sure/app/models/enable_banking_item/importer.rb

class EnableBankingItem::Importer
  # Maximum number of pagination requests to prevent infinite loops
  # Enable Banking typically returns ~100 transactions per page, so 100 pages = ~10,000 transactions
  MAX_PAGINATION_PAGES = 100

  # Balance type priority: prefer booked balances over available balances.
  # Available types (CLAV, ITAV) include overdraft/credit capacity and inflate balances.
  BALANCE_TYPE_PRIORITY = %w[CLBD XPCD ITBD CLAV ITAV].freeze

  attr_reader :enable_banking_item, :enable_banking_provider

  def initialize(enable_banking_item, enable_banking_provider:)
    @enable_banking_item = enable_banking_item
    @enable_banking_provider = enable_banking_provider
  end

  def import
    unless enable_banking_item.session_valid?
      enable_banking_item.update!(status: :requires_update)
      return { success: false, error: "Session expired or invalid", accounts_updated: 0, transactions_imported: 0 }
    end

    session_data = fetch_session_data
    unless session_data
      error_msg = @session_error || "Failed to fetch session data"
      return { success: false, error: error_msg, accounts_updated: 0, transactions_imported: 0 }
    end

    # Store raw payload
    begin
      enable_banking_item.upsert_enable_banking_snapshot!(session_data)
    rescue => e
      Rails.logger.error "EnableBankingItem::Importer - Failed to store session snapshot: #{e.message}"
    end

    # Update accounts from session
    accounts_updated = 0
    accounts_failed = 0

    if session_data[:accounts].present?
      existing_uids = enable_banking_item.enable_banking_accounts
                                         .joins(:account_provider)
                                         .pluck(:uid)
                                         .map(&:to_s)

      # Enable Banking API returns accounts as an array of UIDs (strings) in the session response
      # We need to handle both array of strings and array of hashes
      session_data[:accounts].each do |account_data|
        # Handle both string UIDs and hash objects
        # Use identification_hash as the stable identifier across sessions
        uid = if account_data.is_a?(String)
          account_data
        elsif account_data.is_a?(Hash)
          (account_data[:identification_hash] || account_data[:uid] || account_data["identification_hash"] || account_data["uid"])&.to_s
        else
          nil
        end

        next unless uid.present?

        # Only update if this account was previously linked
        next unless existing_uids.include?(uid)

        begin
          # For string UIDs, we don't have account data to update - skip the import_account call
          # The account data will be fetched via balances/transactions endpoints
          if account_data.is_a?(Hash)
            import_account(account_data)
            accounts_updated += 1
          end
        rescue => e
          accounts_failed += 1
          Rails.logger.error "EnableBankingItem::Importer - Failed to update account #{uid}: #{e.message}"
        end
      end
    end

    # Fetch balances and transactions for linked accounts
    transactions_imported = 0
    transactions_failed = 0

    linked_accounts_query = enable_banking_item.enable_banking_accounts.joins(:account_provider).joins(:account).merge(Account.visible)

    linked_accounts_query.each do |enable_banking_account|
      begin
        fetch_and_update_balance(enable_banking_account)

        result = fetch_and_store_transactions(enable_banking_account)
        if result[:success]
          transactions_imported += result[:transactions_count]
        else
          transactions_failed += 1
        end
      rescue => e
        transactions_failed += 1
        Rails.logger.error "EnableBankingItem::Importer - Failed to process account #{enable_banking_account.uid}: #{e.message}"
      end
    end

    result = {
      success: accounts_failed == 0 && transactions_failed == 0,
      accounts_updated: accounts_updated,
      accounts_failed: accounts_failed,
      transactions_imported: transactions_imported,
      transactions_failed: transactions_failed
    }
    if !result[:success] && (accounts_failed > 0 || transactions_failed > 0)
      parts = []
      parts << "#{accounts_failed} #{'account'.pluralize(accounts_failed)} failed" if accounts_failed > 0
      parts << "#{transactions_failed} #{'transaction'.pluralize(transactions_failed)} failed" if transactions_failed > 0
      result[:error] = parts.join(", ")
    end
    result
  end

  private

    def extract_friendly_error_message(exception)
      [ exception, exception.cause ].compact.each do |ex|
        case ex
        when SocketError then return "DNS resolution failed: check your network/DNS configuration"
        when Net::OpenTimeout, Net::ReadTimeout then return "Connection timed out: the Enable Banking API may be unreachable"
        when Errno::ECONNREFUSED then return "Connection refused: the Enable Banking API is unreachable"
        end
      end

