/*
Real-time Online/Offline Charging System (OCS) for Telecom & ISP environments
Copyright (C) ITsysCOM GmbH
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>
*/

package engine

import (
	"errors"
	"fmt"
	"reflect"
	"strings"
	"sync"
	"time"

	"github.com/cgrates/cgrates/config"
	"github.com/cgrates/cgrates/utils"
	"github.com/cgrates/rpcclient"
)

const (
	MetaNot            = "*not"
	MetaString         = "*string"
	MetaPrefix         = "*prefix"
	MetaSuffix         = "*suffix"
	MetaEmpty          = "*empty"
	MetaExists         = "*exists"
	MetaTimings        = "*timings"
	MetaRSR            = "*rsr"
	MetaStatS          = "*stats"
	MetaDestinations   = "*destinations"
	MetaMinCapPrefix   = "*min_"
	MetaMaxCapPrefix   = "*max_"
	MetaLessThan       = "*lt"
	MetaLessOrEqual    = "*lte"
	MetaGreaterThan    = "*gt"
	MetaGreaterOrEqual = "*gte"
	MetaResources      = "*resources"

	MetaNotString       = "*notstring"
	MetaNotPrefix       = "*notprefix"
	MetaNotSuffix       = "*notsuffix"
	MetaNotEmpty        = "*notempty"
	MetaNotExists       = "*notexists"
	MetaNotTimings      = "*nottimings"
	MetaNotRSR          = "*notrsr"
	MetaNotStatS        = "*notstats"
	MetaNotDestinations = "*notdestinations"
	MetaNotResources    = "*notresources"
)

func NewFilterS(cfg *config.CGRConfig,
	statSChan, resSChan chan rpcclient.RpcClientConnection, dm *DataManager) (fS *FilterS) {
	fS = &FilterS{
		statSChan: statSChan,
		resSChan:  resSChan,
		dm:        dm,
		cfg:       cfg,
	}
	if len(cfg.FilterSCfg().StatSConns) != 0 {
		fS.connStatS()
	}
	if len(cfg.FilterSCfg().ResourceSConns) != 0 {
		fS.connResourceS()
	}
	return
}

// FilterS is a service used to take decisions in case of filters
// uses lazy connections where necessary to avoid deadlocks on service startup
type FilterS struct {
	cfg                   *config.CGRConfig
	statSChan, resSChan   chan rpcclient.RpcClientConnection // reference towards internal statS connection, used for lazy connect
	statSConns, resSConns rpcclient.RpcClientConnection
	sSConnMux, rSConnMux  sync.RWMutex // make sure only one goroutine attempts connecting
	dm                    *DataManager
}

// connStatS returns will connect towards StatS
func (fS *FilterS) connStatS() (err error) {
	fS.sSConnMux.Lock()
	defer fS.sSConnMux.Unlock()
	if fS.statSConns != nil { // connection was populated between locks
		return
	}
	fS.statSConns, err = NewRPCPool(rpcclient.POOL_FIRST,
		fS.cfg.TlsCfg().ClientKey, fS.cfg.TlsCfg().ClientCerificate,
		fS.cfg.TlsCfg().CaCertificate, fS.cfg.GeneralCfg().ConnectAttempts,
		fS.cfg.GeneralCfg().Reconnects, fS.cfg.GeneralCfg().ConnectTimeout,
		fS.cfg.GeneralCfg().ReplyTimeout, fS.cfg.FilterSCfg().StatSConns,
		fS.statSChan, fS.cfg.GeneralCfg().InternalTtl, true)
	return
}

// connResourceS returns will connect towards ResourceS
func (fS *FilterS) connResourceS() (err error) {
	fS.rSConnMux.Lock()
	defer fS.rSConnMux.Unlock()
	if fS.resSConns != nil { // connection was populated between locks
		return
	}
	fS.resSConns, err = NewRPCPool(rpcclient.POOL_FIRST,
		fS.cfg.TlsCfg().ClientKey, fS.cfg.TlsCfg().ClientCerificate,
		fS.cfg.TlsCfg().CaCertificate, fS.cfg.GeneralCfg().ConnectAttempts,
		fS.cfg.GeneralCfg().Reconnects, fS.cfg.GeneralCfg().ConnectTimeout,
		fS.cfg.GeneralCfg().ReplyTimeout, fS.cfg.FilterSCfg().ResourceSConns,
		fS.resSChan, fS.cfg.GeneralCfg().InternalTtl, true)
	return
}

