#include <windows.h>
#include <stdio.h>
#include "currencyConverter.h"

//0 = pound, 1 = euro, 2 = dollar. 1st item = FROM, 2nd item = TO
const char currencies[3][7] = {"Pound", "Euro", "Dollar"};
const float conversions[3][3] = {{1.0, 1.4513, 1.873}, {0.6889, 1.0, 1.2903}, {0.534, 0.775, 1.0}};

float parseFloat (HWND hwnd, int itemID, BOOL &sucess);
void performConversion (HWND hwnd);
BOOL CALLBACK digCCEventListener (HWND hwnd, UINT event, WPARAM object, LPARAM lParam);

float parseFloat (HWND hwnd, int itemID, BOOL &success)
{
	
	float amount = 0.0f;
	int strLen = GetWindowTextLength(GetDlgItem(hwnd, itemID));	
	success = (strLen > 0);
	
	if (success) //Make sure something is typed
	{
		
		strLen++; //The original value does not include the NULL character
		//Reserves so many places in memory for the new char array
		char* buffer = (char*)GlobalAlloc(GPTR, strLen);

		//Gets the string and puts it in the buffer
		GetDlgItemText(hwnd, txtAmount, buffer, strLen);
		amount = atof(buffer); //Converts the string into a float
		GlobalFree((HANDLE)buffer); //Removes the array from memory
		
	}
	
	return amount;
	
}	
	
void performConversion (HWND hwnd)
{

	BOOL success;
	float amount = parseFloat(hwnd, txtAmount, success);
	
	if (!success)
	{
		MessageBox(hwnd, "Please enter a currency amount", "Missing fields", MB_OK | MB_ICONEXCLAMATION);
	}
	else if (amount < 0.01f)
	{
		MessageBox(hwnd, "Please only enter positive currency amounts", "Invalid range", MB_OK | MB_ICONEXCLAMATION);
	}
	else if (amount > 1000000.0f)
	{
		MessageBox(hwnd, "Please enter currency amounts under one million", "Invalid range", MB_OK | MB_ICONEXCLAMATION);
	}
	else
	{
							
		char strAnswer[15];
		unsigned short int fromIndex = SendMessage(GetDlgItem(hwnd, cboxFrom), CB_GETCURSEL, 0, 0);
		unsigned short int toIndex = SendMessage(GetDlgItem(hwnd, cboxTo), CB_GETCURSEL, 0, 0);
		float answer = amount * conversions[fromIndex][toIndex];					
		
		if (toIndex == 0)
		{
			sprintf(strAnswer, "£%7.2f", answer);
		}
		else if (toIndex == 1)
		{
			sprintf(strAnswer, "€%7.2f", answer);
		}
		else
		{
			sprintf(strAnswer, "$%7.2f", answer);
		}

		SetDlgItemText(hwnd, lblAnswer, strAnswer);
		
	}		
	
}	
	
BOOL CALLBACK digCCEventListener (HWND hwnd, UINT event, WPARAM object, LPARAM lParam)
{

	if (event == WM_INITDIALOG)
	{
		//Get a handle for the object to send messages to
		HWND handleCboxFrom = GetDlgItem(hwnd, cboxFrom);
		HWND handleCboxTo = GetDlgItem(hwnd, cboxTo);
		
		for (int i = 0; i < 3; i++)
		{
			
			SendMessage(handleCboxFrom, CB_ADDSTRING, 0, (LPARAM)(LPCTSTR)currencies[i]);
			SendMessage(handleCboxTo, CB_ADDSTRING, 0, (LPARAM)(LPCTSTR)currencies[i]);
			
		}

		//Set the selected item in the combo box, WPARAM = index, LPARAM = 0
		SendMessage(handleCboxFrom, CB_SETCURSEL, 0, 0);
		SendMessage(handleCboxTo, CB_SETCURSEL, 1, 0);
		
		SetDlgItemText(hwnd, txtAmount, "1.0");
		performConversion(hwnd);
		
	}
	else if (event == WM_COMMAND)
	{
		
		int objectID = LOWORD(object);	
		
		if (objectID == cmdConvert)
		{
			performConversion(hwnd);			
		}
		else if (objectID == cmdClose)
		{
			EndDialog(hwnd, objectID);
		}		
		
	}
	else if (event == WM_CLOSE)
	{		
		EndDialog(hwnd, object);
	}
	else
	{
		return false;
	}
	
	return true;

}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR args, int nCmdShow)
{
	return DialogBox(hInstance, MAKEINTRESOURCE(digCC), NULL, digCCEventListener);
}