/* $NetBSD: dtmf.c,v 1.5 2026/04/03 08:37:46 mlelstv Exp $ */

/*
 * Copyright (c) 2010 Jared D. McNeill <jmcneill@invisible.ca>
 * Copyright (c) 2026 Michael van ELst <mlelstv@netbsd.org>
 * All rights reserved.
 *
 * 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
 */

#include <sys/endian.h>

#include <err.h>
#include <fcntl.h>
#include <math.h>
#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>

#include "dtmf.h"

/* dialtone frequency pair */
struct dialtone {
        float a;
        float b;
};

#define PI2     (3.14159265358979323846f * 2)

static void
dtmf_create(int16_t *buf, unsigned int sample_rate,
    unsigned short sample_length, unsigned short channels,
    unsigned int chanmask, float freq1, float freq2,
    unsigned attack, unsigned decay)
{
        int c;
        unsigned i;
        size_t sample_count = sample_rate * sample_length / 1000;
        float gain;
        int16_t v;

        for (i = 0; i < sample_count; i++) {
                if (i < attack)
                        gain = 1.0 * i / attack;
                else if (sample_count - i < decay)
                        gain = 1.0 * (sample_count - i) / decay;
                else
                        gain = 1.0;
                for (c = 0; c < channels; c++) {
                        if ((chanmask & (1 << c)) == 0)
                                continue;
                        v = (
                                sin(i * PI2 * (freq1 / sample_rate)) +
                                sin(i * PI2 * (freq2 / sample_rate))
                            ) * gain * 16383;
                        buf[c] = htole16(v);
                }
                buf += channels;
        }
}

static void
dtmf_new(int16_t **buf, size_t *buflen, unsigned int sample_rate,
    unsigned short sample_length, unsigned short channels,
    unsigned int chanmask, struct dialtone dt)
{
        size_t oldlen, more;

        oldlen = *buflen;
        more = sample_rate * sample_length / 1000 * sizeof(**buf) * channels;

        *buflen = oldlen + more;
        *buf = realloc(*buf, *buflen);
        if (*buf == NULL) {
                warn("realloc");
                return;
        }
        memset((*buf) + oldlen/sizeof(**buf), 0, more);

        if (dt.a > 0 || dt.b > 0)
                dtmf_create((*buf) + oldlen/sizeof(**buf),
                    sample_rate, sample_length, channels, chanmask,
                    dt.a, dt.b, 500, 800);
}

static struct dialtone tones[] = {
        { 697, 1209 }, /* 1 */
        { 697, 1336 }, /* 2 */
        { 697, 1477 }, /* 3 */
        { 697, 1633 }, /* 4 */
        { 770, 1209 }, /* 5 */
        { 770, 1336 }, /* 6 */
        { 770, 1477 }, /* 7 */
        { 770, 1633 }, /* 8 */
        { 852, 1209 }, /* 9 */
        { 852, 1336 }, /* . */
        { 852, 1477 }, /* 0 */
        { 852, 1633 }, /* # */
        { 941, 1209 }, /* A */
        { 941, 1336 }, /* B */
        { 941, 1477 }, /* C */
        { 941, 1633 }  /* D */
};
#define TONES "123456789.0#ABCD"

static struct dialtone dialtone = { 350.0, 440.0 };
static struct dialtone reordertone = { 480.0, 620.0 };
static struct dialtone ringingtone = { 440.0, 480.0 };
static struct dialtone silence = { 0.0, 0.0 };
        
int
dtmf_dial(const char *number, unsigned int sample_rate,
        unsigned int channels, unsigned int chanmask,
        int16_t **bufp, size_t *buflenp)
{
        size_t buflen;
        int i;
        char ch, *p;

        *bufp = NULL;
        buflen = 0;

        /* dial tone */
        dtmf_new(bufp, &buflen, sample_rate, 2000,
            channels, chanmask, dialtone);
        dtmf_new(bufp, &buflen, sample_rate, 65,
            channels, chanmask, silence);

        if (*number == '\0')
                goto no_number;

        /* number */
        while ((ch = *number++) != '\0') {
                p = strchr(TONES, ch);
                if (p == NULL) {
                        dtmf_new(bufp, &buflen, sample_rate, 130,
                            channels, chanmask, silence);
                } else {
                        i = p - TONES;
                        dtmf_new(bufp, &buflen, sample_rate, 65,
                            channels, chanmask, tones[i]);
                        dtmf_new(bufp, &buflen, sample_rate, 65,
                            channels, chanmask, silence);
                }
        }

        /* pause */
        dtmf_new(bufp, &buflen, sample_rate, 325,
            channels, chanmask, silence);

        if (chanmask & 0x55555555) {
                /* even channel */

                /* reorder tone */
                for (i=0; i<12; ++i) {
                        dtmf_new(bufp, &buflen, sample_rate, 250,
                            channels, chanmask, reordertone);
                        dtmf_new(bufp, &buflen, sample_rate, 250,
                            channels, chanmask, silence);
                }

                /* pause */
                dtmf_new(bufp, &buflen, sample_rate, 2000,
                    channels, chanmask, silence);
        } else {
                /* odd channel */

                /* ringing tone */
                dtmf_new(bufp, &buflen, sample_rate, 2000,
                    channels, chanmask, ringingtone);
                dtmf_new(bufp, &buflen, sample_rate, 4000,
                    channels, chanmask, silence);
                dtmf_new(bufp, &buflen, sample_rate, 2000,
                    channels, chanmask, ringingtone);

                /* pause */
                dtmf_new(bufp, &buflen, sample_rate, 250,
                    channels, chanmask, silence);
        }

no_number:
        *buflenp = buflen;
        return *bufp == NULL;
}