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

#define BUFFER_SIZE 100
#define FILE_HEADER_STRING "__info2_image_file_format__"

// =====================================================
// Hilfsfunktion 1
// Datei öffnen + Header prüfen + Metadaten lesen
// =====================================================

static FILE *openFileAndReadHeader(const char *path, unsigned short *count, unsigned short *width, unsigned short *height)
{
    // Schritt 1: Datei öffnen
    FILE *file = fopen(path, "rb");
    if (!file) { 
        fprintf(stderr, "Error: Cannot open file '%s'\n", path);
        return NULL;
    }

    // Schritt 2: Header-String prüfen
    char buffer[BUFFER_SIZE] = {0};
    size_t headerLen = strlen(FILE_HEADER_STRING);

    if (fread(buffer, sizeof(char), headerLen, file) != headerLen) {
        fprintf(stderr, "Error: Cannot read file header (file too small?)\n");
        fclose(file);
        return NULL;
    }

    if (strncmp(buffer, FILE_HEADER_STRING, headerLen) != 0) {
        fprintf(stderr, "Error: Invalid file header. Expected '%s', got: %.24s\n", 
                FILE_HEADER_STRING, buffer);
        fclose(file);
        return NULL;
    }

    // Schritt 3: Metadaten lesen (Reihenfolge: count, width, height)
    // WICHTIG: Diese Reihenfolge (Anzahl, Breite, Höhe) entspricht
    // der Aufgabenstellung und dem in den Tests verwendeten Format.
    if (fread(count, sizeof(unsigned short), 1, file) != 1) {
        fprintf(stderr, "Error: Cannot read image count\n");
        fclose(file);
        return NULL;
    }
    if (fread(width, sizeof(unsigned short), 1, file) != 1) {
        fprintf(stderr, "Error: Cannot read image width\n");
        fclose(file);
        return NULL;
    }
    if (fread(height, sizeof(unsigned short), 1, file) != 1) {
        fprintf(stderr, "Error: Cannot read image height\n");
        fclose(file);
        return NULL;
    }

    // Input-Validierung: Prüfe auf ungültige Dimensionen
    if (*count == 0) {
        fprintf(stderr, "Error: Image count is 0\n");
        fclose(file);
        return NULL;
    }
    if (*width == 0) {
        fprintf(stderr, "Error: Image width is 0\n");
        fclose(file);
        return NULL;
    }
    if (*height == 0) {
        fprintf(stderr, "Error: Image height is 0\n");
        fclose(file);
        return NULL;
    }

    // Erfolg: offene Datei zurückgeben, Position ist nach Metadaten
    return file;
}

// -----------------------------------------------------
// Hilfsfunktion 2: Speicher für die gesamte Serie anlegen
// -----------------------------------------------------
static GrayScaleImageSeries *allocateSeries(unsigned short count,
                                           unsigned short width,
                                           unsigned short height)
{
    GrayScaleImageSeries *series = malloc(sizeof(GrayScaleImageSeries));
    if (!series) return NULL;

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

    if (!series->images || !series->labels)
    {
        clearSeries(series);
        return NULL;
    }

    // Bilddimensionen in jedes Struktur-Element übernehmen
    for (unsigned short i = 0; i < count; i++)
    {
        series->images[i].width = width;
        series->images[i].height = height;
    }

    return series;
}

// -----------------------------------------------------
// Hilfsfunktion 3: EIN BILD + EIN LABEL lesen
// -----------------------------------------------------
static int readSingleImage(FILE *file, GrayScaleImage *img, unsigned char *label)
{
    unsigned int pixelCount = img->width * img->height;

    img->buffer = malloc(pixelCount * sizeof(GrayScalePixelType));
    if (!img->buffer)
        return 0;

    if (fread(img->buffer, sizeof(GrayScalePixelType), pixelCount, file) != pixelCount)
        return 0;

    if (fread(label, sizeof(unsigned char), 1, file) != 1)
        return 0;

    return 1;
}

// =====================================================
// Hauptfunktion: Liest komplette Bilderserie
// =====================================================
GrayScaleImageSeries *readImages(const char *path)
{
    unsigned short count = 0, width = 0, height = 0;

    // Schritt 1-3: Datei öffnen + Header + Metadaten
    FILE *file = openFileAndReadHeader(path, &count, &width, &height);
    if (!file) {
        // Fehler bereits geloggt von openFileAndReadHeader()
        return NULL;
    }

    // Schritt 4: Bilderserie allokieren
    GrayScaleImageSeries *series = allocateSeries(count, width, height);
    if (!series) {
        fprintf(stderr, "Error: Cannot allocate image series\n");
        fclose(file);
        return NULL;
    }

    // Schritt 5: Alle Bilder + Labels lesen
    for (unsigned short i = 0; i < count; i++) {
        if (!readSingleImage(file, &series->images[i], &series->labels[i])) {
            fprintf(stderr, "Error: Cannot read image %u\n", i);
            clearSeries(series);
            fclose(file);
            return NULL;
        }
    }

    fclose(file);
    return series;
}

// =====================================================
// Speicher-Freigabe
// =====================================================
void clearSeries(GrayScaleImageSeries *series)
{
    if (!series)
        return;

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

    free(series);
}