#include "proto_msg.h"
#include <google/protobuf/descriptor.h>
#include <string>

using namespace std;
using namespace google::protobuf;

// 4 byte total msg len, including this 4 bytes
// 4 byte name len
// name string not null ended
// protobuf data
ProtoMessage *ProtoMsgCodec::decode(unsigned char* buf, size_t size) 
{
    if (size < 8) {
        return nullptr;
    }
    char *p = (char *)buf;
    uint32_t msglen = *(uint32_t *)buf;
    uint32_t namelen = *(uint32_t *)(buf + 4);
    if (size < msglen || size < 4 + namelen) {
        return nullptr;
    }
    string typeName(p + 8, namelen);
    ProtoMessage *msg = NULL;
    const ProtoDescriptor *des = DescriptorPool::generated_pool()->FindMessageTypeByName(typeName);
    if (des) {
        const ProtoMessage *proto = MessageFactory::generated_factory()->GetPrototype(des);
        if (proto) {
            msg = proto->New();
        }
    }
    if (msg == NULL) {
        return nullptr;
    }
    int r = msg->ParseFromArray(p + 8 + namelen, msglen - 8 - namelen);
    if (!r) {
        delete msg;
        return nullptr;
    }
    return msg;
}

unsigned char* ProtoMsgCodec::encode(ProtoMessage *msg, size_t& msgSize) {
	if (!msg)
		return nullptr;
    const string &typeName = msg->GetDescriptor()->full_name();
	uint32_t buf_size = 4 + 4 + typeName.size() + msg->ByteSize();
	unsigned char* buf = new unsigned char[buf_size];
	if (!buf)
		return nullptr;
	*(uint32_t*)buf = buf_size;
	size_t offset = 4;
	*(uint32_t*)(buf + offset) = typeName.size();
	offset += 4;
	memcpy_s(buf + offset, buf_size, typeName.data(), typeName.size());
	offset += typeName.size();
    msg->SerializeToArray(buf + offset, msg->ByteSize());
	msgSize = buf_size;
	return buf;
}