// Copyright (c) 2008, Rodrigo Braz Monteiro
// All rights reserved.
//
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//     this list of conditions and the following disclaimer.
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// Aegisub Project http://www.aegisub.org/
//
// $Id$

/// @file video_provider_cache.cpp
/// @brief Aggregate video provider caching previously requested frames
/// @ingroup video_input
///

#include "config.h"
#include "main.h"

#include "video_provider_cache.h"

/// DOCME
/// @class CachedFrame
/// @brief DOCME
///
/// DOCME
struct CachedFrame {
	/// DOCME
	AegiVideoFrame frame;

	/// DOCME
	int n;
};

/// @brief Constructor 
/// @param parent 
///
VideoProviderCache::VideoProviderCache(VideoProvider *parent)
: master(parent)
, cacheMax(OPT_GET("Provider/Video/Cache/Size")->GetInt() << 20) // convert MB to bytes
{
}

/// @brief Destructor 
///
VideoProviderCache::~VideoProviderCache() {
	while (cache.size()) {
		cache.front().frame.Clear();
		cache.pop_front();
	}
}

/// @brief Get frame 
/// @param n 
/// @return 
///
const AegiVideoFrame VideoProviderCache::GetFrame(int n) {
	// See if frame is cached
	CachedFrame cached;
	for (std::list<CachedFrame>::iterator cur=cache.begin();cur!=cache.end();cur++) {
		cached = *cur;
		if (cached.n == n) {
			cache.erase(cur);
			cache.push_back(cached);
			return cached.frame;
		}
	}

	// Not cached, retrieve it
	const AegiVideoFrame frame = master->GetFrame(n);
	const AegiVideoFrame *srcFrame = &frame;

	// Cache frame
	Cache(n,*srcFrame);
	return *srcFrame;
}

/// @brief Add to cache 
/// @param n     
/// @param frame 
void VideoProviderCache::Cache(int n,const AegiVideoFrame frame) {
	// Cache full, use frame at front
	if (GetCurCacheSize() >= cacheMax) {
		cache.push_back(cache.front());
		cache.pop_front();
	}

	// Cache not full, insert new one
	else {
		cache.push_back(CachedFrame());
	}

	// Cache
	cache.back().n = n;
	cache.back().frame.CopyFrom(frame);
}

/// @brief Get the current size of the cache
/// @return Returns the size in bytes
unsigned VideoProviderCache::GetCurCacheSize() {
	int sz = 0;
	for (std::list<CachedFrame>::iterator i = cache.begin(); i != cache.end(); i++)
		sz += i->frame.memSize;
	return sz;
}