/* transport_stdio.c — host transport over stdin/stdout (docs/flow.md §3).
 *
 * read() must never block, so stdin is put into non-blocking mode. This is
 * the whole of what the Pico USB CDC transport will have to provide too.
 */
#include "rubo/rubo.h"

#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>

static int stdio_open(rubo_transport_t *t)
{
    (void)t;
    int fl = fcntl(STDIN_FILENO, F_GETFL, 0);
    if (fl < 0) return -1;
    return fcntl(STDIN_FILENO, F_SETFL, fl | O_NONBLOCK);
}

static int stdio_read(rubo_transport_t *t, uint8_t *buf, size_t len)
{
    (void)t;
    ssize_t n = read(STDIN_FILENO, buf, len);
    if (n < 0) {
        if (errno == EAGAIN || errno == EWOULDBLOCK) return 0;
        return -1;
    }
    if (n == 0) return -1;                 /* EOF */
    return (int)n;
}

static int stdio_write(rubo_transport_t *t, const uint8_t *buf, size_t len)
{
    (void)t;
    size_t off = 0;
    while (off < len) {
        ssize_t n = write(STDOUT_FILENO, buf + off, len - off);
        if (n <= 0) return -1;
        off += (size_t)n;
    }
    return (int)len;
}

static bool stdio_connected(rubo_transport_t *t) { (void)t; return true; }

static void stdio_close(rubo_transport_t *t) { (void)t; }

rubo_transport_t *rubo_transport_stdio(void)
{
    static rubo_transport_t t = {
        .open      = stdio_open,
        .read      = stdio_read,
        .write     = stdio_write,
        .connected = stdio_connected,
        .close     = stdio_close,
        .mtu       = 256,
        .ctx       = NULL,
    };
    return &t;
}