// Copyright 2024 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,
// 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 sessionexpr

import (
	"context"
	"math"
	"time"

	"github.com/pingcap/tidb/pkg/errctx"
	"github.com/pingcap/tidb/pkg/expression/exprctx"
	"github.com/pingcap/tidb/pkg/expression/expropt"
	"github.com/pingcap/tidb/pkg/expression/exprstatic"
	infoschema "github.com/pingcap/tidb/pkg/infoschema/context"
	"github.com/pingcap/tidb/pkg/parser/ast"
	"github.com/pingcap/tidb/pkg/parser/auth"
	"github.com/pingcap/tidb/pkg/parser/mysql"
	"github.com/pingcap/tidb/pkg/privilege"
	"github.com/pingcap/tidb/pkg/sessionctx"
	"github.com/pingcap/tidb/pkg/sessionctx/vardef"
	"github.com/pingcap/tidb/pkg/sessionctx/variable"
	"github.com/pingcap/tidb/pkg/types"
	"github.com/pingcap/tidb/pkg/util"
	contextutil "github.com/pingcap/tidb/pkg/util/context"
	"github.com/pingcap/tidb/pkg/util/intest"
	"github.com/pingcap/tidb/pkg/util/logutil"
	"github.com/pingcap/tidb/pkg/util/mathutil"
	"github.com/tikv/client-go/v2/oracle"
	"go.uber.org/zap"
)

// ExprContext should implement the `ExprContext` interface.
var _ exprctx.ExprContext = &ExprContext{}

// ExprContext implements `ExprContext`
type ExprContext struct {
	sctx sessionctx.Context
	*EvalContext
}

// NewExprContext creates a new ExprContext.
func NewExprContext(sctx sessionctx.Context) *ExprContext {
	return &ExprContext{
		sctx:        sctx,
		EvalContext: NewEvalContext(sctx),
	}
}

// GetEvalCtx returns the EvalContext.
func (ctx *ExprContext) GetEvalCtx() exprctx.EvalContext {
	return ctx.EvalContext
}

// GetCharsetInfo gets charset and collation for current context.
func (ctx *ExprContext) GetCharsetInfo() (string, string) {
	return ctx.sctx.GetSessionVars().GetCharsetInfo()
}

// GetDefaultCollationForUTF8MB4 returns the default collation of UTF8MB4.
func (ctx *ExprContext) GetDefaultCollationForUTF8MB4() string {
	return ctx.sctx.GetSessionVars().DefaultCollationForUTF8MB4
}

// GetBlockEncryptionMode returns the variable block_encryption_mode
func (ctx *ExprContext) GetBlockEncryptionMode() string {
	blockMode, ok := ctx.sctx.GetSessionVars().GetSystemVar(vardef.BlockEncryptionMode)
	if !ok {
		return vardef.DefBlockEncryptionMode
	}
	return blockMode
}

// GetSysdateIsNow returns a bool to determine whether Sysdate is an alias of Now function.
// It is the value of variable `tidb_sysdate_is_now`.
func (ctx *ExprContext) GetSysdateIsNow() bool {
	return ctx.sctx.GetSessionVars().SysdateIsNow
}

// GetNoopFuncsMode returns the noop function mode: OFF/ON/WARN values as 0/1/2.
func (ctx *ExprContext) GetNoopFuncsMode() int {
	return ctx.sctx.GetSessionVars().NoopFuncsMode
}

// Rng is used to generate random values.
func (ctx *ExprContext) Rng() *mathutil.MysqlRng {
	return ctx.sctx.GetSessionVars().Rng
}

// IsUseCache indicates whether to cache the build expression in plan cache.
// If SetSkipPlanCache is invoked, it should return false.
func (ctx *ExprContext) IsUseCache() bool {
	return ctx.sctx.GetSessionVars().StmtCtx.UseCache()
}

// SetSkipPlanCache sets to skip the plan cache and records the reason.
func (ctx *ExprContext) SetSkipPlanCache(reason string) {
	ctx.sctx.GetSessionVars().StmtCtx.SetSkipPlanCache(reason)
}

// AllocPlanColumnID allocates column id for plan.
func (ctx *ExprContext) AllocPlanColumnID() int64 {
	return ctx.sctx.GetSessionVars().AllocPlanColumnID()
}

// IsInNullRejectCheck returns whether the expression is in null reject check.
func (ctx *ExprContext) IsInNullRejectCheck() bool {
	return false
}

