/*
 * SPDX-License-Identifier: AGPL-3.0-only
 * Copyright (c) 2022-2023, daeuniverse Organization <dae@v2raya.org>
 */

package control

import (
	"encoding/binary"
	"fmt"
	"github.com/daeuniverse/dae/pkg/trie"
	"net/netip"
	"strconv"

	"github.com/cilium/ebpf"
	"github.com/daeuniverse/dae/common"
	"github.com/daeuniverse/dae/common/consts"
	"github.com/daeuniverse/dae/component/routing"
	"github.com/daeuniverse/dae/component/routing/domain_matcher"
	"github.com/daeuniverse/dae/config"
	"github.com/daeuniverse/dae/pkg/config_parser"
	"github.com/sirupsen/logrus"
)

type RoutingMatcherBuilder struct {
	log                *logrus.Logger
	outboundName2Id    map[string]uint8
	bpf                *bpfObjects
	rules              []bpfMatchSet
	simulatedLpmTries  [][]netip.Prefix
	simulatedDomainSet []routing.DomainSet
	fallback           *routing.Outbound
}

func NewRoutingMatcherBuilder(log *logrus.Logger, rules []*config_parser.RoutingRule, outboundName2Id map[string]uint8, bpf *bpfObjects, fallback config.FunctionOrString) (b *RoutingMatcherBuilder, err error) {
	b = &RoutingMatcherBuilder{log: log, outboundName2Id: outboundName2Id, bpf: bpf}
	rulesBuilder := routing.NewRulesBuilder(log)
	rulesBuilder.RegisterFunctionParser(consts.Function_Domain, routing.PlainParserFactory(b.addDomain))
	rulesBuilder.RegisterFunctionParser(consts.Function_Ip, routing.IpParserFactory(b.addIp))
	rulesBuilder.RegisterFunctionParser(consts.Function_SourceIp, routing.IpParserFactory(b.addSourceIp))
	rulesBuilder.RegisterFunctionParser(consts.Function_Port, routing.PortRangeParserFactory(b.addPort))
	rulesBuilder.RegisterFunctionParser(consts.Function_SourcePort, routing.PortRangeParserFactory(b.addSourcePort))
	rulesBuilder.RegisterFunctionParser(consts.Function_L4Proto, routing.L4ProtoParserFactory(b.addL4Proto))
	rulesBuilder.RegisterFunctionParser(consts.Function_Mac, routing.MacParserFactory(b.addSourceMac))
	rulesBuilder.RegisterFunctionParser(consts.Function_ProcessName, routing.ProcessNameParserFactory(b.addProcessName))
	rulesBuilder.RegisterFunctionParser(consts.Function_IpVersion, routing.IpVersionParserFactory(b.addIpVersion))
	if err = rulesBuilder.Apply(rules); err != nil {
		return nil, err
	}

	if err = b.addFallback(fallback); err != nil {
		return nil, err
	}

	return b, nil
}

func (b *RoutingMatcherBuilder) outboundToId(outbound string) (uint8, error) {
	var outboundId uint8
	switch outbound {
	case consts.OutboundLogicalOr.String():
		outboundId = uint8(consts.OutboundLogicalOr)
	case consts.OutboundLogicalAnd.String():
		outboundId = uint8(consts.OutboundLogicalAnd)
	case consts.OutboundMustRules.String():
		outboundId = uint8(consts.OutboundMustRules)
	default:
		var ok bool
		outboundId, ok = b.outboundName2Id[outbound]
		if !ok {
			return 0, fmt.Errorf("outbound (group) %v not found; please define it in section \"group\"", strconv.Quote(outbound))
		}
	}
	return outboundId, nil
}

func (b *RoutingMatcherBuilder) addDomain(f *config_parser.Function, key string, values []string, outbound *routing.Outbound) (err error) {
	switch consts.RoutingDomainKey(key) {
	case consts.RoutingDomainKey_Regex,
		consts.RoutingDomainKey_Full,
		consts.RoutingDomainKey_Keyword,
		consts.RoutingDomainKey_Suffix:
	default:
		return fmt.Errorf("addDomain: unsupported key: %v", key)
	}
	b.simulatedDomainSet = append(b.simulatedDomainSet, routing.DomainSet{
		Key:       consts.RoutingDomainKey(key),
		RuleIndex: len(b.rules),
		Domains:   values,
	})
	outboundId, err := b.outboundToId(outbound.Name)
	if err != nil {
		return err
	}
	b.rules = append(b.rules, bpfMatchSet{
		Type:     uint8(consts.MatchType_DomainSet),
		Not:      f.Not,
		Outbound: outboundId,
		Mark:     outbound.Mark,
		Must:     outbound.Must,
	})
	return nil
}

