/******************************************************
Name: 

Filename: Create.cpp
******************************************************/
#include "Tree.h"

// The following function will read a double from a string

char* GetDouble(char *expression, double *result)
{
	char *c_expr=expression;
	double c_val=0;
// Compute integer part
	while ((*c_expr>='0') && (*c_expr<='9'))
	{
		c_val= c_val*10 + (*c_expr - '0');
		c_expr++;
	}
	if (*c_expr=='.') // we have a decimal part
	{
// Compute decimal part
		double c_mult=0.1;
		c_expr++;
		while ((*c_expr>='0') && (*c_expr<='9'))
		{
			c_val+= c_mult * (*c_expr - '0');
			c_expr++;
			c_mult*=0.1;
		}
	}
// Set result
	*result=c_val;
// Check for errors	
	if(c_expr==expression)
	{
		return NULL;
	}
// All ok!	
	return c_expr;
}

// Forward declaration of function HandleSum is needed because it is used from HandleProduct

char *HandleSum(char *expression, CTree **tree);

// Will handle an expression substring considering it a product
// Return value: the new position in the evaluated expression
// Will set the computed expression tree in variable "tree"

char *HandleProduct(char *expression, CTree **tree)
{
	char *c_expr=expression;
	CTree *head=new CTree;
	
	if(head==NULL)
	{
		return NULL;
	}
	
// Creating subtree for the first part of the product in head->left
	if(*c_expr=='(') // Open parenthesis
	{
		c_expr++;
		c_expr=HandleSum(c_expr,&head->left); // compute the tree for the sum in the paranthesis
		if(c_expr==NULL)
		{
			return NULL;
		}
		if(*c_expr!=')') // Parenthesis needs to be closed
		{
			return NULL;
		}
		c_expr++;
	}
	else
	{
		c_expr=GetDouble(c_expr,&head->value); // No paranthesis, we have just a value
		if(c_expr==NULL)
		{
			return NULL;
		}
	}
	
// Checking if we have a second part
	if(*c_expr!='*')
	{
		// We don't have a second part
		if(head->left!=NULL) // If we have already computed a subtree return this
		{
			*tree=head->left;
			delete(head);
		}
		else // Otherwise return a leaf
		{
			head->type=TYPE_LEAF;
			*tree=head;
		}
		return c_expr;
	}

// Creating subtree for the first part of the product in head->right
	c_expr++;	
	head->type=TYPE_MULTIPLY_NODE;
	if(head->left==NULL) // We have a second part of the product so put first(left) part in a subtree if not already so
	{
		head->left=new CTree;
		head->left->type=TYPE_LEAF;
		head->left->value=head->value;
	}
	c_expr=HandleProduct(c_expr,&head->right); // Computing second part subtree
	if(c_expr==NULL)
	{
		return NULL;
	}

// Returning results
	*tree=head;	
	return c_expr;
}

// Will handle an expression substring considering it a sum
// Return value: the new position in the evaluated expression
// Will set the computed expression tree in variable "tree"

char *HandleSum(char *expression, CTree **tree)
{
	char *c_expr=expression;
	CTree *head=new CTree;

	if(head==NULL)
	{
		return NULL;
	}
	
// Creating subtree for the first part of the sum in head->left
	c_expr=HandleProduct(c_expr,&head->left);
	if(c_expr==NULL)
	{
		return NULL;
	}

// Checking if we have a second part
	if(*c_expr!='+')
	{
		// We don't have a second part
		*tree=head->left;
		delete(head);
		return c_expr;
	}

// Creating subtree for the second part of the sum in head->right
	
	head->type=TYPE_ADD_NODE;
	c_expr++;	
	c_expr=HandleSum(c_expr,&head->right);
	if(c_expr==NULL)
	{
		return NULL;
	}

// Returning results
	*tree=head;	
	return c_expr;
}