#include "gbos.h"
/* more [file]: page a file (or stdin) one screenful at a time.
 *
 * The terminal is 40x18, so anything longer than a screen scrolls off before
 * you can read it (try `ls` on a full disk, or `cat` on a wget dump). This
 * prints 17 lines, then paints a --More-- bar and waits for a keypress:
 * SELECT opens the on-screen keyboard, any key pages forward, 'q' quits.
 *
 * Keys come from pollin()/pollcon(), NOT stdin - so `cat file | more` still
 * has a keyboard even though its stdin is the pipe. (pollcon also means the
 * host can drive it over the link with tools/gbtype.) */

#define PAGE  17 /* TROWS - 1: leave a row for the bar */
#define TCOLS 40

static void sgr(unsigned char n) { /* emit ESC [ n m */
    putc(27);
    putc('[');
    putu(n);
    putc('m');
}

/* show the bar, block until a key arrives; 0 = the user asked to quit */
static unsigned char waitkey(void) {
    unsigned char c;
    sgr(44);
    sgr(37); /* white on blue */
    puts("--More--");
    sgr(0);
    for (;;) {
        c = pollin();          /* on-screen keyboard */
        if (!c) c = pollcon(); /* link-injected console bytes */
        if (c) break;
        yield(); /* cooperative: let other procs run */
    }
    puts("\r        \r"); /* wipe the bar, stay on the same row */
    return (c == 'q' || c == 'Q') ? 0 : 1;
}

void main(void) {
    char *argv[4];
    unsigned char argc = argv_parse(argv, 4);
    unsigned char fd = NOFD, rows = 0, col = 0;
    int ch;

    if (argc > 0 && argv[0][0] != '-') {
        fd = open(argv[0], O_READ);
        if (fd == EISDIR) {
            puts("more: is a directory");
            nl();
            sexit(2);
        }
        if (fd == NOFD) {
            puts("more: no such file");
            nl();
            sexit(2);
        }
    }

    for (;;) {
        if (fd == NOFD) {
            char c = readc();
            ch = (c == EOF) ? -1 : c;
        } else ch = fgetc(fd);
        if (ch < 0) break;
        putc((char)ch);

        /* count screen rows, not input lines: a 100-char line wraps to three */
        if (ch == '\n') {
            rows++;
            col = 0;
        } else if (ch != '\r' && ++col == TCOLS) {
            rows++;
            col = 0;
        }

        if (rows >= PAGE) {
            if (!waitkey()) break;
            rows = 0;
        }
    }
    if (fd != NOFD) close(fd);
}