#!/usr/local/bin/perl

=head1 NAME

B<msgiddb> - update database mapping Message-ID to message file names

=head1 SYNOPSIS

B<msgiddb> I<dbfile> I<message-files>

=head1 DESCRIPTION

For each I<message-file>, read its Message-ID and use as key in I<dbfile>.
Check for its presence in the JSON-serialized list stored as the value;
if absent, append and update the db.

For messages with multiple Message-ID fields, concatenate all the values and use
that as the key.

I<message-file> names are used exactly; no path components are stripped.

=cut

use strict;
use warnings;
use v5.14;

use DB_File;
use JSON::PP;
use List::Util 'first';

use FindBin;
use lib $FindBin::Bin;

require 'minc';

sub push_dblist {
    my $db            = shift;
    my $key           = shift;
    my $value         = shift;
    my $current_value = $db->{$key};
    my $values;
    if ($current_value) {
        $values = decode_json($current_value);
        if ( first { defined($_) } @$values ) {
            return;
        }
    }
    else {
        my @tmp;
        $values = \@tmp;
    }
    push( @$values, $value );
    $db->{$key} = encode_json($values);
}

if ( !caller() ) {
    my $dbfn = shift;
    tie( my %db, 'DB_File', $dbfn ) or die("tie(DB_File, $dbfn): $!");

    my $errors = 0;
    for my $fn (@ARGV) {
        my $msgids = get_headers($fn)->{'message-id'};
        if ( !( defined($msgids) && @$msgids ) ) {
            say STDERR "$fn has no message-id";
            $errors++;
            next;
        }
        my $msgid = join( '', @$msgids );
        push_dblist( \%db, $msgid, $fn );
    }
    exit($errors);
}