/*
** Copyright (C) 2008-2021 Dirk-Jan C. Binnema <djcb@djcbsoftware.nl>
**
** 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, write to the Free Software Foundation,
** Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
**
*/
#include <mu-query.hh>

#include <stdexcept>
#include <string>
#include <cctype>
#include <cstring>
#include <sstream>
#include <cmath>

#include <stdlib.h>
#include <xapian.h>
#include <glib/gstdio.h>

#include "mu-msg-fields.h"
#include "mu-query-results.hh"
#include "mu-query-match-deciders.hh"
#include "mu-query-threads.hh"
#include <mu-xapian.hh>

using namespace Mu;

struct Query::Private {
	Private(const Store& store) : store_{store}, parser_{store_} {}
	// New
	// bool calculate_threads (Xapian::Enquire& enq, size maxnum);

	Xapian::Enquire
	make_enquire(const std::string& expr, MuMsgFieldId sortfieldid, QueryFlags qflags) const;
	Xapian::Enquire make_related_enquire(const StringSet& thread_ids,
	                                     MuMsgFieldId     sortfieldid,
	                                     QueryFlags       qflags) const;

	Option<QueryResults> run_threaded(QueryResults&&   qres,
	                                  Xapian::Enquire& enq,
	                                  QueryFlags       qflags,
	                                  size_t           max_size) const;
	Option<QueryResults> run_singular(const std::string& expr,
	                                  MuMsgFieldId       sortfieldid,
	                                  QueryFlags         qflags,
	                                  size_t             maxnum) const;
	Option<QueryResults> run_related(const std::string& expr,
	                                 MuMsgFieldId       sortfieldid,
	                                 QueryFlags         qflags,
	                                 size_t             maxnum) const;
	Option<QueryResults> run(const std::string& expr,
	                         MuMsgFieldId       sortfieldid,
	                         QueryFlags         qflags,
	                         size_t             maxnum) const;

	const Store& store_;
	const Parser parser_;
};

Query::Query(const Store& store) : priv_{std::make_unique<Private>(store)} {}

Query::Query(Query&& other) = default;

Query::~Query() = default;

static Xapian::Enquire&
maybe_sort(Xapian::Enquire& enq, MuMsgFieldId sortfieldid, QueryFlags qflags)
{
	if (sortfieldid != MU_MSG_FIELD_ID_NONE)
		enq.set_sort_by_value(static_cast<Xapian::valueno>(sortfieldid),
		                      any_of(qflags & QueryFlags::Descending));
	return enq;
}

Xapian::Enquire
Query::Private::make_enquire(const std::string& expr,
                             MuMsgFieldId       sortfieldid,
                             QueryFlags         qflags) const
{
	Xapian::Enquire enq{store_.database()};

	if (expr.empty() || expr == R"("")")
		enq.set_query(Xapian::Query::MatchAll);
	else {
		WarningVec warns;
		const auto tree{parser_.parse(expr, warns)};
		for (auto&& w : warns)
			g_warning("query warning: %s", to_string(w).c_str());
		enq.set_query(xapian_query(tree));
		g_debug("qtree: %s", to_string(tree).c_str());
	}

	return maybe_sort(enq, sortfieldid, qflags);
}

Xapian::Enquire
Query::Private::make_related_enquire(const StringSet& thread_ids,
                                     MuMsgFieldId     sortfieldid,
                                     QueryFlags       qflags) const
{
	Xapian::Enquire    enq{store_.database()};
	static std::string pfx(1, mu_msg_field_xapian_prefix(MU_MSG_FIELD_ID_THREAD_ID));

	std::vector<Xapian::Query> qvec;
	for (auto&& t : thread_ids)
		qvec.emplace_back(pfx + t);
	Xapian::Query qr{Xapian::Query::OP_OR, qvec.begin(), qvec.end()};
	enq.set_query(qr);

	return maybe_sort(enq, sortfieldid, qflags);
}

struct ThreadKeyMaker : public Xapian::KeyMaker {
	ThreadKeyMaker(const QueryMatches& matches) : match_info_(matches) {}
	std::string operator()(const Xapian::Document& doc) const override
	{
		const auto it{match_info_.find(doc.get_docid())};
		return (it == match_info_.end()) ? "" : it->second.thread_path;
	}
	const QueryMatches& match_info_;
};

Option<QueryResults>
Query::Private::run_threaded(QueryResults&&   qres,
                             Xapian::Enquire& enq,
                             QueryFlags       qflags,
                             size_t           maxnum) const
{
	const auto descending{any_of(qflags & QueryFlags::Descending)};

	calculate_threads(qres, descending);

	ThreadKeyMaker key_maker{qres.query_matches()};
	enq.set_sort_by_key(&key_maker, descending);

	DeciderInfo minfo;
	minfo.matches = qres.query_matches();
	auto mset{enq.get_mset(0, maxnum, {}, make_thread_decider(qflags, minfo).get())};
	mset.fetch();

	return QueryResults{mset, std::move(qres.query_matches())};
}

Option<QueryResults>
Query::Private::run_singular(const std::string& expr,
                             MuMsgFieldId       sortfieldid,
                             QueryFlags         qflags,
                             size_t             maxnum) const
{
	// i.e. a query _without_ related messages, but still possibly
	// with threading.
	//
	// In the threading case, the sortfield-id is ignored, we always sort by
	// date (since threading the threading results are always by date.)

