checktx.go

package main

import (
	"bytes"
	"fmt"

	"github.com/dgraph-io/badger"
	abcitypes "github.com/tendermint/tendermint/abci/types"
)

func (app *KVStoreApplication) isValid(tx []byte) (code uint32) {
	// check format
	parts := bytes.Split(tx, []byte("="))
	if len(parts) != 2 {
		return 1
	}

	key, value := parts[0], parts[1]

	// check if the same key=value already exists
	err := app.db.View(func(txn *badger.Txn) error {
		item, err := txn.Get(key)
		if err != nil && err != badger.ErrKeyNotFound {
			return err
		}
		if err == nil {
			return item.Value(func(val []byte) error {
				if bytes.Equal(val, value) {
					code = 2
				}
				return nil
			})
		}
		return nil
	})
	if err != nil {
		panic(err)
	}

	return code
}

func (app *KVStoreApplication) CheckTx(req abcitypes.RequestCheckTx) abcitypes.ResponseCheckTx {
	fmt.Println("Check", req)

	code := app.isValid(req.Tx)
	return abcitypes.ResponseCheckTx{Code: code, GasWanted: 1}
}