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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"
)
// adapter represents a container that contain a handler function
// and convert a it to a http.Handler
type adapter interface {
invoke(context.Context, http.ResponseWriter, *http.Request) (interface{}, error)
}
// genericAdapter represents a common adapter
type genericAdapter struct {
inContext bool
method reflect.Value
numIn int
types []reflect.Type
cacheArgs []reflect.Value // cache args
}
// Accept zero parameter adapter
type simplePlainAdapter struct {
inContext bool
method reflect.Value
cacheArgs []reflect.Value
}
// Accept only one parameter adapter
type simpleUnaryAdapter struct {
outContext bool
argType reflect.Type
method reflect.Value
cacheArgs []reflect.Value // cache args
}
func makeGenericAdapter(method reflect.Value, inContext bool) *genericAdapter {
var noSupportExists = false
t := method.Type()
numIn := t.NumIn()
a := &genericAdapter{
inContext: inContext,
method: method,
numIn: numIn,
types: make([]reflect.Type, numIn),
cacheArgs: make([]reflect.Value, numIn),
}
for i := 0; i < numIn; i++ {
in := t.In(i)
if in != contextType && !isBuiltinType(in) {
if noSupportExists {
panic("function should accept only one customize type")
}
if in.Kind() != reflect.Ptr {
panic("customize type should be a pointer(" + in.PkgPath() + "." + in.Name() + ")")
}
noSupportExists = true
}
a.types[i] = in
}
return a
}
func (a *genericAdapter) invoke(ctx context.Context, w http.ResponseWriter, r *http.Request) (interface{}, error) {
values := a.cacheArgs
for i := 0; i < a.numIn; i++ {
typ := a.types[i]
v, ok := supportTypes[typ]
if ok {
value, err := v(r)
if err != nil {
return nil, err
}
values[i] = value
} else if typ == contextType {
values[i] = reflect.ValueOf(ctx)
} else {
d := reflect.New(a.types[i].Elem()).Interface()
err := json.NewDecoder(r.Body).Decode(d)
if err != nil {
return nil, err
}
values[i] = reflect.ValueOf(d)
}
}
var err error
results := a.method.Call(values)
payload := results[0].Interface()
if e := results[1].Interface(); e != nil {
err = e.(error)
}
return payload, err
}
func (a *simplePlainAdapter) invoke(ctx context.Context, w http.ResponseWriter, r *http.Request) (interface{}, error) {
if a.inContext {
a.cacheArgs[0] = reflect.ValueOf(ctx)
}
var err error
results := a.method.Call(a.cacheArgs)
payload := results[0].Interface()
if e := results[1].Interface(); e != nil {
err = e.(error)
}
return payload, err
}
func (a *simpleUnaryAdapter) invoke(ctx context.Context, w http.ResponseWriter, r *http.Request) (interface{}, error) {
data := reflect.New(a.argType.Elem()).Interface()
err := json.NewDecoder(r.Body).Decode(data)
if err != nil {
return nil, err
}
a.cacheArgs[0] = reflect.ValueOf(data)
results := a.method.Call(a.cacheArgs)
payload := results[0].Interface()
if e := results[1].Interface(); e != nil {
err = e.(error)
}
return payload, err
}
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