1 files changed, 81 insertions, 0 deletions
diff --git a/internal/httputil/http.go b/internal/httputil/http.go
new file mode 100644
index 00000000..9197371a
--- /dev/null
+++ b/internal/httputil/http.go
@@ -0,0 +1,81 @@
+// Copyright 2020 The Matrix.org Foundation C.I.C.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package httputil
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/url"
+	"strings"
+
+	opentracing "github.com/opentracing/opentracing-go"
+	"github.com/opentracing/opentracing-go/ext"
+)
+
+// PostJSON performs a POST request with JSON on an internal HTTP API
+func PostJSON(
+	ctx context.Context, span opentracing.Span, httpClient *http.Client,
+	apiURL string, request, response interface{},
+) error {
+	jsonBytes, err := json.Marshal(request)
+	if err != nil {
+		return err
+	}
+
+	parsedAPIURL, err := url.Parse(apiURL)
+	if err != nil {
+		return err
+	}
+
+	parsedAPIURL.Path = InternalPathPrefix + strings.TrimLeft(parsedAPIURL.Path, "/")
+	apiURL = parsedAPIURL.String()
+
+	req, err := http.NewRequest(http.MethodPost, apiURL, bytes.NewReader(jsonBytes))
+	if err != nil {
+		return err
+	}
+
+	// Mark the span as being an RPC client.
+	ext.SpanKindRPCClient.Set(span)
+	carrier := opentracing.HTTPHeadersCarrier(req.Header)
+	tracer := opentracing.GlobalTracer()
+
+	if err = tracer.Inject(span.Context(), opentracing.HTTPHeaders, carrier); err != nil {
+		return err
+	}
+
+	req.Header.Set("Content-Type", "application/json")
+
+	res, err := httpClient.Do(req.WithContext(ctx))
+	if res != nil {
+		defer (func() { err = res.Body.Close() })()
+	}
+	if err != nil {
+		return err
+	}
+	if res.StatusCode != http.StatusOK {
+		var errorBody struct {
+			Message string `json:"message"`
+		}
+		if msgerr := json.NewDecoder(res.Body).Decode(&errorBody); msgerr == nil {
+			return fmt.Errorf("Internal API: %d from %s: %s", res.StatusCode, apiURL, errorBody.Message)
+		}
+		return fmt.Errorf("Internal API: %d from %s", res.StatusCode, apiURL)
+	}
+	return json.NewDecoder(res.Body).Decode(response)
+}