# frozen_string_literal: true

# Released under the MIT License.
# Copyright, 2018-2026, by Samuel Williams.
# Copyright, 2026, by Shopify Inc.

require "async/semaphore"
require "async/barrier"
require "sus/fixtures/async"

require "async/chainable_async"

describe Async::Semaphore do
	include Sus::Fixtures::Async::ReactorContext
	let(:semaphore) {subject.new}
	
	with "#async" do
		let(:repeats) {10}
		let(:limit) {4}
		
		it "should process work in batches" do
			semaphore = Async::Semaphore.new(limit)
			current, maximum = 0, 0
			
			result = repeats.times.map do |i|
				semaphore.async do |task|
					current += 1
					maximum = [current, maximum].max
					sleep(rand * 0.01)
					current -= 1
					
					i
				end
			end.collect(&:wait)
			
			# Verify that the maximum number of concurrent tasks was the specificed limit:
			expect(maximum).to be == limit
			
			# Verify that the results were in the correct order:
			expect(result).to be == (0...repeats).to_a
		end
		
		it "only allows one task at a time" do
			semaphore = Async::Semaphore.new(1)
			order = []
			
			3.times.map do |i|
				semaphore.async do |task|
					order << i
					sleep(0.01)
					order << i
				end
			end.collect(&:wait)
			
			expect(order).to be == [0, 0, 1, 1, 2, 2]
		end
		
		it "allows tasks to execute concurrently" do
			semaphore = Async::Semaphore.new(3)
			order = []
			concurrent = nil
			
			3.times.map do |i|
				semaphore.async do |task|
					order << i
					sleep(0.01)
					concurrent ||= order.dup
					order << i
				end
			end.collect(&:wait)
			
			expect(concurrent).to be == [0, 1, 2]
			expect(order.sort).to be == [0, 0, 1, 1, 2, 2]
		end
	end
	
	with "#waiting" do
		let(:semaphore) {Async::Semaphore.new(0)}
		
		it "handles exceptions thrown while waiting" do
			expect do
				reactor.with_timeout(0.001) do
					semaphore.acquire do
					end
				end
			end.to raise_exception(Async::TimeoutError)
			
			expect(semaphore.waiting).to be(:empty?)
		end
	end
	
	with "#count" do
		it "should count number of current acquisitions" do
			expect(semaphore.count).to be == 0
			
			semaphore.acquire do
				expect(semaphore.count).to be == 1
			end
		end
	end
	
	with "#limit" do
		it "should have a default limit" do
			expect(semaphore.limit).to be == 1
		end
	end
	
	with "#empty?" do
		it "should be empty unless acquired" do
			expect(semaphore).to be(:empty?)
			
			semaphore.acquire do
				expect(semaphore).not.to be(:empty?)
			end
		end
	end
	
	with "#blocking?" do
		it "will be blocking when acquired" do
			expect(semaphore).not.to be(:blocking?)
			
			semaphore.acquire do
				expect(semaphore).to be(:blocking?)
			end
		end
	end
	
	with "#acquire/#release" do
		it "works when called without block" do
			semaphore.acquire
			
			expect(semaphore.count).to be == 1
			
			semaphore.release
			
			expect(semaphore.count).to be == 0
		end
	end
	
	with "barrier" do
		let(:capacity) {2}
		let(:barrier) {Async::Barrier.new}
		let(:repeats) {capacity * 2}
		
		it "should execute several tasks and wait using a barrier" do
			repeats.times do
				semaphore.async(parent: barrier) do |task|
					sleep(0.01)
				end
			end
			
			expect(barrier.size).to be == repeats
			barrier.wait
		end
	end
	
	with "#limit" do
		it "has a default limit of 1" do
			expect(semaphore).to have_attributes(limit: be == 1)
			expect(semaphore).not.to be(:blocking?)
		end
	end
	
	with "#limit=" do
		it "releases tasks when limit is increased" do
			semaphore.acquire
			expect(semaphore).to have_attributes(count: be == 1)
			expect(semaphore).to be(:blocking?)
			
			task = Async do
				semaphore.acquire
			end
			
			semaphore.limit = 2
			task.wait
			
			expect(semaphore.count).to be == 2
		end
		
		it "blocks tasks when limit is decreased" do
			semaphore.limit = 2
			semaphore.acquire
			semaphore.acquire
			
			expect(semaphore).to have_attributes(count: be == 2)
			expect(semaphore).to be(:blocking?)
			
			task = Async do
				semaphore.acquire
			end
			
			semaphore.limit = 1
			semaphore.release
			semaphore.release
			task.wait
			
			expect(semaphore.count).to be == 1
		end
	end
	
	it_behaves_like Async::ChainableAsync
end