// IsConstantPropagateCheck returns whether the ctx is in constant propagate check.
func (ctx *ExprContext) IsConstantPropagateCheck() bool {
	return false
}

// GetWindowingUseHighPrecision determines whether to compute window operations without loss of precision.
// see https://dev.mysql.com/doc/refman/8.0/en/window-function-optimization.html for more details.
func (ctx *ExprContext) GetWindowingUseHighPrecision() bool {
	return ctx.sctx.GetSessionVars().WindowingUseHighPrecision
}

// GetGroupConcatMaxLen returns the value of the 'group_concat_max_len' system variable.
func (ctx *ExprContext) GetGroupConcatMaxLen() uint64 {
	return ctx.sctx.GetSessionVars().GroupConcatMaxLen
}

// ConnectionID indicates the connection ID of the current session.
// If the context is not in a session, it should return 0.
func (ctx *ExprContext) ConnectionID() uint64 {
	return ctx.sctx.GetSessionVars().ConnectionID
}

// IsReadonlyUserVar checks whether the user variable is readonly.
func (ctx *ExprContext) IsReadonlyUserVar(name string) bool {
	m := ctx.sctx.GetPlanCtx().GetReadonlyUserVarMap()
	_, ok := m[name]
	return ok
}

// IntoStatic turns the ExprContext into a ExprContext.
func (ctx *ExprContext) IntoStatic() *exprstatic.ExprContext {
	return exprstatic.MakeExprContextStatic(ctx)
}

// EvalContext implements the `expression.EvalContext` interface to provide evaluation context in session.
type EvalContext struct {
	sctx  sessionctx.Context
	props expropt.OptionalEvalPropProviders
}

// NewEvalContext creates a new EvalContext.
func NewEvalContext(sctx sessionctx.Context) *EvalContext {
	ctx := &EvalContext{sctx: sctx}
	// set all optional properties
	ctx.setOptionalProp(currentUserProp(sctx))
	ctx.setOptionalProp(expropt.NewSessionVarsProvider(sctx))
	ctx.setOptionalProp(infoSchemaProp(sctx))
	ctx.setOptionalProp(expropt.KVStorePropProvider(sctx.GetStore))
	ctx.setOptionalProp(sqlExecutorProp(sctx))
	ctx.setOptionalProp(sequenceOperatorProp(sctx))
	ctx.setOptionalProp(expropt.NewAdvisoryLockPropProvider(sctx))
	ctx.setOptionalProp(expropt.DDLOwnerInfoProvider(sctx.IsDDLOwner))
	ctx.setOptionalProp(expropt.PrivilegeCheckerProvider(func() expropt.PrivilegeChecker { return ctx }))
	// When EvalContext is created from a session, it should contain all the optional properties.
	intest.Assert(ctx.props.PropKeySet().IsFull())
	return ctx
}

func (ctx *EvalContext) setOptionalProp(prop exprctx.OptionalEvalPropProvider) {
	intest.AssertFunc(func() bool {
		return !ctx.props.Contains(prop.Desc().Key())
	})
	ctx.props.Add(prop)
}

// Sctx returns the innert session context
func (ctx *EvalContext) Sctx() sessionctx.Context {
	return ctx.sctx
}

// CtxID returns the context id.
func (ctx *EvalContext) CtxID() uint64 {
	return ctx.sctx.GetSessionVars().StmtCtx.CtxID()
}

// SQLMode returns the sql mode
func (ctx *EvalContext) SQLMode() mysql.SQLMode {
	return ctx.sctx.GetSessionVars().SQLMode
}

// TypeCtx returns the types.Context
func (ctx *EvalContext) TypeCtx() (tc types.Context) {
	tc = ctx.sctx.GetSessionVars().StmtCtx.TypeCtx()
	if intest.EnableAssert {
		exprctx.AssertLocationWithSessionVars(tc.Location(), ctx.sctx.GetSessionVars())
	}
	return
}

// ErrCtx returns the errctx.Context
func (ctx *EvalContext) ErrCtx() errctx.Context {
	return ctx.sctx.GetSessionVars().StmtCtx.ErrCtx()
}

// Location returns the timezone info
func (ctx *EvalContext) Location() *time.Location {
	tc := ctx.TypeCtx()
	return tc.Location()
}

