/**
 * \file
 * \brief Source code for the Cache class
 * \author Copyright (c) 2011 Jonathan Thomas
 */

#include "../include/Cache.h"

using namespace std;
using namespace openshot;

// Default constructor, max frames to cache is 20
Cache::Cache() : max_frames(20) { };

// Constructor that sets the max frames to cache
Cache::Cache(int max_frames) : max_frames(max_frames) { };

// Add a Frame to the cache
void Cache::Add(int frame_number, Frame frame)
{
	// Only add frame if it does not exist in the cache
	if (!frames.count(frame_number))
	{
		// Add frame to queue and map
		frames[frame_number] = frame;
		frame_numbers.push(frame_number);

		// Clean up older frames (that exceed the max frames)
		CleanUp();
	}
	else
	{
		// Frame already exists... so just update the cache
		frames.erase(frame_number);
		frames[frame_number] = frame;
	}
}

// Check for the existance of a frame in the cache
bool Cache::Exists(int frame_number)
{
	// Is frame number cached
	if (frames.count(frame_number))
		return true;
	else
		return false;
}

// Return the front frame and remove it
Frame Cache::Pop()
{
	// Remove the oldest frame
	int frame_to_remove = frame_numbers.front();

	// Get the front frame
	Frame f = GetFrame(frame_to_remove);

	// Remove frame_number and frame
	frame_numbers.pop();
	frames.erase(frame_to_remove);

	// Return the frame
	return f;
}

// Get a frame from the cache
Frame Cache::GetFrame(int frame_number)
{
	// Does frame exists in cache?
	if (Exists(frame_number))
	{
		// return the Frame object
		return frames[frame_number];
	}
	else
		// throw an exception for the missing frame
		throw OutOfBoundsFrame("Frame not found in the cache", frame_number, -1);
}

// Get the front frame in this cache
Frame Cache::GetFront()
{
	// Return oldest frame in the cache
	return GetFrame(frame_numbers.front());
}

// Clear the cache of all frames
void Cache::Clear()
{
	// clear map
	frames.clear();

	// pop each of the frames from the queue... which emptys the queue
	while(!frame_numbers.empty()) frame_numbers.pop();
}

// Count the frames in the queue
int Cache::Count()
{
	// Return the number of frames in the cache
	return frames.size();
}

// Clean up cached frames that exceed the number in our max_frames variable
void Cache::CleanUp()
{
	// check against max size
	if (frame_numbers.size() > max_frames)
	{
		// Remove the oldest frame
		int frame_to_remove = frame_numbers.front();

		// Remove frame_number and frame
		frame_numbers.pop();
		frames.erase(frame_to_remove);
	}
}

// Display the list of cache and clear the cache (mainly for debugging reasons)
void Cache::DisplayAndClear()
{
	cout << "----- Cache List (" << frames.size() << ") ------" << endl;
	int i = 1;
	while(!frame_numbers.empty())
	{
		// Print the frame number
		int frame_number = frame_numbers.front();
		cout << " " << i << ") --- Frame " << frame_number << endl;

		// Remove this frame
		frame_numbers.pop();
		frames.erase(frame_number);

		// increment counter
		i++;
	}
}