// Pass will check all filters wihin filterIDs and require them passing for dataProvider
// there should be at least one filter passing, ie: if filters are not active event will fail to pass
// receives the event as DataProvider so we can accept undecoded data (ie: HttpRequest)
func (fS *FilterS) Pass(tenant string, filterIDs []string,
	ev config.DataProvider) (pass bool, err error) {
	if len(filterIDs) == 0 {
		return true, nil
	}
	for _, fltrID := range filterIDs {
		f, err := fS.dm.GetFilter(tenant, fltrID,
			true, true, utils.NonTransactional)
		if err != nil {
			if err == utils.ErrNotFound {
				err = utils.ErrPrefixNotFound(fltrID)
			}
			return false, err
		}
		if f.ActivationInterval != nil &&
			!f.ActivationInterval.IsActiveAtTime(time.Now()) { // not active
			continue
		}
		for _, fltr := range f.Rules {
			if pass, err = fltr.Pass(ev, fS.statSConns, tenant); err != nil || !pass {
				return pass, err
			}
		}
		pass = true
	}
	return
}

// NewFilterFromInline parses an inline rule into a compiled Filter
func NewFilterFromInline(tenant, inlnRule string) (f *Filter, err error) {
	ruleSplt := strings.Split(inlnRule, utils.InInFieldSep)
	if len(ruleSplt) < 3 {
		return nil, fmt.Errorf("inline parse error for string: <%s>", inlnRule)
	}
	f = &Filter{
		Tenant: tenant,
		ID:     inlnRule,
		Rules: []*FilterRule{{
			Type:      ruleSplt[0],
			FieldName: ruleSplt[1],
			Values:    strings.Split(strings.Join(ruleSplt[2:], utils.InInFieldSep), utils.INFIELD_SEP),
		}},
	}
	if err = f.Compile(); err != nil {
		return nil, err
	}
	return
}

type Filter struct {
	Tenant             string
	ID                 string
	Rules              []*FilterRule
	ActivationInterval *utils.ActivationInterval
}

func (flt *Filter) TenantID() string {
	return utils.ConcatenatedKey(flt.Tenant, flt.ID)
}

// Compile will compile the underlaying request filters where necessary (ie. regexp rules)
func (f *Filter) Compile() (err error) {
	for _, rf := range f.Rules {
		if err = rf.CompileValues(); err != nil {
			return
		}
	}
	return
}

func NewFilterRule(rfType, fieldName string, vals []string) (*FilterRule, error) {
	var negative bool
	rType := rfType
	if strings.HasPrefix(rfType, MetaNot) {
		rType = "*" + strings.TrimPrefix(rfType, MetaNot)
		negative = true
	}
	if !utils.IsSliceMember([]string{MetaString, MetaPrefix, MetaSuffix,
		MetaTimings, MetaRSR, MetaStatS, MetaDestinations, MetaEmpty,
		MetaExists, MetaLessThan, MetaLessOrEqual, MetaGreaterThan,
		MetaGreaterOrEqual, MetaResources}, rType) {
		return nil, fmt.Errorf("Unsupported filter Type: %s", rfType)
	}
	if fieldName == "" && utils.IsSliceMember([]string{MetaString, MetaPrefix, MetaSuffix,
		MetaTimings, MetaDestinations, MetaLessThan, MetaEmpty, MetaExists,
		MetaLessOrEqual, MetaGreaterThan, MetaGreaterOrEqual}, rType) {
		return nil, fmt.Errorf("FieldName is mandatory for Type: %s", rfType)
	}
	if len(vals) == 0 && utils.IsSliceMember([]string{MetaString, MetaPrefix, MetaSuffix,
		MetaTimings, MetaRSR, MetaDestinations, MetaLessThan, MetaLessOrEqual,
		MetaGreaterThan, MetaGreaterOrEqual}, rType) {
		return nil, fmt.Errorf("Values is mandatory for Type: %s", rfType)
	}
	rf := &FilterRule{
		Type:      rfType,
		FieldName: fieldName,
		Values:    vals,
		negative:  utils.BoolPointer(negative),
	}
	if err := rf.CompileValues(); err != nil {
		return nil, err
	}
	return rf, nil
}

