Ben Kraft
118 lines
3.2 KiB
Go
118 lines
3.2 KiB
Go
package graphql
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import (
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"bytes"
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"context"
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"encoding/json"
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"fmt"
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"net/http"
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"github.com/vektah/gqlparser/gqlerror"
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)
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// Client is the interface that the generate code calls into to actually make
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// requests.
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type Client interface {
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// MakeRequest must make a request to the client's GraphQL API.
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//
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// ctx is the context that should be used to make this request. If context
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// is disabled in the genql settings, this will be set to
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// context.Background().
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//
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// query is the literal string representing the GraphQL query, e.g.
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// `query myQuery { myField }`. variables contains the GraphQL variables
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// to be sent along with the query, or may be nil if there are none.
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// Typically, GraphQL APIs will accept a JSON payload of the form
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// {"query": "query myQuery { ... }", "variables": {...}}`
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// but MakeRequest may use some other transport, handle extensions, or set
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// other parameters, if it wishes.
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//
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// retval is a pointer to the struct representing the query result, e.g.
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// new(myQueryResponse). Typically, GraphQL APIs will return a JSON
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// payload of the form
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// {"data": {...}, "errors": {...}}
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// and retval is designed so that `data` will json-unmarshal into `retval`.
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// (Errors are returned.) But again, MakeRequest may customize this.
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MakeRequest(
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ctx context.Context,
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query string,
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retval interface{},
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variables map[string]interface{},
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) error
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}
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type client struct {
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endpoint string
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method string
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httpClient *http.Client
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}
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// NewClient returns a Client which makes requests to the given endpoint,
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// suitable for most users.
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//
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// The client makes POST requests to the given GraphQL endpoint using standard
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// GraphQL HTTP-over-JSON transport. It will use the given http client, or
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// http.DefaultClient if a nil client is passed.
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//
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// The typical method of adding authentication headers is to wrap the client's
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// Transport to add those headers. See example/caller.go for an example.
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func NewClient(endpoint string, httpClient *http.Client) Client {
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if httpClient == nil {
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httpClient = http.DefaultClient
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}
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return &client{endpoint, http.MethodPost, httpClient}
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}
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type payload struct {
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Query string `json:"query"`
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Variables map[string]interface{} `json:"variables"`
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}
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type response struct {
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Data json.RawMessage `json:"data"`
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Errors gqlerror.List `json:"errors"`
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}
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func (c *client) MakeRequest(ctx context.Context, query string, retval interface{}, variables map[string]interface{}) error {
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body, err := json.Marshal(payload{
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Query: query,
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Variables: variables,
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})
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if err != nil {
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return err
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}
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req, err := http.NewRequest(
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c.method,
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c.endpoint,
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bytes.NewReader(body))
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if err != nil {
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return err
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}
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if ctx != nil {
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req = req.WithContext(ctx)
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}
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resp, err := c.httpClient.Do(req)
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if err != nil {
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return err
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}
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defer resp.Body.Close()
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if resp.StatusCode != http.StatusOK {
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return fmt.Errorf("returned error %v: %v", resp.Status, string(body))
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}
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var dataAndErrors response
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err = json.NewDecoder(resp.Body).Decode(&dataAndErrors)
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if err != nil {
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return err
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}
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if len(dataAndErrors.Errors) > 0 {
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return dataAndErrors.Errors
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}
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return json.Unmarshal(dataAndErrors.Data, &retval)
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}
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