// C program for Huffman Coding
#include <stdio.h>
#include <stdlib.h>

// This constant can be avoided by explicitly
// calculating height of Huffman Tree
#define MAX_TREE_HT 100

// A Huffman tree node
struct MinHeapNode {

    // One of the input characters
    char data;

    // Frequency of the character
    unsigned freq;

    // Left and right child of this node
    struct MinHeapNode *left, *right;
};

// A Min Heap:  Collection of
// min-heap (or Huffman tree) nodes
struct MinHeap {

    // Current size of min heap
    unsigned size;

    // capacity of min heap
    unsigned capacity;

    // Array of minheap node pointers
    struct MinHeapNode **array;
};

// A utility function allocate a new
// min heap node with given character
// and frequency of the character
struct MinHeapNode *newNode(char data, unsigned freq) {
    struct MinHeapNode *temp
            = (struct MinHeapNode *) malloc
                    (sizeof(struct MinHeapNode));

    temp->left = temp->right = NULL;
    temp->data = data;
    temp->freq = freq;

    return temp;
}

// A utility function to create
// a min heap of given capacity
struct MinHeap *createMinHeap(unsigned capacity) {

    struct MinHeap *minHeap
            = (struct MinHeap *) malloc(sizeof(struct MinHeap));

    // current size is 0
    minHeap->size = 0;

    minHeap->capacity = capacity;

    minHeap->array
            = (struct MinHeapNode **) malloc(minHeap->
            capacity * sizeof(struct MinHeapNode *));
    return minHeap;
}

// A utility function to
// swap two min heap nodes
void swapMinHeapNode(struct MinHeapNode **a,
                     struct MinHeapNode **b) {

    struct MinHeapNode *t = *a;
    *a = *b;
    *b = t;
}

// The standard minHeapify function.
void minHeapify(struct MinHeap *minHeap, int idx) {

    int smallest = idx;
    int left = 2 * idx + 1;
    int right = 2 * idx + 2;

    if (left < minHeap->size && minHeap->array[left]->
            freq < minHeap->array[smallest]->freq)
        smallest = left;

    if (right < minHeap->size && minHeap->array[right]->
            freq < minHeap->array[smallest]->freq)
        smallest = right;

    if (smallest != idx) {
        swapMinHeapNode(&minHeap->array[smallest],
                        &minHeap->array[idx]);
        minHeapify(minHeap, smallest);
    }
}

// A utility function to check
// if size of heap is 1 or not
int isSizeOne(struct MinHeap *minHeap) {

    return (minHeap->size == 1);
}

// A standard function to extract
// minimum value node from heap
struct MinHeapNode *extractMin(struct MinHeap *minHeap) {

    struct MinHeapNode *temp = minHeap->array[0];
    minHeap->array[0]
            = minHeap->array[minHeap->size - 1];

    --minHeap->size;
    minHeapify(minHeap, 0);

    return temp;
}

// A utility function to insert
// a new node to Min Heap
void insertMinHeap(struct MinHeap *minHeap,
                   struct MinHeapNode *minHeapNode) {

    ++minHeap->size;
    int i = minHeap->size - 1;

    while (i && minHeapNode->freq < minHeap->array[(i - 1) / 2]->freq) {

        minHeap->array[i] = minHeap->array[(i - 1) / 2];
        i = (i - 1) / 2;
    }

    minHeap->array[i] = minHeapNode;
}

// A standard function to build min heap
void buildMinHeap(struct MinHeap *minHeap) {

    int n = minHeap->size - 1;
    int i;

    for (i = (n - 1) / 2; i >= 0; --i)
        minHeapify(minHeap, i);
}

// A utility function to print an array of size n
void printArr(int arr[], int n) {
    int i;
    for (i = 0; i < n; ++i)
        printf("%d", arr[i]);

    printf("\n");
}

// Utility function to check if this node is leaf
int isLeaf(struct MinHeapNode *root) {

