enable Banking's page, was told to approve in
 *   the bank's app, and no approval request ever arrived.
 * - psu_types, when present and non-empty, must include the PSU type we are
 *   authorizing as: a method scoped to 'personal' must never be pinned for a
 *   'business' consent (and vice versa). A missing or empty psu_types means
 *   the method applies to all PSU types.
 */
export function selectPreferredAuthMethod(
  authMethods: AuthMethod[] | undefined,
  psuType: 'personal' | 'business'
): AuthMethod | undefined {
  return authMethods?.find(
    (m) =>
      m.approach === 'DECOUPLED' &&
      m.hidden_method === true &&
      (!m.psu_types || m.psu_types.length === 0 || m.psu_types.includes(psuType))
  )
}

/**
 * Resolve the auth method to pin for a given bank, with full metadata so the
 * caller can log approach/hidden_method/psu_types, or undefined to let Enable
 * Banking use the ASPSP's default flow. Selection rules live in
 * selectPreferredAuthMethod. Returns undefined on lookup failure so banks
 * that already work are untouched.
 */
export async function getPreferredAuthMethodDetails(
  aspspName: string,
  country: string,
  psuType: 'personal' | 'business'
): Promise<AuthMethod | undefined> {
  try {
    const aspsps = await getASPSPs(country, psuType)
    const aspsp = aspsps.find((a) => a.name === aspspName)
    return selectPreferredAuthMethod(aspsp?.auth_methods, psuType)
  } catch (error) {
    console.error('[enable-banking] getPreferredAuthMethod failed; using ASPSP default', {
      aspspName,
      country,
      psuType,
      error: error instanceof Error ? error.message : String(error),
    })
    return undefined
  }
}

/**
 * Name-only convenience wrapper around getPreferredAuthMethodDetails: the
 * value to send as auth_method on POST /auth, or undefined for the ASPSP
 * default.
 */
export async function getPreferredAuthMethod(
  aspspName: string,
  country: string,
  psuType: 'personal' | 'business'
): Promise<string | undefined> {
  const method = await getPreferredAuthMethodDetails(aspspName, country, psuType)
  return method?.name
}

/**
 * Start bank authorization flow
 *
 * @param aspspName - The name of the ASPSP (bank) exactly as returned from /aspsps
 * @param aspspCountry - The country code (e.g., 'SE')
 * @param redirectUrl - URL to redirect user after bank authorization
 * @param state - State parameter returned in callback (e.g., user ID)
 * @param psuType - Type of user: 'personal' or 'business'
 * @param authMethod - Optional Enable Banking auth_method name. When omitted,
 *   Enable Banking uses the ASPSP's visible default method. See
 *   getPreferredAuthMethod for why we pin Mobile BankID at some banks.
 */
export async function startAuthorization(
  aspspName: string,
  aspspCountry: string,
  redirectUrl: string,
  state: string,
  psuType: 'personal' | 'business' = 'personal',
  authMethod?: string,
  companyId?: string
): Promise<AuthResponse> {
  // Calculate consent validity (90 days)
  const validUntil = new Date()
  validUntil.setDate(validUntil.getDate() + 90)

  const requestBody: {
    access: { valid_until: string }
    aspsp: { name: string; country: string }
    state: string
    redirect_url: string
    psu_type: 'personal' | 'business'
    auth_method?: string
  } = {
    access: {
      valid_until: validUntil.toISOString()
    },
    aspsp: {
      name: aspspName,
      country: aspspCountry
    },
    state,
    redirect_url: redirectUrl,
    psu_type: psuType
  }
  if (authMethod) {
    requestBody.auth_method = authMethod
  }