      msg = exception.message.to_s
      return "DNS resolution failed: check your network/DNS configuration" if msg.include?("getaddrinfo") || msg.match?(/name or service not known/i)
      return "Connection timed out: the Enable Banking API may be unreachable" if msg.include?("execution expired") || msg.include?("timeout") || msg.match?(/timed out/i)
      return "Connection refused: the Enable Banking API is unreachable" if msg.include?("ECONNREFUSED") || msg.match?(/connection refused/i)

      msg
    end

    def fetch_session_data
      enable_banking_provider.get_session(session_id: enable_banking_item.session_id)
    rescue Provider::EnableBanking::EnableBankingError => e
      if e.error_type == :unauthorized || e.error_type == :not_found
        enable_banking_item.update!(status: :requires_update)
      end
      Rails.logger.error "EnableBankingItem::Importer - Enable Banking API error: #{e.message}"
      @session_error = extract_friendly_error_message(e)
      nil
    rescue => e
      Rails.logger.error "EnableBankingItem::Importer - Unexpected error fetching session: #{e.class} - #{e.message}"
      @session_error = extract_friendly_error_message(e)
      nil
    end

    def import_account(account_data)
      # Use identification_hash as the stable identifier across sessions
      uid = account_data[:identification_hash] || account_data[:uid]

      enable_banking_account = enable_banking_item.enable_banking_accounts.find_by(uid: uid.to_s)
      return unless enable_banking_account

      enable_banking_account.upsert_enable_banking_snapshot!(account_data)
      enable_banking_account.save!
    end

    def fetch_and_update_balance(enable_banking_account)
      balance_data = enable_banking_provider.get_account_balances(account_id: enable_banking_account.api_account_id)

      # Enable Banking returns an array of balances
      balances = balance_data[:balances] || []
      return if balances.empty?

      # Find the most relevant balance (prefer booked over available types)
      balance = select_balance(balances)

      if balance.present?
        amount = balance.dig(:balance_amount, :amount) || balance[:amount]
        currency = balance.dig(:balance_amount, :currency) || balance[:currency]

        if amount.present?
          enable_banking_account.update!(
            current_balance: amount.to_d,
            currency: currency.presence || enable_banking_account.currency
          )
        end
      end
    rescue Provider::EnableBanking::EnableBankingError => e
      Rails.logger.error "EnableBankingItem::Importer - Error fetching balance for account #{enable_banking_account.uid}: #{e.message}"
    end

    def select_balance(balances)
      BALANCE_TYPE_PRIORITY.each do |type|
        found = balances.find { |b| b[:balance_type] == type }
        return found if found
      end
      balances.first
    end

    def fetch_and_store_transactions(enable_banking_account)
      start_date = determine_sync_start_date(enable_banking_account)

      all_transactions = []
      continuation_key = nil
      previous_continuation_key = nil
      page_count = 0

      # Paginate through all transactions with safeguards against infinite loops
      loop do
        page_count += 1

        # Safeguard: prevent infinite loops from excessive pagination
        if page_count > MAX_PAGINATION_PAGES
          Rails.logger.error(
            "EnableBankingItem::Importer - Pagination limit exceeded for account #{enable_banking_account.uid}. " \
            "Stopped after #{MAX_PAGINATION_PAGES} pages (#{all_transactions.count} transactions). " \
            "Last continuation_key: #{continuation_key.inspect}"
          )
          break
        end

        transactions_data = enable_banking_provider.get_account_transactions(
          account_id: enable_banking_account.api_account_id,
          date_from: start_date,
          continuation_key: continuation_key
        )

        transactions = transactions_data[:transactions] || []
        all_transactions.concat(transactions)

        previous_continuation_key = continuation_key
        continuation_key = transactions_data[:continuation_key]

        # Safeguard: detect repeated continuation_key (provider returning same key)
        if continuation_key.present? && continuation_key == previous_continuation_key
          Rails.logger.error(
            "EnableBankingItem::Importer - Repeated continuation_key detected for account #{enable_banking_account.uid}. " \
            "Breaking loop after #{page_count} pages (#{all_transactions.count} transactions). " \
            "Repeated key: #{continuation_key.inspect}, last response had #{transactions.count} transactions"
          )
          break
        end

        break if continuation_key.blank?
      end

      # Deduplicate API response: Enable Banking sometimes returns the same logical
      # transaction with different entry_reference IDs in the same response.
      # Remove content-level duplicates before storing. (Issue #954)
      all_transactions = deduplicate_api_transactions(all_transactions)

      transactions_count = all_transactions.count

      if all_transactions.any?
        existing_transactions = enable_banking_account.raw_transactions_payload.to_a
        existing_ids = existing_transactions.map { |tx|
          tx = tx.with_indifferent_access
          tx[:transaction_id].presence || tx[:entry_reference].presence
        }.compact.to_set

        new_transactions = all_transactions.select do |tx|
          # Use transaction_id if present, otherwise fall back to entry_reference
          tx_id = tx[:transaction_id].presence || tx[:entry_reference].presence
          tx_id.present? && !existing_ids.include?(tx_id)
        end

        if new_transactions.any?
          enable_banking_account.upsert_enable_banking_transactions_snapshot!(existing_transactions + new_transactions)
        end
      end

