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graphql.go
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graphql.go
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// Package graphql provides a low level GraphQL client.
//
// // create a client (safe to share across requests)
// client := graphql.NewClient("https://machinebox.io/graphql")
//
// // make a request
// req := graphql.NewRequest(`
// query ($key: String!) {
// items (id:$key) {
// field1
// field2
// field3
// }
// }
// `)
//
// // set any variables
// req.Var("key", "value")
//
// // run it and capture the response
// var respData ResponseStruct
// if err := client.Run(ctx, req, &respData); err != nil {
// log.Fatal(err)
// }
//
// # Specify client
//
// To specify your own http.Client, use the WithHTTPClient option:
//
// httpclient := &http.Client{}
// client := graphql.NewClient("https://machinebox.io/graphql", graphql.WithHTTPClient(httpclient))
package graphql
import (
"bytes"
"context"
"encoding/json"
"fmt"
"io"
"mime/multipart"
"net/http"
"github.com/pkg/errors"
)
// Client is a client for interacting with a GraphQL API.
type Client struct {
endpoint string
httpClient *http.Client
useMultipartForm bool
// closeReq will close the request body immediately allowing for reuse of client
closeReq bool
// Log is called with various debug information.
// To log to standard out, use:
// client.Log = func(s string) { log.Println(s) }
Log func(s string)
}
// NewClient makes a new Client capable of making GraphQL requests.
func NewClient(endpoint string, opts ...ClientOption) *Client {
c := &Client{
endpoint: endpoint,
Log: func(string) {},
}
for _, optionFunc := range opts {
optionFunc(c)
}
if c.httpClient == nil {
c.httpClient = http.DefaultClient
}
return c
}
func (c *Client) logf(format string, args ...interface{}) {
c.Log(fmt.Sprintf(format, args...))
}
// Run executes the query and unmarshals the response from the data field
// into the response object.
// Pass in a nil response object to skip response parsing.
// If the request fails or the server returns an error, the first error
// will be returned.
func (c *Client) Run(ctx context.Context, req *Request, resp interface{}) error {
select {
case <-ctx.Done():
return newGraphQLError(ctx.Err())
default:
}
if len(req.files) > 0 && !c.useMultipartForm {
return newGraphQLError(errors.New("cannot send files with PostFields option"))
}
if c.useMultipartForm {
return newGraphQLError(c.runWithPostFields(ctx, req, resp))
}
return newGraphQLError(c.runWithJSON(ctx, req, resp))
}
func (c *Client) runWithJSON(ctx context.Context, req *Request, resp interface{}) error {
var requestBody bytes.Buffer
requestBodyObj := struct {
Query string `json:"query"`
Variables map[string]interface{} `json:"variables"`
}{
Query: req.q,
Variables: req.vars,
}
if err := json.NewEncoder(&requestBody).Encode(requestBodyObj); err != nil {
return errors.Wrap(err, "encode body")
}
c.logf(">> variables: %v", req.vars)
c.logf(">> query: %s", req.q)
gr := &graphResponse{
Data: resp,
}
r, err := http.NewRequest(http.MethodPost, c.endpoint, &requestBody)
if err != nil {
return err
}
r.Close = c.closeReq
r.Header.Set("Content-Type", "application/json; charset=utf-8")
r.Header.Set("Accept", "application/json; charset=utf-8")
for key, values := range req.Header {
for _, value := range values {
r.Header.Add(key, value)
}
}
c.logf(">> headers: %v", r.Header)
r = r.WithContext(ctx)
res, err := c.httpClient.Do(r)
if err != nil {
return err
}
defer res.Body.Close()
if res.StatusCode != http.StatusOK {
return &HttpError{
Err: fmt.Errorf("server returned a non-200 status code: %v", res.StatusCode),
Response: res,
}
}
var buf bytes.Buffer
if _, err := io.Copy(&buf, res.Body); err != nil {
return errors.Wrap(err, "reading body")
}
c.logf("<< %s", buf.String())
if err := json.NewDecoder(&buf).Decode(&gr); err != nil {
return errors.Wrap(err, "decoding response")
}
if len(gr.Errors) > 0 {
// return first error
return &gr.Errors[0]
}
return nil
}
func (c *Client) runWithPostFields(ctx context.Context, req *Request, resp interface{}) error {
var requestBody bytes.Buffer
writer := multipart.NewWriter(&requestBody)
if err := writer.WriteField("query", req.q); err != nil {
return errors.Wrap(err, "write query field")
}
var variablesBuf bytes.Buffer
if len(req.vars) > 0 {
variablesField, err := writer.CreateFormField("variables")
if err != nil {
return errors.Wrap(err, "create variables field")
}
if err := json.NewEncoder(io.MultiWriter(variablesField, &variablesBuf)).Encode(req.vars); err != nil {
return errors.Wrap(err, "encode variables")
}
}
for i := range req.files {
part, err := writer.CreateFormFile(req.files[i].Field, req.files[i].Name)
if err != nil {
return errors.Wrap(err, "create form file")
}
if _, err := io.Copy(part, req.files[i].R); err != nil {
return errors.Wrap(err, "preparing file")
}
}
if err := writer.Close(); err != nil {
return errors.Wrap(err, "close writer")
}
c.logf(">> variables: %s", variablesBuf.String())
c.logf(">> files: %d", len(req.files))
c.logf(">> query: %s", req.q)
gr := &graphResponse{
Data: resp,
}
r, err := http.NewRequest(http.MethodPost, c.endpoint, &requestBody)
if err != nil {
return err
}
r.Close = c.closeReq
r.Header.Set("Content-Type", writer.FormDataContentType())
r.Header.Set("Accept", "application/json; charset=utf-8")
for key, values := range req.Header {
for _, value := range values {
r.Header.Add(key, value)
}
}
c.logf(">> headers: %v", r.Header)
r = r.WithContext(ctx)
res, err := c.httpClient.Do(r)
if err != nil {
return err
}
defer res.Body.Close()
if res.StatusCode != http.StatusOK {
return fmt.Errorf("server returned a non-200 status code: %v", res.StatusCode)
}
var buf bytes.Buffer
if _, err := io.Copy(&buf, res.Body); err != nil {
return errors.Wrap(err, "reading body")
}
c.logf("<< %s", buf.String())
if err := json.NewDecoder(&buf).Decode(&gr); err != nil {
return errors.Wrap(err, "decoding response")
}
if len(gr.Errors) > 0 {
// return first error
return &gr.Errors[0]
}
return nil
}
// WithHTTPClient specifies the underlying http.Client to use when
// making requests.
