#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <fcntl.h>

#include <string.h>

#include <sys/stat.h>
#include <sys/types.h>
#include <dirent.h>

#include <pwd.h>


static char *nexttoksep(char **strp, char *sep)
{
    char *p = strsep(strp,sep);
    return (p == 0) ? "" : p;
}
static char *nexttok(char **strp)
{
    return nexttoksep(strp, " ");
}

#define SHOW_PRIO 1
#define SHOW_TIME 2

static int display_flags = 0;

static int ps_line(int pid, int tid, char *namefilter)
{
    char statline[1024];
    char cmdline[1024];
    char user[32];
    struct stat stats;
    int fd, r;
    char *ptr, *name, *state;
    int ppid, tty;
    unsigned wchan, rss, vss, eip;
    unsigned utime, stime;
    int prio, nice, rtprio, sched;
    struct passwd *pw;
    
    sprintf(statline, "/proc/%d", pid);
    stat(statline, &stats);

    if(tid) {
        sprintf(statline, "/proc/%d/task/%d/stat", pid, tid);
        cmdline[0] = 0;
    } else {
        sprintf(statline, "/proc/%d/stat", pid);
        sprintf(cmdline, "/proc/%d/cmdline", pid);    
        fd = open(cmdline, O_RDONLY);
        if(fd == 0) {
            r = 0;
        } else {
            r = read(fd, cmdline, 1023);
            close(fd);
            if(r < 0) r = 0;
        }
        cmdline[r] = 0;
    }
    
    fd = open(statline, O_RDONLY);
    if(fd == 0) return -1;
    r = read(fd, statline, 1023);
    close(fd);
    if(r < 0) return -1;
    statline[r] = 0;

    ptr = statline;
    nexttok(&ptr); // skip pid
    ptr++;          // skip "("

    name = ptr;
    ptr = strrchr(ptr, ')'); // Skip to *last* occurence of ')',
    *ptr++ = '\0';           // and null-terminate name.

    ptr++;          // skip " "
    state = nexttok(&ptr);
    ppid = atoi(nexttok(&ptr));
    nexttok(&ptr); // pgrp
    nexttok(&ptr); // sid
    tty = atoi(nexttok(&ptr));
    
    nexttok(&ptr); // tpgid
    nexttok(&ptr); // flags
    nexttok(&ptr); // minflt
    nexttok(&ptr); // cminflt
    nexttok(&ptr); // majflt
    nexttok(&ptr); // cmajflt
#if 1
    utime = atoi(nexttok(&ptr));
    stime = atoi(nexttok(&ptr));
#else
    nexttok(&ptr); // utime
    nexttok(&ptr); // stime
#endif
    nexttok(&ptr); // cutime
    nexttok(&ptr); // cstime
    prio = atoi(nexttok(&ptr));
    nice = atoi(nexttok(&ptr));
    nexttok(&ptr); // threads
    nexttok(&ptr); // itrealvalue
    nexttok(&ptr); // starttime
    vss = strtoul(nexttok(&ptr), 0, 10); // vsize
    rss = strtoul(nexttok(&ptr), 0, 10); // rss
    nexttok(&ptr); // rlim
    nexttok(&ptr); // startcode
    nexttok(&ptr); // endcode
    nexttok(&ptr); // startstack
    nexttok(&ptr); // kstkesp
    eip = strtoul(nexttok(&ptr), 0, 10); // kstkeip
    nexttok(&ptr); // signal
    nexttok(&ptr); // blocked
    nexttok(&ptr); // sigignore
    nexttok(&ptr); // sigcatch
    wchan = strtoul(nexttok(&ptr), 0, 10); // wchan
    nexttok(&ptr); // nswap
    nexttok(&ptr); // cnswap
    nexttok(&ptr); // exit signal
    nexttok(&ptr); // processor
    rtprio = atoi(nexttok(&ptr)); // rt_priority
    sched = atoi(nexttok(&ptr)); // scheduling policy
    
    tty = atoi(nexttok(&ptr));
    
    if(tid != 0) {
        ppid = pid;
        pid = tid;
    }

    pw = getpwuid(stats.st_uid);
    if(pw == 0) {
        sprintf(user,"%d",(int)stats.st_uid);
    } else {
        strcpy(user,pw->pw_name);
    }
    
    if(!namefilter || !strncmp(name, namefilter, strlen(namefilter))) {
        printf("%-8s %-5d %-5d %-5d %-5d", user, pid, ppid, vss / 1024, rss * 4);
        if(display_flags&SHOW_PRIO)
            printf(" %-5d %-5d %-5d %-5d", prio, nice, rtprio, sched);
        printf(" %08x %08x %s %s", wchan, eip, state, cmdline[0] ? cmdline : name);
        if(display_flags&SHOW_TIME)
            printf(" (u:%d, s:%d)", utime, stime);
        printf("\n");
    }
    return 0;
}


void ps_threads(int pid, char *namefilter)
{
    char tmp[128];
    DIR *d;
    struct dirent *de;

    sprintf(tmp,"/proc/%d/task",pid);
    d = opendir(tmp);
    if(d == 0) return;
    
    while((de = readdir(d)) != 0){
        if(isdigit(de->d_name[0])){
            int tid = atoi(de->d_name);
            if(tid == pid) continue;
            ps_line(pid, tid, namefilter);
        }
    }
    closedir(d);    
}

int ps_main(int argc, char **argv)
{
    DIR *d;
    struct dirent *de;
    char *namefilter = 0;
    int pidfilter = 0;
    int threads = 0;
    
    d = opendir("/proc");
    if(d == 0) return -1;

    while(argc > 1){
        if(!strcmp(argv[1],"-t")) {
            threads = 1;
        } else if(!strcmp(argv[1],"-x")) {
            display_flags |= SHOW_TIME;
        } else if(!strcmp(argv[1],"-p")) {
            display_flags |= SHOW_PRIO;
        }  else if(isdigit(argv[1][0])){
            pidfilter = atoi(argv[1]);
        } else {
            namefilter = argv[1];
        }
        argc--;
        argv++;
    }

    printf("USER     PID   PPID  VSIZE RSS   %sWCHAN    PC         NAME\n", 
           (display_flags&SHOW_PRIO)?"PRIO  NICE  RTPRI SCHED ":"");
    while((de = readdir(d)) != 0){
        if(isdigit(de->d_name[0])){
            int pid = atoi(de->d_name);
            if(!pidfilter || (pidfilter == pid)) {
                ps_line(pid, 0, namefilter);
                if(threads) ps_threads(pid, namefilter);
            }
        }
    }
    closedir(d);
    return 0;
}