#!/usr/bin/perl

# dependencies:
#   sox ("play" command)
#   festival (text to speech)

use strict;
use POSIX;
use Time::HiRes;

our $ogg_file = "/usr/share/apps/accelerando/sounds/metronome_click.ogg";
our $click_length = .0507; # seconds, the length of the ogg file
our $decompressed_sound_file = POSIX::tmpnam().'.wav';
         # ...temporary decompressed copy of the ogg file, for efficiency; 
         # cleaned up in the END block

my $cmd = "sox $ogg_file $decompressed_sound_file";
system($cmd)==0 or die "Error executing this command: $cmd";

# The following only really works if a child process isn't running. If it is, the child gets the signal,
# and we just have to test the return value.
$SIG{INT} = sub{ clean_up()};
$SIG{QUIT} = sub{ clean_up()};

my $player_delay = 0;
  # estimated time to play the wave file, in seconds; this will be updated later, based on real-time
  # data about how fast we're actually going; on a modern system, putting this at zero seems to
  # have no observable effect on the tempo

my $initial = ask("Initial tempo",60);
my $timesig = ask("Number of beats per bar",4);
my $bars = ask("Number of bars before increasing the tempo",999999);
my $add = ask("Amount to add to the tempo after the first time",0);
my $between = ask("Beats between changes of tempo",1);

if (1) {
  time_delay(7); # time for the musician to get ready, in seconds
  text_to_speech("ready")==0 or clean_up();
  time_delay(1);
  text_to_speech("go")==0 or clean_up();
  time_delay(1);
}

my $frac = 1+$add/$initial;
print "The tempo will be increased by a factor of $frac each time.\n";
for (my $tempo=$initial; $tempo<500; $tempo*=$frac) {
  print int($tempo)." beats per minute\n";
  text_to_speech(int($tempo))==0 or clean_up();
  my $dt = 60/$tempo;
  my ($t,$last_t);
  for (my $bar=1; $bar<=$bars; $bar++) {
    for (my $beat=1; $beat<=$timesig; $beat++) {
      click()==0 or clean_up();
      my $delay = $dt - $click_length - $player_delay; # seconds
      time_delay($delay); # because sleep() doesn't work for short times
      $t = clock();
      if (defined $last_t) {
        my $real_dt = $t-$last_t; # amount of time that actually elapsed
        #print "real_dt=$real_dt\n";
        my $correction = $real_dt-$dt; # positive if we fell behind
        if ($correction>.05) {$correction=.05} # don't let it go crazy if the cpu just got busy for a second
        $correction *= .5; # avoid undamped oscillations, etc.
        $player_delay += $correction;
        if ($player_delay<0) {$player_delay=0}
        #print "real_dt=$real_dt, player_delay=$player_delay, corr=$correction, player_delay=$player_delay\n";
      }
      $last_t = $t;
	  }
  }
  time_delay($dt*$between); # seconds
}

exit; # automatically does a clean_up(), in END{} block

#----------------------------------------------------------------------------------

sub time_delay {
  my $t = shift; # seconds
  #select undef,undef,undef,$t; # because sleep() doesn't work for short times
  Time::HiRes::usleep($t*1_000_000);
}

sub ask {
  my $prompt = shift;
  my $default = '';
  my $show_default = '';
  if (@_) {$default=shift; $show_default=" ($default)"}
  print "$prompt${show_default}?\n";
  my $answer = <STDIN>;
  chomp $answer;
  if ($answer eq '') {$answer=$default}
  return $answer;
}

sub click {
  my $cmd = "play --silent $decompressed_sound_file"; # --silent means not to print anything to stdout
  my $r= system($cmd);
  if ($r!=0) {print "Return code $r from $cmd\n"}
  return $r;
}


BEGIN {
  my $startup_time = seconds_since_epoch();
  sub clock {
    my $s = seconds_since_epoch();
    return sprintf "%d.%09d",($s-$startup_time),time_nanoseconds();
  }

  sub seconds_since_epoch {
    # return `date +%s`; # GNU only
    my ($s,$usec) = Time::HiRes::gettimeofday();
    return $s;
  }

  sub time_nanoseconds { # the nanoseconds part of the time since the epoch
    # return `date +%N`;
    my ($s,$usec) = Time::HiRes::gettimeofday();
    return $usec*1000;
  }
}

sub text_to_speech {
  my $text = shift;
  my $cmd = "echo '$text' |  festival --tts";
  my $r= system($cmd);
  if ($r!=0) {print "Return code $r from $cmd\n"}
  return $r;
}

sub clean_up {
  unlink $decompressed_sound_file;
  exit;
}

END {
  clean_up();
}

1;