// Matrix Construct
//
// Copyright (C) Matrix Construct Developers, Authors & Contributors
// Copyright (C) 2016-2019 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.

#pragma once
#define HAVE_IRCD_DB_PREFETCHER_H

namespace ircd::db
{
	struct prefetcher extern *prefetcher;
}

struct ircd::db::prefetcher
{
	struct request;
	using closure = std::function<bool (request &)>;

	ctx::dock dock;
	std::deque<request> queue;
	ctx::context context;
	size_t cache_hits {0};
	size_t request_workers {0};
	size_t request_counter {0};
	size_t directs_counter {0};
	size_t handles_counter {0};
	size_t handled_counter {0};
	size_t fetches_counter {0};
	size_t fetched_counter {0};
	size_t cancels_counter {0};
	size_t fetched_bytes_key {0};
	size_t fetched_bytes_val {0};
	microseconds total_snd_req {0us};
	microseconds total_req_fin {0us};

	size_t wait_pending();
	void request_handle(request &);
	size_t request_cleanup() noexcept;
	void request_worker();
	void handle();
	void worker();

  public:
	size_t cancel(const closure &);
	size_t cancel(database &);         // Cancel all for db
	size_t cancel(column &);           // Cancel all for column

	bool operator()(column &, const string_view &key, const gopts &);

	prefetcher();
	~prefetcher() noexcept;
};

struct ircd::db::prefetcher::request
{
	database *d {nullptr};             // database instance
	uint32_t cid {0};                  // column ID
	uint32_t len {0};                  // length of key
	steady_point snd;                  // submitted by user
	steady_point req;                  // request sent to database
	steady_point fin;                  // result from database
	char key[208] alignas(16);         // key buffer

	explicit operator string_view() const noexcept;

	request(database &d, const column &c, const string_view &key) noexcept;
	request() = default;
};

static_assert
(
	sizeof(ircd::db::prefetcher::request) == 256,
	"struct ircd::db::prefetcher::request fell out of alignment"
);