zold-io/zold

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lib/zold/head.rb

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# frozen_string_literal: true

# Copyright (c) 2018-2020 Zerocracy, Inc.
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the 'Software'), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.

require_relative 'txn'

# Head of a wallet.
# Author:: Yegor Bugayenko (yegor256@gmail.com)
# Copyright:: Copyright (c) 2018 Yegor Bugayenko
# License:: MIT
module Zold
  # Head of the wallet.
  class Head
    # When can't parse them.
    class CantParse < StandardError; end

    def initialize(file)
      @file = file
    end

    def flush
      # nothing
    end

    def fetch
      raise "Wallet file '#{@file}' is absent" unless File.exist?(@file)
      lines = []
      File.open(@file) do |f|
        lines << f.readline.strip while lines.count < 4 && !f.eof?
      end
      raise CantParse, "Not enough lines in #{@file}, just #{lines.count}" if lines.count < 4
      lines
    end
  end

  # Cached head.
  # Author:: Yegor Bugayenko (yegor256@gmail.com)
  # Copyright:: Copyright (c) 2018 Yegor Bugayenko
  # License:: MIT
  class CachedHead
    def initialize(head)
      @head = head
    end

    def flush
      @fetch = nil
    end

    def fetch
      @fetch ||= @head.fetch
    end
  end
end