lei: implement various deduplication strategies

For writing mboxes and Maildirs, users may wish to use
stricter or looser deduplication strategies.  This
gives them more control.

1 files changed, 96 insertions, 0 deletions

diff --git a/lib/PublicInbox/LeiDedupe.pm b/lib/PublicInbox/LeiDedupe.pm
new file mode 100644
index 00000000..c6eb7196
--- /dev/null
+++ b/lib/PublicInbox/LeiDedupe.pm
@@ -0,0 +1,96 @@
+# Copyright (C) 2020 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+package PublicInbox::LeiDedupe;
+use strict;
+use v5.10.1;
+use PublicInbox::SharedKV;
+use PublicInbox::ContentHash qw(content_hash);
+
+# n.b. mutt sets most of these headers not sure about Bytes
+our @OID_IGNORE = qw(Status X-Status Content-Length Lines Bytes);
+
+# best-effort regeneration of OID when augmenting existing results
+sub _regen_oid ($) {
+        my ($eml) = @_;
+        my @stash; # stash away headers we shouldn't have in git
+        for my $k (@OID_IGNORE) {
+                my @v = $eml->header_raw($k) or next;
+                push @stash, [ $k, \@v ];
+                $eml->header_set($k); # restore below
+        }
+        my $dig = Digest::SHA->new(1); # XXX SHA256 later
+        my $buf = $eml->as_string;
+        $dig->add('blob '.length($buf)."\0");
+        $dig->add($buf);
+        undef $buf;
+
+        for my $kv (@stash) { # restore stashed headers
+                my ($k, @v) = @$kv;
+                $eml->header_set($k, @v);
+        }
+        $dig->digest;
+}
+
+sub _oidbin ($) { defined($_[0]) ? pack('H*', $_[0]) : undef }
+
+# the paranoid option
+sub dedupe_oid () {
+        my $skv = PublicInbox::SharedKV->new;
+        ($skv, sub { # may be called in a child process
+                my ($eml, $oid) = @_;
+                $skv->set_maybe(_oidbin($oid) // _regen_oid($eml), '');
+        });
+}
+
+# dangerous if there's duplicate messages with different Message-IDs
+sub dedupe_mid () {
+        my $skv = PublicInbox::SharedKV->new;
+        ($skv, sub { # may be called in a child process
+                my ($eml, $oid) = @_;
+                # TODO: lei will support non-public messages w/o Message-ID
+                my $mid = $eml->header_raw('Message-ID') // _oidbin($oid) //
+                        content_hash($eml);
+                $skv->set_maybe($mid, '');
+        });
+}
+
+# our default deduplication strategy (used by v2, also)
+sub dedupe_content () {
+        my $skv = PublicInbox::SharedKV->new;
+        ($skv, sub { # may be called in a child process
+                my ($eml) = @_; # oid = $_[1], ignored
+                $skv->set_maybe(content_hash($eml), '');
+        });
+}
+
+# no deduplication at all
+sub dedupe_none () { (undef, sub { 1 }) }
+
+sub new {
+        my ($cls, $lei) = @_;
+        my $dd = $lei->{opt}->{dedupe} // 'content';
+        my $dd_new = $cls->can("dedupe_$dd") //
+                        die "unsupported dedupe strategy: $dd\n";
+        bless [ $dd_new->() ], $cls; # [ $skv, $cb ]
+}
+
+# returns true on unseen messages according to the deduplication strategy,
+# returns false if seen
+sub is_dup {
+        my ($self, $eml, $oid) = @_;
+        !$self->[1]->($eml, $oid);
+}
+
+sub prepare_dedupe {
+        my ($self) = @_;
+        my $skv = $self->[0];
+        $skv ? $skv->dbh : undef;
+}
+
+sub pause_dedupe {
+        my ($self) = @_;
+        my $skv = $self->[0];
+        delete($skv->{dbh}) if $skv;
+}
+
+1;