// Copyright 2017 Vector Creations Ltd
//
// 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 (
	"encoding/json"
	"io/ioutil"
	"net/http"
	"unicode/utf8"

	"github.com/matrix-org/dendrite/clientapi/jsonerror"
	"github.com/matrix-org/util"
)

// UnmarshalJSONRequest into the given interface pointer. Returns an error JSON response if
// there was a problem unmarshalling. Calling this function consumes the request body.
func UnmarshalJSONRequest(req *http.Request, iface interface{}) *util.JSONResponse {
	// encoding/json allows invalid utf-8, matrix does not
	// https://matrix.org/docs/spec/client_server/r0.6.1#api-standards
	body, err := ioutil.ReadAll(req.Body)
	if err != nil {
		util.GetLogger(req.Context()).WithError(err).Error("ioutil.ReadAll failed")
		resp := jsonerror.InternalServerError()
		return &resp
	}

	if !utf8.Valid(body) {
		return &util.JSONResponse{
			Code: http.StatusBadRequest,
			JSON: jsonerror.NotJSON("Body contains invalid UTF-8"),
		}
	}

	if err := json.Unmarshal(body, iface); err != nil {
		// TODO: We may want to suppress the Error() return in production? It's useful when
		// debugging because an error will be produced for both invalid/malformed JSON AND
		// valid JSON with incorrect types for values.
		return &util.JSONResponse{
			Code: http.StatusBadRequest,
			JSON: jsonerror.BadJSON("The request body could not be decoded into valid JSON. " + err.Error()),
		}
	}
	return nil
}