/*
 * Copyright (c) 2006-2023, RT-Thread Development Team
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Change Logs:
 * Date           Author       Notes
 * 2023-11-13     Shell        init ver.
 */

#include "../bsd_porting.h"
#include "../terminal.h"

/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2008 Ed Schouten <ed@FreeBSD.org>
 * All rights reserved.
 *
 * Portions of this software were developed under sponsorship from Snow
 * B.V., the Netherlands.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * TTY input queue buffering.
 *
 * Unlike the output queue, the input queue has more features that are
 * needed to properly implement various features offered by the TTY
 * interface:
 *
 * - Data can be removed from the tail of the queue, which is used to
 *   implement backspace.
 * - Once in a while, input has to be `canonicalized'. When ICANON is
 *   turned on, this will be done after a CR has been inserted.
 *   Otherwise, it should be done after any character has been inserted.
 * - The input queue can store one bit per byte, called the quoting bit.
 *   This bit is used by TTYDISC to make backspace work on quoted
 *   characters.
 *
 * In most cases, there is probably less input than output, so unlike
 * the outq, we'll stick to 128 byte blocks here.
 */

static int ttyinq_flush_secure = 1;

#define TTYINQ_QUOTESIZE (TTYINQ_DATASIZE / BMSIZE)
#define BMSIZE           32
#define GETBIT(tib, boff) \
    ((tib)->tib_quotes[(boff) / BMSIZE] & (1 << ((boff) % BMSIZE)))
#define SETBIT(tib, boff) \
    ((tib)->tib_quotes[(boff) / BMSIZE] |= (1 << ((boff) % BMSIZE)))
#define CLRBIT(tib, boff) \
    ((tib)->tib_quotes[(boff) / BMSIZE] &= ~(1 << ((boff) % BMSIZE)))

struct ttyinq_block
{
    struct ttyinq_block *tib_prev;
    struct ttyinq_block *tib_next;
    uint32_t tib_quotes[TTYINQ_QUOTESIZE];
    char tib_data[TTYINQ_DATASIZE];
};

static uma_zone_t ttyinq_zone;

#define TTYINQ_INSERT_TAIL(ti, tib)                     \
    do                                                  \
    {                                                   \
        if (ti->ti_end == 0)                            \
        {                                               \
            tib->tib_prev = NULL;                       \
            tib->tib_next = ti->ti_firstblock;          \
            ti->ti_firstblock = tib;                    \
        }                                               \
        else                                            \
        {                                               \
            tib->tib_prev = ti->ti_lastblock;           \
            tib->tib_next = ti->ti_lastblock->tib_next; \
            ti->ti_lastblock->tib_next = tib;           \
        }                                               \
        if (tib->tib_next != NULL)                      \
            tib->tib_next->tib_prev = tib;              \
        ti->ti_nblocks++;                               \
    } while (0)

#define TTYINQ_REMOVE_HEAD(ti)                           \
    do                                                   \
    {                                                    \
        ti->ti_firstblock = ti->ti_firstblock->tib_next; \
        if (ti->ti_firstblock != NULL)                   \
            ti->ti_firstblock->tib_prev = NULL;          \
        ti->ti_nblocks--;                                \
    } while (0)

#define TTYINQ_RECYCLE(ti, tib)             \
    do                                      \
    {                                       \
        if (ti->ti_quota <= ti->ti_nblocks) \
            uma_zfree(ttyinq_zone, tib);    \
        else                                \
            TTYINQ_INSERT_TAIL(ti, tib);    \
    } while (0)

int ttyinq_setsize(struct ttyinq *ti, struct lwp_tty *tp, size_t size)
{
    struct ttyinq_block *tib;

    ti->ti_quota = howmany(size, TTYINQ_DATASIZE);

    while (ti->ti_quota > ti->ti_nblocks)
    {
        /*
         * List is getting bigger.
         * Add new blocks to the tail of the list.
         *
         * We must unlock the TTY temporarily, because we need
         * to allocate memory. This won't be a problem, because
         * in the worst case, another thread ends up here, which
         * may cause us to allocate too many blocks, but this
         * will be caught by the loop below.
         */
        tty_unlock(tp);
        tib = uma_zalloc(ttyinq_zone, M_WAITOK);
        tty_lock(tp);

        if (tty_gone(tp))
        {
            uma_zfree(ttyinq_zone, tib);
            return -ENXIO;
        }

        TTYINQ_INSERT_TAIL(ti, tib);
    }
    return 0;
}

void ttyinq_free(struct ttyinq *ti)
{
    struct ttyinq_block *tib;

    ttyinq_flush(ti);
    ti->ti_quota = 0;

    while ((tib = ti->ti_firstblock) != NULL)
    {
        TTYINQ_REMOVE_HEAD(ti);
        uma_zfree(ttyinq_zone, tib);
    }

