synapsecns/sanguine

package l2gateway

import (
    "bytes"
    "fmt"

    "github.com/ethereum/go-ethereum/common"
    ethTypes "github.com/ethereum/go-ethereum/core/types"
)

// EventType is the type of the bridge watcher
//
//go:generate go run golang.org/x/tools/cmd/stringer -type=EventType
type EventType uint

const (
    // WithdrawETHEvent is the event type for the WithdrawETH event.
    WithdrawETHEvent EventType = iota + 2
    // WithdrawERC20Event is the event type for the WithdrawERC20 event.
    WithdrawERC20Event
    // FinalizeDepositETHEvent is the event type for the FinalizeDepositETH event.
    FinalizeDepositETHEvent
    // FinalizeDepositERC20Event is the event type for the FinalizeDepositERC20 event.
    FinalizeDepositERC20Event
)

// Parser parses events from the l2gateway contracat.
type Parser interface {
    // ParseEvent parses the event from the log.
    ParseEvent(log ethTypes.Log) (_ EventType, event interface{}, ok bool)
}
type parserImpl struct {
    filterer *L2GatewayRouterFilterer
}

// NewParser creates a new parser for the l2gateway contract.
func NewParser(l2GatewayAddress common.Address) (Parser, error) {
    parser, err := NewL2GatewayRouterFilterer(l2GatewayAddress, nil)
    if err != nil {
        return nil, fmt.Errorf("could not create %T: %w", L2GatewayRouterFilterer{}, err)
    }

    return &parserImpl{filterer: parser}, nil
}

// nolint: cyclop
func (p parserImpl) ParseEvent(log ethTypes.Log) (_ EventType, event interface{}, ok bool) {
    // return an unknown event to avoid cases where user failed to check the event type
    // make it high enough to make it obvious (we start iotas at +1, see uber style guide for details)
    noOpEvent := EventType(len(topicMap()) + 1)

    if len(log.Topics) == 0 {
        return noOpEvent, nil, false
    }
    nillableEventType := eventTypeFromTopic(log.Topics[0])
    if nillableEventType == nil {
        return noOpEvent, nil, false
    }

    eventType := *nillableEventType

    switch eventType {
    case WithdrawETHEvent:
        requested, err := p.filterer.ParseWithdrawETH(log)
        if err != nil {
            return noOpEvent, nil, false
        }
        return eventType, requested, true
    case WithdrawERC20Event:
        requested, err := p.filterer.ParseWithdrawERC20(log)
        if err != nil {
            return noOpEvent, nil, false
        }
        return eventType, requested, true
    case FinalizeDepositETHEvent:
        proven, err := p.filterer.ParseFinalizeDepositETH(log)
        if err != nil {
            return noOpEvent, nil, false
        }
        return eventType, proven, true
    case FinalizeDepositERC20Event:
        claimed, err := p.filterer.ParseFinalizeDepositERC20(log)
        if err != nil {
            return noOpEvent, nil, false
        }
        return eventType, claimed, true
    }

    return eventType, nil, true
}

// topicMap maps events to topics.
// this is returned as a function to assert immutability.
func topicMap() map[EventType]common.Hash {
    return map[EventType]common.Hash{
        WithdrawETHEvent:          WithdrawETHTopic,
        WithdrawERC20Event:        WithdrawERC20Topic,
        FinalizeDepositETHEvent:   FinalizeDepositETHTopic,
        FinalizeDepositERC20Event: FinalizeDepositERC20Topic,
    }
}

// eventTypeFromTopic gets the event type from the topic
// returns nil if the topic is not found.
func eventTypeFromTopic(ogTopic common.Hash) *EventType {
    for eventType, topic := range topicMap() {
        if bytes.Equal(ogTopic.Bytes(), topic.Bytes()) {
            return &eventType
        }
    }
    return nil
}