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client.go
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client.go
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/*
Package w3 implements a blazing fast and modular Ethereum JSON RPC client with
first-class ABI support.
*/
package w3
import (
"context"
"fmt"
"reflect"
"strings"
"github.com/ethereum/go-ethereum/rpc"
"github.com/meltingclock/w3/w3types"
"golang.org/x/time/rate"
)
// Client represents a connection to an RPC endpoint.
type Client struct {
client *rpc.Client
// rate limiter
rl *rate.Limiter
rlCostFunc func(methods []string) (cost int)
}
// NewClient returns a new Client given an rpc.Client client.
func NewClient(client *rpc.Client, opts ...Option) *Client {
c := &Client{
client: client,
}
for _, opt := range opts {
if opt == nil {
continue
}
opt(c)
}
return c
}
// Dial returns a new Client connected to the URL rawurl. An error is returned
// if the connection establishment fails.
//
// The supported URL schemes are "http", "https", "ws" and "wss". If rawurl is a
// file name with no URL scheme, a local IPC socket connection is established.
func Dial(rawurl string, opts ...Option) (*Client, error) {
client, err := rpc.Dial(rawurl)
if err != nil {
return nil, err
}
return NewClient(client, opts...), nil
}
// MustDial is like [Dial] but panics if the connection establishment fails.
func MustDial(rawurl string, opts ...Option) *Client {
client, err := Dial(rawurl, opts...)
if err != nil {
panic(fmt.Sprintf("w3: %s", err))
}
return client
}
// Close closes the RPC connection and cancels any in-flight requests.
//
// Close implements the [io.Closer] interface.
func (c *Client) Close() error {
c.client.Close()
return nil
}
// CallCtx creates the final RPC request, sends it, and handles the RPC
// response.
//
// An error is returned if RPC request creation, networking, or RPC response
// handling fails.
func (c *Client) CallCtx(ctx context.Context, calls ...w3types.RPCCaller) error {
// no requests = nothing to do
if len(calls) <= 0 {
return nil
}
// create requests
batchElems := make([]rpc.BatchElem, len(calls))
var err error
for i, req := range calls {
batchElems[i], err = req.CreateRequest()
if err != nil {
return err
}
}
// invoke rate limiter
if err := c.rateLimit(ctx, batchElems); err != nil {
return err
}
// do requests
if len(batchElems) > 1 {
// batch requests if >1 request
err = c.client.BatchCallContext(ctx, batchElems)
if err != nil {
return err
}
} else {
// non-batch requests if 1 request
batchElem := batchElems[0]
err = c.client.CallContext(ctx, batchElem.Result, batchElem.Method, batchElem.Args...)
if err != nil {
switch reflect.TypeOf(err).String() {
case "*rpc.jsonError":
batchElems[0].Error = err
default:
return err
}
}
}
// handle responses
var callErrs CallErrors
for i, req := range calls {
err = req.HandleResponse(batchElems[i])
if err != nil {
if callErrs == nil {
callErrs = make(CallErrors, len(calls))
}
callErrs[i] = err
}
}
if len(callErrs) > 0 {
return callErrs
}
return nil
}
// Call is like [Client.CallCtx] with ctx equal to context.Background().
func (c *Client) Call(calls ...w3types.RPCCaller) error {
return c.CallCtx(context.Background(), calls...)
}
// SubscribeCtx creates a new subscription and returns a [rpc.ClientSubscription].
func (c *Client) SubscribeCtx(ctx context.Context, s w3types.RPCSubscriber) (*rpc.ClientSubscription, error) {
namespace, ch, params, err := s.CreateRequest()
if err != nil {
return nil, err
}
return c.client.Subscribe(ctx, namespace, ch, params...)
}
// Subscribe is like [Client.SubscribeCtx] with ctx equal to context.Background().
func (c *Client) Subscribe(s w3types.RPCSubscriber) (*rpc.ClientSubscription, error) {
return c.SubscribeCtx(context.Background(), s)
}
func (c *Client) rateLimit(ctx context.Context, batchElems []rpc.BatchElem) error {
if c.rl == nil {
return nil
}
if c.rlCostFunc == nil {
// limit requests
return c.rl.Wait(ctx)
}
// limit requests based on Compute Units (CUs)
methods := make([]string, len(batchElems))
for i, batchElem := range batchElems {
methods[i] = batchElem.Method
}
cost := c.rlCostFunc(methods)
return c.rl.WaitN(ctx, cost)
}
// CallErrors is an error type that contains the errors of multiple calls. The
// length of the error slice is equal to the number of calls. Each error at a
// given index corresponds to the call at the same index. An error is nil if the
// corresponding call was successful.
type CallErrors []error
func (e CallErrors) Error() string {
if len(e) == 1 && e[0] != nil {
return fmt.Sprintf("w3: call failed: %s", e[0])
}
var errors []string
for i, err := range e {
if err == nil {
continue
}
errors = append(errors, fmt.Sprintf("call[%d]: %s", i, err))
}
var plr string
if len(errors) > 1 {
plr = "s"
}
return fmt.Sprintf("w3: %d call%s failed:\n%s", len(errors), plr, strings.Join(errors, "\n"))
}
func (e CallErrors) Is(target error) bool {
_, ok := target.(CallErrors)
return ok
}
// An Option configures a Client.
type Option func(*Client)
// WithRateLimiter sets the rate limiter for the client. Set the optional argument
// costFunc to nil to limit the number of requests. Supply a costFunc to limit
// the the number of requests based on individual RPC calls for advanced rate
// limiting by e.g. Compute Units (CUs). Note that only if len(methods) > 1, the
// calls are sent in a batch request.
func WithRateLimiter(rl *rate.Limiter, costFunc func(methods []string) (cost int)) Option {
return func(c *Client) {
c.rl = rl
c.rlCostFunc = costFunc
}
}