class Ztimer

# File lib/ztimer.rb, line 71
def self.method_missing(name, *args, &block)
  @default_instance ||= Ztimer.new(concurrency: 20)
  @default_instance.send(name, *args, &block)
end

# File lib/ztimer.rb, line 11
def initialize(concurrency: 20)
  @concurrency  = concurrency
  @watcher      = Ztimer::Watcher.new(){|slot| execute(slot) }
  @workers_lock = Mutex.new
  @count_lock   = Mutex.new
  @queue        = Queue.new
  @running      = 0
  @count        = 0
end

# File lib/ztimer.rb, line 31
def after(milliseconds, &callback)
  enqueued_at = utc_microseconds
  expires_at  = enqueued_at + milliseconds * 1000
  slot        = Slot.new(enqueued_at, expires_at, -1, &callback)

  add(slot)

  return slot
end

# File lib/ztimer.rb, line 21
def async(&callback)
  enqueued_at = utc_microseconds
  slot        = Slot.new(enqueued_at, enqueued_at, -1, &callback)

  incr_counter!
  execute(slot)

  return slot
end

# File lib/ztimer.rb, line 55
def concurrency=(new_value)
  raise ArgumentError.new("Invalid concurrency value: #{new_value}") unless new_value.is_a?(Fixnum) && new_value >= 1
  @concurrency = new_value
end

# File lib/ztimer.rb, line 41
def every(milliseconds, &callback)
  enqueued_at = utc_microseconds
  expires_at  = enqueued_at + milliseconds * 1000
  slot        = Slot.new(enqueued_at, expires_at, milliseconds * 1000, &callback)

  add(slot)

  return slot
end

# File lib/ztimer.rb, line 51
def jobs_count
  return @watcher.jobs
end

# File lib/ztimer.rb, line 61
def stats
  {
    running:   @running,
    scheduled: @watcher.jobs,
    executing: @queue.size,
    total:     @count
  }
end

# File lib/ztimer.rb, line 78
def add(slot)
  incr_counter!
  @watcher << slot
end

# File lib/ztimer.rb, line 87
def execute(slot)
  @queue << slot

  @workers_lock.synchronize do
    [@concurrency - @running, @queue.size].min.times do
      @running += 1
      start_new_thread!
    end
  end
end

# File lib/ztimer.rb, line 83
def incr_counter!
  @count_lock.synchronize{ @count += 1 }
end

# File lib/ztimer.rb, line 98
def start_new_thread!
  worker = Thread.new do
    begin
      loop do
        current_slot = nil
        @workers_lock.synchronize do
          current_slot = @queue.pop(true) unless @queue.empty?
        end
        break if current_slot.nil?

        begin
          current_slot.executed_at = utc_microseconds
          current_slot.callback.call(current_slot) unless current_slot.callback.nil? || current_slot.canceled?
        rescue => e
          STDERR.puts e.inspect + (e.backtrace ? "\n" + e.backtrace.join("\n") : "")
        end
      end
    rescue ThreadError
      puts "queue is empty"
    end
    @workers_lock.synchronize { @running -= 1 }
  end
  worker.abort_on_exception = true
end

# File lib/ztimer.rb, line 123
def utc_microseconds
  return Time.now.to_f * 1_000_000
end