//----------------------------------------------------------------------------//
//                           GNU GPL OS/K                                     //
//                                                                            //
//  Desc:       Buffer library                                                //
//                                                                            //
//                                                                            //
//  Copyright © 2018-2019 The OS/K Team                                       //
//                                                                            //
//  This file is part of OS/K.                                                //
//                                                                            //
//  OS/K is free software: you can redistribute it and/or modify              //
//  it under the terms of the GNU General Public License as published by      //
//  the Free Software Foundation, either version 3 of the License, or         //
//  any later version.                                                        //
//                                                                            //
//  OS/K is distributed in the hope that it will be useful,                   //
//  but WITHOUT ANY WARRANTY//without even the implied warranty of            //
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the             //
//  GNU General Public License for more details.                              //
//                                                                            //
//  You should have received a copy of the GNU General Public License         //
//  along with OS/K.  If not, see <https://www.gnu.org/licenses/>.            //
//----------------------------------------------------------------------------//

#include <kernel/buf.h>

error_t bputc(Buffer_t *buf, uchar ch);

//
// Writes a character on a buffer
//
error_t BPutOnBuf(Buffer_t *buf, uchar ch)
{
    error_t rc;
    assert(buf && buf->initDone == INITOK);

    if (!buf) return EINVAL;
    if (buf->state != BS_RDWR && buf->state != BS_WRONLY) {
        return EBADF;
    }

    ExAcquireLock(&buf->lock);
    rc = bputc(buf, ch);
    ExReleaseLock(&buf->lock);
    return rc;
}

//
// Internal, unlocked version of BPutOnBuf
//
error_t bputc(Buffer_t *buf, uchar ch)
{
    error_t rc = EOK;
    size_t bufSize, pbCount;

    // Implements playback / scrolling up when line buffering
    // Note that '\n', '\r' and '\t' can never occur in the buffer
    // That should change; there should be a flag for it
    if (buf->flags & BF_LINE) {

        // Deal with carriage returns
        if (ch == '\r') {
            buf->wp -= buf->lastLF;
            buf->lastLF = 0;
            assert(buf->wp >= buf->buf);
        }

        // Deal with tabs... we need a tabSize field
        // We assume tabs are 4 characters long for now
        else if (ch == '\t') {
            rc = bputc(buf, ' ');

            while (buf->lastLF % 4 > 0) {
                rc = bputc(buf, ' ');
            }
            if (rc > 0) return rc;
        }

        // Deal with line feeds by filling the rest of the line with spaces
        // We need a field for choosing a different filler, e.g. '\0'
        else if (ch == '\n') {
            assert(buf->lastLF < buf->lineLen);
            while (buf->lastLF > 0) {
                rc = bputc(buf, ' ');
            }
            if (rc > 0) return rc;
            if (buf->flusher) buf->flusher(buf); 
        }

        // Just a regular character
        else {
            // Do we have to scroll up?
            if (buf->wp == buf->buf + buf->size) {
                // Yes, so we give up a whole playback buffer worth
                // of lines so we don't have to do this too often
                // (basically we make the current buffer a pb one)
                bufSize = buf->nLines * buf->lineLen;
                pbCount = (buf->size / bufSize) - 1;

                // Paranoia check
                assert(buf->size >= (size_t)(buf->nLines * buf->lineLen));

                // If we only have one playback buffer we just give up a line
                if (pbCount == 0) {
                    // Use of memcpy() is safe because the source occur
                    // after the destination
                    memcpy(buf->buf, buf->buf + buf->lineLen,
                                     buf->size - buf->lineLen);
                    buf->wp -= buf->lineLen;
                }

                // We do have a playback buffer worth of lines to give up
                else {
                    memcpy(buf->buf, buf->buf + bufSize,
                                     buf->size - bufSize);
                    buf->wp -= buf->lineLen;
                }
            }

            // Write it
            *buf->wp++ = ch;

            // Did we reach the end of line?
            if (++buf->lastLF == buf->lineLen) {
                buf->lastLF = 0;
            }
        }

        return EOK;
    }

    // No scrolling up when not line-buffering
    else {
        if (buf->wp == buf->buf + buf->size) {
            buf->state = BS_EOF;
        }

        return ENOSYS;
    }
}