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graphql.go
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graphql.go
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package graphql
import (
"bytes"
"context"
"encoding/json"
"fmt"
"io/ioutil"
"net/http"
"github.com/shurcooL/graphql/internal/jsonutil"
"golang.org/x/net/context/ctxhttp"
)
// Client is a GraphQL client.
type Client struct {
url string // GraphQL server URL.
httpClient *http.Client
}
// NewClient creates a GraphQL client targeting the specified GraphQL server URL.
// If httpClient is nil, then http.DefaultClient is used.
func NewClient(url string, httpClient *http.Client) *Client {
if httpClient == nil {
httpClient = http.DefaultClient
}
return &Client{
url: url,
httpClient: httpClient,
}
}
// Query executes a single GraphQL query request,
// with a query derived from q, populating the response into it.
// q should be a pointer to struct that corresponds to the GraphQL schema.
func (c *Client) Query(ctx context.Context, q interface{}, variables map[string]interface{}) error {
return c.do(ctx, queryOperation, q, variables)
}
// Mutate executes a single GraphQL mutation request,
// with a mutation derived from m, populating the response into it.
// m should be a pointer to struct that corresponds to the GraphQL schema.
func (c *Client) Mutate(ctx context.Context, m interface{}, variables map[string]interface{}) error {
return c.do(ctx, mutationOperation, m, variables)
}
// do executes a single GraphQL operation.
func (c *Client) do(ctx context.Context, op operationType, v interface{}, variables map[string]interface{}) error {
var query string
switch op {
case queryOperation:
query = constructQuery(v, variables)
case mutationOperation:
query = constructMutation(v, variables)
}
in := struct {
Query string `json:"query"`
Variables map[string]interface{} `json:"variables,omitempty"`
}{
Query: query,
Variables: variables,
}
var buf bytes.Buffer
err := json.NewEncoder(&buf).Encode(in)
if err != nil {
return err
}
resp, err := ctxhttp.Post(ctx, c.httpClient, c.url, "application/json", &buf)
if err != nil {
return err
}
defer resp.Body.Close()
if resp.StatusCode != http.StatusOK {
body, _ := ioutil.ReadAll(resp.Body)
return fmt.Errorf("non-200 OK status code: %v body: %q", resp.Status, body)
}
var out struct {
Data *json.RawMessage
Errors errors
//Extensions interface{} // Unused.
}
err = json.NewDecoder(resp.Body).Decode(&out)
if err != nil {
// TODO: Consider including response body in returned error, if deemed helpful.
return err
}
if out.Data != nil {
err := jsonutil.UnmarshalGraphQL(*out.Data, v)
if err != nil {
// TODO: Consider including response body in returned error, if deemed helpful.
return err
}
}
if len(out.Errors) > 0 {
return out.Errors
}
return nil
}
// errors represents the "errors" array in a response from a GraphQL server.
// If returned via error interface, the slice is expected to contain at least 1 element.
//
// Specification: https://facebook.github.io/graphql/#sec-Errors.
type errors []struct {
Message string
Locations []struct {
Line int
Column int
}
}
// Error implements error interface.
func (e errors) Error() string {
return e[0].Message
}
type operationType uint8
const (
queryOperation operationType = iota
mutationOperation
//subscriptionOperation // Unused.
)