  // In connector mode the hosted bank proxy meters the per-company connection
  // quota, so it needs to know which company this authorization is for. This is
  // gated on bankConnectorMode(), NOT merely on companyId: on hosted and on
  // own-credentials self-hosts companyId is always set, and sending an internal
  // company UUID to the real Enable Banking API is both a needless behavior
  // change and an identifier leak to a third-party processor. Off the connector
  // path the direct request stays byte-identical.
  const authHeaders =
    companyId && bankConnectorMode() ? { [CONNECTOR_COMPANY_HEADER]: companyId } : undefined

  const response = await authenticatedFetch('/auth', {
    method: 'POST',
    body: JSON.stringify(requestBody),
    ...(authHeaders ? { headers: authHeaders } : {}),
  })

  if (!response.ok) {
    const body = await response.text()
    console.error('[enable-banking] startAuthorization failed', {
      status: response.status,
      statusText: response.statusText,
      body,
      aspspName,
      aspspCountry,
      psuType,
      redirectUrl,
      apiUrl: ENABLE_BANKING_API_URL,
      requestBody: JSON.stringify(requestBody),
    })
    throw new Error(`Failed to start bank connection (${response.status}): ${body}`)
  }

  return response.json()
}

/**
 * Create a session after user completes bank authorization
 *
 * @param code - The authorization code from callback
 * @param connectorState - The signed connector state echoed back through the
 *   hosted callback in connector mode. The bank proxy binds the /sessions
 *   exchange to the pending row it signed at /auth time (single-use, race-safe),
 *   so it is required in connector mode and absent on the direct path.
 */
export async function createSession(code: string, connectorState?: string): Promise<SessionResponse> {
  const response = await authenticatedFetch('/sessions', {
    method: 'POST',
    body: JSON.stringify(connectorState ? { code, connector_state: connectorState } : { code })
  })

  if (!response.ok) {
    const body = await response.text()
    console.error('[enable-banking] createSession failed', {
      status: response.status,
      statusText: response.statusText,
      body,
      hasCode: !!code,
      codeLength: code?.length,
      apiUrl: ENABLE_BANKING_API_URL,
    })
    throw new Error(`Failed to create bank session (${response.status}): ${body}`)
  }

  return response.json()
}

/**
 * Get session details
 *
 * @param sessionId - The session ID
 */
export async function getSession(sessionId: string): Promise<SessionResponse> {
  const response = await authenticatedFetchWithRetry(`/sessions/${sessionId}`)

  if (!response.ok) {
    const body = await response.text()
    console.error('[enable-banking] getSession failed', {
      status: response.status,
      statusText: response.statusText,
      body,
      sessionId,
    })
    throw new Error(`Failed to get session (${response.status}): ${body}`)
  }

  return response.json()
}

/**
 * Session lifecycle values that mean the consent can no longer be used. Kept
 * deliberately narrow: an unrecognized status resolves to 'unknown' and leaves
 * the stored connection state untouched, because wrongly flipping a live
 * connection to 'expired' costs the user a full BankID re-authorization.
 */
const SESSION_DEAD_STATUSES = new Set([
  'CANCELLED',
  'CLOSED',
  'EXPIRED',
  'INVALID',
  'REJECTED',
  'REVOKED',
])

/**
 * Session lifecycle values that mean the consent is usable. Anything outside
 * both sets (including a response carrying no status at all) is 'unknown':
 * claiming 'alive' for a value we do not recognize would be asserting more
 * than the probe actually established.
 */
const SESSION_ALIVE_STATUSES = new Set(['AUTHORIZED', 'VALID', 'ACTIVE'])

export type SessionHealth = 'alive' | 'dead' | 'unknown'