    MPASS(ti->ti_nblocks == 0);
}

int ttyinq_read_uio(struct ttyinq *ti, struct lwp_tty *tp, struct uio *uio,
                    size_t rlen, size_t flen)
{
    MPASS(rlen <= uio->uio_resid);

    while (rlen > 0)
    {
        int error;
        struct ttyinq_block *tib;
        size_t cbegin, cend, clen;

        /* See if there still is data. */
        if (ti->ti_begin == ti->ti_linestart)
            return 0;
        tib = ti->ti_firstblock;
        if (tib == NULL)
            return 0;

        /*
         * The end address should be the lowest of these three:
         * - The write pointer
         * - The blocksize - we can't read beyond the block
         * - The end address if we could perform the full read
         */
        cbegin = ti->ti_begin;
        cend = MIN(MIN(ti->ti_linestart, ti->ti_begin + rlen), TTYINQ_DATASIZE);
        clen = cend - cbegin;
        MPASS(clen >= flen);
        rlen -= clen;

        /*
         * We can prevent buffering in some cases:
         * - We need to read the block until the end.
         * - We don't need to read the block until the end, but
         *   there is no data beyond it, which allows us to move
         *   the write pointer to a new block.
         */
        if (cend == TTYINQ_DATASIZE || cend == ti->ti_end)
        {
            /*
             * Fast path: zero copy. Remove the first block,
             * so we can unlock the TTY temporarily.
             */
            TTYINQ_REMOVE_HEAD(ti);
            ti->ti_begin = 0;

            /*
             * Because we remove the first block, we must
             * fix up the block offsets.
             */
#define CORRECT_BLOCK(t)          \
    do                            \
    {                             \
        if (t <= TTYINQ_DATASIZE) \
            t = 0;                \
        else                      \
            t -= TTYINQ_DATASIZE; \
    } while (0)
            CORRECT_BLOCK(ti->ti_linestart);
            CORRECT_BLOCK(ti->ti_reprint);
            CORRECT_BLOCK(ti->ti_end);
#undef CORRECT_BLOCK

            /*
             * Temporary unlock and copy the data to
             * userspace. We may need to flush trailing
             * bytes, like EOF characters.
             */
            tty_unlock(tp);
            error = uiomove(tib->tib_data + cbegin, clen - flen, uio);
            tty_lock(tp);

            /* Block can now be readded to the list. */
            TTYINQ_RECYCLE(ti, tib);
        }
        else
        {
            char ob[TTYINQ_DATASIZE - 1];

            /*
             * Slow path: store data in a temporary buffer.
             */
            memcpy(ob, tib->tib_data + cbegin, clen - flen);
            ti->ti_begin += clen;
            MPASS(ti->ti_begin < TTYINQ_DATASIZE);

            /* Temporary unlock and copy the data to userspace. */
            tty_unlock(tp);
            error = uiomove(ob, clen - flen, uio);
            tty_lock(tp);
        }

        if (error != 0)
            return error;
        if (tty_gone(tp))
            return -ENXIO;
    }

    return 0;
}

rt_inline void ttyinq_set_quotes(struct ttyinq_block *tib, size_t offset,
                                 size_t length, int value)
{
    if (value)
    {
        /* Set the bits. */
        for (; length > 0; length--, offset++) SETBIT(tib, offset);
    }
    else
    {
        /* Unset the bits. */
        for (; length > 0; length--, offset++) CLRBIT(tib, offset);
    }
}

size_t ttyinq_write(struct ttyinq *ti, const void *buf, size_t nbytes,
                    int quote)
{
    const char *cbuf = buf;
    struct ttyinq_block *tib;
    unsigned int boff;
    size_t l;

    while (nbytes > 0)
    {
        boff = ti->ti_end % TTYINQ_DATASIZE;

        if (ti->ti_end == 0)
        {
            /* First time we're being used or drained. */
            MPASS(ti->ti_begin == 0);
            tib = ti->ti_firstblock;
            if (tib == NULL)
            {
                /* Queue has no blocks. */
                break;
            }
            ti->ti_lastblock = tib;
        }
        else if (boff == 0)
        {
            /* We reached the end of this block on last write. */
            tib = ti->ti_lastblock->tib_next;
            if (tib == NULL)
            {
                /* We've reached the watermark. */
                break;
            }
            ti->ti_lastblock = tib;
        }
        else
        {
            tib = ti->ti_lastblock;
        }

        /* Don't copy more than was requested. */
        l = MIN(nbytes, TTYINQ_DATASIZE - boff);
        MPASS(l > 0);
        memcpy(tib->tib_data + boff, cbuf, l);

        /* Set the quoting bits for the proper region. */
        ttyinq_set_quotes(tib, boff, l, quote);

        cbuf += l;
        nbytes -= l;
        ti->ti_end += l;
    }

    return (cbuf - (const char *)buf);
}

int ttyinq_write_nofrag(struct ttyinq *ti, const void *buf, size_t nbytes,
                        int quote)
{
    size_t ret __unused;

    if (ttyinq_bytesleft(ti) < nbytes)
        return -1;

