#include "gbos.h"
/* tr [-d] SET1 [SET2]: translate or delete characters, stdin to stdout.
 *
 *   ls | tr a-z A-Z          ranges work
 *   cat f | tr -d aeiou      -d deletes instead of mapping
 *   echo a b | tr \\s \\n      \\s \\t \\n name characters the shell cannot quote
 *
 * ASCII only (a 128-entry map on the stack), and like tr(1) a short SET2 is
 * padded with its last character. */

#define SETMAX 64

/* The shell has no quoting, so a space or a tab cannot be typed as an
   argument: "-d ' '" arrives as three tokens. Escapes are how you name them
   here - \s space, \t tab, \n newline, \\ backslash. */
static char unesc1(const char *s, unsigned char *used) {
    *used = 1;
    if (s[0] != '\\' || !s[1]) return s[0];
    *used = 2;
    switch (s[1]) {
        case 's': return ' ';
        case 't': return '\t';
        case 'n': return '\n';
        case 'r': return '\r';
        default: return s[1];
    }
}

/* expand "a-z0-9_" into the characters it names; returns how many */
static unsigned char expand(const char *s, char *out, unsigned char max) {
    unsigned char n = 0, i = 0;
    char a, b;
    while (s[i] && n < max) {
        unsigned char ua, ub;
        a = unesc1(s + i, &ua);
        if (s[i + ua] == '-' && s[i + ua + 1]) { /* a range */
            b = unesc1(s + i + ua + 1, &ub);
            while (a <= b && n < max) out[n++] = a++;
            i += ua + 1 + ub;
        } else {
            out[n++] = a;
            i += ua;
        }
    }
    return n;
}

void main(void) {
    char *argv[8];
    char s1[SETMAX], s2[SETMAX];
    unsigned char map[128];
    unsigned char argc = argv_parse(argv, 8);
    unsigned char del = hasflag(argv, argc, 'd');
    unsigned char i, n1 = 0, n2 = 0, k;
    char *set1 = 0, *set2 = 0;
    char c;

    for (i = 0; i < argc; i++) {
        /* a bare "-" is a SET, not a flag: `tr . -` maps dots to dashes */
        if (argv[i][0] == '-' && argv[i][1]) continue;
        if (!set1) set1 = argv[i];
        else if (!set2) set2 = argv[i];
    }
    if (!set1 || (!del && !set2)) {
        puts("usage: tr [-d] SET1 [SET2]");
        nl();
        sexit(2);
    }
    n1 = expand(set1, s1, SETMAX);
    if (set2) n2 = expand(set2, s2, SETMAX);

    for (i = 0; i < 128; i++) map[i] = i; /* identity, then patch */
    for (k = 0; k < n1; k++) {
        unsigned char from = (unsigned char)s1[k] & 127;
        if (del) map[from] = 0; /* 0 = drop it */
        else map[from] = (unsigned char)s2[k < n2 ? k : n2 - 1];
    }

    for (;;) {
        c = readc();
        if (c == EOF) break;
        if ((unsigned char)c < 128) {
            unsigned char o = map[(unsigned char)c];
            if (o) putc((char)o);
        } else putc(c);
    }
}