	const auto singular_qflags{qflags | QueryFlags::Leader};
	const auto threading{any_of(qflags & QueryFlags::Threading)};

	DeciderInfo minfo{};
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wextra"
	auto enq{make_enquire(expr, threading ? MU_MSG_FIELD_ID_DATE : sortfieldid, qflags)};
#pragma GCC diagnostic ignored "-Wswitch-default"
#pragma GCC diagnostic pop
	auto mset{enq.get_mset(0, maxnum, {}, make_leader_decider(singular_qflags, minfo).get())};
	mset.fetch();

	auto qres{QueryResults{mset, std::move(minfo.matches)}};

	return threading ? run_threaded(std::move(qres), enq, qflags, maxnum) : qres;
}

static Option<std::string>
opt_string(const Xapian::Document& doc, MuMsgFieldId id) noexcept
{
	std::string val = xapian_try([&] { return doc.get_value(id); }, std::string{""});
	if (val.empty())
		return Nothing;
	else
		return Some(std::move(val));
}

Option<QueryResults>
Query::Private::run_related(const std::string& expr,
                            MuMsgFieldId       sortfieldid,
                            QueryFlags         qflags,
                            size_t             maxnum) const
{
	// i.e. a query _with_ related messages and possibly with threading.
	//
	// In the threading case, the sortfield-id is ignored, we always sort by
	// date (since threading the threading results are always by date.);
	// moreover, in either threaded or non-threaded case, we sort the first
	// ("leader") query by date, i.e, we prefer the newest or oldest
	// (descending) messages.
	const auto leader_qflags{QueryFlags::Leader | qflags};
	const auto threading{any_of(qflags & QueryFlags::Threading)};

	// Run our first, "leader" query
	DeciderInfo minfo{};
	auto        enq{make_enquire(expr, MU_MSG_FIELD_ID_DATE, leader_qflags)};
	const auto  mset{
            enq.get_mset(0, maxnum, {}, make_leader_decider(leader_qflags, minfo).get())};

	// Gather the thread-ids we found
	mset.fetch();
	for (auto it = mset.begin(); it != mset.end(); ++it) {
		auto thread_id{opt_string(it.get_document(), MU_MSG_FIELD_ID_THREAD_ID)};
		if (thread_id)
			minfo.thread_ids.emplace(std::move(*thread_id));
	}

	// Now, determine the "related query".
	//
	// In the threaded-case, we search among _all_ messages, since complete
	// threads are preferred; no need to sort in that case since the search
	// is unlimited and the sorting happens during threading.
	auto       r_enq{make_related_enquire(minfo.thread_ids,
                                        threading ? MU_MSG_FIELD_ID_NONE : sortfieldid,
                                        qflags)};
	const auto r_mset{r_enq.get_mset(0,
	                                 threading ? store_.size() : maxnum,
	                                 {},
	                                 make_related_decider(qflags, minfo).get())};
	auto       qres{QueryResults{r_mset, std::move(minfo.matches)}};
	return threading ? run_threaded(std::move(qres), r_enq, qflags, maxnum) : qres;
}

Option<QueryResults>
Query::Private::run(const std::string& expr,
                    MuMsgFieldId       sortfieldid,
                    QueryFlags         qflags,
                    size_t             maxnum) const
{
	const auto eff_maxnum{maxnum == 0 ? store_.size() : maxnum};
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wextra"
	const auto eff_sortfield{sortfieldid == MU_MSG_FIELD_ID_NONE ? MU_MSG_FIELD_ID_DATE
	                                                             : sortfieldid};
#pragma GCC diagnostic pop
	if (any_of(qflags & QueryFlags::IncludeRelated))
		return run_related(expr, eff_sortfield, qflags, eff_maxnum);
	else
		return run_singular(expr, eff_sortfield, qflags, eff_maxnum);
}

Option<QueryResults>
Query::run(const std::string& expr,
           MuMsgFieldId       sortfieldid,
           QueryFlags         qflags,
           size_t             maxnum) const
try {
	// some flags are for internal use only.
	g_return_val_if_fail(none_of(qflags & QueryFlags::Leader), Nothing);

	StopWatch sw{format("ran query '%s'; related: %s; threads: %s; max-size: %zu",
	                    expr.c_str(),
	                    any_of(qflags & QueryFlags::IncludeRelated) ? "yes" : "no",
	                    any_of(qflags & QueryFlags::Threading) ? "yes" : "no",
	                    maxnum)};

	return priv_->run(expr, sortfieldid, qflags, maxnum);

} catch (...) {
	return Nothing;
}

size_t
Query::count(const std::string& expr) const
{
	return xapian_try(
	    [&] {
		    const auto enq{priv_->make_enquire(expr, MU_MSG_FIELD_ID_NONE, {})};
		    auto       mset{enq.get_mset(0, priv_->store_.size())};
		    mset.fetch();
		    return mset.size();
	    },
	    0);
}

std::string
Query::parse(const std::string& expr, bool xapian) const
{
	WarningVec warns;
	const auto tree{priv_->parser_.parse(expr, warns)};
	for (auto&& w : warns)
		g_warning("query warning: %s", to_string(w).c_str());

	if (xapian)
		return xapian_query(tree).get_description();
	else
		return to_string(tree);
}