//itemFilter is used for *stats and *resources filter type
type itemFilter struct {
	ItemID      string
	FilterType  string
	FilterValue string
}

// FilterRule filters requests coming into various places
// Pass rule: default negative, one mathing rule should pass the filter
type FilterRule struct {
	Type          string            // Filter type (*string, *timing, *rsr_filters, *stats, *lt, *lte, *gt, *gte)
	FieldName     string            // Name of the field providing us the Values to check (used in case of some )
	Values        []string          // Filter definition
	rsrFields     config.RSRParsers // Cache here the RSRFilter Values
	negative      *bool
	statItems     []*itemFilter // Cached compiled itemFilter out of Values
	resourceItems []*itemFilter // Cached compiled itemFilter out of Values
}

// Separate method to compile RSR fields
func (rf *FilterRule) CompileValues() (err error) {
	switch rf.Type {
	case MetaRSR, MetaNotRSR:
		if rf.rsrFields, err = config.NewRSRParsersFromSlice(rf.Values, true); err != nil {
			return
		}
	case MetaStatS, MetaNotStatS:
		//value for filter of type *stats needs to be in the following form:
		//*gt#acd:StatID:ValueOfMetric
		rf.statItems = make([]*itemFilter, len(rf.Values))
		for i, val := range rf.Values {
			valSplt := strings.Split(val, utils.InInFieldSep)
			if len(valSplt) != 3 {
				return fmt.Errorf("Value %s needs to contain at least 3 items", val)
			}
			// valSplt[0] filter type with metric
			// valSplt[1] id of the statQueue
			// valSplt[2] value to compare
			rf.statItems[i] = &itemFilter{
				FilterType:  valSplt[0],
				ItemID:      valSplt[1],
				FilterValue: valSplt[2],
			}
		}
	case MetaResources, MetaNotResources:
		//value for filter of type *resources needs to be in the following form:
		//*gt:ResourceID:ValueOfUsage
		rf.resourceItems = make([]*itemFilter, len(rf.Values))
		for i, val := range rf.Values {
			valSplt := strings.Split(val, utils.InInFieldSep)
			if len(valSplt) != 3 {
				return fmt.Errorf("Value %s needs to contain at least 3 items", val)
			}
			// valSplt[0] filter type
			// valSplt[1] id of the Resource
			// valSplt[2] value to compare
			rf.resourceItems[i] = &itemFilter{
				FilterType:  valSplt[0],
				ItemID:      valSplt[1],
				FilterValue: valSplt[2],
			}
		}
	}
	return
}

// Pass is the method which should be used from outside.
func (fltr *FilterRule) Pass(dP config.DataProvider,
	rpcClnt rpcclient.RpcClientConnection, tenant string) (result bool, err error) {
	if fltr.negative == nil {
		fltr.negative = utils.BoolPointer(strings.HasPrefix(fltr.Type, MetaNot))
	}

	switch fltr.Type {
	case MetaString, MetaNotString:
		result, err = fltr.passString(dP)
	case MetaEmpty, MetaNotEmpty:
		result, err = fltr.passEmpty(dP)
	case MetaExists, MetaNotExists:
		result, err = fltr.passExists(dP)
	case MetaPrefix, MetaNotPrefix:
		result, err = fltr.passStringPrefix(dP)
	case MetaSuffix, MetaNotSuffix:
		result, err = fltr.passStringSuffix(dP)
	case MetaTimings, MetaNotTimings:
		result, err = fltr.passTimings(dP)
	case MetaDestinations, MetaNotDestinations:
		result, err = fltr.passDestinations(dP)
	case MetaRSR, MetaNotRSR:
		result, err = fltr.passRSR(dP)
	case MetaStatS, MetaNotStatS:
		result, err = fltr.passStatS(dP, rpcClnt, tenant)
	case MetaLessThan, MetaLessOrEqual, MetaGreaterThan, MetaGreaterOrEqual:
		result, err = fltr.passGreaterThan(dP)
	case MetaResources, MetaNotResources:
		result, err = fltr.passResourceS(dP, rpcClnt, tenant)
	default:
		err = utils.ErrPrefixNotErrNotImplemented(fltr.Type)
	}
	if err != nil {
		return false, err
	}
	return result != *(fltr.negative), nil
}

