+# Copyright (C) 2020 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+# IMAP search query parser. cf RFC 3501
+
+# We currently compile Xapian queries to a string which is fed
+# to Xapian's query parser. However, we may use Xapian-provided
+# Query object API to build an optree, instead.
+package PublicInbox::IMAPsearchqp;
+use strict;
+use Parse::RecDescent;
+use Time::Local qw(timegm);
+use POSIX qw(strftime);
+our $q = bless {}, __PACKAGE__; # singleton, reachable in generated P::RD
+my @MoY = qw(JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC);
+my %MM = map {; $MoY[$_-1] => sprintf('%02u', $_) } (1..12);
+
+# IMAP to Xapian header search key mapping
+my %IH2X = (
+ TEXT => '',
+ SUBJECT => 's:',
+ BODY => 'b:',
+ FROM => 'f:',
+ TO => 't:',
+ CC => 'c:',
+ # BCC => 'bcc:', # TODO
+
+ # IMAP allows searching arbitrary headers via
+ # "HEADER $field_name $string" which gets silly expensive.
+ # We only allow the headers we already index.
+ 'MESSAGE-ID' => 'm:',
+ 'LIST-ID' => 'l:',
+ # KEYWORD # TODO ? dfpre,dfpost,...
+);
+
+sub uid_set_xap ($$) {
+ my ($self, $seq_set) = @_;
+ my @u;
+ do {
+ my $u = $self->{imap}->range_step(\$seq_set);
+ die $u unless ref($u); # break out of the parser on error
+ push @u, "uid:$u->[0]..$u->[1]";
+ } while ($seq_set);
+ push(@{$q->{xap}}, @u > 1 ? '('.join(' OR ', @u).')' : $u[0]);
+}
+
+sub xap_only ($;$) {
+ my ($self, $query) = @_;
+ delete $self->{sql}; # query too complex for over.sqlite3
+ push @{$self->{xap}}, $query if defined($query);
+
+ # looks like we can't use SQLite-only, convert SQLite UID
+ # ranges to Xapian:
+ if (my $uid = delete $self->{uid}) {
+ uid_set_xap($self, $_) for @$uid;
+ }
+ 1;
+}
+
+sub ih2x {
+ my ($self, $field_name, $s) = @_; # $self == $q
+ $s =~ /\A"(.*?)"\z/s and $s = $1;
+
+ # AFAIK Xapian can't handle [*"] in probabilistic terms,
+ # and it relies on lowercase
+ my $xk = defined($field_name) ? ($IH2X{$field_name} // '') : '';
+ xap_only($self,
+ lc(join(' ', map { qq[$xk"$_"] } split(/[\*"\s]+/, $s))));
+ 1;
+}
+
+sub subq_enter {
+ xap_only($q);
+ my $old = delete($q->{xap}) // [];
+ my $nr = push @{$q->{stack}}, $old;
+ die 'BAD deep recursion' if $nr > 10;
+ $q->{xap} = [];
+}
+
+sub subq_leave {
+ my $child = delete $q->{xap};
+ my $parent = $q->{xap} = pop @{$q->{stack}};
+ push(@$parent, @$child > 1 ? '('.join(' ', @$child).')' : $child->[0]);
+ 1;
+}
+
+sub yyyymmdd ($) {
+ my ($item) = @_;
+ my ($dd, $mon, $yyyy) = split(/-/, $item->{date}, 3);
+ my $mm = $MM{$mon} // die "BAD month: $mon";
+ wantarray ? ($yyyy, $mm, sprintf('%02u', $dd))
+ : timegm(0, 0, 0, $dd, $mm - 1, $yyyy);
+}
+
+sub SENTSINCE {
+ my ($self, $item) = @_;
+ my ($yyyy, $mm, $dd) = yyyymmdd($item);
+ push @{$self->{xap}}, "d:$yyyy$mm$dd..";
+ my $sql = $self->{sql} or return 1;
+ my $ds = timegm(0, 0, 0, $dd, $mm - 1, $yyyy);
+ $$sql .= " AND ds >= $ds";
+}
+
+sub SENTON {
+ my ($self, $item) = @_;
+ my ($yyyy, $mm, $dd) = yyyymmdd($item);
+ my $ds = timegm(0, 0, 0, $dd, $mm - 1, $yyyy);
+ my $end = $ds + 86399; # no leap day
+ my $dt_end = strftime('%Y%m%d%H%M%S', gmtime($end));
+ push @{$self->{xap}}, "dt:$yyyy$mm$dd"."000000..$dt_end";
+ my $sql = $self->{sql} or return 1;
+ $$sql .= " AND ds >= $ds AND ds <= $end";
+}
+
+sub SENTBEFORE {
+ my ($self, $item) = @_;
+ my ($yyyy, $mm, $dd) = yyyymmdd($item);
+ push @{$self->{xap}}, "d:..$yyyy$mm$dd";
+ my $sql = $self->{sql} or return 1;
+ my $ds = timegm(0, 0, 0, $dd, $mm - 1, $yyyy);
+ $$sql .= " AND ds <= $ds";
+}
+
+sub ON {
+ my ($self, $item) = @_;
+ my $ts = yyyymmdd($item);
+ my $end = $ts + 86399; # no leap day
+ push @{$self->{xap}}, "ts:$ts..$end";
+ my $sql = $self->{sql} or return 1;
+ $$sql .= " AND ts >= $ts AND ts <= $end";
+}
+
+sub BEFORE {
+ my ($self, $item) = @_;
+ my $ts = yyyymmdd($item);
+ push @{$self->{xap}}, "ts:..$ts";
+ my $sql = $self->{sql} or return 1;