/**
 * Ask Enable Banking whether a PSD2 session is still usable, without fetching
 * any account data.
 *
 * Until this existed, a connection only ever learned its session was dead by
 * TRYING to sync: a bank that invalidates a consent server-side (several
 * ASPSPs drop the previous session when the same PSU authorizes again) left
 * the row sitting at status 'active' with a stale last_synced_at, so the UI
 * kept presenting old balances as current. Never throws: probing is a
 * best-effort health signal, and 'unknown' is always a safe answer.
 */
export async function probeSessionHealth(sessionId: string): Promise<SessionHealth> {
  try {
    const response = await authenticatedFetchWithRetry(`/sessions/${sessionId}`)
    const body = await response.text()

    if (!response.ok) {
      if (isSessionExpiredResponse(response.status, body)) return 'dead'
      // The session record itself is gone: nothing left to sync with.
      if (response.status === 404) return 'dead'
      return 'unknown'
    }

    try {
      const parsed = JSON.parse(body) as SessionResponse
      const status = typeof parsed.status === 'string' ? parsed.status.toUpperCase() : null
      if (status && SESSION_DEAD_STATUSES.has(status)) return 'dead'
      if (status && SESSION_ALIVE_STATUSES.has(status)) return 'alive'
    } catch {
      // Unparseable body on a 200: treat as inconclusive, not as dead.
      return 'unknown'
    }
    return 'unknown'
  } catch (error) {
    console.warn('[enable-banking] probeSessionHealth failed', {
      sessionId,
      error: error instanceof Error ? error.message : String(error),
    })
    return 'unknown'
  }
}

/**
 * Delete/revoke a session
 *
 * @param sessionId - The session ID to revoke
 */
export async function deleteSession(sessionId: string): Promise<void> {
  const response = await authenticatedFetch(`/sessions/${sessionId}`, {
    method: 'DELETE'
  })

  if (!response.ok) {
    const body = await response.text()
    // A session Enable Banking has already dropped (404, or a 401/403 naming
    // an expired/closed session) is the expected answer when we revoke a
    // connection whose PSD2 consent ran out: every caller catches and carries
    // on, so it does not belong in the error panel.
    const alreadyGone = response.status === 404 || isSessionExpiredResponse(response.status, body)
    const logLine = {
      status: response.status,
      statusText: response.statusText,
      body,
      sessionId,
    }
    if (alreadyGone) {
      console.warn('[enable-banking] deleteSession: session already gone at Enable Banking', logLine)
    } else {
      console.error('[enable-banking] deleteSession failed', logLine)
    }
    throw new Error(`Failed to revoke session (${response.status}): ${body}`)
  }
}

/**
 * Get account balances
 *
 * @param accountUid - The account UID (from session.accounts[].uid)
 */
export async function getAccountBalances(accountUid: string): Promise<Balance[]> {
  const response = await authenticatedFetchWithRetry(`/accounts/${accountUid}/balances`)

  if (!response.ok) {
    const body = await response.text()
    console.error('[enable-banking] getAccountBalances failed', {
      status: response.status,
      statusText: response.statusText,
      body,
      accountUid,
    })
    throw new Error(`Failed to get account balances (${response.status}): ${body}`)
  }

  const data: BalanceResponse = await response.json()
  return data.balances || []
}

// Balance-type preference orders. ASPSPs report types either as camelCase
// names or ISO 20022 codes; both spellings of each type are accepted,
// case-insensitively. Booked answers "what has the bank settled", available
// answers "what can be spent right now" (the covering-decision number).
// closingBooked (settled, definitive) wins over expected, which wins over
// interimBooked (intraday booked): fall through to less-final booked types
// only when the stabler one is absent, and to the generic first-entry
// fallback only when no booked type exists at all.
const BOOKED_BALANCE_TYPES = ['closingbooked', 'clbd', 'expected', 'xpcd', 'interimbooked', 'itbd']
const AVAILABLE_BALANCE_TYPES = [
  'interimavailable',
  'itav',
  'closingavailable',
  'clav',
  'forwardavailable',
  'fwav',
]

function pickBalanceByType(balances: Balance[], preference: string[]): Balance | undefined {
  for (const type of preference) {
    const match = balances.find(b => b.balance_type?.toLowerCase() === type)
    if (match) return match
  }
  return undefined
}

