/*
 *
 * Copyright 2014 gRPC authors. 
 *
 * 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 grpc

import (
	"math"
	"sync"

	"github.com/golang/protobuf/proto"
)

// Codec defines the interface gRPC uses to encode and decode messages. 
// Note that implementations of this interface must be thread safe;
// a Codec's methods can be called from concurrent goroutines. 
type Codec interface {
	// Marshal returns the wire format of v.
	Marshal(v interface{}) ([]byte, error)
	// Unmarshal parses the wire format into v.
	Unmarshal(data []byte, v interface{}) error
	// String returns the name of the Codec implementation.  The returned
	// string will be used as part of content type in transmission. 
	String() string
}

// protoCodec is a Codec implementation with protobuf.  It is the default codec for gRPC. 
type protoCodec struct {
}

type cachedProtoBuffer struct {
	lastMarshaledSize uint32
	proto. Buffer
}

func capToMaxInt32(val int) uint32 {
	if val > math. MaxInt32 {
		return uint32(math. MaxInt32)
	}
	return uint32(val)
}

func (p protoCodec) marshal(v interface{}, cb *cachedProtoBuffer) ([]byte, error) {
	protoMsg := v.(proto. Message)
	newSlice := make([]byte, 0, cb.lastMarshaledSize)

	cb. SetBuf(newSlice)
	cb. Reset()
	if err := cb. Marshal(protoMsg); err ! = nil {
		return nil, err
	}
	out := cb. Bytes()
	cb.lastMarshaledSize = capToMaxInt32(len(out))
	return out, nil
}

func (p protoCodec) Marshal(v interface{}) ([]byte, error) {
	cb := protoBufferPool. Get().(*cachedProtoBuffer)
	out, err := p.marshal(v, cb)

	// put back buffer and lose the ref to the slice
	cb. SetBuf(nil)
	protoBufferPool. Put(cb)
	return out, err
}

func (p protoCodec) Unmarshal(data []byte, v interface{}) error {
	cb := protoBufferPool. Get().(*cachedProtoBuffer)
	cb. SetBuf(data)
	v.(proto. Message).Reset()
	err := cb. Unmarshal(v.(proto. Message))
	cb. SetBuf(nil)
	protoBufferPool. Put(cb)
	return err
}

func (protoCodec) String() string {
	return "proto"
}

var protoBufferPool = &sync. Pool{
	New: func() interface{} {
		return &cachedProtoBuffer{
			Buffer:            proto. Buffer{},
			lastMarshaledSize: 16,
		}
	},
}
