// The Construct
//
// Copyright (C) The Construct Developers, Authors & Contributors
// Copyright (C) 2016-2020 Jason Volk <jason@zemos.net>
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice is present in all copies. The
// full license for this software is available in the LICENSE file.

/// Residence of the events database instance pointer.
decltype(ircd::m::dbs::events)
ircd::m::dbs::events;

/// Coarse variable for enabling the uncompressed cache on the events database;
/// note this conf item is only effective by setting an environmental variable
/// before daemon startup. It has no effect in any other regard.
decltype(ircd::m::dbs::cache_enable)
ircd::m::dbs::cache_enable
{
	{ "name",     "ircd.m.dbs.cache.enable" },
	{ "default",  true                      },
};

/// Coarse variable for enabling the compressed cache on the events database;
/// note this conf item is only effective by setting an environmental variable
/// before daemon startup. It has no effect in any other regard.
decltype(ircd::m::dbs::cache_comp_enable)
ircd::m::dbs::cache_comp_enable
{
	{ "name",     "ircd.m.dbs.cache.comp.enable" },
	{ "default",  false                          },
};

/// Coarse toggle for the prefetch phase before the transaction building
/// handlers (indexers) are called. If this is false, prefetching will be
/// disabled; otherwise the opts passed to write() control whether
/// prefetching is enabled.
decltype(ircd::m::dbs::prefetch_enable)
ircd::m::dbs::prefetch_enable
{
	{ "name",     "ircd.m.dbs.prefetch.enable" },
	{ "default",  true                         },
};

/// The size of the memory buffer for new writes to the DB (backed by the WAL
/// on disk). When this buffer is full it is flushed to sorted SST files on
/// disk. If this is 0, a per-column value can be used; otherwise this value
/// takes precedence as a total value for all columns. (db_write_buffer_size)
decltype(ircd::m::dbs::mem_write_buffer_size)
ircd::m::dbs::mem_write_buffer_size
{
	{ "name",     "ircd.m.dbs.mem.write_buffer_size" },
	{ "default",  0L                                 },
};

/// Value determines the size of writes when creating SST files (i.e during
/// compaction). Consider that write calls are yield-points for IRCd and the
/// time spent filling the write buffer between calls may hog the CPU doing
/// compression during that time etc. (writable_file_max_buffer_size)
decltype(ircd::m::dbs::sst_write_buffer_size)
ircd::m::dbs::sst_write_buffer_size
{
	{
		{ "name",     "ircd.m.dbs.sst.write_buffer_size" },
		{ "default",  long(1_MiB)                        },
	},
	[](conf::item<void> &)
	{
		static const string_view key{"writable_file_max_buffer_size"};
		const size_t &value{sst_write_buffer_size};
		if(events && !events->slave)
			db::setopt(*events, key, lex_cast(value));
	}
};

//
// opts
//

decltype(ircd::m::dbs::opts::event_refs_all)
ircd::m::dbs::opts::event_refs_all{[]
{
	char full[event_refs_all.size()];
	memset(full, '1', sizeof(full));
	return decltype(event_refs_all)
	{
		full, sizeof(full)
	};
}()};

decltype(ircd::m::dbs::opts::appendix_all)
ircd::m::dbs::opts::appendix_all{[]
{
	char full[appendix_all.size()];
	memset(full, '1', sizeof(full));
	return decltype(appendix_all)
	{
		full, sizeof(full)
	};
}()};

//
// Basic write suite
//

namespace ircd::m::dbs
{
	static size_t _prefetch(const event &, const opts &);
	static size_t _index(db::txn &, const event &, const opts &);
	static size_t blacklist(db::txn &txn, const event::id &, const opts &);
}

size_t
ircd::m::dbs::write(db::txn &txn,
                    const event &event,
                    const opts &opts)
try
{
	if(opts.event_idx == 0 && opts.blacklist)
		return blacklist(txn, event.event_id, opts);

	if(unlikely(opts.event_idx == 0))
		throw panic
		{
			"Cannot write to database: no index specified for event."
		};

	return _index(txn, event, opts);
}
catch(const std::exception &e)
{
	log::error
	{
		log, "Event %s txn building error :%s",
		string_view{event.event_id},
		e.what()
	};

	throw;
}

size_t
ircd::m::dbs::prefetch(const event &event,
                       const opts &opts)
try
{
	if(!prefetch_enable)
		return false;

	return _prefetch(event, opts);
}
catch(const std::exception &e)
{
	log::error
	{
		log, "Event %s txn prefetching error :%s",
		string_view{event.event_id},
		e.what()
	};

	return false;
}

size_t
ircd::m::dbs::blacklist(db::txn &txn,
                        const event::id &event_id,
                        const opts &opts)
{
	// An entry in the event_idx column with a value 0 is blacklisting
	// because 0 is not a valid event_idx. Thus a value here can only
	// have the value zero.
	assert(opts.event_idx == 0);
	assert(!event_id.empty());

	static const m::event::idx &zero_idx{0UL};
	static const byte_view<string_view> zero_value
	{
		zero_idx
	};