/**
 * Get account balance from one BALANCES call: the booked amount (falling back
 * to the first reported balance, as before) plus the available amount when the
 * ASPSP reports one. One call: both figures come from the same quota-limited
 * response, so exposing `available` costs nothing extra.
 *
 * Returns null when the ASPSP reports NO balances at all. The old behavior
 * fabricated `amount: 0` here; once balances became user-facing ("how much
 * money is in the bank", covering decisions before payment runs) a fabricated
 * zero with a fresh timestamp is dangerous, so the caller keeps its previous
 * stored value instead.
 */
export async function getAccountBalance(
  accountUid: string
): Promise<{ amount: number; date: string; available: number | null } | null> {
  const balances = await getAccountBalances(accountUid)

  // Prefer closingBooked, then expected, then first available
  const balance = pickBalanceByType(balances, BOOKED_BALANCE_TYPES) || balances[0]

  if (!balance) {
    return null
  }

  const availableBalance = pickBalanceByType(balances, AVAILABLE_BALANCE_TYPES)
  const available = availableBalance
    ? parseFloat(availableBalance.balance_amount.amount)
    : null

  return {
    amount: parseFloat(balance.balance_amount.amount),
    date: balance.reference_date || new Date().toISOString().split('T')[0],
    available: available != null && Number.isFinite(available) ? available : null,
  }
}

/**
 * Get account transactions
 *
 * @param accountUid - The account UID
 * @param dateFrom - Start date (YYYY-MM-DD)
 * @param dateTo - End date (YYYY-MM-DD)
 * @param continuationKey - Pagination key from previous response
 */
export async function getAccountTransactions(
  accountUid: string,
  dateFrom?: string,
  dateTo?: string,
  continuationKey?: string,
  strategy?: TransactionsFetchStrategy
): Promise<TransactionsResponse> {
  const params = new URLSearchParams()
  if (dateFrom) params.set('date_from', dateFrom)
  if (dateTo) params.set('date_to', dateTo)
  if (continuationKey) params.set('continuation_key', continuationKey)
  if (strategy) params.set('strategy', strategy)
  params.set('limit', String(DEFAULT_PAGE_SIZE))

  const queryString = params.toString()
  const endpoint = `/accounts/${accountUid}/transactions${queryString ? `?${queryString}` : ''}`

  const response = await authenticatedFetchWithRetry(endpoint)

  if (!response.ok) {
    const body = await response.text()
    console.error('[enable-banking] getAccountTransactions failed', {
      status: response.status,
      statusText: response.statusText,
      body,
      accountUid,
      dateFrom,
      dateTo,
      strategy,
      hasContinuationKey: !!continuationKey,
    })
    if (isSessionExpiredResponse(response.status, body)) {
      throw new SessionExpiredError(response.status, body)
    }
    throw new TransactionsFetchError(response.status, body)
  }

  return response.json()
}

/**
 * Get all transactions with pagination
 */
export async function getAllTransactions(
  accountUid: string,
  dateFrom?: string,
  dateTo?: string,
  strategy?: TransactionsFetchStrategy
): Promise<Transaction[]> {
  const allTransactions: Transaction[] = []
  let continuationKey: string | undefined
  let page = 0
  let activeStrategy = strategy
  // date_from is narrowed in place when the ASPSP rejects the window (below).
  let activeDateFrom = dateFrom

  while (true) {
    let response: TransactionsResponse
    try {
      response = await getAccountTransactions(
        accountUid,
        activeDateFrom,
        dateTo,
        continuationKey,
        activeStrategy
      )
    } catch (err) {
      // Apply the same first-page recovery as getAllTransactionsWithRaw. Only
      // TransactionsFetchError carries the status/body needed to decide;
      // network errors and the like propagate untouched.
      if (err instanceof TransactionsFetchError) {
        const recovery = planFirstPageRecovery({
          status: err.status,
          body: err.body,
          page,
          hasContinuationKey: !!continuationKey,
          activeStrategy,
          activeDateFrom,
          dateTo,
        })
        if (recovery.type === 'drop-strategy') {
          console.warn('[enable-banking] strategy rejected by API, retrying without strategy', {
            accountUid,
            strategy: activeStrategy,
            body: err.body,
          })
          activeStrategy = undefined
          continue
        }
        if (recovery.type === 'narrow') {
          console.warn('[enable-banking] ASPSP rejected history window, retrying with narrower date_from', {
            accountUid,
            previousDateFrom: activeDateFrom,
            nextDateFrom: recovery.dateFrom,
            dateTo,
            body: err.body,
          })
          activeDateFrom = recovery.dateFrom
          continue
        }
      }
      throw err
    }

