#!/usr/bin/perl
#
# Wireless Signal Tone Generator
# Copyright (C) 2008  Timm Murray
# 
# This program 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 2 of the License, or
# (at your option) any later version.

# This program 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 this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
#

use strict;
use warnings;
use Audio::Data;
use Audio::Play;
use Time::HiRes 'usleep';

my $DEBUG        = 0;
$ENV{PATH}       = '/bin:/usr/bin';

# Highest and lowest frequencies played
my $LOW_FREQ     = 400;
my $HIGH_FREQ    = 2600;

# Highest and lowest signal power (usually expressed in negative dB)
my $LOW_SIGNAL   = -100;
my $HIGH_SIGNAL  = 0;

# Amplitude of the sine wave generated
my $AMP          = 0.1;

# Timing factors for the program sleeping and the sine wave length, respectively
my $SLEEP_DELAY  = 500_000;  # microseconds
my $AUDIO_DELAY  = 0.5;  # seconds (can be decimal number)

# The granularity of the scale
my $SCALE        = 100;

# Interface name to check
my $INTERFACE    = 'wlan0';

# Path to iwconfig program
my $IWCONFIG     = '/sbin/iwconfig';


my $audio_play = Audio::Play->new;
$SIG{INT} = sub {
    $audio_play->flush;
    exit 0;
};

my @freq_scale    = scale( $HIGH_FREQ, $LOW_FREQ, $SCALE );
my @signal_scale  = scale( $HIGH_SIGNAL, $LOW_SIGNAL, $SCALE );
my %scale = map { $signal_scale[$_] => $freq_scale[$_] } 0 .. $#signal_scale;


sub set_rate
{
    my ($audio_data, $audio_play) = @_;
    $audio_data->rate( 8000 );

    if( $audio_data->rate != $audio_play->rate ) {
        $audio_play->rate( $audio_data->rate );

        if( $audio_data->rate != $audio_play->rate ) {
            warn "Converting to " . $audio_play->rate . " Hz\n";
            $audio_data->rate( $audio_play->rate );
        }
    }

    return 1;
}

sub scale
{
    my ($high, $low, $scale) = @_;

    my $range = $high - $low;
    my $percent = $range / $scale;

    my @scale = map $low + $percent * $_, 0 .. $scale;
    return @scale;
}

sub get_signal
{
    my $got = `$IWCONFIG $INTERFACE`;
    my ($signal) = $got =~ / Signal \s+ level [:=] \s* ([\d\-]+) /x;

    $signal = $HIGH_SIGNAL  if $signal > $HIGH_SIGNAL;
    $signal = $LOW_SIGNAL   if $signal < $LOW_SIGNAL;
    return $signal;
}

sub debug
{
    my ($in) = @_;
    print $in . "\n" if $DEBUG;
    return 1;
}

{
    my @signal = map -1 * $_, 0 .. 100;
    my $i = 0;

    sub get_test_signal
    {
        $i = 0 if $i > $#signal;
        return $signal[$i++];
    }
}


{
    while( 1 ) {
        #my $signal = get_test_signal;
        my $signal = get_signal;
        my $freq = $scale{$signal};
        debug( "Signal ${signal}dB, freq ${freq}" );

        my $audio_data = Audio::Data->new;
        set_rate( $audio_data, $audio_play );

        $audio_data->tone( $freq, $AUDIO_DELAY, $AMP );
        $audio_play->play( $audio_data );

        usleep $SLEEP_DELAY;
    }
}