	db::txn::append
	{
		txn, event_idx,
		{
			opts.op,
			string_view{event_id},
			zero_value
		}
	};

	return true;
}

//
// Internal interface
//

namespace ircd::m::dbs
{
	static size_t _prefetch_room_redact(const event &, const opts &);
	static void _index_room_redact(db::txn &, const event &, const opts &);

	static size_t _prefetch_room(const event &, const opts &);
	static void _index_room(db::txn &, const event &, const opts &);

	static size_t _prefetch_event(const event &, const opts &);
	static void _index_event(db::txn &, const event &, const opts &);
}

size_t
ircd::m::dbs::_index(db::txn &txn,
                     const event &event,
                     const opts &opts)
{
	size_t ret(0);
	_index_event(txn, event, opts);

	if(json::get<"room_id"_>(event))
		_index_room(txn, event, opts);

	return ret;
}

size_t
ircd::m::dbs::_prefetch(const event &event,
                        const opts &opts)
{
	size_t ret(0);
	ret += _prefetch_event(event, opts);

	if(json::get<"room_id"_>(event))
		ret += _prefetch_room(event, opts);

	return ret;
}

void
ircd::m::dbs::_index_event(db::txn &txn,
                           const event &event,
                           const opts &opts)
{
	if(opts.appendix.test(appendix::EVENT_ID))
		_index_event_id(txn, event, opts);

	if(opts.appendix.test(appendix::EVENT_COLS))
		_index_event_cols(txn, event, opts);

	if(opts.appendix.test(appendix::EVENT_JSON))
		_index_event_json(txn, event, opts);

	if(opts.appendix.test(appendix::EVENT_SENDER))
		_index_event_sender(txn, event, opts);

	if(opts.appendix.test(appendix::EVENT_TYPE))
		_index_event_type(txn, event, opts);

	if(opts.appendix.test(appendix::EVENT_STATE))
		_index_event_state(txn, event, opts);

	if(opts.appendix.test(appendix::EVENT_REFS) && opts.event_refs.any())
		_index_event_refs(txn, event, opts);

	if(opts.appendix.test(appendix::EVENT_HORIZON_RESOLVE) && opts.horizon_resolve.any())
		_index_event_horizon_resolve(txn, event, opts);
}

size_t
ircd::m::dbs::_prefetch_event(const event &event,
                              const opts &opts)
{
	size_t ret(0);
	if(opts.appendix.test(appendix::EVENT_ID))
		;//ret += _prefetch_event_id(txn, event, opts);

	if(opts.appendix.test(appendix::EVENT_COLS))
		;//ret += _prefetch_event_cols(txn, event, opts);

	if(opts.appendix.test(appendix::EVENT_JSON))
		;//ret += _prefetch_event_json(txn, event, opts);

	if(opts.appendix.test(appendix::EVENT_SENDER))
		;//ret += _prefetch_event_sender(txn, event, opts);

	if(opts.appendix.test(appendix::EVENT_TYPE))
		;//ret += _prefetch_event_type(txn, event, opts);

	if(opts.appendix.test(appendix::EVENT_STATE))
		;//ret += _prefetch_event_state(txn, event, opts);

	if(opts.appendix.test(appendix::EVENT_REFS) && opts.event_refs.any())
		ret += _prefetch_event_refs(event, opts);

	if(opts.appendix.test(appendix::EVENT_HORIZON_RESOLVE) && opts.horizon_resolve.any())
		ret += _prefetch_event_horizon_resolve(event, opts);

	return ret;
}

void
ircd::m::dbs::_index_room(db::txn &txn,
                          const event &event,
                          const opts &opts)
{
	assert(!empty(json::get<"room_id"_>(event)));

	if(opts.appendix.test(appendix::ROOM_EVENTS))
		_index_room_events(txn, event, opts);

	if(opts.appendix.test(appendix::ROOM_TYPE))
		_index_room_type(txn, event, opts);

	if(opts.appendix.test(appendix::ROOM_HEAD))
		_index_room_head(txn, event, opts);

	if(opts.appendix.test(appendix::ROOM_HEAD_RESOLVE))
		_index_room_head_resolve(txn, event, opts);

	if(opts.appendix.test(appendix::ROOM_STATE))
		_index_room_state(txn, event, opts);

	if(opts.appendix.test(appendix::ROOM_STATE_SPACE))
		_index_room_state_space(txn, event, opts);

	if(opts.appendix.test(appendix::ROOM_JOINED) && at<"type"_>(event) == "m.room.member")
		_index_room_joined(txn, event, opts);

	if(opts.appendix.test(appendix::ROOM_REDACT) && json::get<"type"_>(event) == "m.room.redaction")
		_index_room_redact(txn, event, opts);
}

size_t
ircd::m::dbs::_prefetch_room(const event &event,
                             const opts &opts)
{
	assert(!empty(json::get<"room_id"_>(event)));

	size_t ret(0);
	if(opts.appendix.test(appendix::ROOM_EVENTS))
		;//ret += _prefetch_room_events(event, opts);

