#include "gbos.h"
/* grep [-v][-i][-n] PAT [file]: print the lines of a file (or stdin) that
 * contain the substring PAT. Plain substring matching, no regex - '.' and '*'
 * are literal characters. -v inverts the match, -i folds case, -n prefixes
 * each hit with its line number.
 *
 * NB: no statics here. A program's _DATA area starts at $A000, which is also
 * where the shell leaves the command line (usr/sh.c ARGV0), so statics would
 * eat argv. Locals live on the task stack below $BFFF and are always safe. */

#define MAXLINE 80 /* two terminal rows; longer lines are clipped */

static char fold(char c, unsigned char ic) {
    if (ic && c >= 'A' && c <= 'Z') return (char)(c + 32);
    return c;
}

/* is pat[] present anywhere in line[0..len)? */
static unsigned char contains(char *line, unsigned char len, char *pat, unsigned char ic) {
    unsigned char i, j;
    if (!pat[0]) return 1; /* empty pattern matches all */
    for (i = 0; i < len; i++) {
        for (j = 0;; j++) {
            if (!pat[j]) return 1;   /* ran out of pattern: a hit */
            if (i + j >= len) break; /* ran out of line: no hit here */
            if (fold(line[i + j], ic) != fold(pat[j], ic)) break;
        }
    }
    return 0;
}

void main(void) {
    char *argv[8];
    char line[MAXLINE];
    unsigned char argc = argv_parse(argv, 8);
    unsigned char inv = hasflag(argv, argc, 'v') ? 1 : 0;
    unsigned char ic = hasflag(argv, argc, 'i') ? 1 : 0;
    unsigned char num = hasflag(argv, argc, 'n') ? 1 : 0;
    unsigned char i, len = 0, hits = 0, fd = NOFD;
    unsigned int lineno = 0;
    char *pat = 0, *fname = 0;
    int ch;

    /* first non-flag word is the pattern, second (if any) is the file */
    for (i = 0; i < argc; i++) {
        if (argv[i][0] == '-') continue;
        if (!pat) pat = argv[i];
        else {
            fname = argv[i];
            break;
        }
    }
    if (!pat) {
        puts("usage: grep [-vin] PAT [file]");
        nl();
        sexit(2);
    }

    if (fname) {
        fd = open(fname, O_READ);
        if (fd == EISDIR) {
            puts("grep: is a directory");
            nl();
            sexit(2);
        }
        if (fd == NOFD) {
            puts("grep: no such file");
            nl();
            sexit(2);
        }
    }

    for (;;) {
        if (fd == NOFD) {
            char c = readc();
            ch = (c == EOF) ? -1 : c;
        } else ch = fgetc(fd);
        if (ch == '\r') continue;    /* CRLF: the LF ends the line */
        if (ch >= 0 && ch != '\n') { /* ordinary character */
            if (len < MAXLINE) line[len++] = (char)ch;
            continue;
        }
        if (ch < 0 && len == 0) break; /* EOF, nothing pending */
        lineno++;
        if (contains(line, len, pat, ic) != inv) {
            if (num) {
                putu(lineno);
                putc(':');
            }
            writes(line, len); /* one batched render */
            nl();
            hits = 1;
        }
        len = 0;
        if (ch < 0) break; /* EOF after a final partial line */
    }
    if (fd != NOFD) close(fd);
    sexit(hits ? 0 : 1); /* grep(1) exit convention */
}