mu/lib/mu-xapian.cc

/*
** Copyright (C) 2017 Dirk-Jan C. Binnema <djcb@djcbsoftware.nl>
**
**  This library is free software; you can redistribute it and/or
**  modify it under the terms of the GNU Lesser General Public License
**  as published by the Free Software Foundation; either version 2.1
**  of the License, or (at your option) any later version.
**
**  This library 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
**  Lesser General Public License for more details.
**
**  You should have received a copy of the GNU Lesser General Public
**  License along with this library; if not, write to the Free
**  Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
**  02110-1301, USA.
*/

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /*HAVE_CONFIG_H*/

#include <xapian.h>
#include "mu-xapian.hh"
#include <utils/mu-error.hh>

using namespace Mu;

static Xapian::Query
xapian_query_op(const Mu::Tree& tree)
{
	Xapian::Query::op op;

#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wswitch-enum"
	switch (tree.node.type) {
	case Node::Type::OpNot: // OpNot x ::= <all> AND NOT x
		if (tree.children.size() != 1)
			throw std::runtime_error("invalid # of children");
		return Xapian::Query(Xapian::Query::OP_AND_NOT,
		                     Xapian::Query::MatchAll,
		                     xapian_query(tree.children.front()));
	case Node::Type::OpAnd: op = Xapian::Query::OP_AND; break;
	case Node::Type::OpOr: op = Xapian::Query::OP_OR; break;
	case Node::Type::OpXor: op = Xapian::Query::OP_XOR; break;
	case Node::Type::OpAndNot: op = Xapian::Query::OP_AND_NOT; break;
	default: throw Mu::Error(Error::Code::Internal, "invalid op"); // bug
	}
#pragma GCC diagnostic pop
	std::vector<Xapian::Query> childvec;
	for (const auto& subtree : tree.children)
		childvec.emplace_back(xapian_query(subtree));

	return Xapian::Query(op, childvec.begin(), childvec.end());
}

static Xapian::Query
make_query(const Value* val, const std::string& str, bool maybe_wildcard)
{
	const auto vlen{str.length()};
	if (!maybe_wildcard || vlen <= 1 || str[vlen - 1] != '*')
		return Xapian::Query(val->prefix + str);
	else
		return Xapian::Query(Xapian::Query::OP_WILDCARD,
		                     val->prefix + str.substr(0, vlen - 1));
}

static Xapian::Query
xapian_query_value(const Mu::Tree& tree)
{
	const auto v = dynamic_cast<Value*>(tree.node.data.get());
	if (!v->phrase)
		return make_query(v, v->value, true /*maybe-wildcard*/);

	const auto parts = split(v->value, " ");
	if (parts.empty())
		return Xapian::Query::MatchNothing; // shouldn't happen

	if (parts.size() == 1)
		return make_query(v, parts.front(), true /*maybe-wildcard*/);

	std::vector<Xapian::Query> phvec;
	for (const auto& p : parts)
		phvec.emplace_back(make_query(v, p, false /*no wildcards*/));

	return Xapian::Query(Xapian::Query::OP_PHRASE, phvec.begin(), phvec.end());
}

static Xapian::Query
xapian_query_range(const Mu::Tree& tree)
{
	const auto r{dynamic_cast<Range*>(tree.node.data.get())};

	return Xapian::Query(Xapian::Query::OP_VALUE_RANGE,
	                     (Xapian::valueno)r->id,
	                     r->lower,
	                     r->upper);
}

Xapian::Query
Mu::xapian_query(const Mu::Tree& tree)
{
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wswitch-enum"
	switch (tree.node.type) {
	case Node::Type::Empty: return Xapian::Query();
	case Node::Type::OpNot:
	case Node::Type::OpAnd:
	case Node::Type::OpOr:
	case Node::Type::OpXor:
	case Node::Type::OpAndNot: return xapian_query_op(tree);
	case Node::Type::Value: return xapian_query_value(tree);
	case Node::Type::Range: return xapian_query_range(tree);
	default: throw Mu::Error(Error::Code::Internal, "invalid query"); // bug
	}
#pragma GCC diagnostic pop
}