[PATCH] WIP: add thread subqueries.

[David Bremner <david@tethera.net>]

This is a quick implimentation of Jani's suggestion. Performance is
not great in some obvious cases, but maybe that doesn't matter
---

I just wrote this while waiting for dinner to cook, so it might be
full of bugs, and or strange effects of hunger.

If you're interested in this feature, please test, let me know if it's
workable for your use case.  The syntax here is thread:{$query}. The
usual caveats about whitespace apply. The running example is

	     thread:{from:me} and thread:{from:jian} and not thread:{from:dave}

Since each of those typically expands to a large number of threads
(and is processed independently), this can take a bit of time to process.
If we like the idea, maybe some caching can help.


 lib/Makefile.local |  3 ++-
 lib/database.cc    |  6 ++++-
 lib/thread-fp.cc   | 68 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 lib/thread-fp.h    | 42 +++++++++++++++++++++++++++++++++
 4 files changed, 117 insertions(+), 2 deletions(-)
 create mode 100644 lib/thread-fp.cc
 create mode 100644 lib/thread-fp.h

diff --git a/lib/Makefile.local b/lib/Makefile.local
index 0b5c4b08..1c1b96f1 100644
--- a/lib/Makefile.local
+++ b/lib/Makefile.local
@@ -57,7 +57,8 @@ libnotmuch_cxx_srcs =		\
 	$(dir)/query-fp.cc      \
 	$(dir)/config.cc	\
 	$(dir)/regexp-fields.cc	\
-	$(dir)/thread.cc
+	$(dir)/thread.cc \
+	$(dir)/thread-fp.cc
 
 libnotmuch_modules := $(libnotmuch_c_srcs:.c=.o) $(libnotmuch_cxx_srcs:.cc=.o)
 
diff --git a/lib/database.cc b/lib/database.cc
index 8f0e22a8..be63fdbb 100644
--- a/lib/database.cc
+++ b/lib/database.cc
@@ -21,6 +21,7 @@
 #include "database-private.h"
 #include "parse-time-vrp.h"
 #include "query-fp.h"
+#include "thread-fp.h"
 #include "regexp-fields.h"
 #include "string-util.h"
 
@@ -258,7 +259,8 @@ prefix_t prefix_table[] = {
     { "directory",		"XDIRECTORY",	NOTMUCH_FIELD_NO_FLAGS },
     { "file-direntry",		"XFDIRENTRY",	NOTMUCH_FIELD_NO_FLAGS },
     { "directory-direntry",	"XDDIRENTRY",	NOTMUCH_FIELD_NO_FLAGS },
-    { "thread",			"G",		NOTMUCH_FIELD_EXTERNAL },
+    { "thread",			"G",		NOTMUCH_FIELD_EXTERNAL |
+						NOTMUCH_FIELD_PROCESSOR },
     { "tag",			"K",		NOTMUCH_FIELD_EXTERNAL |
 						NOTMUCH_FIELD_PROCESSOR },
     { "is",			"K",		NOTMUCH_FIELD_EXTERNAL |
@@ -317,6 +319,8 @@ _setup_query_field (const prefix_t *prefix, notmuch_database_t *notmuch)
 	    fp = (new DateFieldProcessor())->release ();
 	else if (STRNCMP_LITERAL(prefix->name, "query") == 0)
 	    fp = (new QueryFieldProcessor (*notmuch->query_parser, notmuch))->release ();
+	else if (STRNCMP_LITERAL(prefix->name, "thread") == 0)
+	    fp = (new ThreadFieldProcessor (*notmuch->query_parser, notmuch))->release ();
 	else
 	    fp = (new RegexpFieldProcessor (prefix->name, prefix->flags,
 					    *notmuch->query_parser, notmuch))->release ();
diff --git a/lib/thread-fp.cc b/lib/thread-fp.cc
new file mode 100644
index 00000000..7cfe0721
--- /dev/null
+++ b/lib/thread-fp.cc
@@ -0,0 +1,68 @@
+/* thread-fp.cc - "thread:" field processor glue
+ *
+ * This file is part of notmuch.
+ *
+ * Copyright © 2016 David Bremner
+ *
+ * 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 https://www.gnu.org/licenses/ .
+ *
+ * Author: David Bremner <david@tethera.net>
+ */
+
+#include "database-private.h"
+#include "thread-fp.h"
+#include <iostream>
+
+#if HAVE_XAPIAN_FIELD_PROCESSOR
+
+Xapian::Query
+ThreadFieldProcessor::operator() (const std::string & str)
+{
+    notmuch_status_t status;
+
+    if (str.at (0) == '{') {
+	if (str.length() > 1 && str.at (str.size () - 1) == '}'){
+	    std::string subquery_str = str.substr(1,str.size () - 2);
+	    notmuch_query_t *subquery = notmuch_query_create (notmuch, subquery_str.c_str());
+	    notmuch_threads_t *threads;
+	    notmuch_thread_t *thread;
+	    std::vector<std::string> terms;
+
+	    if (!subquery)
+		throw Xapian::QueryParserError ("failed to create subquery for '" + subquery_str + "'");
+
+	    status = notmuch_query_search_threads (subquery, &threads);
+	    if (status)
+		throw Xapian::QueryParserError ("failed to search threads for '" + subquery_str + "'");
+
+
+	    for (; notmuch_threads_valid (threads);  notmuch_threads_move_to_next (threads)) {
+		std::string term = "G";
+
+		thread = notmuch_threads_get (threads);
+		term += notmuch_thread_get_thread_id (thread);
+		terms.push_back (term);
+	    }
+	    return Xapian::Query (Xapian::Query::OP_OR, terms.begin(), terms.end());
+	} else {
+	    throw Xapian::QueryParserError ("missing } in '" + str + "'");
+	}
+    } else {
+	/* literal thread id */
+	std::string term = "G"+str;
+	return Xapian::Query (term);
+    }
+
+}
+#endif
diff --git a/lib/thread-fp.h b/lib/thread-fp.h
new file mode 100644
index 00000000..13725978
--- /dev/null
+++ b/lib/thread-fp.h
@@ -0,0 +1,42 @@
+/* thread-fp.h - thread field processor glue
+ *
+ * This file is part of notmuch.
+ *
+ * Copyright © 2017 David Bremner
+ *
+ * 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 https://www.gnu.org/licenses/ .
+ *
+ * Author: David Bremner <david@tethera.net>
+ */
+
+#ifndef NOTMUCH_THREAD_FP_H
+#define NOTMUCH_THREAD_FP_H
+
+#include <xapian.h>
+#include "notmuch.h"
+
+#if HAVE_XAPIAN_FIELD_PROCESSOR
+class ThreadFieldProcessor : public Xapian::FieldProcessor {
+ protected:
+    Xapian::QueryParser &parser;
+    notmuch_database_t *notmuch;
+
+ public:
+    ThreadFieldProcessor (Xapian::QueryParser &parser_, notmuch_database_t *notmuch_)
+	: parser(parser_), notmuch(notmuch_) { };
+
+    Xapian::Query operator()(const std::string & str);
+};
+#endif
+#endif /* NOTMUCH_THREAD_FP_H */
-- 
2.14.1