use v6.d;
use MaildirIndexer::Index;
unit class MaildirIndexer::Index::ByAddresses does MaildirIndexer::Index;
use MaildirIndexer::LogTimelineSchema;
use MaildirIndexer::Email;

# most of this is copied from
# p6-Algorithm-NaiveBayes:auth<cpan:TITSUKI>:ver<0.04>, in particular the
# Algorithm::NaiveBayes::Classifier::Bernoulli class

has Array[Str] %!addresses-for-file;
# I'd like to type-constrain these BagHash-es, but the compiler
# currently dies if I try
has BagHash $!count-by-address-and-mailbox .= new;
has BagHash $!known-addresses .= new;
has BagHash $!count-by-mailbox .= new;
has $!total-count;

method dump() {
}

submethod account-for(Str @addresses,Str $mailbox,Int $step) {
    $!total-count += $step;
    $!count-by-mailbox{$mailbox} += $step;

    for @addresses -> Str $addr {
        $!known-addresses{$addr} += $step;
        $!count-by-address-and-mailbox{$addr => $mailbox} += $step;
    }
}

method add-mail(MaildirIndexer::Email:D $email, Str:D $mailbox --> Nil) {
    MaildirIndexer::LogTimelineSchema::Index::Add.log: :class('ByAddresses'),:$mailbox, -> {
        my Str @addresses = $email.addresses or return;
        %!addresses-for-file{ $email.path } = @addresses;

        self.account-for(@addresses,$mailbox,1);

        return;
    }
}

method del-path(IO:D $file, Str:D $mailbox --> Nil) {
    MaildirIndexer::LogTimelineSchema::Index::Rm.log: :class('ByAddresses'),:$mailbox, -> {
        my Str @addresses = %!addresses-for-file{$file.path} or return;

        self.account-for(@addresses,$mailbox,-1);

        return;
    }
}

submethod p-address-given-mailbox(Str $addr, Str $mailbox) {
    my $a = 1e-15 + $!count-by-address-and-mailbox{$addr => $mailbox};
    my $b = 1 + $!count-by-mailbox{$mailbox};
    return $a / $b;
}

submethod predict-mailbox-given-addresses(@addresses) {
    my %prediction;
    my Bag $addr-bag .= new(|@addresses);

    for $!count-by-mailbox.keys -> Str $mailbox {
        my $p = $!count-by-mailbox{$mailbox} / $!total-count;

        for $!known-addresses.keys -> Str $addr {
            my $addr-p = self.p-address-given-mailbox($addr,$mailbox);
            if ($addr-bag{$addr}) {
                $p *= $addr-p;
            }
            else {
                $p *= 1 - $addr-p;
            }
        }

        %prediction{$mailbox} = $p;
    }

    return %prediction;
}

method mailbox-for-email(MaildirIndexer::Email:D $email --> Str) {
    my Str $result;
    MaildirIndexer::LogTimelineSchema::Index::Find.log: :class('ByAddresses'), -> {
        my %prediction = self.predict-mailbox-given-addresses($email.addresses);

        my @most-probable-mailboxes = %prediction.pairs.sort(*.value);

        if @most-probable-mailboxes -> $_ { $result = .[*-1].key }
    }
    return $result;
}