#include<stdio.h>
#include<stdlib.h>
#include<sys/stat.h>
#include<sys/types.h>
#include<dirent.h>
#include<unistd.h>
#include<pwd.h>
#include<grp.h>
#include<string.h>
#include<time.h>

const double version=1.0;

int command_l=0;
int command_R=0;
int command_h=0;

int currentYear;

typedef struct File{
    char accessRights[11];
    int userId;
    int groupId;
    unsigned long size;
    time_t time;
    char name[256];
    int isDir;
} File;

char *getPath(char *path, char *file)
{
    int pathLen=strlen(path);
    int fileLen=strlen(path);
    char *fullPath=(char*)malloc((pathLen+fileLen+2)*sizeof(char));
    strcpy(fullPath,path);
    if(pathLen && path[pathLen-1]!='/')
    {
        fullPath[pathLen]='/';
        strcpy(fullPath+pathLen+1,file);
        fullPath[pathLen+fileLen+1]='\0';
    }
    else
    {
        strcpy(fullPath+pathLen+1,file);
        fullPath[pathLen+fileLen+1]='\0';
    }
    return fullPath;
}

void getAccessRights(File *container, struct stat *file)
{
    container->accessRights[0]=S_ISDIR(file->st_mode) ? 'd' : '-';
    container->accessRights[1]=(file->st_mode & S_IRUSR) ? 'r' : '-';
    container->accessRights[2]=(file->st_mode & S_IWUSR) ? 'w' : '-';
    container->accessRights[3]=(file->st_mode & S_IXUSR) ? 'x' : '-';
    container->accessRights[4]=(file->st_mode & S_IRGRP) ? 'r' : '-';
    container->accessRights[5]=(file->st_mode & S_IWGRP) ? 'w' : '-';
    container->accessRights[6]=(file->st_mode & S_IXGRP) ? 'x' : '-';
    container->accessRights[7]=(file->st_mode & S_IROTH) ? 'r' : '-';
    container->accessRights[8]=(file->st_mode & S_IWOTH) ? 'w' : '-';
    container->accessRights[9]=(file->st_mode & S_IXOTH) ? 'x' : '-';
    container->accessRights[10]='\0';
}

char *humanReadable(unsigned long bytes)
{
    double bytesDouble=(double)bytes;
    char *sizestr=(char*)malloc(12*sizeof(char));
    char symbols[6]={'B','K','M','G','T','P'};
    int i=0;
    while(i<=5 && bytesDouble>=1024.0)
    {
        bytesDouble/=1024.0;
        i++;
    }
    if((int)(10*bytesDouble)%10==0)
        sprintf(sizestr,"%d%c",(int)bytesDouble,symbols[i]);
    else
        sprintf(sizestr,"%.1lf%c",bytesDouble,symbols[i]);
    return sizestr;
}

char *convertTime(unsigned long time)
{
    time_t now=time;
    struct tm *ptm=localtime(&time);
    char *timestr=(char*) malloc(256*sizeof(char));
    if (ptm->tm_year==currentYear)
		strftime(timestr,256,"%d %b %R",ptm);
	else
		strftime(timestr,256,"%d %b %G",ptm);
	return timestr;
}

void printFile(File *container, int l, int h)
{
    if(container->name[0]=='.')
        return;
    if(l)
    {
        struct passwd *uid=getpwuid(container->userId);
        struct group *gid=getgrgid(container->groupId);
        char *tm=convertTime(container->time);
        printf("%s %s %s ", container->accessRights, uid->pw_name, gid->gr_name);
        if(h)
        {
            char *humanReadableSize=humanReadable(container->size);
            printf("%s ", humanReadableSize);
        }
        else
            printf("%ld ",container->size);
            printf("%s %s\n",tm,container->name);
        }
    else
        printf("%s\t",container->name);
}

void printHelp()
{
    printf("This program lists the files and subdirectories in a given directory.\n\n");
    printf("The following options are available:\n\n");
    printf("  -l\t\tLists files in the long format, including access rights, number of links, owner name, group name, size, date of last modification and name of file.\n\n");
    printf("  -h\t\tWhen used with the -l option, lists sizes with unit suffixes: (B)yte, (K)ilobyte, (M)egabyte, (G)igabyte, (T)erabyte and (P)etabyte.\n\n");
    printf("  -R\t\tRecursively lists subdirectories encountered.\n\n");
    printf("  --help\t\tLists available options.\n\n");
    printf("  --version\tPrints current version and author.\n");
    exit(0);
}

void printVersion()
{
    printf("MyLS version %.1lf\n",version);
    printf("Made by Mateusz Wlodarczyk\n");
    printf("UMK 2019\n");
    exit(0);
}

void listDir(char *name, int l, int R, int h)
{
    DIR *dir;
    struct dirent *dp;
    struct stat statbuf;
    if((dir=opendir(name))==NULL)
    {
        perror("Couldn't open the directory");
        return;
    }
    int filesNumber=0;
    while((dp=readdir(dir))!=NULL)
        filesNumber++;
    closedir(dir);
    if(filesNumber==2) return;
    File *allFiles=(File*)malloc(sizeof(File)*(filesNumber));
    int filesOpened=0;
    int dirNumber= 0;
    int iDir=0;
    int i;
    if((dir=opendir(name))==NULL)
    {
        perror("Couldn't open the directory");
        return;
    }
    while((dp=readdir(dir))!=NULL)
    {
        char *fullName=getPath(name,dp->d_name);
        File *file=allFiles+filesOpened;
        if(stat(fullName,&statbuf))
        {
            perror("Couldn't open the file");
            free(fullName);
            continue;
        }
        strcpy(file->name,dp->d_name);
        getAccessRights(file,&statbuf);
        file->size=(long)statbuf.st_size;
        file->userId=statbuf.st_uid;
        file->groupId=statbuf.st_gid;
        file->time=statbuf.st_mtime;
        file->isDir=dp->d_type==DT_DIR ? 1 : 0;
        if(file->isDir==1)
            dirNumber++;
        filesOpened++;
        free(fullName);
    }
    for(i=0;i<filesOpened;i++)
        printFile(allFiles+i, l, h);
    printf("\n");
    if(!R || dirNumber==2)
    {
        free(allFiles);
        closedir(dir);
        return;
    }
    File *dirList=(File*)malloc(sizeof(File)*dirNumber);
    for(i=0;i<filesOpened;i++)
    {
        if(allFiles[i].isDir)
        {
            if(strcmp(allFiles[i].name,".")==0 || strcmp(allFiles[i].name,"..")==0)
                continue;
            dirList[iDir++]=allFiles[i];
        }
    }
    free(allFiles);
    closedir(dir);
    for(i = 0;i<iDir;i++)
    {
        char *Name=getPath(name,dirList[i].name);
        listDir(Name,l,R,h);
        free(Name);
    }
    free(dirList);
}

int main(int argc, char **argv)
{
    int i;
    while((i=getopt(argc,argv,"lRh"))!=-1)
    {
        switch(i)
        {
            case 'l':
                command_l=1;
                break;
            case 'R':
                command_R=1;
                break;
            case 'h':
                command_h=1;
                break;
        }
    }
    for(i=1;i<argc;i++)
    {
        if(strcmp(argv[i],"--help")==0)
            printHelp();
        else if(strcmp(argv[i],"--version")==0)
            printVersion();
    }
    time_t currentTime=time(NULL);
    struct tm *pctm=localtime(&currentTime);
    currentYear=pctm->tm_year;
    if(optind<argc)
        listDir(argv[optind],command_l,command_R,command_h);
    else
        listDir(".",command_l,command_R,command_h);
    exit(0);
}