// AppendWarning append warnings to the context.
func (ctx *EvalContext) AppendWarning(err error) {
	ctx.sctx.GetSessionVars().StmtCtx.AppendWarning(err)
}

// AppendNote appends notes to the context.
func (ctx *EvalContext) AppendNote(err error) {
	ctx.sctx.GetSessionVars().StmtCtx.AppendNote(err)
}

// WarningCount gets warning count.
func (ctx *EvalContext) WarningCount() int {
	return int(ctx.sctx.GetSessionVars().StmtCtx.WarningCount())
}

// TruncateWarnings truncates warnings begin from start and returns the truncated warnings.
func (ctx *EvalContext) TruncateWarnings(start int) []contextutil.SQLWarn {
	return ctx.sctx.GetSessionVars().StmtCtx.TruncateWarnings(start)
}

// CopyWarnings copies the warnings to dst
func (ctx *EvalContext) CopyWarnings(dst []contextutil.SQLWarn) []contextutil.SQLWarn {
	return ctx.sctx.GetSessionVars().StmtCtx.CopyWarnings(dst)
}

// CurrentDB returns the current database name
func (ctx *EvalContext) CurrentDB() string {
	return ctx.sctx.GetSessionVars().CurrentDB
}

// CurrentTime returns the current time
func (ctx *EvalContext) CurrentTime() (time.Time, error) {
	return getStmtTimestamp(ctx.sctx)
}

// GetMaxAllowedPacket returns the value of the 'max_allowed_packet' system variable.
func (ctx *EvalContext) GetMaxAllowedPacket() uint64 {
	return ctx.sctx.GetSessionVars().MaxAllowedPacket
}

// GetTiDBRedactLog returns the value of the 'tidb_redact_log' system variable.
func (ctx *EvalContext) GetTiDBRedactLog() string {
	return ctx.sctx.GetSessionVars().EnableRedactLog
}

// GetDefaultWeekFormatMode returns the value of the 'default_week_format' system variable.
func (ctx *EvalContext) GetDefaultWeekFormatMode() string {
	mode, ok := ctx.sctx.GetSessionVars().GetSystemVar(vardef.DefaultWeekFormat)
	if !ok || mode == "" {
		return "0"
	}
	return mode
}

// GetDivPrecisionIncrement returns the specified value of DivPrecisionIncrement.
func (ctx *EvalContext) GetDivPrecisionIncrement() int {
	return ctx.sctx.GetSessionVars().GetDivPrecisionIncrement()
}

// GetOptionalPropSet gets the optional property set from context
func (ctx *EvalContext) GetOptionalPropSet() exprctx.OptionalEvalPropKeySet {
	return ctx.props.PropKeySet()
}

// GetOptionalPropProvider gets the optional property provider by key
func (ctx *EvalContext) GetOptionalPropProvider(key exprctx.OptionalEvalPropKey) (exprctx.OptionalEvalPropProvider, bool) {
	return ctx.props.Get(key)
}

// RequestVerification verifies user privilege
func (ctx *EvalContext) RequestVerification(db, table, column string, priv mysql.PrivilegeType) bool {
	checker := privilege.GetPrivilegeManager(ctx.sctx)
	if checker == nil {
		return true
	}
	return checker.RequestVerification(ctx.sctx.GetSessionVars().ActiveRoles, db, table, column, priv)
}

// RequestDynamicVerification verifies user privilege for a DYNAMIC privilege.
func (ctx *EvalContext) RequestDynamicVerification(privName string, grantable bool) bool {
	checker := privilege.GetPrivilegeManager(ctx.sctx)
	if checker == nil {
		return true
	}
	return checker.RequestDynamicVerification(ctx.sctx.GetSessionVars().ActiveRoles, privName, grantable)
}

// GetParamValue returns the value of the parameter by index.
func (ctx *EvalContext) GetParamValue(idx int) (types.Datum, error) {
	params := ctx.sctx.GetSessionVars().PlanCacheParams.AllParamValues()
	if idx >= len(params) {
		return types.Datum{}, exprctx.ErrParamIndexExceedParamCounts
	}
	return params[idx], nil
}

// GetUserVarsReader returns the user variables.
func (ctx *EvalContext) GetUserVarsReader() variable.UserVarsReader {
	return ctx.sctx.GetSessionVars().UserVars
}

