# Copyright (c) 2018 Yegor Bugayenko
#
# 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 'time'
require_relative '../log'
require_relative '../score'
require_relative '../verbose_thread'
require_relative '../atomic_file'

# The farm of scores.
# Author:: Yegor Bugayenko (yegor256@gmail.com)
# Copyright:: Copyright (c) 2018 Yegor Bugayenko
# License:: MIT
module Zold
  # Farm
  class Farm
    # Empty farm
    class Empty
      def best
        []
      end
    end

    attr_reader :best
    def initialize(invoice, cache, log: Log::Quiet.new)
      @log = log
      @cache = cache
      @invoice = invoice
      @scores = []
      @threads = []
      @best = []
      @semaphore = Mutex.new
    end

    def to_json
      {
        threads: @threads.count,
        scores: @scores.size,
        best: @best.count
      }
    end

    def start(host, port, strength: 8, threads: 8)
      @log.debug('Zero-threads farm won\'t score anything!') if threads.zero?
      @scores = Queue.new
      h = history(threads)
      h.each { |s| @scores << s }
      @best << (h[0] || Score.new(Time.now, host, port, @invoice, strength: strength))
      @log.info("#{@scores.size} scores pre-loaded, the best is: #{@best[0]}")
      @threads = (1..threads).map do |t|
        Thread.new do
          VerboseThread.new(@log).run do
            Thread.current.name = "farm-#{t}"
            loop do
              if @scores.length < 4
                @scores << Score.new(
                  Time.now, host, port, @invoice,
                  strength: strength
                )
              end
              s = @scores.pop
              next unless s.valid?
              next if s.expired?
              next if s.strength < strength
              @semaphore.synchronize do
                save(s)
                before = @best.map(&:value).max
                @best << s
                after = @best.map(&:value).max
                @best.reject! { |b| b.value < after }
                @log.debug("#{Thread.current.name}: best score is #{@best[0]}") if before != after
              end
              @scores << s.next
            end
          end
        end
      end
      @log.debug("Farm started with #{threads} threads at #{host}:#{port}")
    end

    def stop
      @threads.each do |t|
        t.exit
        @log.debug("Thread #{t.name} terminated")
      end
      @log.debug('Farm stopped')
    end

    private

    def save(score)
      AtomicFile.new(@cache).write((history + [score]).map(&:to_s).join("\n"))
    end

    def history(max = 16)
      if File.exist?(@cache)
        AtomicFile.new(@cache).read
          .split(/\n/)
          .map { |t| Score.parse(t) }
          .reject(&:expired?)
          .select(&:valid?)
          .sort_by(&:value)
          .reverse
          .take(max)
      else
        []
      end
    end
  end
end