func (fltr *FilterRule) passString(dP config.DataProvider) (bool, error) {
	strVal, err := config.GetDynamicString(fltr.FieldName, dP)
	if err != nil {
		if err == utils.ErrNotFound {
			return false, nil
		}
		return false, err
	}
	for _, val := range fltr.Values {
		sval, err := config.GetDynamicString(val, dP)
		if err != nil {
			continue
		}
		if strVal == sval {
			return true, nil
		}
	}
	return false, nil
}

func (fltr *FilterRule) passExists(dP config.DataProvider) (bool, error) {
	_, err := config.GetDynamicInterface(fltr.FieldName, dP)
	if err != nil {
		if err == utils.ErrNotFound {
			return false, nil
		}
		return false, err
	}
	return true, nil
}

func (fltr *FilterRule) passEmpty(dP config.DataProvider) (bool, error) {
	val, err := config.GetDynamicInterface(fltr.FieldName, dP)
	if err != nil {
		if err == utils.ErrNotFound {
			return true, nil
		}
		return false, err
	}
	if val == nil {
		return true, nil
	}
	rval := reflect.ValueOf(val)
	if rval.Type().Kind() == reflect.Ptr {
		if rval.IsNil() {
			return true, nil
		}
		rval = rval.Elem()
	}
	switch rval.Type().Kind() {
	case reflect.String:
		return rval.Interface() == "", nil
	case reflect.Slice:
		return rval.Len() == 0, nil
	case reflect.Map:
		return len(rval.MapKeys()) == 0, nil
	default:
		return false, nil
	}
}

func (fltr *FilterRule) passStringPrefix(dP config.DataProvider) (bool, error) {
	strVal, err := config.GetDynamicString(fltr.FieldName, dP)
	if err != nil {
		if err == utils.ErrNotFound {
			return false, nil
		}
		return false, err
	}
	for _, prfx := range fltr.Values {
		prfx, err := config.GetDynamicString(prfx, dP)
		if err != nil {
			continue
		}
		if strings.HasPrefix(strVal, prfx) {
			return true, nil
		}
	}
	return false, nil
}

func (fltr *FilterRule) passStringSuffix(dP config.DataProvider) (bool, error) {
	strVal, err := config.GetDynamicString(fltr.FieldName, dP)
	if err != nil {
		if err == utils.ErrNotFound {
			return false, nil
		}
		return false, err
	}
	for _, prfx := range fltr.Values {
		prfx, err := config.GetDynamicString(prfx, dP)
		if err != nil {
			continue
		}
		if strings.HasSuffix(strVal, prfx) {
			return true, nil
		}
	}
	return false, nil
}

// ToDo when Timings will be available in DataDb
func (fltr *FilterRule) passTimings(dP config.DataProvider) (bool, error) {
	return false, utils.ErrNotImplemented
}

func (fltr *FilterRule) passDestinations(dP config.DataProvider) (bool, error) {
	dst, err := config.GetDynamicString(fltr.FieldName, dP)
	if err != nil {
		if err == utils.ErrNotFound {
			return false, nil
		}
		return false, err
	}
	for _, p := range utils.SplitPrefix(dst, MIN_PREFIX_MATCH) {
		if destIDs, err := dm.DataDB().GetReverseDestination(p, false, utils.NonTransactional); err == nil {
			for _, dID := range destIDs {
				for _, valDstID := range fltr.Values {
					valDstID, err := config.GetDynamicString(valDstID, dP)
					if err != nil {
						continue
					}
					if valDstID == dID {
						return true, nil
					}
				}
			}
		}
	}
	return false, nil
}

func (fltr *FilterRule) passRSR(dP config.DataProvider) (bool, error) {
	_, err := fltr.rsrFields.ParseDataProviderWithInterfaces(dP, utils.NestingSep)
	if err != nil {
		if err == utils.ErrNotFound || err == utils.ErrFilterNotPassingNoCaps {
			return false, nil
		}
		return false, err
	}
	return true, nil
}