      { success: true, transactions_count: transactions_count }
    rescue Provider::EnableBanking::EnableBankingError => e
      Rails.logger.error "EnableBankingItem::Importer - Error fetching transactions for account #{enable_banking_account.uid}: #{e.message}"
      { success: false, transactions_count: 0, error: e.message }
    rescue => e
      Rails.logger.error "EnableBankingItem::Importer - Unexpected error fetching transactions for account #{enable_banking_account.uid}: #{e.class} - #{e.message}"
      { success: false, transactions_count: 0, error: e.message }
    end

    # Deduplicate transactions from the Enable Banking API response.
    # Some banks return the same logical transaction multiple times with different
    # entry_reference IDs. We build a composite content key that includes
    # transaction_id (when present) alongside date, amount, currency, creditor,
    # debtor, remittance_information, and status. Per the Enable Banking API docs
    # transaction_id is not guaranteed to be unique, so it cannot be used as
    # the sole dedup criterion. Including it in the composite key preserves
    # legitimately distinct transactions with identical content but different
    # transaction_ids (e.g. two laundromat payments on the same day). (Issue #954)
    def deduplicate_api_transactions(transactions)
      seen = {}
      duplicates_removed = 0

      result = transactions.select do |tx|
        tx = tx.with_indifferent_access
        key = build_transaction_content_key(tx)

        if seen[key]
          duplicates_removed += 1
          false
        else
          seen[key] = true
          true
        end
      end

      if duplicates_removed > 0
        Rails.logger.info(
          "EnableBankingItem::Importer - Removed #{duplicates_removed} content-level " \
          "duplicate(s) from API response (#{transactions.count} → #{result.count} transactions)"
        )
      end

      result
    end

    # Build a composite key for deduplication. Two transactions with different
    # entry_reference values but identical content fields (including
    # transaction_id and credit_debit_indicator) are considered duplicates.
    # transaction_id is included as one component — not a standalone key —
    # because the Enable Banking API docs state it is not guaranteed to be
    # unique. credit_debit_indicator (CRDT/DBIT) is included because
    # transaction_amount.amount is always positive — without it, a payment
    # and a same-day refund of the same amount would produce identical keys.
    # Known limitation: when transaction_id is nil for both, pure content
    # comparison applies. This means two genuinely distinct transactions
    # with identical content (same date, amount, direction, creditor, etc.)
    # and no transaction_id would collapse to one. In practice, banks that
    # omit transaction_id rarely produce such exact duplicates in the same
    # API response; timestamps or remittance info usually differ. (Issue #954)
    def build_transaction_content_key(tx)
      date = tx[:booking_date].presence || tx[:value_date]
      amount = tx.dig(:transaction_amount, :amount).presence || tx[:amount]
      currency = tx.dig(:transaction_amount, :currency).presence || tx[:currency]
      creditor = tx.dig(:creditor, :name).presence || tx[:creditor_name]
      debtor = tx.dig(:debtor, :name).presence || tx[:debtor_name]
      remittance = tx[:remittance_information]
      remittance_key = remittance.is_a?(Array) ? remittance.compact.map(&:to_s).sort.join("|") : remittance.to_s
      status = tx[:status]
      tid = tx[:transaction_id]
      direction = tx[:credit_debit_indicator]

      [ date, amount, currency, creditor, debtor, remittance_key, status, tid, direction ].map(&:to_s).join("\x1F")
    end

    def determine_sync_start_date(enable_banking_account)
      has_stored_transactions = enable_banking_account.raw_transactions_payload.to_a.any?

      # Use user-configured sync_start_date if set, otherwise default
      user_start_date = enable_banking_item.sync_start_date

      if has_stored_transactions
        # For incremental syncs, get transactions from 7 days before last sync
        if enable_banking_item.last_synced_at
          enable_banking_item.last_synced_at.to_date - 7.days
        else
          30.days.ago.to_date
        end
      else
        # Initial sync: use user's configured date or default to 3 months
        user_start_date || 3.months.ago.to_date
      end
    end
end