Add stash scraper type (#269)

* Add stash scraper type

* Add graphql client to vendor

* Embed stash credentials in URL

* Fill URL from scraped scene

* Nil IDs returned from remote stash

* Nil check

vendor/github.com/shurcooL/graphql/graphql.go

@@ -0,0 +1,123 @@
+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.
+)