func (fltr *FilterRule) passStatS(dP config.DataProvider,
	stats rpcclient.RpcClientConnection, tenant string) (bool, error) {
	if stats == nil || reflect.ValueOf(stats).IsNil() {
		return false, errors.New("Missing StatS information")
	}
	for _, statItem := range fltr.statItems {
		statValues := make(map[string]float64)
		if err := stats.Call(utils.StatSv1GetQueueFloatMetrics,
			&utils.TenantID{Tenant: tenant, ID: statItem.ItemID}, &statValues); err != nil {
			return false, err
		}
		//convert statValues to map[string]interface{}
		ifaceStatValues := make(map[string]interface{})
		for key, val := range statValues {
			ifaceStatValues[key] = val
		}
		//convert ifaceStatValues into a NavigableMap so we can send it to passGreaterThan
		nM := config.NewNavigableMap(ifaceStatValues)
		//split the type in exact 2 parts
		//special cases like *gt#sum#Usage
		fltrType := strings.SplitN(statItem.FilterType, utils.STATS_CHAR, 2)
		if len(fltrType) < 2 {
			return false, errors.New(fmt.Sprintf("<%s> Invalid format for filter of type *stats", utils.FilterS))
		}
		//compose the newFilter
		fltr, err := NewFilterRule(fltrType[0],
			utils.DynamicDataPrefix+utils.Meta+fltrType[1], []string{statItem.FilterValue})
		if err != nil {
			return false, err
		}
		//send it to passGreaterThan
		if val, err := fltr.passGreaterThan(nM); err != nil || !val {
			//in case of error return false and error
			//and in case of not pass return false and nil
			return false, err
		}
	}
	return true, nil
}

func (fltr *FilterRule) passGreaterThan(dP config.DataProvider) (bool, error) {
	fldIf, err := config.GetDynamicInterface(fltr.FieldName, dP)
	if err != nil {
		if err == utils.ErrNotFound {
			return false, nil
		}
		return false, err
	}
	if fldStr, castStr := fldIf.(string); castStr { // attempt converting string since deserialization fails here (ie: time.Time fields)
		fldIf = utils.StringToInterface(fldStr)
	}
	orEqual := false
	if fltr.Type == MetaGreaterOrEqual ||
		fltr.Type == MetaLessThan {
		orEqual = true
	}
	for _, val := range fltr.Values {
		sval, err := config.GetDynamicInterface(val, dP)
		if err != nil {
			continue
		}
		if gte, err := utils.GreaterThan(fldIf, sval, orEqual); err != nil {
			return false, err
		} else if utils.IsSliceMember([]string{MetaGreaterThan, MetaGreaterOrEqual}, fltr.Type) && gte {
			return true, nil
		} else if utils.IsSliceMember([]string{MetaLessThan, MetaLessOrEqual}, fltr.Type) && !gte {
			return true, nil
		}
	}
	return false, nil
}

func (fltr *FilterRule) passResourceS(dP config.DataProvider,
	resourceS rpcclient.RpcClientConnection, tenant string) (bool, error) {
	if resourceS == nil || reflect.ValueOf(resourceS).IsNil() {
		return false, errors.New("Missing ResourceS information")
	}
	for _, resItem := range fltr.resourceItems {
		//take total usage for resource
		var reply *Resource
		if err := resourceS.Call(utils.ApierV1GetResource,
			&utils.TenantID{Tenant: tenant, ID: resItem.ItemID}, &reply); err != nil {
			return false, err
		}
		data := map[string]interface{}{
			utils.Usage: reply.totalUsage(),
		}
		//convert data into a NavigableMap so we can send it to passGreaterThan
		nM := config.NewNavigableMap(data)
		//compose the newFilter
		fltr, err := NewFilterRule(resItem.FilterType,
			utils.DynamicDataPrefix+utils.Usage, []string{resItem.FilterValue})
		if err != nil {
			return false, err
		}
		// send it to passGreaterThan
		if val, err := fltr.passGreaterThan(nM); err != nil || !val {
			//in case of error return false and error
			//and in case of not pass return false and nil
			return false, err
		}
	}
	return true, nil
}