    return !(root->left) && !(root->right);
}

// Creates a min heap of capacity
// equal to size and inserts all character of
// data[] in min heap. Initially size of
// min heap is equal to capacity
struct MinHeap *createAndBuildMinHeap(char data[], int freq[], int size) {

    struct MinHeap *minHeap = createMinHeap(size);

    for (int i = 0; i < size; ++i)
        minHeap->array[i] = newNode(data[i], freq[i]);

    minHeap->size = size;
    buildMinHeap(minHeap);

    return minHeap;
}

// The main function that builds Huffman tree
struct MinHeapNode *buildHuffmanTree(char data[], int freq[], int size) {
    struct MinHeapNode *left, *right, *top;

    // Step 1: Create a min heap of capacity
    // equal to size.  Initially, there are
    // modes equal to size.
    struct MinHeap *minHeap = createAndBuildMinHeap(data, freq, size);

    // Iterate while size of heap doesn't become 1
    while (!isSizeOne(minHeap)) {

        // Step 2: Extract the two minimum
        // freq items from min heap
        left = extractMin(minHeap);
        right = extractMin(minHeap);

        // Step 3:  Create a new internal
        // node with frequency equal to the
        // sum of the two nodes frequencies.
        // Make the two extracted node as
        // left and right children of this new node.
        // Add this node to the min heap
        // '$' is a special value for internal nodes, not used
        top = newNode('$', left->freq + right->freq);

        top->left = left;
        top->right = right;

        insertMinHeap(minHeap, top);
    }

    // Step 4: The remaining node is the
    // root node and the tree is complete.
    return extractMin(minHeap);
}

// Prints huffman codes from the root of Huffman Tree.
// It uses arr[] to store codes
void printCodes(struct MinHeapNode *root, int arr[], int top) {

    // Assign 0 to left edge and recur
    if (root->left) {

        arr[top] = 0;
        printCodes(root->left, arr, top + 1);
    }

    // Assign 1 to right edge and recur
    if (root->right) {

        arr[top] = 1;
        printCodes(root->right, arr, top + 1);
    }

    // If this is a leaf node, then
    // it contains one of the input
    // characters, print the character
    // and its code from arr[]
    if (isLeaf(root)) {

        printf("%c: ", root->data);
        printArr(arr, top);
    }
}

// The main function that builds a
// Huffman Tree and print codes by traversing
// the built Huffman Tree
void HuffmanCodes(char data[], int freq[], int size) {
    // Construct Huffman Tree
    struct MinHeapNode *root
            = buildHuffmanTree(data, freq, size);

    // Print Huffman codes using
    // the Huffman tree built above
    int arr[MAX_TREE_HT], top = 0;

    printCodes(root, arr, top);
}

// Driver program to test above functions
int main() {
    FILE *fp;

    fp = fopen("/home/tj/CLionProjects/untitled/test.txt", "r");
    if (fp == NULL) {
        printf("file does not exist");
        exit(1);
    }

    /* a buffer to hold the count of characters 0,...,256; it is
     * initialized to zero on every element */
    int count[256] = {0};

    char words[256];

    int freq[256];
    /* loop counter */
    int k;

    /* a holder for each character (stored as int) */
    int c;
    int counter =0;

    /* for as long as we can get characters... */
    while ((c = fgetc(fp))) {

        /* break if end of file */
        if (c == EOF) break;

        /* otherwise add one to the count of that particular character */
        count[c] += 1;
        counter++;
    }

    /* now print the results; only if the count is different from
     * zero */
    for (k = 0; k < 256; k++) {
        if (count[k] > 0) {
            words[k] = k;
            freq[k] = count[k];
            printf("char %c occurs %d times\n", k, count[k]);
        }
    }
/* close the file */
    fclose(fp);

    int size = sizeof(words) / sizeof(words[0]);

    HuffmanCodes(words, count, size);

    return 0;
}