#include "head.h"


// 小文件的接收
void recvMinFile(int sockfd, int fd, train_t train){
    printf("小文件接收\n");
    while(1){
        bzero(&train, sizeof(train));
        // 接收数据的长度
        recvn(sockfd, &train.length, sizeof(train.length));
        if(train.length == 0){
            break;
        }
        // 接收内容
        recvn(sockfd, train.data, train.length);
        write(fd, train.data, train.length);
    }
}


// 大文件的接收, mmap方式
void recvMaxFile(int sockfd, int fd, off_t filesize){
    printf("大文件接收\n");
    ftruncate(fd, filesize);
    char *p = (char *)mmap(NULL, filesize, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
    ERROR_CHECK(p, MAP_FAILED, "mmap");
    recvn(sockfd, p, filesize);
    munmap(p, filesize);
}


// 续传的接收
void recvAgain(int sockfd, int fd, off_t filesize, off_t offset){
    printf("续传接收\n");
    ftruncate(fd, filesize);
    char *p = (char *)mmap(NULL, filesize, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
    ERROR_CHECK(p, MAP_FAILED, "mmap");
    recvn(sockfd, p+offset, filesize-offset);
    munmap(p, filesize);
}



int recvFile(int sockfd){
    train_t train1, train2, train3, train4, train5;

    // step1：接收文件名长度和文件名
    bzero(&train1,sizeof(train1));
    recvn(sockfd, &train1.length, sizeof(train1.length));
    recvn(sockfd, train1.data, train1.length);
    //printf("train1.data = %s\n", train1.data);
    if(train1.length == 0){
        recvn(sockfd, &train1.length, sizeof(train1.length));
        recvn(sockfd, train1.data, train1.length);
    }
    // 打开文件，若不存在则新建文件
    char newPath[4096] = {0};
    sprintf(newPath, "%s/%s", ".", train1.data);
    int fd = open(newPath, O_RDWR|O_CREAT, 0666);
    ERROR_CHECK(fd, -1, "open");

    // step2：接收文件总大小
    bzero(&train2,sizeof(train2));
    off_t fileSize;
    recvn(sockfd, &train2.length, sizeof(train2.length));
    recvn(sockfd, train2.data, train2.length);
    memcpy(&fileSize, train2.data, sizeof(off_t));
    //printf("fileSize = %ld\n", fileSize);

    // step3：收取发送方的md5码
    bzero(&train3,sizeof(train3));
    unsigned char mdFromSender[16];
    recvn(sockfd, &train3.length, sizeof(train3.length));
    recvn(sockfd, train3.data, train3.length);
    for(int i=0; i<train3.length; i++){
        mdFromSender[i] = train3.data[i];
    }
    printf("recv md5 done!\n");

    // step4：发送initSize，对于文件的发送方相当于偏移量
    bzero(&train4,sizeof(train4));
    struct stat statbuf;
    fstat(fd, &statbuf);
    off_t initSize = statbuf.st_size;
    printf("offset = %ld\n", initSize);
    train4.length = sizeof(statbuf.st_size);
    memcpy(train4.data, &statbuf.st_size, train4.length);
    send(sockfd, &train4, sizeof(train4.length)+train4.length, MSG_NOSIGNAL);


    // 若接收方已存在同名文件且文件大小与发送方一致，
    // 则计算md5码，再和发送方的md5码比较
    if(initSize == fileSize){
        // 接收方自己的md5码
        MD5_CTX ctx;
        MD5_Init(&ctx);
        char buf[4096];
        while(1){
            bzero(buf, sizeof(buf));
            ssize_t sret = read(fd, buf, sizeof(buf));
            if(sret == 0){
                break;
            }
            MD5_Update(&ctx, buf, sret);
        }
        unsigned char mdFromRecver[16];   // 将要保存md5码16个字节的二进
        MD5_Final(mdFromRecver, &ctx);

        int flag = 0;
        for(int i=0; i<16; i++){
            if(mdFromRecver[i] != mdFromSender[i]){
                // 同名文件且文件大小一致， 但md5码不一致
                flag = 1;
                printf("此接收文件有错\n");
                return -1;
            }
        }
        if(flag == 0){
            // 同名文件且文件大小一致，md5码也一致
            printf("秒传模式\n");
            printf("recv file done!\n");
            printf("此接收文件无错\n");
            return 0;
        }
    }
    else{
        if(initSize > 0){
            // 续传的接收
            recvAgain(sockfd, fd, fileSize, initSize);
        }
        else if(initSize == 0 && fileSize >= 100*1024*1024){
            // 大文件接收
            recvMaxFile(sockfd, fd, fileSize);
        }
        else if(initSize == 0 && fileSize < 100*1024*1024){
            // 小文件接收
            recvMinFile(sockfd, fd, train5);
        }
    }
    printf("recv file done!\n");


    // 接收完文件内容后lseek到开头
    lseek(fd, 0, SEEK_SET);


    // 非秒传模式，接收完文件后再计算接收方自己的md5码
    MD5_CTX ctx;
    MD5_Init(&ctx);
    char buf[4096];
    while(1){
        bzero(buf, sizeof(buf));
        ssize_t  sret = read(fd, buf, sizeof(buf));
        if(sret == 0){
            break;
        }
        MD5_Update(&ctx, buf, sret);
    }
    unsigned char mdFromRecver[16];   // 将要保存md5码16个字节的二进
    MD5_Final(mdFromRecver, &ctx);


    // 比较两个md5码
    for(int i=0; i<16; i++){
        if(mdFromRecver[i] != mdFromSender[i]){
            printf("此接收文件有错\n");
            return -1;
        }
    }

    printf("此接收文件无错误\n");
    return 0;
}