/**
 * 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'

// 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
  available_auth_methods?: AuthMethod[]
}

export interface AuthMethod {
  name: string
  title?: string
  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
}

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
}

// Legacy types for backward compatibility
export interface Bank {
  id: string
  name: string
  bic?: string
  countries: string[]
  logo_url?: string
}

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
}

// API Helper

async function authenticatedFetch(
  endpoint: string,
  options: RequestInit = {}
): Promise<Response> {
  const url = `${ENABLE_BANKING_API_URL}${endpoint}`

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

  return response
}

// API Functions

/**
 * Get list of supported banks (ASPSPs) for a country
 */
export async function getASPSPs(country: string = 'SE'): Promise<ASPSP[]> {
  const response = await authenticatedFetch(`/aspsps?country=${country}`)

  if (!response.ok) {
    const error = await response.text()
    console.error('Failed to fetch ASPSPs:', error)
    throw new Error('Failed to fetch banks')
  }

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

/**
 * Get list of supported banks (legacy format for backward compatibility)
 */
export async function getSupportedBanks(): Promise<Bank[]> {
  try {
    const aspsps = await getASPSPs('SE')

    return aspsps.map((aspsp) => ({
      id: `${aspsp.name.toLowerCase().replace(/\s+/g, '-')}-se`,
      name: aspsp.name,
      bic: aspsp.bic,
      countries: [aspsp.country],
      logo_url: aspsp.logo,
    }))
  } catch (error) {
    console.error('Error fetching banks:', error)
    // Return fallback list
    return [
      { id: 'nordea-se', name: 'Nordea', bic: 'NDEASESS', countries: ['SE'] },
      { id: 'seb-se', name: 'SEB', bic: 'ESSESESS', countries: ['SE'] },
      { id: 'swedbank-se', name: 'Swedbank', bic: 'SWEDSESS', countries: ['SE'] },
      { id: 'handelsbanken-se', name: 'Handelsbanken', bic: 'HANDSESS', countries: ['SE'] },
    ]
  }
}

/**
 * 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'
 */
export async function startAuthorization(
  aspspName: string,
  aspspCountry: string,
  redirectUrl: string,
  state: string,
  psuType: 'personal' | 'business' = 'personal'
): Promise<AuthResponse> {
  // Calculate consent validity (90 days)
  const validUntil = new Date()
  validUntil.setDate(validUntil.getDate() + 90)

  const requestBody = {
    access: {
      valid_until: validUntil.toISOString()
    },
    aspsp: {
      name: aspspName,
      country: aspspCountry
    },
    state,
    redirect_url: redirectUrl,
    psu_type: psuType
  }

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

  if (!response.ok) {
    const error = await response.text()
    console.error('Failed to start authorization:', error)
    throw new Error('Failed to start bank connection')
  }

  return response.json()
}

/**
 * Create a session after user completes bank authorization
 *
 * @param code - The authorization code from callback
 */
export async function createSession(code: string): Promise<SessionResponse> {
  const response = await authenticatedFetch('/sessions', {
    method: 'POST',
    body: JSON.stringify({ code })
  })

  if (!response.ok) {
    const error = await response.text()
    console.error('Failed to create session:', error)
    throw new Error('Failed to create bank session')
  }

  return response.json()
}

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

  if (!response.ok) {
    throw new Error('Failed to get session')
  }

  return response.json()
}

/**
 * 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) {
    throw new Error('Failed to revoke session')
  }
}

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

  if (!response.ok) {
    throw new Error('Failed to get account balances')
  }

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

/**
 * Get account balance (returns booked balance amount)
 */
export async function getAccountBalance(
  accountUid: string
): Promise<{ amount: number; date: string }> {
  const balances = await getAccountBalances(accountUid)

  // Prefer closingBooked, then expected, then first available
  const balance =
    balances.find(b => b.balance_type === 'closingBooked') ||
    balances.find(b => b.balance_type === 'expected') ||
    balances[0]

  if (!balance) {
    return { amount: 0, date: new Date().toISOString().split('T')[0] }
  }

  return {
    amount: parseFloat(balance.balance_amount.amount),
    date: balance.reference_date || new Date().toISOString().split('T')[0]
  }
}

/**
 * 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
): 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)

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

  const response = await authenticatedFetch(endpoint)

  if (!response.ok) {
    throw new Error('Failed to get transactions')
  }

  return response.json()
}

/**
 * Get all transactions with pagination
 */
export async function getAllTransactions(
  accountUid: string,
  dateFrom?: string,
  dateTo?: string
): Promise<Transaction[]> {
  const allTransactions: Transaction[] = []
  let continuationKey: string | undefined

  do {
    const response = await getAccountTransactions(
      accountUid,
      dateFrom,
      dateTo,
      continuationKey
    )

    allTransactions.push(...response.transactions)
    continuationKey = response.continuation_key
  } while (continuationKey)

  return allTransactions
}

/**
 * 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,
    description: tx.remittance_information?.filter(r => r.trim()).join(' ') ||
                 (isCredit ? debtorName : creditorName) ||
                 'Unknown',
    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
  }
}

/**
 * Get transactions in legacy format
 */
export async function getTransactions(
  accountUid: string,
  fromDate?: string,
  toDate?: string,
  accountCurrency: string = 'SEK'
): Promise<BankTransaction[]> {
  const transactions = await getAllTransactions(accountUid, fromDate, toDate)
  return transactions.map(tx => convertTransaction(tx, accountCurrency))
}

// 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)
}