+ $$sql .= " AND ts <= $ts";
+}
+
+sub SINCE {
+ my ($self, $item) = @_;
+ my $ts = yyyymmdd($item);
+ push @{$self->{xap}}, "ts:$ts..";
+ my $sql = $self->{sql} or return 1;
+ $$sql .= " AND ts >= $ts";
+}
+
+sub uid_set ($$) {
+ my ($self, $seq_set) = @_;
+ if ($self->{sql}) {
+ push @{$q->{uid}}, $seq_set;
+ } else { # we've gone Xapian-only
+ uid_set_xap($self, $seq_set);
+ }
+ 1;
+}
+
+sub msn_set {
+ my ($self, $seq_set) = @_;
+ PublicInbox::IMAP::msn_to_uid_range(
+ $self->{msn2uid} //= $self->{imap}->msn2uid, $seq_set);
+ uid_set($self, $seq_set);
+}
+
+my $prd = Parse::RecDescent->new(<<'EOG');
+<nocheck>
+{ my $q = $PublicInbox::IMAPsearchqp::q; }
+search_key : search_key1(s) { $return = $q }
+search_key1 : "ALL" | "RECENT" | "UNSEEN" | "NEW"
+ | OR_search_keys
+ | NOT_search_key
+ | LARGER_number
+ | SMALLER_number
+ | SENTSINCE_date
+ | SENTON_date
+ | SENTBEFORE_date
+ | SINCE_date
+ | ON_date
+ | BEFORE_date
+ | FROM_string
+ | HEADER_field_name_string
+ | TO_string
+ | CC_string
+ | BCC_string
+ | SUBJECT_string
+ | UID_set
+ | MSN_set
+ | sub_query
+ | <error>
+
+SENTSINCE_date : 'SENTSINCE' date { $q->SENTSINCE(\%item) }
+SENTON_date : 'SENTON' date { $q->SENTON(\%item) }
+SENTBEFORE_date : 'SENTBEFORE' date { $q->SENTBEFORE(\%item) }
+
+SINCE_date : 'SINCE' date { $q->SINCE(\%item) }
+ON_date : 'ON' date { $q->ON(\%item) }
+BEFORE_date : 'BEFORE' date { $q->BEFORE(\%item) }
+
+MSN_set : sequence_set { $q->msn_set($item{sequence_set}) }
+UID_set : "UID" sequence_set { $q->uid_set($item{sequence_set}) }
+LARGER_number : "LARGER" number { $q->xap_only("bytes:$item{number}..") }
+SMALLER_number : "SMALLER" number { $q->xap_only("bytes:..$item{number}") }
+# pass "NOT" through XXX is this right?
+OP_NOT : "NOT" { $q->xap_only('NOT') }
+NOT_search_key : OP_NOT search_key1
+OP_OR : "OR" {
+ $q->xap_only('OP_OR');
+ my $cur = delete $q->{xap};
+ push @{$q->{stack}}, $cur;
+ $q->{xap} = [];
+}
+search_key_a : search_key1
+{
+ my $ka = delete $q->{xap};
+ $q->{xap} = [];
+ push @{$q->{stack}}, $ka;
+}
+OR_search_keys : OP_OR search_key_a search_key1
+{
+ my $kb = delete $q->{xap};
+ my $ka = pop @{$q->{stack}};
+ my $xap = $q->{xap} = pop @{$q->{stack}};
+ my $op = pop @$xap;
+ $op eq 'OP_OR' or die "BAD expected OR: $op";
+ $ka = @$ka > 1 ? '('.join(' ', @$ka).')' : $ka->[0];
+ $kb = @$kb > 1 ? '('.join(' ', @$kb).')' : $kb->[0];
+ push @$xap, "($ka OR $kb)";
+}
+HEADER_field_name_string : "HEADER" field_name string
+{
+ $q->ih2x($item{field_name}, $item{string});
+}
+FROM_string : "FROM" string { $q->ih2x('FROM', $item{string}) }
+TO_string : "TO" string { $q->ih2x('TO', $item{string}) }
+CC_string : "CC" string { $q->ih2x('CC', $item{string}) }
+BCC_string : "BCC" string { $q->ih2x('BCC', $item{string}) }
+SUBJECT_string : "SUBJECT" string { $q->ih2x('SUBJECT', $item{string}) }
+op_subq_enter : '(' { $q->subq_enter }
+sub_query : op_subq_enter search_key1(s) ')' { $q->subq_leave }
+
+field_name : /[\x21-\x39\x3b-\x7e]+/
+string : quoted | literal
+literal : /[^"\(\) \t]+/ # bogus, I know
+quoted : /"[^"]*"/
+number : /[0-9]+/
+date : /[0123]?[0-9]-[A-Z]{3}-[0-9]{4,}/
+sequence_set : /\A[0-9][0-9,:]*[0-9\*]?\z/
+EOG
+
+sub parse {
+ my ($imap, $query) = @_;
+ my $sql = '';
+ %$q = (sql => \$sql, imap => $imap); # imap = PublicInbox::IMAP obj
+ # $::RD_TRACE = 1;
+ my $res = eval { $prd->search_key(uc($query)) };
+ return $@ if $@ && $@ =~ /\ABAD /;
+ return 'BAD unexpected result' if !$res || $res != $q;
+ if (exists $q->{sql}) {
+ delete $q->{xap};
+ if (my $uid = delete $q->{uid}) {
+ my @u;
+ for my $uid_set (@$uid) {
+ my $u = $q->{imap}->range_step(\$uid_set);
+ return $u if !ref($u);
+ push @u, "num >= $u->[0] AND num <= $u->[1]";
+ }
+ $sql .= ' AND ('.join(' OR ', @u).')';
+ }
+ } else {
+ $q->{xap} = join(' ', @{$q->{xap}});
+ }
+ delete @$q{qw(imap msn2uid)};
+ $q;
+}
+
+1