    /* We should always be able to write it back. */
    ret = ttyinq_write(ti, buf, nbytes, quote);
    MPASS(ret == nbytes);

    return 0;
}

void ttyinq_canonicalize(struct ttyinq *ti)
{
    ti->ti_linestart = ti->ti_reprint = ti->ti_end;
    ti->ti_startblock = ti->ti_reprintblock = ti->ti_lastblock;
}

size_t ttyinq_findchar(struct ttyinq *ti, const char *breakc, size_t maxlen,
                       char *lastc)
{
    struct ttyinq_block *tib = ti->ti_firstblock;
    unsigned int boff = ti->ti_begin;
    unsigned int bend =
        MIN(MIN(TTYINQ_DATASIZE, ti->ti_linestart), ti->ti_begin + maxlen);

    MPASS(maxlen > 0);

    if (tib == NULL)
        return 0;

    while (boff < bend)
    {
        if (strchr(breakc, tib->tib_data[boff]) && !GETBIT(tib, boff))
        {
            *lastc = tib->tib_data[boff];
            return (boff - ti->ti_begin + 1);
        }
        boff++;
    }

    /* Not found - just process the entire block. */
    return (bend - ti->ti_begin);
}

void ttyinq_flush(struct ttyinq *ti)
{
    struct ttyinq_block *tib;

    ti->ti_begin = 0;
    ti->ti_linestart = 0;
    ti->ti_reprint = 0;
    ti->ti_end = 0;

    /* Zero all data in the input queue to get rid of passwords. */
    if (ttyinq_flush_secure)
    {
        for (tib = ti->ti_firstblock; tib != NULL; tib = tib->tib_next)
            memset(&tib->tib_data, 0, sizeof tib->tib_data);
    }
}

int ttyinq_peekchar(struct ttyinq *ti, char *c, int *quote)
{
    unsigned int boff;
    struct ttyinq_block *tib = ti->ti_lastblock;

    if (ti->ti_linestart == ti->ti_end)
        return -1;

    MPASS(ti->ti_end > 0);
    boff = (ti->ti_end - 1) % TTYINQ_DATASIZE;

    *c = tib->tib_data[boff];
    *quote = GETBIT(tib, boff);

    return 0;
}

void ttyinq_unputchar(struct ttyinq *ti)
{
    MPASS(ti->ti_linestart < ti->ti_end);

    if (--ti->ti_end % TTYINQ_DATASIZE == 0)
    {
        /* Roll back to the previous block. */
        ti->ti_lastblock = ti->ti_lastblock->tib_prev;
        /*
         * This can only fail if we are unputchar()'ing the
         * first character in the queue.
         */
        MPASS((ti->ti_lastblock == NULL) == (ti->ti_end == 0));
    }
}

void ttyinq_reprintpos_set(struct ttyinq *ti)
{
    ti->ti_reprint = ti->ti_end;
    ti->ti_reprintblock = ti->ti_lastblock;
}

void ttyinq_reprintpos_reset(struct ttyinq *ti)
{
    ti->ti_reprint = ti->ti_linestart;
    ti->ti_reprintblock = ti->ti_startblock;
}

static void ttyinq_line_iterate(struct ttyinq *ti,
                                ttyinq_line_iterator_t *iterator, void *data,
                                unsigned int offset, struct ttyinq_block *tib)
{
    unsigned int boff;

    /* Use the proper block when we're at the queue head. */
    if (offset == 0)
        tib = ti->ti_firstblock;

    /* Iterate all characters and call the iterator function. */
    for (; offset < ti->ti_end; offset++)
    {
        boff = offset % TTYINQ_DATASIZE;
        MPASS(tib != NULL);

        /* Call back the iterator function. */
        iterator(data, tib->tib_data[boff], GETBIT(tib, boff));

        /* Last byte iterated - go to the next block. */
        if (boff == TTYINQ_DATASIZE - 1)
            tib = tib->tib_next;
    }
}

void ttyinq_line_iterate_from_linestart(struct ttyinq *ti,
                                        ttyinq_line_iterator_t *iterator,
                                        void *data)
{
    ttyinq_line_iterate(ti, iterator, data, ti->ti_linestart,
                        ti->ti_startblock);
}

void ttyinq_line_iterate_from_reprintpos(struct ttyinq *ti,
                                         ttyinq_line_iterator_t *iterator,
                                         void *data)
{
    ttyinq_line_iterate(ti, iterator, data, ti->ti_reprint,
                        ti->ti_reprintblock);
}

static int ttyinq_startup(void)
{
    ttyinq_zone = uma_zcreate("ttyinq", sizeof(struct ttyinq_block), NULL, NULL,
                              NULL, NULL, UMA_ALIGN_PTR, 0);
    return 0;
}
INIT_PREV_EXPORT(ttyinq_startup);

#if 0

SYSINIT(ttyinq, SI_SUB_DRIVERS, SI_ORDER_FIRST, ttyinq_startup, NULL);
#endif