// Copyright 2021 TiKV 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.

// NOTE: The code in this file is based on code from the
// TiDB project, licensed under the Apache License v 2.0
//
// https://github.com/pingcap/tidb/tree/cc5e161ac06827589c4966674597c137cc9e809c/store/tikv/kv/kv.go
//

package kv

import (
	"math"
	"sync"
	"time"

	"github.com/pingcap/kvproto/pkg/kvrpcpb"
	tikverr "github.com/tikv/client-go/v2/error"
	"github.com/tikv/client-go/v2/util"
)

// ReturnedValue pairs the Value and AlreadyLocked flag for PessimisticLock return values result.
type ReturnedValue struct {
	Value                []byte
	Exists               bool
	LockedWithConflictTS uint64
	AlreadyLocked        bool
}

// Used for pessimistic lock wait time
// these two constants are special for lock protocol with tikv
// math.MaxInt64 means always wait, -1 means nowait, 0 means the default wait duration in TiKV,
// others meaning lock wait in milliseconds
const (
	LockAlwaysWait = int64(math.MaxInt64)
	LockNoWait     = int64(-1)
)

type lockWaitTimeInMs struct {
	value int64
}

func defaultLockWaitTime() *lockWaitTimeInMs {
	return &lockWaitTimeInMs{value: LockAlwaysWait}
}

// LockCtx contains information for LockKeys method.
type LockCtx struct {
	Killed                  *uint32
	ForUpdateTS             uint64
	lockWaitTime            *lockWaitTimeInMs
	WaitStartTime           time.Time
	ReturnValues            bool
	CheckExistence          bool
	LockOnlyIfExists        bool
	Values                  map[string]ReturnedValue
	MaxLockedWithConflictTS uint64
	ValuesLock              sync.Mutex
	LockExpired             *uint32
	Stats                   *util.LockKeysDetails
	ResourceGroupTag        []byte
	// ResourceGroupTagger is a special tagger used only for PessimisticLockRequest.
	// We did not use tikvrpc.ResourceGroupTagger here because the kv package is a
	// more basic component, and we cannot rely on tikvrpc.Request here, so we treat
	// LockCtx specially.
	ResourceGroupTagger func(*kvrpcpb.PessimisticLockRequest) []byte
	OnDeadlock          func(*tikverr.ErrDeadlock)
	// max_execution_time support - if zero, timeout checking is disabled
	MaxExecutionDeadline time.Time
}

// LockWaitTime returns lockWaitTimeInMs
func (ctx *LockCtx) LockWaitTime() int64 {
	if ctx.lockWaitTime == nil {
		ctx.lockWaitTime = defaultLockWaitTime()
	}
	return ctx.lockWaitTime.value
}

// NewLockCtx creates a LockCtx.
func NewLockCtx(forUpdateTS uint64, lockWaitTime int64, waitStartTime time.Time) *LockCtx {
	return &LockCtx{
		ForUpdateTS:   forUpdateTS,
		lockWaitTime:  &lockWaitTimeInMs{value: lockWaitTime},
		WaitStartTime: waitStartTime,
	}
}

// InitReturnValues creates the map to store returned value.
func (ctx *LockCtx) InitReturnValues(capacity int) {
	ctx.ReturnValues = true
	if ctx.Values == nil {
		ctx.Values = make(map[string]ReturnedValue, capacity)
	}
}

// InitCheckExistence creates the map to store whether each key exists or not.
func (ctx *LockCtx) InitCheckExistence(capacity int) {
	ctx.CheckExistence = true
	if ctx.Values == nil {
		ctx.Values = make(map[string]ReturnedValue, capacity)
	}
}

// GetValueNotLocked returns a value if the key is not already locked.
// (nil, false) means already locked.
func (ctx *LockCtx) GetValueNotLocked(key []byte) ([]byte, bool) {
	rv := ctx.Values[string(key)]
	if !rv.AlreadyLocked {
		return rv.Value, true
	}
	return nil, false
}

// IterateValuesNotLocked applies f to all key-values that are not already
// locked.
func (ctx *LockCtx) IterateValuesNotLocked(f func([]byte, []byte)) {
	ctx.ValuesLock.Lock()
	defer ctx.ValuesLock.Unlock()
	for key, val := range ctx.Values {
		if !val.AlreadyLocked {
			f([]byte(key), val.Value)
		}
	}
}