// IntoStatic turns the EvalContext into a EvalContext.
func (ctx *EvalContext) IntoStatic() *exprstatic.EvalContext {
	return exprstatic.MakeEvalContextStatic(ctx)
}

func getStmtTimestamp(ctx sessionctx.Context) (time.Time, error) {
	if ctx != nil {
		staleTSO, err := ctx.GetSessionVars().StmtCtx.GetStaleTSO()
		if staleTSO != 0 && err == nil {
			return oracle.GetTimeFromTS(staleTSO), nil
		} else if err != nil {
			logutil.BgLogger().Error("get stale tso failed", zap.Error(err))
		}
	}

	now := time.Now()

	if ctx == nil {
		return now, nil
	}

	sessionVars := ctx.GetSessionVars()
	timestampStr, err := sessionVars.GetSessionOrGlobalSystemVar(context.Background(), "timestamp")
	if err != nil {
		return now, err
	}

	timestamp, err := types.StrToFloat(sessionVars.StmtCtx.TypeCtx(), timestampStr, false)
	if err != nil {
		return time.Time{}, err
	}
	seconds, fractionalSeconds := math.Modf(timestamp)
	return time.Unix(int64(seconds), int64(fractionalSeconds*float64(time.Second))), nil
}

func currentUserProp(sctx sessionctx.Context) exprctx.OptionalEvalPropProvider {
	return expropt.CurrentUserPropProvider(func() (*auth.UserIdentity, []*auth.RoleIdentity) {
		vars := sctx.GetSessionVars()
		return vars.User, vars.ActiveRoles
	})
}

func infoSchemaProp(sctx sessionctx.Context) expropt.InfoSchemaPropProvider {
	return func(isDomain bool) infoschema.MetaOnlyInfoSchema {
		if isDomain {
			return sctx.GetLatestInfoSchema()
		}
		return sctx.GetInfoSchema()
	}
}

func sqlExecutorProp(sctx sessionctx.Context) expropt.SQLExecutorPropProvider {
	return func() (expropt.SQLExecutor, error) {
		return sctx.GetRestrictedSQLExecutor(), nil
	}
}

type sequenceOperator struct {
	sctx sessionctx.Context
	db   string
	name string
	tbl  util.SequenceTable
}

func (s *sequenceOperator) GetSequenceID() int64 {
	return s.tbl.GetSequenceID()
}

func (s *sequenceOperator) GetSequenceNextVal() (int64, error) {
	return s.tbl.GetSequenceNextVal(s.sctx, s.db, s.name)
}

func (s *sequenceOperator) SetSequenceVal(newVal int64) (int64, bool, error) {
	return s.tbl.SetSequenceVal(s.sctx, newVal, s.db, s.name)
}

func sequenceOperatorProp(sctx sessionctx.Context) expropt.SequenceOperatorProvider {
	return func(db, name string) (expropt.SequenceOperator, error) {
		sequence, err := util.GetSequenceByName(sctx.GetInfoSchema(), ast.NewCIStr(db), ast.NewCIStr(name))
		if err != nil {
			return nil, err
		}
		return &sequenceOperator{sctx, db, name, sequence}, nil
	}
}

var _ exprctx.StaticConvertibleExprContext = &ExprContext{}

// GetStaticConvertibleEvalContext implements context.StaticConvertibleExprContext.
func (ctx *ExprContext) GetStaticConvertibleEvalContext() exprctx.StaticConvertibleEvalContext {
	return ctx.EvalContext
}

// GetPlanCacheTracker implements context.StaticConvertibleExprContext.
func (ctx *ExprContext) GetPlanCacheTracker() *contextutil.PlanCacheTracker {
	return &ctx.sctx.GetSessionVars().StmtCtx.PlanCacheTracker
}

// GetLastPlanColumnID implements context.StaticConvertibleExprContext.
func (ctx *ExprContext) GetLastPlanColumnID() int64 {
	return ctx.sctx.GetSessionVars().PlanColumnID.Load()
}

var _ exprctx.StaticConvertibleEvalContext = &EvalContext{}

// AllParamValues implements context.StaticConvertibleEvalContext.
func (ctx *EvalContext) AllParamValues() []types.Datum {
	return ctx.sctx.GetSessionVars().PlanCacheParams.AllParamValues()
}

// GetWarnHandler implements context.StaticConvertibleEvalContext.
func (ctx *EvalContext) GetWarnHandler() contextutil.WarnHandler {
	return ctx.sctx.GetSessionVars().StmtCtx.WarnHandler
}