def join(wallet, ledger: '/dev/null', baseline: false)
      if @id.nil?
        @id = wallet.id
        @key = wallet.key
        @network = wallet.network
      end
      unless wallet.network == @network
        @log.error("The wallet is from a different network '#{wallet.network}', ours is '#{@network}'")
        return
      end
      unless wallet.key == @key
        @log.error('Public key mismatch')
        return
      end
      unless wallet.id == @id
        @log.error("Wallet ID mismatch, ours is #{@id}, theirs is #{wallet.id}")
        return
      end
      seen = 0
      added = 0
      pulled = []
      wallet.txns.each do |txn|
        next if @txns.find { |t| t == txn }
        seen += 1
        if txn.amount.negative?
          dup = @txns.find { |t| t.id == txn.id && t.amount.negative? }
          if dup
            @log.error("An attempt to overwrite existing transaction #{dup.to_text.inspect} \
with a new one #{txn.to_text.inspect} from #{wallet.mnemo}")
            next
          end
          unless Signature.new(@network).valid?(@key, wallet.id, txn)
            @log.error("Invalid RSA signature at the transaction ##{txn.id} of #{wallet.id}: #{txn.to_text.inspect}")
            next
          end
        else
          if Id::BANNED.include?(txn.bnf.to_s)
            @log.debug("The paying wallet is banned, #{wallet.id} can't accept this: #{txn.to_text.inspect}")
            next
          end
          dup = @txns.find { |t| t.id == txn.id && t.bnf == txn.bnf && t.amount.positive? }
          if dup
            @log.error("Overwriting #{dup.to_text.inspect} with #{txn.to_text.inspect} \
from #{wallet.mnemo} (same ID/BNF)")
            next
          end
          if !txn.sign.nil? && !txn.sign.empty?
            @log.error("RSA signature is redundant at ##{txn.id} of #{wallet.id}: #{txn.to_text.inspect}")
            next
          end
          unless wallet.prefix?(txn.prefix)
            @log.debug("Payment prefix '#{txn.prefix}' doesn't match \
with the key of #{wallet.id}: #{txn.to_text.inspect}")
            next
          end
          unless @wallets.acq(txn.bnf, &:exists?)
            if baseline
              @log.debug("Paying wallet #{txn.bnf} is absent, \
but the txn in in the baseline: #{txn.to_text.inspect}")
            else
              next if pulled.include?(txn.bnf)
              pulled << txn.bnf
              if yield(txn) && !@wallets.acq(txn.bnf, &:exists?)
                @log.error("Paying wallet #{txn.bnf} file is absent even after PULL: #{txn.to_text.inspect}")
                next
              end
            end
          end
          if @wallets.acq(txn.bnf, &:exists?) &&
            !@wallets.acq(txn.bnf) { |p| p.includes_negative?(txn.id, wallet.id) }
            if baseline
              @log.debug("The beneficiary #{@wallets.acq(txn.bnf, &:mnemo)} of #{@id} \
doesn't have this transaction, but we trust it, since it's a baseline: #{txn.to_text.inspect}")
            else
              if pulled.include?(txn.bnf)
                @log.debug("The beneficiary #{@wallets.acq(txn.bnf, &:mnemo)} of #{@id} \
doesn't have this transaction: #{txn.to_text.inspect}")
                next
              end
              pulled << txn.bnf
              yield(txn)
              unless @wallets.acq(txn.bnf) { |p| p.includes_negative?(txn.id, wallet.id) }
                @log.debug("The beneficiary #{@wallets.acq(txn.bnf, &:mnemo)} of #{@id} \
doesn't have this transaction: #{txn.to_text.inspect}")
                next
              end
            end
          end
        end
        @txns << txn
        added += 1
        next unless txn.amount.negative?
        File.open(ledger, 'a') do |f|
          f.puts(
            [
              Time.now.utc.iso8601,
              txn.id,
              txn.date.utc.iso8601,
              wallet.id,
              txn.bnf,
              txn.amount.to_i * -1,
              txn.prefix,
              txn.details
            ].map(&:to_s).join(';') + "\n"
          )
        end
      end
    end
def join(wallet, ledger: '/dev/null', baseline: false)
      if @id.nil?
