#!/usr/bin/env perl
# Playing with mbsync, I ended up duplicating a few hundred messages when tweaking config
# This is the fix :)
use utf8;
use warnings;
use strict;
use Mail::Box::Manager;
use List::Util qw/sum0/;

my $mgr = Mail::Box::Manager->new(access => 'rw');
my $folder = $mgr->open('/path/to/maildir');
dedup_rec($folder, 0);

sub dedup_rec {
    my ($folder, $level) = @_;
    my %messages;
    my @messages = $folder->messages;

    for my $subfolder ($folder->listSubFolders) {
        dedup_rec($folder->openSubFolder($subfolder, access => 'rw'), $level+1);
    }

    info($level => "Going to process folder @{[ $folder->name ]}");

    if (scalar @messages <= 1) {
        return;
    }

    for my $msg (@messages) {
        my $subj = $msg->subject;
        my $from = join ', ', map { $_->format } $msg->from;
        my $date = $msg->get('Date');

        if ($messages{$subj . $from . $date}++) {
            $msg->delete;
        }
    }

    my $sum = sum0 map { $_ - 1 } values %messages;
    info($level => "Deduped $sum messages in @{[ $folder->name ]}";
}

sub info {
    my ($level, $msg) = @_;
    print "\t" x $level;
    print "$msg\n";
}