    allTransactions.push(...response.transactions)
    continuationKey = response.continuation_key
    page++

    if (page >= MAX_PAGINATION_PAGES) {
      console.warn(`[enable-banking] Pagination cap reached (${MAX_PAGINATION_PAGES} pages) for account ${accountUid}`)
      break
    }
    if (!continuationKey) break
  }

  return allTransactions
}

/**
 * Lookback windows (days before date_to) we step through when an ASPSP rejects
 * the requested transaction history. Descending so each fallback yields a
 * strictly narrower window. PSD2 obliges banks to ~90 days without fresh SCA;
 * the smaller rungs cover banks that cap below that.
 */
const ASPSP_HISTORY_FALLBACK_DAYS = [90, 60, 30] as const

/**
 * Enable Banking wraps upstream-bank failures in a generic envelope, e.g.
 * {"code":400,"message":"Error interacting with ASPSP","error":"ASPSP_ERROR"}.
 * A too-wide history window is the most common trigger: see the date-narrowing
 * fallback in getAllTransactionsWithRaw.
 */
function isAspspError(body: string): boolean {
  return body.includes('ASPSP_ERROR') || body.includes('interacting with ASPSP')
}

/**
 * Given the date_from we just tried, return the next strictly-narrower
 * date_from from ASPSP_HISTORY_FALLBACK_DAYS, anchored to date_to. Returns
 * undefined when no narrower window remains (or date_to is missing), which
 * ends the retry loop. The "strictly narrower" guard keeps the loop monotonic
 * and terminating even if the original window was already short.
 */
function nextNarrowerDateFrom(
  currentDateFrom: string | undefined,
  dateTo: string | undefined
): string | undefined {
  if (!dateTo) return undefined
  const anchor = new Date(`${dateTo}T00:00:00Z`)
  if (!Number.isFinite(anchor.getTime())) return undefined

  for (const days of ASPSP_HISTORY_FALLBACK_DAYS) {
    const candidate = new Date(anchor.getTime() - days * 24 * 60 * 60 * 1000)
      .toISOString()
      .split('T')[0]
    if (!currentDateFrom || candidate > currentDateFrom) {
      return candidate
    }
  }
  return undefined
}

/**
 * First-page recovery policy shared by getAllTransactions and
 * getAllTransactionsWithRaw, so the two pagination loops can't drift. Fallbacks
 * apply only to the very first request (page 0, no continuation_key): a
 * continuation_key is scoped to the window/strategy that produced it, so the
 * query is never rewritten mid-pagination.
 *
 *  - 'drop-strategy' : an unsupported strategy enum: retry the same window.
 *  - 'narrow'        : the ASPSP rejected the history window: retry with a
 *                      narrower date_from (the bank caps history below the ask).
 *  - 'give-up'       : nothing left to try; the caller should rethrow.
 */
type FirstPageRecovery =
  | { type: 'drop-strategy' }
  | { type: 'narrow'; dateFrom: string }
  | { type: 'give-up' }

function planFirstPageRecovery(args: {
  status: number
  body: string
  page: number
  hasContinuationKey: boolean
  activeStrategy: TransactionsFetchStrategy | undefined
  activeDateFrom: string | undefined
  dateTo: string | undefined
}): FirstPageRecovery {
  const { status, body, page, hasContinuationKey, activeStrategy, activeDateFrom, dateTo } = args
  if (status !== 400 || page !== 0 || hasContinuationKey) return { type: 'give-up' }
  // Drop an unsupported strategy first: preserves the full requested window.
  if (activeStrategy) return { type: 'drop-strategy' }
  // Then handle the ASPSP rejecting the window itself (e.g. Danske past ~90
  // days): step date_from toward date_to so a partial sync survives.
  if (isAspspError(body)) {
    const dateFrom = nextNarrowerDateFrom(activeDateFrom, dateTo)
    if (dateFrom) return { type: 'narrow', dateFrom }
  }
  return { type: 'give-up' }
}