//
// NewClient(endpoint, WithHTTPClient(specificHTTPClient))
func WithHTTPClient(httpclient *http.Client) ClientOption {
return func(client *Client) {
client.httpClient = httpclient
}
}
// UseMultipartForm uses multipart/form-data and activates support for
// files.
func UseMultipartForm() ClientOption {
return func(client *Client) {
client.useMultipartForm = true
}
}
// ImmediatelyCloseReqBody will close the req body immediately after each request body is ready
func ImmediatelyCloseReqBody() ClientOption {
return func(client *Client) {
client.closeReq = true
}
}
// ClientOption are functions that are passed into NewClient to
// modify the behaviour of the Client.
type ClientOption func(*Client)
type graphResponse struct {
Data interface{}
Errors []GraphQLError
}
// Request is a GraphQL request.
type Request struct {
q string
vars map[string]interface{}
files []File
// Header represent any request headers that will be set
// when the request is made.
Header http.Header
}
// NewRequest makes a new Request with the specified string.
func NewRequest(q string) *Request {
req := &Request{
q: q,
Header: make(map[string][]string),
}
return req
}
// Var sets a variable.
func (req *Request) Var(key string, value interface{}) {
if req.vars == nil {
req.vars = make(map[string]interface{})
}
req.vars[key] = value
}
// Vars gets the variables for this Request.
func (req *Request) Vars() map[string]interface{} {
return req.vars
}
// Files gets the files in this request.
func (req *Request) Files() []File {
return req.files
}
// Query gets the query string of this request.
func (req *Request) Query() string {
return req.q
}
// File sets a file to upload.
// Files are only supported with a Client that was created with
// the UseMultipartForm option.
func (req *Request) File(fieldname, filename string, r io.Reader) {
req.files = append(req.files, File{
Field: fieldname,
Name: filename,
R: r,
})
}
// File represents a file to upload.
type File struct {
Field string
Name string
R io.Reader
}
type HttpError struct {
Err error
Response *http.Response
}
func (e *HttpError) Error() string {
return e.Err.Error()
}
type GraphQLError struct {
Err error
Message string
Path []string
Extensions GraphQLErrorExtensions
}
type GraphQLErrorExtensions struct {
Code string
ServiceName string
Query string
Variables map[string]string
}
func newGraphQLError(err error) error {
if err == nil {
return nil
}
if gqlErr, ok := err.(*GraphQLError); ok {
return gqlErr
}
return &GraphQLError{
Err: err,
}
}
func (gqlErr *GraphQLError) Error() string {
if gqlErr.Err != nil {
return gqlErr.Err.Error()
} else {
return gqlErr.Message
}
}
func IsClientError(err error) bool {
gqlErr, ok := err.(*GraphQLError)
return ok && gqlErr.Err != nil && len(gqlErr.Extensions.Code) == 0
}
func IsGraphQLError(err error) bool {
gqlErr, ok := err.(*GraphQLError)
return ok && gqlErr.Err == nil && len(gqlErr.Extensions.Code) > 0
}
func IsUnauthorizedError(err error) bool {
gqlErr, ok := err.(*GraphQLError)
return ok && gqlErr.Extensions.Code == "UNAUTHORIZED"
}
func IsInvalidError(err error) bool {
gqlErr, ok := err.(*GraphQLError)
return ok && gqlErr.Extensions.Code == "INVALID"
}
func IsUnprocessableError(err error) bool {
gqlErr, ok := err.(*GraphQLError)
return ok && gqlErr.Extensions.Code == "UNPROCESSABLE"
}
func IsInvalidArgumentsError(err error) bool {
gqlErr, ok := err.(*GraphQLError)
return ok && gqlErr.Extensions.Code == "INVALID_ARGUMENTS"
}
func IsMaintenanceError(err error) bool {
gqlErr, ok := err.(*GraphQLError)
return ok && gqlErr.Extensions.Code == "MAINTENANCE"
}
func IsServerError(err error) bool {
gqlErr, ok := err.(*GraphQLError)
return ok && gqlErr.Extensions.Code == "SERVER_ERROR"
}
func IsInternalServerError(err error) bool {
gqlErr, ok := err.(*GraphQLError)
return ok && gqlErr.Extensions.Code == "INTERNAL_SERVER_ERROR"
}
func IsServiceUnavailableError(err error) bool {
gqlErr, ok := err.(*GraphQLError)
return ok && gqlErr.Extensions.Code == "SERVICE_UNAVAILABLE"
}
func IsNotFoundError(err error) bool {
gqlErr, ok := err.(*GraphQLError)
return ok && gqlErr.Extensions.Code == "NOT_FOUND"
}