lib: add date range query support

Add a custom value range processor to enable date and time searches of
the form date:since..until, where "since" and "until" are expressions
understood by the previously added date/time parser, to restrict the
results to messages within a particular time range (based on the Date:
header).

If "since" or "until" describes date/time at an accuracy of days or
less, the values are rounded according to the accuracy, towards past
for "since" and towards future for "until". For example,
date:november..yesterday would match from the beginning of November
until the end of yesterday. Expressions such as date:today..today
means since the beginning of today until the end of today.

Open-ended ranges are supported (since Xapian 1.2.1), i.e. you can
specify date:..until or date:since.. to not limit the start or end
date, respectively.

CAVEATS:

Xapian does not support spaces in range expressions. You can replace
the spaces with '_', or (in most cases) '-', or (in some cases) leave
the spaces out altogether.

Entering date:expr without ".." (for example date:yesterday) will not
work as you might expect. You can achieve the expected result by
duplicating the expr both sides of ".." (for example
date:yesterday..yesterday).

Open-ended ranges won't work with pre-1.2.1 Xapian, but they don't
produce an error either.

Signed-off-by: Jani Nikula <jani@nikula.org>

lib/Makefile.local

@@ -61,6 +61,7 @@ libnotmuch_c_srcs =		\
 
 libnotmuch_cxx_srcs =		\
 	$(dir)/database.cc	\
+	$(dir)/parse-time-vrp.cc	\
 	$(dir)/directory.cc	\
 	$(dir)/index.cc		\
 	$(dir)/message.cc	\

lib/database-private.h

@@ -52,6 +52,7 @@ struct _notmuch_database {
     Xapian::QueryParser *query_parser;
     Xapian::TermGenerator *term_gen;
     Xapian::ValueRangeProcessor *value_range_processor;
+    Xapian::ValueRangeProcessor *date_range_processor;
 };
 
 /* Return the list of terms from the given iterator matching a prefix.

lib/database.cc

@@ -19,6 +19,7 @@
  */
 
 #include "database-private.h"
+#include "parse-time-vrp.h"
 
 #include <iostream>
 
@@ -710,12 +711,14 @@ notmuch_database_open (const char *path,
 	notmuch->term_gen = new Xapian::TermGenerator;
 	notmuch->term_gen->set_stemmer (Xapian::Stem ("english"));
 	notmuch->value_range_processor = new Xapian::NumberValueRangeProcessor (NOTMUCH_VALUE_TIMESTAMP);
+	notmuch->date_range_processor = new ParseTimeValueRangeProcessor (NOTMUCH_VALUE_TIMESTAMP);
 
 	notmuch->query_parser->set_default_op (Xapian::Query::OP_AND);
 	notmuch->query_parser->set_database (*notmuch->xapian_db);
 	notmuch->query_parser->set_stemmer (Xapian::Stem ("english"));
 	notmuch->query_parser->set_stemming_strategy (Xapian::QueryParser::STEM_SOME);
 	notmuch->query_parser->add_valuerangeprocessor (notmuch->value_range_processor);
+	notmuch->query_parser->add_valuerangeprocessor (notmuch->date_range_processor);
 
 	for (i = 0; i < ARRAY_SIZE (BOOLEAN_PREFIX_EXTERNAL); i++) {
 	    prefix_t *prefix = &BOOLEAN_PREFIX_EXTERNAL[i];
@@ -778,6 +781,8 @@ notmuch_database_close (notmuch_database_t *notmuch)
     notmuch->xapian_db = NULL;
     delete notmuch->value_range_processor;
     notmuch->value_range_processor = NULL;
+    delete notmuch->date_range_processor;
+    notmuch->date_range_processor = NULL;
 }
 
 void

lib/parse-time-vrp.cc

@@ -0,0 +1,61 @@
+/* parse-time-vrp.cc - date range query glue
+ *
+ * This file is part of notmuch.
+ *
+ * Copyright © 2012 Jani Nikula
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see http://www.gnu.org/licenses/ .
+ *
+ * Author: Jani Nikula <jani@nikula.org>
+ */
+
+#include "database-private.h"
+#include "parse-time-vrp.h"
+#include "parse-time-string.h"
+
+#define PREFIX "date:"
+
+/* See *ValueRangeProcessor in xapian-core/api/valuerangeproc.cc */
+Xapian::valueno
+ParseTimeValueRangeProcessor::operator() (std::string &begin, std::string &end)
+{
+    time_t t, now;
+
+    /* Require date: prefix in start of the range... */
+    if (STRNCMP_LITERAL (begin.c_str (), PREFIX))
+	return Xapian::BAD_VALUENO;
+
+    /* ...and remove it. */
+    begin.erase (0, sizeof (PREFIX) - 1);
+
+    /* Use the same 'now' for begin and end. */
+    if (time (&now) == (time_t) -1)
+	return Xapian::BAD_VALUENO;
+
+    if (!begin.empty ()) {
+	if (parse_time_string (begin.c_str (), &t, &now, PARSE_TIME_ROUND_DOWN))
+	    return Xapian::BAD_VALUENO;
+
+	begin.assign (Xapian::sortable_serialise ((double) t));
+    }
+
+    if (!end.empty ()) {
+	if (parse_time_string (end.c_str (), &t, &now, PARSE_TIME_ROUND_UP_INCLUSIVE))
+	    return Xapian::BAD_VALUENO;
+
+	end.assign (Xapian::sortable_serialise ((double) t));
+    }
+
+    return valno;
+}

lib/parse-time-vrp.h

@@ -0,0 +1,40 @@
+/* parse-time-vrp.h - date range query glue
+ *
+ * This file is part of notmuch.
+ *
+ * Copyright © 2012 Jani Nikula
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see http://www.gnu.org/licenses/ .
+ *
+ * Author: Jani Nikula <jani@nikula.org>
+ */
+
+#ifndef NOTMUCH_PARSE_TIME_VRP_H
+#define NOTMUCH_PARSE_TIME_VRP_H
+
+#include <xapian.h>
+
+/* see *ValueRangeProcessor in xapian-core/include/xapian/queryparser.h */
+class ParseTimeValueRangeProcessor : public Xapian::ValueRangeProcessor {
+protected:
+    Xapian::valueno valno;
+
+public:
+    ParseTimeValueRangeProcessor (Xapian::valueno slot_)
+	: valno(slot_) { }
+
+    Xapian::valueno operator() (std::string &begin, std::string &end);
+};
+
+#endif /* NOTMUCH_PARSE_TIME_VRP_H */