#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "imageInput.h"

#define BUFFER_SIZE 100
#define FILE_HEADER_STRING "__info2_image_file_format__"

// TODO Implementieren Sie geeignete Hilfsfunktionen für das Lesen der Bildserie aus einer Datei
//Hilfsfunktion zum Einlesen eines einzigen Bildes
static int read_single_image(FILE *file, unsigned short width, unsigned short height, GrayScaleImage *img, unsigned char *out_label)
{
    size_t pixels_to_read = (size_t)width * height;

    img->width = width; //save width and height read from file in struct
    img->height = height;

    img->buffer = malloc(pixels_to_read * sizeof(GrayScalePixelType)); //allocating needed memory for pixel-buffer 
    if(img->buffer == NULL) //Error case
    {
        printf("%s", "Fehler bei der Speicherreservierung!\n");
        return 0;
    }

    
    if(fread(img->buffer, sizeof(GrayScalePixelType), pixels_to_read, file) != pixels_to_read) //read all pixels one after another
    {
        free(img->buffer); //Error case: free allocated memory
        return 0;
    }
    
    
    if(fread(out_label, sizeof(unsigned char), 1, file) != 1) //read label
    {
        free(img->buffer); //Error case: free allocated memory
        return 0;
    }

    return 1; 
}



// TODO Vervollständigen Sie die Funktion readImages unter Benutzung Ihrer Hilfsfunktionen
GrayScaleImageSeries *readImages(const char *path)
{
    char buffer[BUFFER_SIZE];
    unsigned short num_images;
    unsigned short width;
    unsigned short height;

    
    
    FILE *file = fopen(path, "rb"); 
    
    if(file == NULL) //file can not be opened 
    {
        return NULL;        
    }

    /*********************************************************************************
     * VERIFY IF HEADER FILE IS INCLUDED
     ********************************************************************************/
    fread(buffer, sizeof(buffer[0]), strlen(FILE_HEADER_STRING), file);
    buffer[strlen(FILE_HEADER_STRING)] = '\0';

    if(strcmp(buffer, FILE_HEADER_STRING) != 0) //file does not include file header
    {
        fclose(file);
        return NULL;
    }

    /*********************************************************************************
     * READ AMOUNT, WIDTH, HEIGHT 
     ********************************************************************************/
    fread(&num_images, sizeof(num_images), 1, file);
    fread(&width, sizeof(width), 1, file);
    fread(&height, sizeof(height), 1, file);


    /*********************************************************************************
     * MEMORY ALLOCATION FOR SERIES
     ********************************************************************************/
    GrayScaleImageSeries *series = malloc(sizeof(GrayScaleImageSeries));
    if(series == NULL) //Error: memory cannot be allocated; close file
    {
        fclose(file);
        return NULL;
    }

    series->count = num_images; //save number of images in struct 
    series->images = malloc(num_images * sizeof(GrayScaleImage)); //allocate memory for all images
    series->labels = malloc(num_images * sizeof(unsigned char)); //allocate memory for all labels

    if(series->images == NULL || series->labels == NULL) //Error: memory cannot be allocated: free every memory
    {
        free(series->images);
        free(series->labels);
        free(series);
        
        fclose(file);
        return NULL;
    }


    /*********************************************************************************
     * READ IMAGES
     ********************************************************************************/

    for(int i = 0; i < num_images; i++)
    {
        if(read_single_image(file, width, height, &series->images[i], &series->labels[i]) != 1)
        {
            series->count = i;

            clearSeries(series); //free all allocated memory
            
            fclose(file); //Error case: close file 
            return NULL;
        }
    }
    
    fclose(file);
    


    return series;
}

// TODO Vervollständigen Sie die Funktion clearSeries, welche eine Bildserie vollständig aus dem Speicher freigibt
void clearSeries(GrayScaleImageSeries *series)
{
    if(series == NULL) //pointer points to nothing; nothing to clear
    {
        return;
    }

    if(series->images != NULL) //check if image pointer is valid
    {
        for(int i = 0; i < series->count; i++) //free memory allocated for all images until error occured
        {
            free(series->images[i].buffer); 
        }
        free(series->images); //free memory allocated for image array
    }

    if(series->labels != NULL) //check if label pointer is valid
    {
        free(series->labels); //free memory allocated for label array
    }

    free(series); //free memory allocated for series 
}