	if(opts.appendix.test(appendix::ROOM_TYPE))
		;//ret += _prefetch_room_type(event, opts);

	if(opts.appendix.test(appendix::ROOM_HEAD))
		;//ret += _prefetch_room_head(event, opts);

	if(opts.appendix.test(appendix::ROOM_HEAD_RESOLVE))
		;//ret += _prefetch_room_head_resolve(event, opts);

	if(opts.appendix.test(appendix::ROOM_STATE))
		;//ret += _prefetch_room_state(event, opts);

	if(opts.appendix.test(appendix::ROOM_STATE_SPACE))
		;//ret += _prefetch_room_state_space(event, opts);

	if(opts.appendix.test(appendix::ROOM_JOINED) && at<"type"_>(event) == "m.room.member")
		;//ret += _prefetch_room_joined(event, opts);

	if(opts.appendix.test(appendix::ROOM_REDACT) && json::get<"type"_>(event) == "m.room.redaction")
		ret += _prefetch_room_redact(event, opts);

	return ret;
}

// NOTE: QUERY
void
ircd::m::dbs::_index_room_redact(db::txn &txn,
                                 const event &event,
                                 const opts &opts)
{
	assert(opts.appendix.test(appendix::ROOM_REDACT));
	assert(json::get<"type"_>(event) == "m.room.redaction");

	const auto &target_id
	{
		at<"redacts"_>(event)
	};

	const m::event::idx target_idx
	{
		find_event_idx(target_id, opts)
	};

	if(unlikely(!target_idx))
	{
		log::dwarning
		{
			"Redaction from '%s' missing redaction target '%s'",
			string_view{event.event_id},
			target_id
		};

		if(opts.appendix.test(appendix::EVENT_HORIZON))
			_index_event_horizon(txn, event, opts, target_id);

		return;
	}

	char state_key_buf[event::STATE_KEY_MAX_SIZE];
	const string_view &state_key
	{
		m::get(std::nothrow, target_idx, "state_key", state_key_buf)
	};

	if(!state_key)
		return;

	char type_buf[event::TYPE_MAX_SIZE];
	const string_view &type
	{
		m::get(std::nothrow, target_idx, "type", type_buf)
	};

	assert(!empty(type));
	const ctx::critical_assertion ca;
	thread_local char buf[ROOM_STATE_SPACE_KEY_MAX_SIZE];
	const string_view &key
	{
		room_state_key(buf, at<"room_id"_>(event), type, state_key)
	};

	db::txn::append
	{
		txn, room_state,
		{
			db::op::DELETE,
			key,
		}
	};
}

size_t
ircd::m::dbs::_prefetch_room_redact(const event &event,
                                    const opts &opts)
{
	assert(opts.appendix.test(appendix::ROOM_REDACT));
	assert(json::get<"type"_>(event) == "m.room.redaction");

	const auto &target_id
	{
		at<"redacts"_>(event)
	};

	// If the prefetch was launched we can't do anything more here.
	if(prefetch_event_idx(target_id, opts))
		return 1;

	// If the result is cached we can peek at it for more prefetches.
	const m::event::idx target_idx
	{
		find_event_idx(target_id, opts)
	};

	if(unlikely(!target_idx))
		return 0;

	size_t ret(0);
	ret += m::prefetch(target_idx, "state_key");
	ret += m::prefetch(target_idx, "type");
	return ret;
}

// NOTE: QUERY
size_t
ircd::m::dbs::find_event_idx(const vector_view<event::idx> &idx,
                             const vector_view<const event::id> &event_id,
                             const opts &wopts)
{
	const size_t num
	{
		std::min(idx.size(), event_id.size())
	};

	size_t ret(0);
	if(wopts.interpose)
		for(size_t i(0); i < num; ++i)
		{
			idx[i] = wopts.interpose->val(db::op::SET, "_event_idx", event_id[i], 0UL);
			assert(!idx[i] || idx[i] >= vm::sequence::retired);
			ret += idx[i] != 0;
		}

	// Taken when everything satisfied by interpose
	if(ret == num || !wopts.allow_queries)
		return ret;

	// Only do parallel m::index() if there's no results from the prior
	// queries; they'll get clobbered by the parallel m::index().
	if(likely(!ret))
		return m::index(idx, event_id);

	// Fallback to serial queries.
	for(size_t i(0); i < num; ++i)
	{
		idx[i] = m::index(std::nothrow, event_id[i]);
		ret += idx[i] != 0;
	}

	return ret;
}

size_t
ircd::m::dbs::prefetch_event_idx(const vector_view<const event::id> &event_id,
                                 const opts &wopts)
{
	size_t ret(0);
	for(size_t i(0); i < event_id.size(); ++i)
	{
		if(wopts.interpose)
			if(wopts.interpose->has(db::op::SET, "_event_idx", event_id[i]))
				continue;

		if(wopts.allow_queries)
			ret += m::prefetch(event_id[i], "_event_idx");
	}

	return ret;
}