#include "gbos.h"
/* cp SRC DST: copy a file. There is no rename syscall, so `mv` is this plus
 * rm - and O_WRITE truncates (see fs.asm sys_open .trunc), which is exactly
 * why the SRC == DST case below has to be rejected before opening DST. */

static unsigned char streq(const char *a, const char *b) {
    while (*a && *a == *b) {
        a++;
        b++;
    }
    return (unsigned char)(*a == *b);
}

void main(void) {
    char *argv[4];
    unsigned char argc = argv_parse(argv, 4);
    unsigned char in, out;
    int ch;

    if (argc < 2) {
        puts("usage: cp SRC DST");
        nl();
        sexit(2);
    }
    if (streq(argv[0], argv[1])) {
        puts("cp: SRC and DST are the same file");
        nl();
        sexit(2);
    }

    in = open(argv[0], O_READ);
    if (in == EISDIR) {
        puts("cp: SRC is a directory");
        nl();
        sexit(2);
    }
    if (in == NOFD) {
        puts("cp: no such file: ");
        puts(argv[0]);
        nl();
        sexit(2);
    }

    out = open(argv[1], O_WRITE); /* creates, or truncates an existing file */
    if (out == EISDIR) {
        puts("cp: DST is a directory");
        nl();
        close(in);
        sexit(2);
    }
    if (out == NOFD) {
        puts("cp: cannot create ");
        puts(argv[1]);
        nl();
        close(in);
        sexit(2); /* out of inodes/blocks, or a bad path */
    }

    while ((ch = fgetc(in)) >= 0) fputc(out, (char)ch);
    close(in);
    close(out); /* flushes the inode */
}