#include "gbos.h"
/* gbos shell: prompt -> read a line -> parse -> run, with I/O redirection
   ( > file, < file ) and pipes ( cmd1 | cmd2, via a temp file ).
   Operators must be space-separated (e.g.  cat readme > out ). */

#define ARGV0 ((char *)0xA000)   /* where a child reads its command line */

/* split s into space-separated tokens (NUL-terminated in place). */
static unsigned char tokenize(char *s, char **tok, unsigned char max) {
    unsigned char n = 0;
    for (;;) {
        while (*s == ' ') *s++ = 0;
        if (*s == 0) break;
        if (n < max) tok[n++] = s;
        while (*s && *s != ' ') s++;
    }
    return n;
}

static unsigned char isop(char *t, char c) { return t[0] == c && t[1] == 0; }
static unsigned char iscmd(char *t, char a, char b) {
    return t[0] == a && t[1] == b && t[2] == 0;
}

/* keep the prompt's path string roughly in sync with chdir(). */
static void set_cwd(char *cwd, char *arg) {
    char *d, *s, *last;
    if (arg[0] == '/') {                 /* absolute */
        d = cwd; s = arg;
        while (*s) *d++ = *s++;
        *d = 0;
    } else if (arg[0] == '.' && arg[1] == '.' && arg[2] == 0) {
        last = cwd; d = cwd;
        while (*d) { if (*d == '/') last = d; d++; }
        if (last == cwd) { cwd[0] = '/'; cwd[1] = 0; } else *last = 0;
    } else if (arg[0] == '.' && arg[1] == 0) {
        /* stay */
    } else {                             /* relative: append */
        d = cwd; while (*d) d++;
        if (!(cwd[0] == '/' && cwd[1] == 0)) *d++ = '/';
        s = arg; while (*s) *d++ = *s++;
        *d = 0;
    }
}

/* build the child command line "name\0arg1 arg2\0" at 0xA000 */
static void set_cmdline(char **tok, unsigned char start, unsigned char end) {
    char *p = ARGV0, *t;
    unsigned char i;
    t = tok[start];
    while (*t) *p++ = *t++;
    *p++ = 0;                        /* NUL after the command word */
    for (i = start + 1; i < end; i++) {
        if (i > start + 1) *p++ = ' ';
        t = tok[i];
        while (*t) *p++ = *t++;
    }
    *p = 0;
}

/* run tok[start..end): parse its own >/< redirects, honor forced in/out.
   If bg, launch in the background (don't wait; leave fds to the child). */
static void run(char **tok, unsigned char start, unsigned char end,
                unsigned char infd, unsigned char outfd, unsigned char bg) {
    unsigned char i, cmdend = end, myin = NOFD, myout = NOFD, id, pid;
    for (i = start; i < end; i++) {
        if (isop(tok[i], '>')) {
            if (i + 1 < end) myout = open(tok[i + 1], O_WRITE);
            if (i < cmdend) cmdend = i;
        } else if (isop(tok[i], '<')) {
            if (i + 1 < end) myin = open(tok[i + 1], O_READ);
            if (i < cmdend) cmdend = i;
        }
    }
    id = lookup(tok[start]);
    if (id == NOFD) { puts(tok[start]); puts(": not found"); nl(); goto done; }
    set_cmdline(tok, start, cmdend);
    pid = fork();
    if (pid == 0) {
        if (myin != NOFD) setin(myin);
        else if (infd != NOFD) setin(infd);
        if (myout != NOFD) setout(myout);
        else if (outfd != NOFD) setout(outfd);
        exec(id);
    }
    if (bg) { putc('['); putu(pid); puts("]"); nl(); return; }  /* background */
    /* wait for THIS child; report any background jobs that finish meanwhile */
    for (;;) {
        unsigned char r = wait();
        if (r == pid || r == NOFD) break;
        putc('['); putu(r); puts(" done]"); nl();
    }
done:
    if (myin != NOFD) close(myin);
    if (myout != NOFD) close(myout);
}

void main(void) {
    char line[80];
    char *tok[16];
    char cwd[40];
    cwd[0] = '/'; cwd[1] = 0;
    for (;;) {
        unsigned char nt, i, pipepos, c, bg;
        /* reap finished background jobs */
        { unsigned char p; while ((p = reap())) { putc('['); putu(p); puts(" done]"); nl(); } }
        puts(cwd); puts("# ");
        /* read a line (echoing), stop at newline; exit on EOF */
        i = 0;
        for (;;) {
            c = readc();
            if (c == EOF) poweroff();
            if (c == '\r' || c == '\n') { nl(); break; }
            if (c == 8 || c == 127) {            /* backspace: drop last char */
                if (i > 0) { i--; putc(8); }
                continue;
            }
            if (i < 79) { line[i++] = c; putc(c); }
        }
        line[i] = 0;
        nt = tokenize(line, tok, 16);
        if (nt == 0) continue;
        if (iscmd(tok[0], 'c', 'd')) {              /* cd builtin */
            char *arg = (nt >= 2) ? tok[1] : "/";
            if (chdir(arg) == 0) set_cwd(cwd, arg);
            else { puts("cd: no such directory"); nl(); }
            continue;
        }
        if ((tok[0][0] == 'e' && tok[0][1] == 'x') ||
            (tok[0][0] == 'q' && tok[0][1] == 'u')) poweroff();
        bg = 0;
        if (isop(tok[nt - 1], '&')) { bg = 1; nt--; if (nt == 0) continue; }
        pipepos = 0;
        for (i = 1; i < nt; i++)
            if (isop(tok[i], '|')) { pipepos = i; break; }
        if (pipepos) {
            unsigned char pw = open("__pipe", O_WRITE);
            run(tok, 0, pipepos, NOFD, pw, 0);
            close(pw);
            { unsigned char pr = open("__pipe", O_READ);
              run(tok, pipepos + 1, nt, pr, NOFD, 0);
              close(pr); }
            fremove("__pipe");
        } else {
            run(tok, 0, nt, NOFD, NOFD, bg);
        }
    }
}