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

#define BUFFER_SIZE 100
#define FILE_HEADER_STRING "__info2_image_file_format__"



//HilfsFunktionen:


/* Opens the file in binary mode.
 * path: file path to open (must not be NULL).
 * returns FILE* or NULL on failure.
 */
static FILE *openImageFile(const char *path)
{  
    if (path == NULL)
    {
        return NULL;
    }

    return fopen(path, "rb");
}

/* Reads and checks the file header.
 * file: opened file to read the header from.
 * returns 1 if header is valid, otherwise 0.
 */
static int readAndCheckHeader(FILE *file)
{
    size_t headerLength = strlen(FILE_HEADER_STRING);
    char buffer[BUFFER_SIZE];

    if (headerLength + 1 > BUFFER_SIZE)
    {
        return 0;
    }

    if (fread(buffer, 1, headerLength, file) != headerLength)
    {
        return 0;
    }

    buffer[headerLength] = '\0';

    if (strcmp(buffer, FILE_HEADER_STRING) != 0)
    {
        return 0;
    }

    return 1; /* Header ok */
}


/* Reads metadata: image count, width, and height.
 * file: file to read from; count/width/height are outputs.
 * returns 1 on success or 0 on invalid/zero metadata.
 */
static int readImageMetaData(FILE *file,
                             unsigned short *count,
                             unsigned short *width,
                             unsigned short *height)
{
    if (fread(count, sizeof(unsigned short), 1, file) != 1)
    {    
        return 0;
    }
    if (fread(width, sizeof(unsigned short), 1, file) != 1)
    {
        return 0;
    }
    if (fread(height, sizeof(unsigned short), 1, file) != 1)
    {
        return 0;
    }

    if (*count == 0 || *width == 0 || *height == 0)
    {
        return 0;
    }

    return 1;
}


//Hauptfunktion:


/* Loads all images + labels from a .info2 file.
 * path: file path to load.
 * returns a new GrayScaleImageSeries or NULL on error.
 */
GrayScaleImageSeries *readImages(const char *path)
{
    // 1. Open the file
    FILE *file = openImageFile(path);
    if (file == NULL)
    {
        return NULL;
    }

    // 2. Check the header
    if (!readAndCheckHeader(file))
    {
        fclose(file);
        return NULL;
    }

    // 3. Read image metadata
    unsigned short count = 0;
    unsigned short width = 0;
    unsigned short height = 0;

    if (!readImageMetaData(file, &count, &width, &height))
    {
        fclose(file);
        return NULL;
    }

    // 4. Allocate memory for image series
    GrayScaleImageSeries *series = (GrayScaleImageSeries *)malloc(sizeof(GrayScaleImageSeries));
    if (series == NULL)
    {
        fclose(file);
        return NULL;
    }

    series->count  = count;
    series->images = (GrayScaleImage *)calloc(count, sizeof(GrayScaleImage));
    series->labels = (unsigned char *)malloc(count * sizeof(unsigned char));

    if (series->images == NULL || series->labels == NULL)
    {
        free(series->images);
        free(series->labels);
        free(series);
        fclose(file);
        return NULL;
    }

    // 5. Read the images and labels 
    for (unsigned int i = 0; i < count; i++)
    {
        GrayScaleImage *image = &series->images[i];

        image->width  = (unsigned int)width;
        image->height = (unsigned int)height;

        size_t numPixels = (size_t)width * (size_t)height;

        image->buffer = (GrayScalePixelType *)malloc(numPixels * sizeof(GrayScalePixelType));
        if (image->buffer == NULL)
        {
            for (unsigned int j = 0; j < i; j++)
            {
                free(series->images[j].buffer);
            }
            free(series->images);
            free(series->labels);
            free(series);
            fclose(file);
            return NULL;
        }

        if (fread(image->buffer, sizeof(GrayScalePixelType), numPixels, file) != numPixels)
        {
            for (unsigned int j = 0; j <= i; j++)
            {
                free(series->images[j].buffer);
            }
            free(series->images);
            free(series->labels);
            free(series);
            fclose(file);
            return NULL;
        }

        if (fread(&series->labels[i], sizeof(unsigned char), 1, file) != 1)
        {
            for (unsigned int j = 0; j <= i; j++)
            {
                free(series->images[j].buffer);
            }
            free(series->images);
            free(series->labels);
            free(series);
            fclose(file);
            return NULL;
        }
    }

    fclose(file);
    return series;
}

/* Frees the entire image series.
 * series: image series to free (NULL-safe).
 * returns nothing (void).
 */
void clearSeries(GrayScaleImageSeries *series)
{
    if (series == NULL)
    {
        return;
    }

    if (series->images != NULL)
    {
        for (unsigned int i = 0; i < series->count; i++)
        {
            free(series->images[i].buffer);
            series->images[i].buffer = NULL;
        }
        free(series->images);
        series->images = NULL;
    }

    if (series->labels != NULL)
    {
        free(series->labels);
        series->labels = NULL;
    }

    free(series);
}
