class Async::HTTP::Client

def self.open(*arguments, **options, &block)
	client = self.new(*arguments, **options)
	
	return client unless block_given?
	
	begin
		yield client
	ensure
		client.close
	end
end

def call(request)
	request.scheme ||= self.scheme
	request.authority ||= self.authority
	
	attempt = 0
	
	# We may retry the request if it is possible to do so. https://tools.ietf.org/html/draft-nottingham-httpbis-retry-01 is a good guide for how retrying requests should work.
	begin
		attempt += 1
		
		# As we cache pool, it's possible these pool go bad (e.g. closed by remote host). In this case, we need to try again. It's up to the caller to impose a timeout on this. If this is the last attempt, we force a new connection.
		connection = @pool.acquire
		
		response = make_response(request, connection)
		
		# This signals that the ensure block below should not try to release the connection, because it's bound into the response which will be returned:
		connection = nil
		
		return response
	rescue Protocol::RequestFailed
		# This is a specific case where the entire request wasn't sent before a failure occurred. So, we can even resend non-idempotent requests.
		if connection
			@pool.release(connection)
			connection = nil
		end
		
		if attempt < @retries
			retry
		else
			raise
		end
	rescue SocketError, IOError, EOFError, Errno::ECONNRESET, Errno::EPIPE
		if connection
			@pool.release(connection)
			connection = nil
		end
		
		if request.idempotent? and attempt < @retries
			retry
		else
			raise
		end
	ensure
		@pool.release(connection) if connection
	end
end

def call(request)
	attributes = {
		'http.method': request.method,
		'http.authority': request.authority || self.authority,
		'http.scheme': request.scheme || self.scheme,
		'http.path': request.path,
	}
	
	if protocol = request.protocol
		attributes['http.protocol'] = protocol
	end
	
	if length = request.body&.length
		attributes['http.request.length'] = length
	end
	
	Traces.trace('async.http.client.call', attributes: attributes) do |span|
		if context = Traces.trace_context
			request.headers['traceparent'] = context.to_s
			# request.headers['tracestate'] = context.state
		end
		
		super.tap do |response|
			if status = response&.status
				span['http.status_code'] = status
			end
			
			if length = response.body&.length
				span['http.response.length'] = length
			end
		end
	end
end

def close
	while @pool.busy?
		Console.logger.warn(self) {"Waiting for #{@protocol} pool to drain: #{@pool}"}
		@pool.wait
	end
	
	@pool.close
end

def initialize(endpoint, protocol: endpoint.protocol, scheme: endpoint.scheme, authority: endpoint.authority, retries: DEFAULT_RETRIES, connection_limit: DEFAULT_CONNECTION_LIMIT)
	@endpoint = endpoint
	@protocol = protocol
	
	@retries = retries
	@pool = make_pool(connection_limit)
	
	@scheme = scheme
	@authority = authority
end

def inspect
	"#<#{self.class} authority=#{@authority.inspect}>"
end

def make_pool(connection_limit)
	Async::Pool::Controller.wrap(limit: connection_limit) do
		Console.logger.debug(self) {"Making connection to #{@endpoint.inspect}"}
		
		@protocol.client(@endpoint.connect)
	end
end

def make_response(request, connection)
	response = request.call(connection)
	
	# The connection won't be released until the body is completely read/released.
	::Protocol::HTTP::Body::Completable.wrap(response) do
		@pool.release(connection)
	end
	
	return response
end

def secure?
	@endpoint.secure?
end