        @id = wallet.id
        @key = wallet.key
        @network = wallet.network
      end
      unless wallet.network == @network
        @log.error("The wallet is from a different network '#{wallet.network}', ours is '#{@network}'")
        return
      end
      unless wallet.key == @key
        @log.error('Public key mismatch')
        return
      end
      unless wallet.id == @id
        @log.error("Wallet ID mismatch, ours is #{@id}, theirs is #{wallet.id}")
        return
      end
      seen = 0
      added = 0
      pulled = []
      wallet.txns.each do |txn|
        next if @txns.find { |t| t == txn }
        seen += 1
        if txn.amount.negative?
          dup = @txns.find { |t| t.id == txn.id && t.amount.negative? }
          if dup
            @log.error("An attempt to overwrite existing transaction #{dup.to_text.inspect} \
with a new one #{txn.to_text.inspect} from #{wallet.mnemo}")
            next
          end
          unless Signature.new(@network).valid?(@key, wallet.id, txn)
            @log.error("Invalid RSA signature at the transaction ##{txn.id} of #{wallet.id}: #{txn.to_text.inspect}")
            next
          end
        else
          if Id::BANNED.include?(txn.bnf.to_s)
            @log.debug("The paying wallet is banned, #{wallet.id} can't accept this: #{txn.to_text.inspect}")
            next
          end
          dup = @txns.find { |t| t.id == txn.id && t.bnf == txn.bnf && t.amount.positive? }
          if dup
            @log.error("Overwriting #{dup.to_text.inspect} with #{txn.to_text.inspect} \
from #{wallet.mnemo} (same ID/BNF)")
            next
          end
          if !txn.sign.nil? && !txn.sign.empty?
            @log.error("RSA signature is redundant at ##{txn.id} of #{wallet.id}: #{txn.to_text.inspect}")
            next
          end
          unless wallet.prefix?(txn.prefix)
            @log.debug("Payment prefix '#{txn.prefix}' doesn't match \
with the key of #{wallet.id}: #{txn.to_text.inspect}")
            next
          end
          unless @wallets.acq(txn.bnf, &:exists?)
            if baseline
              @log.debug("Paying wallet #{txn.bnf} is absent, \
but the txn in in the baseline: #{txn.to_text.inspect}")
            else
              next if pulled.include?(txn.bnf)
              pulled << txn.bnf
              if yield(txn) && !@wallets.acq(txn.bnf, &:exists?)
                @log.error("Paying wallet #{txn.bnf} file is absent even after PULL: #{txn.to_text.inspect}")
                next
              end
            end
          end
          if @wallets.acq(txn.bnf, &:exists?) &&
            !@wallets.acq(txn.bnf) { |p| p.includes_negative?(txn.id, wallet.id) }
            if baseline
              @log.debug("The beneficiary #{@wallets.acq(txn.bnf, &:mnemo)} of #{@id} \
doesn't have this transaction, but we trust it, since it's a baseline: #{txn.to_text.inspect}")
            else
              if pulled.include?(txn.bnf)
                @log.debug("The beneficiary #{@wallets.acq(txn.bnf, &:mnemo)} of #{@id} \
doesn't have this transaction: #{txn.to_text.inspect}")
                next
              end
              pulled << txn.bnf
              yield(txn)
              unless @wallets.acq(txn.bnf) { |p| p.includes_negative?(txn.id, wallet.id) }
                @log.debug("The beneficiary #{@wallets.acq(txn.bnf, &:mnemo)} of #{@id} \
doesn't have this transaction: #{txn.to_text.inspect}")
                next
              end
            end
          end
        end
        @txns << txn
        added += 1
        next unless txn.amount.negative?
        File.open(ledger, 'a') do |f|
          f.puts(
            [
              Time.now.utc.iso8601,
              txn.id,
              txn.date.utc.iso8601,
              wallet.id,
              txn.bnf,
              txn.amount.to_i * -1,
              txn.prefix,
              txn.details
            ].map(&:to_s).join(';') + "\n"
          )
        end
      end
    end
Joins a new wallet on top of existing patch. An attempt is made to
 copy as many transactions from the newcoming wallet to the existing
 set of transactions, avoiding mistakes and duplicates.

 A block has to be given. It will be called, if a paying wallet is absent.
 The block will have to return either TRUE or FALSE. TRUE will mean that
 the paying wallet has to be present and we just tried to pull it. If it's
 not present, it's a failure, don't accept the transaction. FALSE will mean
 that the transaction should be accepted, even if the paying wallet is
 absent.

 The "baseline" flag, when set to TRUE, means that we should NOT validate
 the presence of positive incoming transactions in their correspondent
 wallets. We shall just trust them.