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

// 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 (data == NULL || compareFct == NULL)
        return root;

    if (root == NULL)
    {
        // neuer Knoten
        TreeNode *node = 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  = NULL;
        node->right = NULL;

        if (isDuplicate != NULL)
            *isDuplicate = 0;

        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
    {
        // Element bereits vorhanden
        if (isDuplicate != NULL)
        {
            *isDuplicate = 1;
            // Duplikate werden ignoriert
        }
        else
        {
            // Duplikate dürfen eingefügt werden -> wir hängen sie z.B. links an
            root->left = addToTree(root->left, data, dataSize, compareFct, NULL);
        }
    }

    return root;
}

// Interner Stack für die Traversierung (strtok-ähnliches Verhalten)
static StackNode *iterStack = NULL;

// Hilfsfunktion: legt ab start alle linken Knoten auf den Stack
static void pushLeftPath(TreeNode *start)
{
    while (start != NULL)
    {
        iterStack = push(iterStack, start);
        start = start->left;
    }
}

// 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)
{
    if (root != NULL)
    {
        // neue Traversierung starten: alten Stack aufräumen
        if (iterStack != NULL)
        {
            clearStack(iterStack);
            iterStack = NULL;
        }
        pushLeftPath(root);
    }

    if (iterStack == NULL)
        return NULL;

    // Nächsten Knoten holen
    TreeNode *node = (TreeNode *)top(iterStack);
    iterStack = pop(iterStack);

    // rechten Teilbaum dieses Knotens auf den Stack bringen
    if (node->right != NULL)
        pushLeftPath(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 1u + treeSize(root->left) + treeSize(root->right);
}