// AUTHOR: Chris Wild
// DATE: July 25, 1997
#include "ListMsgs.h"

CListMsgs::CListMsgs(): size(0), head(NULL)
{
}

CListMsgs::CListMsgs(HANDLE listHandle)
{
	ReadListMsgs(listHandle);
}

CListMsgs::~CListMsgs()
{
	ListPtr temp;

	while(head != NULL) {
		temp = head;
		head = head->next;
		delete temp;
	}
}

bool CListMsgs::AddItem(int position, Item thisItem)
{
	if((position < 1)
		|| (position > size+1))
		return FALSE;	// bad position
	ListPtr newPtr = new ListNode;
	// should test for success
	newPtr->item = thisItem;
	if (position == 1) {
		newPtr->next = head;
		head = newPtr;
	}
	else {
		ListPtr prev = PtrTo(position-1);
		newPtr->next = prev->next;
		prev->next = newPtr;
	}
	size++;
	return TRUE;
}

bool CListMsgs::DeleteItem(int position)
{
	if((position < 1)
		|| (position > size))
		return FALSE;	// bad position
	ListPtr cur;
	size--;
	if(position == 1) {
		cur = head;
		head = head->next;
	}
	else {
		ListPtr prev = PtrTo(position-1);
		cur = prev->next;
		prev->next = cur->next;
	}
	return TRUE;
}

bool CListMsgs::GetItem(int position, Item& thisItem) const
{
	if((position < 1)
		|| (position > size))
		return FALSE;	// bad position
	ListPtr cur = PtrTo(position);
	thisItem = cur->item;
	return TRUE;
}

ListPtr CListMsgs::PtrTo(int position) const
{
	if( ( position < 1) ||
		( position > size))
		return NULL;
	ListPtr trav = head;
	for(int i = 1; i < position; i++)
		trav = trav->next;
	return trav;
}

//*******
// Read list of messages from archive
// deletes existing list first
// 
bool CListMsgs::ReadListMsgs(HANDLE messages)
{
	ListPtr cur;
	ListPtr prev = NULL;
	DWORD nBytes;

	while(head != NULL) {
		cur = head;
		head = head->next;
		delete cur;
	}
	size = 0;	// reset size

	while (TRUE) {
		cur = new ListNode;
		ReadFile(messages,
			&cur->item,
			sizeof(cur->item),
			&nBytes, NULL);
		if(nBytes == 0) {
			if (prev != NULL)
				prev->next = NULL;
			else
				head = NULL;
			delete cur;	// always allocates one too many
			break;
		}
		size++;
		if(prev == NULL) {
			head = cur;
		}
		else {
			prev->next = cur;
		}
		prev = cur;
	}
	return TRUE;
}


bool CListMsgs::WriteListMsgs(HANDLE messages) const
{
	DWORD nBytes;
	ListPtr trav = head;
	while(trav != NULL) {
		if(!WriteFile(messages,
			&trav->item,
			sizeof(trav->item),
			&nBytes, NULL)) 
			return FALSE;
		trav = trav->next;
	}
	return TRUE;
}

int CListMsgs::length() const
{
	return size;
}