neo-go/pkg/rpc/client/neoscan.go

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package client
import (
"encoding/json"
"errors"
"net/http"
"sort"
"github.com/nspcc-dev/neo-go/pkg/core/state"
"github.com/nspcc-dev/neo-go/pkg/core/transaction"
"github.com/nspcc-dev/neo-go/pkg/rpc/response/result"
"github.com/nspcc-dev/neo-go/pkg/util"
errs "github.com/pkg/errors"
)
/*
Definition of types, helper functions and variables
required for calculation of transaction inputs using
NeoScan API.
*/
type (
// NeoScanServer stores NEOSCAN URL and API path.
NeoScanServer struct {
URL string // "protocol://host:port/"
Path string // path to API endpoint without wallet address
}
// Unspent stores Unspents per asset
Unspent struct {
Unspent state.UnspentBalances
Asset string // "NEO" / "GAS"
Amount util.Fixed8 // total unspent of this asset
}
// NeoScanBalance is a struct of NeoScan response to 'get_balance' request
NeoScanBalance struct {
Balance []*Unspent
Address string
}
)
// GetBalance performs a request to get balance for the address specified.
func (s NeoScanServer) GetBalance(address string) ([]*Unspent, error) {
var (
err error
req *http.Request
res *http.Response
balance NeoScanBalance
client = http.Client{}
balanceURL = s.URL + s.Path
)
if req, err = http.NewRequest(http.MethodGet, balanceURL+address, nil); err != nil {
return nil, errs.Wrap(err, "Failed to compose HTTP request")
}
if res, err = client.Do(req); err != nil {
return nil, errs.Wrap(err, "Failed to perform HTTP request")
}
defer res.Body.Close()
if err = json.NewDecoder(res.Body).Decode(&balance); err != nil {
return nil, errs.Wrap(err, "Failed to decode HTTP response")
}
return balance.Balance, nil
}
func filterSpecificAsset(asset string, balance []*Unspent, assetBalance *Unspent) {
for _, us := range balance {
if us.Asset == asset {
assetBalance.Unspent = us.Unspent
assetBalance.Asset = us.Asset
assetBalance.Amount = us.Amount
return
}
}
}
// CalculateInputs creates input transactions for the specified amount of given asset belonging to specified address.
func (s NeoScanServer) CalculateInputs(address string, assetIDUint util.Uint256, cost util.Fixed8) ([]transaction.Input, util.Fixed8, error) {
var (
err error
us []*Unspent
assetUnspent Unspent
assetID = result.GlobalAssets[assetIDUint.StringLE()]
)
if us, err = s.GetBalance(address); err != nil {
return nil, util.Fixed8(0), errs.Wrapf(err, "Cannot get balance for address %v", address)
}
filterSpecificAsset(assetID, us, &assetUnspent)
return unspentsToInputs(assetUnspent.Unspent, cost)
}
// unspentsToInputs uses UnspentBalances to create a slice of inputs for a new
// transcation containing the required amount of asset.
func unspentsToInputs(utxos state.UnspentBalances, required util.Fixed8) ([]transaction.Input, util.Fixed8, error) {
var (
num, i uint16
selected = util.Fixed8(0)
)
sort.Sort(utxos)
for _, us := range utxos {
if selected >= required {
break
}
selected += us.Value
num++
}
if selected < required {
return nil, util.Fixed8(0), errors.New("cannot compose inputs for transaction; check sender balance")
}
inputs := make([]transaction.Input, 0, num)
for i = 0; i < num; i++ {
inputs = append(inputs, transaction.Input{
PrevHash: utxos[i].Tx,
PrevIndex: utxos[i].Index,
})
}
return inputs, selected, nil
}