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result.go
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result.go
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// Copyright (C) 2023 Gobalsky Labs Limited
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero 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 Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
package ethcall
import (
"bytes"
"context"
"encoding/json"
"fmt"
"strconv"
"text/scanner"
ethcallcommon "code.vegaprotocol.io/vega/core/datasource/external/ethcall/common"
"github.com/PaesslerAG/gval"
"github.com/PaesslerAG/jsonpath"
)
type Result struct {
Bytes []byte
Values []any
Normalised map[string]string
PassesFilters bool
}
func NewResult(spec ethcallcommon.Spec, bytes []byte) (Result, error) {
call, err := NewCall(spec)
if err != nil {
return Result{}, fmt.Errorf("failed to create result: %w", err)
}
return newResult(call, bytes)
}
func newResult(call Call, bytes []byte) (Result, error) {
values, err := call.abi.Unpack(call.method, bytes)
if err != nil {
return Result{}, fmt.Errorf("failed to unpack contract call result: %w", err)
}
normalised, err := normaliseValues(values, call.spec.Normalisers)
if err != nil {
return Result{}, fmt.Errorf("failed to normalise contract call result: %w", err)
}
passesFilters, err := call.filters.Match(normalised)
if err != nil {
return Result{}, fmt.Errorf("error evaluating filters: %w", err)
}
return Result{
Bytes: bytes,
Values: values,
Normalised: normalised,
PassesFilters: passesFilters,
}, nil
}
func normaliseValues(values []any, rules map[string]string) (map[string]string, error) {
// The data in 'values' is relatively well typed, after being unpacked by the ABI.
// For example, a uint256 will be a big.Int, structs returned from the contract call
// will be anonymous go structs rather than a string map etc.. In order to fish data
// out with jsonpath it need to be simple lists, maps, strings and numbers; so we
// serialise to json and then deserialise to an into an []interface{}.
valuesJson, err := json.Marshal(values)
if err != nil {
return nil, fmt.Errorf("unable to serialse values: %v", err)
}
valuesSimple := []interface{}{}
d := json.NewDecoder(bytes.NewBuffer(valuesJson))
// Keep numbers as a json.Number, which holds the original string representation
// otherwise all numbers get cast to float64 which is no good for e.g uint256.
d.UseNumber()
err = d.Decode(&valuesSimple)
if err != nil {
return nil, fmt.Errorf("unable to deserialse values: %v", err)
}
res := make(map[string]string)
for key, path := range rules {
value, err := myJSONPathGet(path, valuesSimple)
if err != nil {
return nil, fmt.Errorf("unable to normalise key %v: %v", key, err)
}
switch v := value.(type) {
case json.Number:
res[key] = v.String()
case int64:
// all of the numbers in the json from the ethereum call result will be
// json.Number and handled above; this case is just for the corner case
// where someone specifies a number as a static value in the json path itself
res[key] = strconv.FormatInt(v, 10)
case string:
res[key] = v
case bool:
res[key] = strconv.FormatBool(v)
default:
return nil, fmt.Errorf("unable to normalise key %v of type %T", key, value)
}
}
return res, nil
}
// myJSONPathGet works exactly like jsonpath.Get(path, values), except that any numbers found
// are returned as int64 rather than float64 which is the default.
// ** in the path expression itself, not the json being queried **
// Evaluation will fail if numbers in the path are not integers.
func myJSONPathGet(path string, values []interface{}) (interface{}, error) {
baselang := jsonpath.Language()
mylang := gval.PrefixExtension(scanner.Int, parseNumberAsInt64)
lang := gval.NewLanguage(baselang, mylang)
eval, err := lang.NewEvaluable(path)
if err != nil {
return nil, err
}
value, err := eval(context.Background(), values)
return value, err
}
func parseNumberAsInt64(c context.Context, p *gval.Parser) (gval.Evaluable, error) {
n, err := strconv.ParseInt(p.TokenText(), 10, 64)
if err != nil {
return nil, err
}
return p.Const(n), nil
}