/**
 * Get all transactions with raw JSON responses for archival.
 * Returns both parsed transactions and the raw response strings.
 *
 * If `strategy` is provided and the API rejects it with a 400 on the first
 * request, retry once without `strategy` so unknown enum values can't break
 * the sync. Logs a warning when the fallback fires.
 *
 * If the ASPSP then still rejects the first page with an ASPSP_ERROR (typically
 * a history window beyond the bank's PSD2 limit, e.g. Danske past ~90 days),
 * progressively narrow date_from toward date_to (90→60→30 days) so a partial
 * sync of the recent window survives instead of failing outright. Logs a
 * warning on each narrowing.
 */
export async function getAllTransactionsWithRaw(
  accountUid: string,
  dateFrom?: string,
  dateTo?: string,
  strategy?: TransactionsFetchStrategy
): Promise<{ transactions: Transaction[]; rawPages: string[] }> {
  const allTransactions: Transaction[] = []
  const rawPages: string[] = []
  let continuationKey: string | undefined
  let page = 0
  let activeStrategy = strategy
  // date_from is narrowed in place when the ASPSP rejects the window (below).
  let activeDateFrom = dateFrom

  while (true) {
    const params = new URLSearchParams()
    if (activeDateFrom) params.set('date_from', activeDateFrom)
    if (dateTo) params.set('date_to', dateTo)
    if (continuationKey) params.set('continuation_key', continuationKey)
    if (activeStrategy) params.set('strategy', activeStrategy)
    params.set('limit', String(DEFAULT_PAGE_SIZE))

    const queryString = params.toString()
    const endpoint = `/accounts/${accountUid}/transactions${queryString ? `?${queryString}` : ''}`

    const response = await authenticatedFetchWithRetry(endpoint)

    if (!response.ok) {
      const body = await response.text()
      const recovery = planFirstPageRecovery({
        status: response.status,
        body,
        page,
        hasContinuationKey: !!continuationKey,
        activeStrategy,
        activeDateFrom,
        dateTo,
      })
      if (recovery.type === 'drop-strategy') {
        console.warn('[enable-banking] strategy rejected by API, retrying without strategy', {
          accountUid,
          strategy: activeStrategy,
          body,
        })
        activeStrategy = undefined
        continue
      }
      if (recovery.type === 'narrow') {
        console.warn('[enable-banking] ASPSP rejected history window, retrying with narrower date_from', {
          accountUid,
          previousDateFrom: activeDateFrom,
          nextDateFrom: recovery.dateFrom,
          dateTo,
          body,
        })
        activeDateFrom = recovery.dateFrom
        continue
      }
      // An expired PSD2 session is an expected end of life for a consent, not
      // a failure: SessionExpiredError below flips the connection to 'expired'
      // and asks the user to re-authorize. Log it at warn so only the genuine
      // ASPSP/upstream failures reach the error panel.
      const sessionExpired = isSessionExpiredResponse(response.status, body)
      const logLine = {
        status: response.status,
        statusText: response.statusText,
        body,
        accountUid,
        dateFrom: activeDateFrom,
        dateTo,
        strategy: activeStrategy,
        page,
        hasContinuationKey: !!continuationKey,
      }
      if (sessionExpired) {
        console.warn('[enable-banking] getAllTransactionsWithRaw: bank session expired', logLine)
        throw new SessionExpiredError(response.status, body)
      }
      console.error('[enable-banking] getAllTransactionsWithRaw failed', logLine)
      throw new Error(`Failed to get transactions (${response.status}): ${body}`)
    }

