// Copyright 2023 PingCAP, Inc.
//
// 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,
// See the License for the specific language governing permissions and
// limitations under the License.

package util

import (
	"context"
	"math"
	"time"

	"github.com/KimMachineGun/automemlimit/memlimit"
	"github.com/pingcap/log"
	"github.com/pingcap/tidb/pkg/util/memory"
	"github.com/pingcap/tiflow/pkg/errors"
	"github.com/shirou/gopsutil/v3/mem"
	"go.uber.org/zap"
)

const memoryMax uint64 = math.MaxUint64

// GetMemoryLimit gets the memory limit of current process based on cgroup.
// If the cgourp is not set or memory.max is set to max, returns the available
// memory of host.
func GetMemoryLimit() (uint64, error) {
	totalMemory, err := memlimit.FromCgroup()
	if err != nil || totalMemory == memoryMax {
		log.Info("no cgroup memory limit", zap.Error(err))
		totalMemory, err = memory.MemTotal()
		if err != nil {
			return 0, errors.Trace(err)
		}
	}
	return totalMemory, nil
}

// CheckMemoryUsage checks if the memory usage is less than the limit.
func CheckMemoryUsage(limit float64) (bool, error) {
	stat, err := mem.VirtualMemory()
	if err != nil {
		return false, err
	}

	log.Info("check memory usage", zap.Any("memory", stat))
	return stat.UsedPercent < limit, nil
}

// WaitMemoryAvailable waits until the memory usage is less than the limit.
func WaitMemoryAvailable(ctx context.Context, limit float64, timeout time.Duration) error {
	ticker := time.NewTicker(time.Second * 5)
	timeoutTimer := time.NewTimer(timeout)
	for {
		select {
		case <-ctx.Done():
			return errors.WrapError(errors.ErrWaitFreeMemoryTimeout, ctx.Err())
		case <-ticker.C:
			hasFreeMemory, err := CheckMemoryUsage(limit)
			if err != nil {
				return err
			}
			if hasFreeMemory {
				return nil
			}
		case <-timeoutTimer.C:
			return errors.ErrWaitFreeMemoryTimeout.GenWithStackByArgs()
		}
	}
}