/* $Id$ */
/*
   Copyright (C) 2003 by David White <dave@whitevine.net>
   Copyright (C) 2005 - 2010 by Yann Dirson <ydirson@altern.org>
   Part of the Battle for Wesnoth Project http://www.wesnoth.org/

   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 2 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.

   See the COPYING file for more details.
*/
/**
 *  @file
 *  Generate random numbers.
 *
 *  There are various ways to get a random number.
 *  rand()              This can be used for things that never are send over the
 *                      network e.g. generate a random map (the final result the
 *                      map is send, but the other players don't need to generate
 *                      the map.
 *
 *  get_random()        A random generator which is synchronized over the network
 *                      this only seems to work when it's used by 1 player at the
 *                      same time. It's synchronized after an event so if an event
 *                      runs at two clients at the same time it gets out of sync
 *                      and sets the entire game out of sync.
 *
 *  game_state::get_random()
 *                      A random generator which is seeded by the host of an MP
 *                      game. This generator is (not yet) synchronized over the
 *                      network. It's only used by [set_variable]rand=. The map
 *                      designer has to make sure it stays in sync. This
 *                      generator can be used at the same time at multiple client
 *                      since the generators are always in sync.
 */

#include "global.hpp"

#include "config.hpp"
#include "log.hpp"
#include "network.hpp"
#include "random.hpp"
#include "rng.hpp"
#include "serialization/string_utils.hpp"
#include "simple_rng.hpp"
#include "util.hpp"

static lg::log_domain log_random("random");
#define DBG_RND LOG_STREAM(debug, log_random)
#define LOG_RND LOG_STREAM(info, log_random)
#define WRN_RND LOG_STREAM(warn, log_random)
#define ERR_RND LOG_STREAM(err, log_random)

namespace {
  rand_rng::rng *random_generator = NULL ;
  int last_seed;
  bool seed_valid = false;
  boost::function<void (int)> new_seed_callback;
}


int get_random()
{
  assert(random_generator!=NULL);
  int r = random_generator->get_random();
  return r ;
}

int get_random_nocheck()
{
  assert(random_generator!=NULL);
  int r = random_generator->get_random_nocheck();
  return r ;
}

const config* get_random_results()
{
  assert(random_generator!=NULL);
  return random_generator->get_random_results();
}


void set_random_results(const config& cfg)
{
  assert(random_generator!=NULL);
  random_generator->set_random_results(cfg);
}


namespace rand_rng
{

void set_seed(int seed)
{
	LOG_RND << "set_seed with " << seed << "\n";
	assert(random_generator!=NULL);
	last_seed = seed;
	seed_valid = true;
	random_generator->set_seed(seed);
	if (new_seed_callback) {
		LOG_RND << "set_seed calling new_seed_callback\n";
		new_seed_callback(seed);
	}
}

void invalidate_seed()
{
	LOG_RND << "invalidate_seed\n";
	assert(random_generator!=NULL);
	last_seed = rand() & 0x7FFFFFFF;
	if (has_valid_seed()) { //aka SRNG is disabled
		random_generator->set_seed(last_seed);
	}
	seed_valid = false;
}

bool has_valid_seed()
{
	//if we're in a SP game the seed is always valid
	return (network::nconnections() == 0) || seed_valid;
}

int get_last_seed()
{
	return last_seed;
}

void set_new_seed_callback(boost::function<void (int)> f)
{
	DBG_RND << "set_new_seed_callback\n";
	new_seed_callback = f;
}

void clear_new_seed_callback()
{
	DBG_RND << "clear_new_seed_callback\n";
	new_seed_callback = NULL;
}



rng::rng() : random_(NULL), random_child_(0), generator_()
{
}

int rng::get_random()
{
	return get_random_private(true);
}

int rng::get_random_nocheck()
{
	return get_random_private(false);
}

int rng::get_random_private(bool check)
{
	if (!random_) {
		int r = generator_.get_next_random();
		LOG_RND << "get_random() returning " << r << " (random_ is null)\n";
		return r;
	}

	size_t random_size = random_->child_count("random");
	if (random_child_ >= random_size) {
		random_child_ = random_size + 1;
		int res = generator_.get_next_random() & 0x7FFFFFFF;
		(random_->add_child("random"))["value"] = res;
		LOG_RND << "get_random() returning " << res << " (added to random_)\n";
		return res;
	} else {
		int mine = generator_.get_next_random();
		int stored = random_->child("random", random_child_++)["value"];
		if (mine != stored) {
			if (check) {
				ERR_RND << "Random number mismatch, mine " << mine << " vs " << stored << "\n";
				//OOS here?
			} else {
				LOG_RND << "Random number mismatch (nocheck), mine " << mine << " vs " << stored << "\n";
			}
		}
		LOG_RND << "get_random() returning " << stored << "\n";
		return stored;
	}
}

const config* rng::get_random_results()
{
	assert(random_ != NULL);

	if (random_child_ <= 0 ||random_child_ > random_->child_count("random")) return NULL;
	const config &res = random_->child("random", random_child_ - 1).child("results");
	return res ? &res : NULL;
}

void rng::set_random_results(const config& cfg)
{
	assert(random_ != NULL);

	if (random_child_ <= 0 ||random_child_ > random_->child_count("random")) return;
	config &r = random_->child("random", random_child_ - 1);
	r.clear_children("results");
	r.add_child("results", cfg);
}

config* rng::random()
{
	return random_;
}

void rng::set_random(config* random)
{
	random_ = random;
	random_child_ = 0;
	return;
}

void rng::set_seed(int seed)
{
	LOG_RND << "Set random seed to " << seed << "\n";
	generator_.seed_random(seed, 0);
}


set_random_generator::set_random_generator(rng* r) : old_(random_generator)
{
	random_generator = r;
}

set_random_generator::~set_random_generator()
{
	random_generator = old_;
}

simple_rng::simple_rng() :
    random_seed_(rand()),
    random_pool_(random_seed_),
    random_calls_(0)
{
}

simple_rng::simple_rng(const config& cfg) :
    /**
	 * @todo  older savegames don't have random_seed stored, evaluate later
     * whether default can be removed again. Look after branching 1.5.
	 */
    random_seed_(cfg["random_seed"].to_int(42)),
    random_pool_(random_seed_),
    random_calls_(0)
{
}

int simple_rng::get_next_random()
{
	random_next();
	++random_calls_;
	DBG_RND << "pulled user random " << random_pool_
		<< " for call " << random_calls_
		<< " with seed " << random_seed_ << '\n';

	return (static_cast<unsigned>(random_pool_ / 65536) % 32768);
}

void simple_rng::seed_random(const unsigned call_count)
{
    seed_random(random_seed_, call_count);
}

void simple_rng::seed_random(const int seed, const unsigned call_count)
{
	random_pool_ = seed;
	random_seed_ = seed;
	for(random_calls_ = 0; random_calls_ < call_count; ++random_calls_) {
		random_next();
	}
	DBG_RND << "Seeded random with " << random_seed_ << " with "
		<< random_calls_ << " calls, pool is now at "
		<< random_pool_ << '\n';
}

void simple_rng::random_next()
{
	// Use the simple random generator as shown in man rand(3).
	// The division is done separately since we also want to
	// quickly go the the wanted index in the random list.
	random_pool_ = random_pool_ * 1103515245 + 12345;
}


} // ends rand_rng namespace