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# frozen_string_literal: true
# Released under the MIT License.
# Copyright, 2025, by Shopify Inc.
# Copyright, 2025, by Samuel Williams.
require_relative "clock"
# @namespace
module Async
# Represents a deadline timeout with decrementing remaining time.
# Includes an efficient representation for zero (non-blocking) timeouts.
# @public Since *Async v2.31*.
class Deadline
# Singleton module for immediate timeouts (zero or negative).
# Avoids object allocation for fast path (non-blocking) timeouts.
module Zero
# Check if the deadline has expired.
# @returns [Boolean] Always returns true since zero timeouts are immediately expired.
def self.expired?
true
end
# Get the remaining time.
# @returns [Integer] Always returns 0 since zero timeouts have no remaining time.
def self.remaining
0
end
end
# Create a deadline for the given timeout.
# @parameter timeout [Numeric | Nil] The timeout duration, or nil for no timeout.
# @returns [Deadline | Nil] A deadline instance, Zero singleton, or nil.
def self.start(timeout)
if timeout.nil?
nil
elsif timeout <= 0
Zero
else
self.new(timeout)
end
end
# Create a new deadline with the specified remaining time.
# @parameter remaining [Numeric] The initial remaining time.
def initialize(remaining)
@remaining = remaining
@start = Clock.now
end
# Get the remaining time, updating internal state.
# Each call to this method advances the internal clock and reduces
# the remaining time by the elapsed duration since the last call.
# @returns [Numeric] The remaining time (may be negative if expired).
def remaining
now = Clock.now
delta = now - @start
@start = now
@remaining -= delta
return @remaining
end
# Check if the deadline has expired.
# @returns [Boolean] True if no time remains.
def expired?
self.remaining <= 0
end
end
end
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