func (b *RoutingMatcherBuilder) addSourceMac(f *config_parser.Function, macAddrs [][6]byte, outbound *routing.Outbound) (err error) {
	var addr16 [16]byte
	values := make([]netip.Prefix, 0, len(macAddrs))
	for _, mac := range macAddrs {
		copy(addr16[10:], mac[:])
		prefix := netip.PrefixFrom(netip.AddrFrom16(addr16), 128)
		values = append(values, prefix)
	}
	lpmTrieIndex := len(b.simulatedLpmTries)
	b.simulatedLpmTries = append(b.simulatedLpmTries, values)
	outboundId, err := b.outboundToId(outbound.Name)
	if err != nil {
		return err
	}
	set := bpfMatchSet{
		Value:    [16]byte{},
		Type:     uint8(consts.MatchType_Mac),
		Not:      f.Not,
		Outbound: outboundId,
		Mark:     outbound.Mark,
		Must:     outbound.Must,
	}
	binary.LittleEndian.PutUint32(set.Value[:], uint32(lpmTrieIndex))
	b.rules = append(b.rules, set)
	return nil
}

func (b *RoutingMatcherBuilder) addIp(f *config_parser.Function, values []netip.Prefix, outbound *routing.Outbound) (err error) {
	lpmTrieIndex := len(b.simulatedLpmTries)
	b.simulatedLpmTries = append(b.simulatedLpmTries, values)
	outboundId, err := b.outboundToId(outbound.Name)
	if err != nil {
		return err
	}
	set := bpfMatchSet{
		Value:    [16]byte{},
		Type:     uint8(consts.MatchType_IpSet),
		Not:      f.Not,
		Outbound: outboundId,
		Mark:     outbound.Mark,
		Must:     outbound.Must,
	}
	binary.LittleEndian.PutUint32(set.Value[:], uint32(lpmTrieIndex))
	b.rules = append(b.rules, set)
	return nil
}

func (b *RoutingMatcherBuilder) addPort(f *config_parser.Function, values [][2]uint16, outbound *routing.Outbound) (err error) {
	for i, value := range values {
		outboundName := consts.OutboundLogicalOr.String()
		if i == len(values)-1 {
			outboundName = outbound.Name
		}
		outboundId, err := b.outboundToId(outboundName)
		if err != nil {
			return err
		}
		b.rules = append(b.rules, bpfMatchSet{
			Type: uint8(consts.MatchType_Port),
			Value: _bpfPortRange{
				PortStart: value[0],
				PortEnd:   value[1],
			}.Encode(),
			Not:      f.Not,
			Outbound: outboundId,
			Mark:     outbound.Mark,
			Must:     outbound.Must,
		})
	}
	return nil
}

func (b *RoutingMatcherBuilder) addSourceIp(f *config_parser.Function, values []netip.Prefix, outbound *routing.Outbound) (err error) {
	lpmTrieIndex := len(b.simulatedLpmTries)
	b.simulatedLpmTries = append(b.simulatedLpmTries, values)
	outboundId, err := b.outboundToId(outbound.Name)
	if err != nil {
		return err
	}
	set := bpfMatchSet{
		Value:    [16]byte{},
		Type:     uint8(consts.MatchType_SourceIpSet),
		Not:      f.Not,
		Outbound: outboundId,
		Mark:     outbound.Mark,
		Must:     outbound.Must,
	}
	binary.LittleEndian.PutUint32(set.Value[:], uint32(lpmTrieIndex))
	b.rules = append(b.rules, set)
	return nil
}

func (b *RoutingMatcherBuilder) addSourcePort(f *config_parser.Function, values [][2]uint16, outbound *routing.Outbound) (err error) {
	for i, value := range values {
		outboundName := consts.OutboundLogicalOr.String()
		if i == len(values)-1 {
			outboundName = outbound.Name
		}
		outboundId, err := b.outboundToId(outboundName)
		if err != nil {
			return err
		}
		b.rules = append(b.rules, bpfMatchSet{
			Type: uint8(consts.MatchType_SourcePort),
			Value: _bpfPortRange{
				PortStart: value[0],
				PortEnd:   value[1],
			}.Encode(),
			Not:      f.Not,
			Outbound: outboundId,
			Mark:     outbound.Mark,
			Must:     outbound.Must,
		})
	}
	return nil
}

func (b *RoutingMatcherBuilder) addL4Proto(f *config_parser.Function, values consts.L4ProtoType, outbound *routing.Outbound) (err error) {
	outboundId, err := b.outboundToId(outbound.Name)
	if err != nil {
		return err
	}
	b.rules = append(b.rules, bpfMatchSet{
		Value:    [16]byte{byte(values)},
		Type:     uint8(consts.MatchType_L4Proto),
		Not:      f.Not,
		Outbound: outboundId,
		Mark:     outbound.Mark,
		Must:     outbound.Must,
	})
	return nil
}

