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// Copyright 2017 PingCAP, Inc.
//
// 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 fn
import (
"context"
"encoding/json"
"net/http"
"reflect"
)
type (
// ErrorEncoder encode error to response body
ErrorEncoder func(ctx context.Context, err error) interface{}
// ResponseEncoder encode payload to response body
ResponseEncoder func(ctx context.Context, payload interface{}) interface{}
// fn represents a handler that contains a bundle of hooks
fn struct {
plugins []PluginFunc
adapter adapter
}
)
var (
errorEncoder ErrorEncoder
responseEncoder ResponseEncoder
)
func failure(ctx context.Context, w http.ResponseWriter, err error) {
statusCode := http.StatusBadRequest
if v, ok := UnwrapErrorStatusCode(err); ok {
statusCode = v
}
w.WriteHeader(statusCode)
_ = json.NewEncoder(w).Encode(errorEncoder(ctx, err))
}
func success(ctx context.Context, w http.ResponseWriter, data interface{}) {
if data == nil || (reflect.ValueOf(data).Kind() == reflect.Ptr && reflect.ValueOf(data).IsNil()) {
w.WriteHeader(http.StatusNoContent)
} else {
_ = json.NewEncoder(w).Encode(responseEncoder(ctx, data))
}
}
func (fn *fn) ServeHTTP(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "application/json; charset=utf-8")
var (
ctx = r.Context()
err error
resp interface{}
)
for _, b := range globalPlugins {
ctx, err = b(ctx, r)
if err != nil {
failure(ctx, w, err)
return
}
}
for _, b := range fn.plugins {
ctx, err = b(ctx, r)
if err != nil {
failure(ctx, w, err)
return
}
}
resp, err = fn.adapter.invoke(ctx, w, r)
if err != nil {
failure(ctx, w, err)
return
}
success(ctx, w, resp)
}
func (fn *fn) Plugin(before ...PluginFunc) *fn {
for _, b := range before {
if b != nil {
fn.plugins = append(fn.plugins, b)
}
}
return fn
}
func init() {
errorEncoder = func(ctx context.Context, err error) interface{} {
return err.Error()
}
responseEncoder = func(ctx context.Context, payload interface{}) interface{} {
return payload
}
}
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