#include <stdlib.h>
#include <string.h>
#include "stack.h"
#include "bintree.h"

// internal helper to push node and all its left descendants onto iterator stack
static void bintree_pushLefts(StackNode **iterStackPtr, TreeNode *n)
{
    while(n != NULL)
    {
        *iterStackPtr = push(*iterStackPtr, n);
        n = n->left;
    }
}

// Adds a copy of data's pointer destination to the tree using compareFct for ordering. Accepts duplicates
// if isDuplicate is NULL, otherwise ignores duplicates and sets isDuplicate to 1 (or to 0 if a new entry is added).
TreeNode *addToTree(TreeNode *root, const void *data, size_t dataSize, CompareFctType compareFct, int *isDuplicate)
{
    if(isDuplicate != NULL)
        *isDuplicate = 0;

    if(root == NULL)
    {
        TreeNode *node = (TreeNode *)malloc(sizeof(TreeNode));
        if(node == NULL)
            return NULL;
        node->data = malloc(dataSize);
        if(node->data == NULL)
        {
            free(node);
            return NULL;
        }
        memcpy(node->data, data, dataSize);
        node->left = node->right = NULL;
        return node;
    }

    int cmp = compareFct(data, root->data);
    if(cmp < 0)
    {
        root->left = addToTree(root->left, data, dataSize, compareFct, isDuplicate);
    }
    else if(cmp > 0)
    {
        root->right = addToTree(root->right, data, dataSize, compareFct, isDuplicate);
    }
    else // equal
    {
        if(isDuplicate != NULL)
        {
            *isDuplicate = 1;
            // do not insert duplicate
        }
        else
        {
            // duplicates allowed -> insert into right subtree
            root->right = addToTree(root->right, data, dataSize, compareFct, isDuplicate);
        }
    }

    return root;
}

// Iterates over the tree given by root. Follows the usage of strtok. If tree is NULL, the next entry of the last tree given is returned in ordering direction.
// Use your implementation of a stack to organize the iterator. Push the root node and all left nodes first. On returning the next element,
// push the top node and push all its left nodes.
void *nextTreeData(TreeNode *root)
{
    static StackNode *iterStack = NULL;

    // If a new tree root is provided -> reset iterator
    if(root != NULL)
    {
        clearStack(iterStack);
        iterStack = NULL;
        bintree_pushLefts(&iterStack, root);
    }

    if(iterStack == NULL)
        return NULL;

    TreeNode *node = (TreeNode *)top(iterStack);
    iterStack = pop(iterStack);

    if(node->right != NULL)
        bintree_pushLefts(&iterStack, node->right);

    return node->data;
}

// Releases all memory resources (including data copies).
void clearTree(TreeNode *root)
{
    if(root == NULL)
        return;

    clearTree(root->left);
    clearTree(root->right);

    free(root->data);
    free(root);
}

// Returns the number of entries in the tree given by root.
unsigned int treeSize(const TreeNode *root)
{
    if(root == NULL)
        return 0;
    return 1 + treeSize(root->left) + treeSize(root->right);
}