// Copyright (c) 2026 Tigera, Inc. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package daemon

import (
	"time"

	. "github.com/onsi/ginkgo/v2"
	. "github.com/onsi/gomega"
)

var _ = Describe("shutDownProcess", func() {
	// shutDownProcess never returns: it reports the reason to the shutdown
	// monitor and then panics as a backstop.  Run it in a goroutine and
	// recover so a stray panic can't outlive the spec.
	runInBackground := func(fc *DataplaneConnector, reason string) <-chan any {
		panicked := make(chan any, 1)
		go func() {
			defer func() { panicked <- recover() }()
			fc.shutDownProcess(reason)
		}()
		return panicked
	}

	// Regression test for the start-of-day deadlock: if the shutdown monitor
	// (the only reader of failureReportChan) hasn't started, the report send
	// must not block forever.  Before the fix, the panic backstop sat after
	// an unconditional blocking send, so this hung indefinitely.
	It("panics instead of blocking when the shutdown monitor never reads", func() {
		fc := &DataplaneConnector{
			failureReportChan:     make(chan string), // Unbuffered, no reader.
			shutdownReportTimeout: 100 * time.Millisecond,
		}

		panicked := runInBackground(fc, reasonConfigChanged)
		Eventually(panicked, "5s").Should(Receive(Not(BeNil())))
	})

	It("delivers the reason to the monitor and then panics as a backstop", func() {
		reportChan := make(chan string)
		fc := &DataplaneConnector{
			failureReportChan:     reportChan,
			shutdownReportTimeout: 100 * time.Millisecond,
		}

		received := make(chan string, 1)
		go func() { received <- <-reportChan }()

		panicked := runInBackground(fc, reasonConfigChanged)

		// The reason reaches the monitor: the send is not lost.
		Eventually(received, "5s").Should(Receive(Equal(reasonConfigChanged)))
		// The backstop still fires once the monitor fails to tear us down.
		Eventually(panicked, "5s").Should(Receive(Not(BeNil())))
	})
})