#include "pch.h"
#include "Cache.h"

Cache::Cache(void)
{
	this->size = 0;
	this->head = NULL;
	this->tail = NULL;
}

Cache::~Cache(void)
{
}

void Cache::Empty(fz_context *mu_ctx)
{
	if (this != nullptr) {
		cache_entry_t *curr_entry = this->head;

		while (curr_entry != NULL)
		{
			cache_entry_t *old_entry = curr_entry;
			curr_entry = old_entry->next;
			fz_drop_display_list(mu_ctx, old_entry->dlist);
			delete old_entry;
		}
		this->size = 0;
		this->head = NULL;
		this->tail = NULL;
	}
}

void Cache::AddEntry(int value, fz_display_list *dlist, fz_context *mu_ctx)
{
	std::lock_guard<std::mutex> lock(cache_lock);

	/* If full, then delete the tail */
	if (size >= MAX_DISPLAY_CACHE_SIZE)
	{
		cache_entry_t *curr_entry = this->tail;
		cache_entry_t *prev_entry = curr_entry->prev;

		if (prev_entry != NULL)
			prev_entry->next = NULL;
		else
			head = NULL;

		tail = prev_entry;

		/* Decrement the caches rc of this list */
		fz_drop_display_list(mu_ctx, curr_entry->dlist);
		delete curr_entry;
		size--;
	}

	/* Make a new entry and stick at head */
	cache_entry_t *new_entry = new cache_entry_t;

	new_entry->dlist = dlist;
	new_entry->index = value;
	new_entry->prev = NULL;
	if (head == NULL)
	{
		new_entry->next = NULL;
		head = new_entry;
		tail = new_entry;
	}
	else
	{
		new_entry->next = head;
		head->prev = new_entry;
		head = new_entry;
	}
	size++;
	/* We are going to use this item now */
	fz_keep_display_list(mu_ctx, new_entry->dlist);
}

fz_display_list* Cache::UseEntry(int value, fz_context *mu_ctx)
{
	std::lock_guard<std::mutex> lock(cache_lock);
	cache_entry_t *curr_entry = this->head;

	while (curr_entry != NULL)
	{
		if (curr_entry->index == value)
			break;
		curr_entry = curr_entry->next;
	}
	if (curr_entry != NULL)
	{
		fz_keep_display_list(mu_ctx, curr_entry->dlist);
		/* Move this to the front */
		if (curr_entry != head)
		{
			cache_entry_t *prev_entry = curr_entry->prev;
			cache_entry_t *next_entry = curr_entry->next;
			prev_entry->next = next_entry;

			if (next_entry != NULL)
				next_entry->prev = prev_entry;
			else
				tail = prev_entry;

			curr_entry->prev = NULL;
			curr_entry->next = head;
			head->prev = curr_entry;
			head = curr_entry;
		}
		return curr_entry->dlist;
	}
	else
		return NULL;
}