    const rawText = await response.text()
    rawPages.push(rawText)

    const data: TransactionsResponse = JSON.parse(rawText)
    allTransactions.push(...data.transactions)
    continuationKey = data.continuation_key
    page++

    if (page >= MAX_PAGINATION_PAGES) {
      console.warn(`[enable-banking] Pagination cap reached (${MAX_PAGINATION_PAGES} pages) for account ${accountUid}`)
      break
    }
    if (!continuationKey) break
  }

  return { transactions: allTransactions, rawPages }
}

/**
 * Convert Enable Banking transaction to legacy format
 */
export function convertTransaction(tx: Transaction, accountCurrency: string): BankTransaction {
  const rawAmount = parseFloat(tx.transaction_amount.amount)

  // Use credit_debit_indicator to determine sign
  // CRDT = credit (money in) = positive
  // DBIT = debit (money out) = negative
  const isCredit = tx.credit_debit_indicator === 'CRDT'
  const amount = isCredit ? Math.abs(rawAmount) : -Math.abs(rawAmount)

  // Get counterparty name from creditor/debtor objects or direct fields
  const creditorName = tx.creditor?.name || tx.creditor_name
  const debtorName = tx.debtor?.name || tx.debtor_name

  return {
    id: tx.entry_reference || tx.transaction_id || `${tx.booking_date}_${rawAmount}`,
    date: tx.value_date || tx.booking_date || new Date().toISOString().split('T')[0],
    booking_date: tx.booking_date || tx.value_date || new Date().toISOString().split('T')[0],
    amount,
    currency: tx.transaction_amount.currency || accountCurrency,
    // Fallback chain: bank's payment message → counterparty name → a Swedish
    // label derived from the ISO 20022 / MCC codes the bank DID send (card
    // purchases, ATM, fees, interest) → 'Okänd transaktion'. The final fallback
    // is also normalized at the ingest boundary, so any leftover lands as the
    // same Swedish neutral.
    description: tx.remittance_information?.filter(r => r.trim()).join(' ') ||
                 (isCredit ? debtorName : creditorName) ||
                 deriveTransactionLabel({
                   bankTransactionCode: tx.bank_transaction_code,
                   proprietaryBankTransactionCode: tx.proprietary_bank_transaction_code,
                   mcc: tx.merchant_category_code,
                   isCredit,
                 }) ||
                 FALLBACK_DESCRIPTION,
    counterparty_name: isCredit ? debtorName : creditorName,
    counterparty_account: isCredit
      ? tx.debtor_account?.iban || tx.debtor_account?.bban
      : tx.creditor_account?.iban || tx.creditor_account?.bban,
    merchant_category_code: tx.merchant_category_code,
    bank_transaction_code: tx.bank_transaction_code,
    proprietary_bank_transaction_code: tx.proprietary_bank_transaction_code,
  }
}

/**
 * Whether the current configuration targets the sandbox API
 */
export function isSandboxMode(): boolean {
  return ENABLE_BANKING_API_URL.includes('tilisy')
}

// Utility functions

/**
 * Check if consent is expiring soon (within 7 days)
 */
export function isConsentExpiringSoon(expiresAt: string | null): boolean {
  if (!expiresAt) return false

  const expiryDate = new Date(expiresAt)
  const warningDate = new Date()
  warningDate.setDate(warningDate.getDate() + 7)

  return expiryDate <= warningDate
}

/**
 * Get days until consent expires
 */
export function getDaysUntilExpiry(expiresAt: string | null): number | null {
  if (!expiresAt) return null

  const expiryDate = new Date(expiresAt)
  const now = new Date()
  const diffTime = expiryDate.getTime() - now.getTime()
  const diffDays = Math.ceil(diffTime / (1000 * 60 * 60 * 24))

  return Math.max(0, diffDays)
}