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client.go
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client.go
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// Package httputil provides abstractions around the common needs of HTTP. It
// also allows swapping in and out the HTTP client.
package httputil
import (
"bytes"
"context"
"io"
"mime/multipart"
"time"
"github.com/pkg/errors"
"github.com/zBNF/arikawa/v3/utils/httputil/httpdriver"
"github.com/zBNF/arikawa/v3/utils/json"
)
// StatusTooManyRequests is the HTTP status code discord sends on rate-limiting.
const StatusTooManyRequests = 429
// Retries is the default attempts to retry if the API returns an error before
// giving up. If the value is smaller than 1, then requests will retry forever.
var Retries uint = 5
type Client struct {
httpdriver.Client
SchemaEncoder
// OnRequest, if not nil, will be copied and prefixed on each Request.
OnRequest []RequestOption
// OnResponse is called after every Do() call. Response might be nil if Do()
// errors out. The error returned will override Do's if it's not nil.
OnResponse []ResponseFunc
// Timeout is the maximum amount of time the client will wait for a request
// to finish. If this is 0 or smaller the Client won't time out. Otherwise,
// the timeout will be used as deadline for context of every request.
Timeout time.Duration
// Default to the global Retries variable (5).
Retries uint
context context.Context
}
func NewClient() *Client {
return &Client{
Client: httpdriver.NewClient(),
SchemaEncoder: &DefaultSchema{},
Retries: Retries,
context: context.Background(),
}
}
// Copy returns a shallow copy of the client.
func (c *Client) Copy() *Client {
cl := new(Client)
*cl = *c
return cl
}
// WithContext returns a client copy of the client with the given context.
func (c *Client) WithContext(ctx context.Context) *Client {
c = c.Copy()
c.context = ctx
return c
}
// Context is a shared context for all future calls. It's Background by
// default.
func (c *Client) Context() context.Context {
return c.context
}
// applyOptions tries to apply all options. It does not halt if a single option
// fails, and the error returned is the latest error.
func (c *Client) applyOptions(r httpdriver.Request, extra []RequestOption) (e error) {
for _, opt := range c.OnRequest {
if err := opt(r); err != nil {
e = err
}
}
for _, opt := range extra {
if err := opt(r); err != nil {
e = err
}
}
return
}
// MultipartWriter is the interface for a data structure that can write into a
// multipart writer.
type MultipartWriter interface {
WriteMultipart(body *multipart.Writer) error
}
// MeanwhileMultipart concurrently encodes and writes the given multipart writer
// at the same time. The writer will be called in another goroutine, but the
// writer will be closed when MeanwhileMultipart returns.
func (c *Client) MeanwhileMultipart(
writer MultipartWriter,
method, url string, opts ...RequestOption) (httpdriver.Response, error) {
r, w := io.Pipe()
body := multipart.NewWriter(w)
// Ensure the writer is closed by the time this function exits, so
// WriteMultipart will exit.
defer w.Close()
go func() {
err := writer.WriteMultipart(body)
body.Close()
w.CloseWithError(err)
}()
// Prepend the multipart writer and the correct Content-Type header options.
opts = PrependOptions(
opts,
WithBody(r),
WithContentType(body.FormDataContentType()),
)
// Request with the current client and our own context:
return c.Request(method, url, opts...)
}
// FastRequest performs a request without waiting for the body.
func (c *Client) FastRequest(method, url string, opts ...RequestOption) error {
r, err := c.Request(method, url, opts...)
if err != nil {
return err
}
return r.GetBody().Close()
}
// RequestJSON performs a request and unmarshals the JSON body into "to".
func (c *Client) RequestJSON(to interface{}, method, url string, opts ...RequestOption) error {
r, err := c.Request(method, url, opts...)
if err != nil {
return err
}
var body, status = r.GetBody(), r.GetStatus()
defer body.Close()
// No content, working as intended (tm)
if status == httpdriver.NoContent {
return nil
}
// to is nil for some reason. Ignore.
if to == nil {
return nil
}
if err := json.DecodeStream(body, to); err != nil {
return JSONError{err}
}
return nil
}
// Request performs a request and returns a response with an unread body. The
// caller must close it manually.
func (c *Client) Request(method, url string, opts ...RequestOption) (httpdriver.Response, error) {
response, cancel, err := c.request(method, url, opts)
if err != nil {
if cancel != nil {
cancel()
}
return nil, err
}
if cancel != nil {
return wrapCancelableResponse(response, cancel), nil
}
return response, nil
}
func (c *Client) request(
method, url string,
opts []RequestOption) (r httpdriver.Response, cancel context.CancelFunc, doErr error) {
// Error that represents the latest error in the chain.
var onRespErr error
var status int
ctx := c.context
if c.Timeout > 0 {
ctx, cancel = context.WithTimeout(ctx, c.Timeout)
}
// The c.Retries < 1 check ensures that we retry forever if that field is
// less than 1.
for i := uint(0); c.Retries < 1 || i < c.Retries; i++ {
q, err := c.Client.NewRequest(ctx, method, url)
if err != nil {
doErr = RequestError{err}
return
}
if err := c.applyOptions(q, opts); err != nil {
// We failed to apply an option, so we should call all OnResponse
// handler to clean everything up.
for _, fn := range c.OnResponse {
fn(q, nil)
}
doErr = errors.Wrap(err, "failed to apply http request options")
return
}
r, doErr = c.Client.Do(q)
// Call OnResponse() even if the request failed.
for _, fn := range c.OnResponse {
// Be sure to call ALL OnResponse handlers.
if err := fn(q, r); err != nil {
onRespErr = err
}
}
if onRespErr != nil || doErr != nil {
continue
}
if status = r.GetStatus(); status == StatusTooManyRequests || status >= 500 {
continue
}
break
}
if onRespErr != nil {
doErr = errors.Wrap(onRespErr, "OnResponse handler failed")
return
}
// If all retries failed, then wrap and return.
if doErr != nil {
doErr = RequestError{doErr}
return
}
// Response received, but with a failure status code:
if status < 200 || status > 299 {
// Try and parse the body.
var body = r.GetBody()
defer body.Close()
// This rarely happens, so we can (probably) make an exception for it.
buf := bytes.Buffer{}
buf.ReadFrom(body)
httpErr := &HTTPError{
Status: status,
Body: buf.Bytes(),
}
// Optionally unmarshal the error.
json.Unmarshal(httpErr.Body, httpErr)
doErr = httpErr
}
return
}