/* ss-hw/pressure.c
 *
 * Pressure sensor functions.
 *
 * Copyright (C) 2003, 2004
 * Andy Goth     <unununium@openverse.com>
 *
 * This code is available under the GNU General Public License; see COPYING. */

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>

#include "evlist/evlist.h"
#include "prjlibs/vec.h"
#include "ss-hw/pressure.h"

#define BUF VEC_ELTS(byte_t, &dev->buf_in)

#define PACKET_LEN 13
#define PACKET_DELIM "\r\n>"

typedef struct pressure {
    device_t* user;
    int state;
    int doors;
} pressure_t;

static int pressure_cleanup (device_t* dev);
static int pressure_open    (device_t* dev);
static int pressure_incoming(device_t* dev);

int pressure_init(device_t* dev, device_t* user)
{
    pressure_t* state = malloc(sizeof(pressure_t));
    if (state == NULL) return -1;
    state->user = user;

    dev->sw_state    = state            ;
    dev->buf_size    = PACKET_LEN       ;
    dev->sw_cleanup  = pressure_cleanup ;
    dev->sw_open     = pressure_open    ;
    dev->sw_incoming = pressure_incoming;

    return 0;
}

static int pressure_cleanup(device_t* dev)
{
    free(dev->sw_state);

    dev->buf_size    = 0   ;
    dev->sw_state    = NULL;
    dev->sw_cleanup  = NULL;
    dev->sw_open     = NULL;
    dev->sw_incoming = NULL;

    return 0;
}

static int pressure_open(device_t* dev)
{
    ((pressure_t*)dev->sw_state)->state = 0;
    ((pressure_t*)dev->sw_state)->doors = 4;
    return 0;
}

static int pressure_incoming(device_t* dev)
{
    /*           BUF[ 0 1 2 3456 789a b c ]
     * Packet format: \r\n> aaaa aaaa d d
     *                `-.-' ||||        |
     *                  |   ||||        `- door sensors
     *                  |   |||`---------- pressure sensor 4
     *                  |   ||`----------- pressure sensor 3
     *                  |   |`------------ pressure sensor 2
     *                  |   `------------- pressure sensor 1
     *                  `----------------- framing marker (3 bytes)
     * *state:
     *   0 - out of sync     2 - found \n
     *   1 - found \r        3 - in sync
     * *doors:
     *   0 - no doors open   2 - right door open  4 - uninitialized
     *   1 - left door open  3 - both doors open */

    int i;
    int cursor = 0;
    pressure_t* pressure = dev->sw_state;
    int* state = &pressure->state;

    if (VEC_LEN(byte_t, &dev->buf_in) != PACKET_LEN) {
        /* Not a full buffer... try again later. */
        return 0;
    }

    if (*state == 3) {
        if (strncmp(BUF, PACKET_DELIM, 3) != 0) {
            /* Lost sync... :^( */
            *state = 0;
        } else {
            /* Still have sync. */
            goto have_sync;
        }
    }

    /* Attempt to resync. */
    for (i = 0; i < PACKET_LEN; ++i) {
        if (BUF[i] == PACKET_DELIM[*state]) {
            /* Possible sync. */
            ++*state;
            if (*state == 3) {
                /* Sync success.  Realign data. */
                i -= 2;
                if (i > 0) {
                    /* Discard junk data at start of buffer. */
                    VEC_SHIFTN(byte_t, &dev->buf_in, i);
                    return 0;
                } else if (i < 0) {
                    /* Place delimiter at start of buffer. */
                    VEC_POPN(byte_t, &dev->buf_in, -i);
                    VEC_UNSHIFTN(byte_t, &dev->buf_in, PACKET_DELIM, -i);
                    cursor = -i;
                }
                goto have_sync;
            }
        } else {
            /* Sync failure.  Maybe next byte? */
            *state = 0;
        }
    }

    /* Sync failure.  Discard buffer.  Try again next packet. */
    VEC_TRUNC(byte_t, &dev->buf_in, 0);
    return 0;

have_sync:

    /* Good data. */
    user_send_pressure(pressure->user, BUF[3], BUF[4], BUF[5], BUF[6]);

    if (pressure->doors != (BUF[12] & 3)) {
        /* Door change. */
        pressure->doors = BUF[12] & 3;
        user_send_doors(pressure->user, (BUF[12] & 2) ? 1 : 0,
                                        (BUF[12] & 1) ? 1 : 0);
    }

    VEC_TRUNC(byte_t, &dev->buf_in, cursor);

    return 0;
}

/* vim: set ts=4 sts=4 sw=4 tw=80 et: */