// Copyright 2022 TiKV Project Authors.
//
// 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 id

import (
	"context"
	"strconv"
	"sync"
	"testing"

	"github.com/stretchr/testify/require"
	"github.com/tikv/pd/pkg/utils/etcdutil"
)

const (
	rootPath   = "/pd"
	leaderPath = "/pd/leader"
	allocPath  = "alloc_id"
	label      = "idalloc"
	memberVal  = "member"
	step       = uint64(500)
)

// TestMultipleAllocator tests situation where multiple allocators that
// share rootPath and member val update their ids concurrently.
func TestMultipleAllocator(t *testing.T) {
	re := require.New(t)
	_, client, clean := etcdutil.NewTestEtcdCluster(t, 1)
	defer clean()

	// Put memberValue to leaderPath to simulate an election success.
	_, err := client.Put(context.Background(), leaderPath, memberVal)
	re.NoError(err)

	wg := sync.WaitGroup{}
	for i := range 3 {
		iStr := strconv.Itoa(i)
		wg.Add(1)
		// All allocators share rootPath and memberVal, but they have different allocPaths, labels and steps.
		allocator := NewAllocator(&AllocatorParams{
			Client:    client,
			RootPath:  rootPath,
			AllocPath: allocPath + iStr,
			Label:     label + iStr,
			Member:    memberVal,
			Step:      step * uint64(i), // allocator 0, 1, 2 should have step size 1000 (default), 500, 1000 respectively.
		})
		go func(re *require.Assertions, allocator Allocator) {
			defer wg.Done()
			testAllocator(re, allocator)
		}(re, allocator)
	}
	wg.Wait()
}

// testAllocator sequentially updates given allocator and check if values are expected.
func testAllocator(re *require.Assertions, allocator Allocator) {
	startID, _, err := allocator.Alloc(1)
	re.NoError(err)
	for i := startID + 1; i < startID+step*20; i++ {
		id, _, err := allocator.Alloc(1)
		re.NoError(err)
		re.Equal(i, id)
	}
}