func (b *RoutingMatcherBuilder) addIpVersion(f *config_parser.Function, values consts.IpVersionType, outbound *routing.Outbound) (err error) {
	outboundId, err := b.outboundToId(outbound.Name)
	if err != nil {
		return err
	}
	b.rules = append(b.rules, bpfMatchSet{
		Value:    [16]byte{byte(values)},
		Type:     uint8(consts.MatchType_IpVersion),
		Not:      f.Not,
		Outbound: outboundId,
		Mark:     outbound.Mark,
		Must:     outbound.Must,
	})
	return nil
}

func (b *RoutingMatcherBuilder) addProcessName(f *config_parser.Function, values [][consts.TaskCommLen]byte, outbound *routing.Outbound) (err error) {
	for i, value := range values {
		outboundName := consts.OutboundLogicalOr.String()
		if i == len(values)-1 {
			outboundName = outbound.Name
		}
		outboundId, err := b.outboundToId(outboundName)
		if err != nil {
			return err
		}
		matchSet := bpfMatchSet{
			Type:     uint8(consts.MatchType_ProcessName),
			Not:      f.Not,
			Outbound: outboundId,
			Mark:     outbound.Mark,
			Must:     outbound.Must,
		}
		copy(matchSet.Value[:], value[:])
		b.rules = append(b.rules, matchSet)
	}
	return nil
}

func (b *RoutingMatcherBuilder) addFallback(fallbackOutbound config.FunctionOrString) (err error) {
	outbound, err := routing.ParseOutbound(config.FunctionOrStringToFunction(fallbackOutbound))
	if err != nil {
		return err
	}
	outboundId, err := b.outboundToId(outbound.Name)
	if err != nil {
		return err
	}
	b.rules = append(b.rules, bpfMatchSet{
		Type:     uint8(consts.MatchType_Fallback),
		Outbound: outboundId,
		Mark:     outbound.Mark,
		Must:     outbound.Must,
	})
	return nil
}

func (b *RoutingMatcherBuilder) BuildKernspace(log *logrus.Logger) (err error) {
	// Update lpm_array_map.
	for i, cidrs := range b.simulatedLpmTries {
		var keys []_bpfLpmKey
		var values []uint32
		for _, cidr := range cidrs {
			keys = append(keys, cidrToBpfLpmKey(cidr))
			values = append(values, 1)
		}
		m, err := b.bpf.newLpmMap(keys, values)
		if err != nil {
			return fmt.Errorf("newLpmMap: %w", err)
		}
		// We cannot invoke BpfMapBatchUpdate when value is ebpf.Map.
		if err = b.bpf.LpmArrayMap.Update(uint32(i), m, ebpf.UpdateAny); err != nil {
			m.Close()
			return fmt.Errorf("Update: %w", err)
		}
		m.Close()
	}
	// Write routings.
	// Fallback rule MUST be the last.
	if b.rules[len(b.rules)-1].Type != uint8(consts.MatchType_Fallback) {
		return fmt.Errorf("fallback rule MUST be the last")
	}
	routingsLen := uint32(len(b.rules))
	routingsKeys := common.ARangeU32(routingsLen)
	if _, err = BpfMapBatchUpdate(b.bpf.RoutingMap, routingsKeys, b.rules, &ebpf.BatchOptions{
		ElemFlags: uint64(ebpf.UpdateAny),
	}); err != nil {
		return fmt.Errorf("BpfMapBatchUpdate: %w", err)
	}
	log.Infof("Routing match set len: %v/%v", len(b.rules), consts.MaxMatchSetLen)

	return nil
}

func (b *RoutingMatcherBuilder) BuildUserspace() (matcher *RoutingMatcher, err error) {
	// Build domainMatcher
	domainMatcher := domain_matcher.NewAhocorasickSlimtrie(b.log, consts.MaxMatchSetLen)
	for _, domains := range b.simulatedDomainSet {
		domainMatcher.AddSet(domains.RuleIndex, domains.Domains, domains.Key)
	}
	// Build Ip matcher.
	var lpmMatcher []*trie.Trie
	for _, prefixes := range b.simulatedLpmTries {
		t, err := trie.NewTrieFromPrefixes(prefixes)
		if err != nil {
			return nil, err
		}
		lpmMatcher = append(lpmMatcher, t)
	}
	if err = domainMatcher.Build(); err != nil {
		return nil, err
	}

	// Write routings.
	// Fallback rule MUST be the last.
	if b.rules[len(b.rules)-1].Type != uint8(consts.MatchType_Fallback) {
		return nil, fmt.Errorf("fallback rule MUST be the last")
	}

	return &RoutingMatcher{
		lpmMatcher:    lpmMatcher,
		domainMatcher: domainMatcher,
		matches:       b.rules,
	}, nil
}
