Add Final Project: Todo-App in C

exercises/final_project/todo_c/todo.c

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+// ============================================
+// Final-Projekt: Todo-App in C
+// Ein vollständiges CLI-Programm mit CRUD-Operationen
+// ============================================
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdbool.h>
+#include <time.h>
+
+#define MAX_TODOS 100
+#define MAX_TITLE 100
+#define MAX_DESC 500
+#define DATA_FILE "todos.dat"
+
+// Datenstruktur für ein Todo
+typedef struct {
+    int id;
+    char title[MAX_TITLE];
+    char description[MAX_DESC];
+    bool completed;
+    time_t created_at;
+} Todo;
+
+// Datenstruktur für die Todo-Liste
+typedef struct {
+    Todo items[MAX_TODOS];
+    int count;
+} TodoList;
+
+// Funktionsprototypen
+void todo_init(TodoList* list);
+void todo_add(TodoList* list, const char* title, const char* description);
+void todo_list(const TodoList* list);
+void todo_complete(TodoList* list, int id);
+void todo_delete(TodoList* list, int id);
+void todo_save(const TodoList* list);
+void todo_load(TodoList* list);
+void print_menu(void);
+void clear_input_buffer(void);
+
+// ============================================
+// IMPLEMENTATION
+// ============================================
+
+void todo_init(TodoList* list) {
+    list->count = 0;
+    for (int i = 0; i < MAX_TODOS; i++) {
+        list->items[i].id = 0;
+        list->items[i].title[0] = '\0';
+        list->items[i].description[0] = '\0';
+        list->items[i].completed = false;
+        list->items[i].created_at = 0;
+    }
+}
+
+void todo_add(TodoList* list, const char* title, const char* description) {
+    if (list->count >= MAX_TODOS) {
+        printf("Fehler: Maximale Anzahl erreicht!\n");
+        return;
+    }
+    
+    Todo* new_todo = &list->items[list->count];
+    new_todo->id = list->count + 1;
+    strncpy(new_todo->title, title, MAX_TITLE - 1);
+    new_todo->title[MAX_TITLE - 1] = '\0';
+    strncpy(new_todo->description, description, MAX_DESC - 1);
+    new_todo->description[MAX_DESC - 1] = '\0';
+    new_todo->completed = false;
+    new_todo->created_at = time(NULL);
+    
+    list->count++;
+    printf("Todo #%d hinzugefügt!\n", new_todo->id);
+}
+
+void todo_list(const TodoList* list) {
+    if (list->count == 0) {
+        printf("Keine Todos vorhanden.\n");
+        return;
+    }
+    
+    printf("\n=== DEINE TODOS ===\n");
+    printf("%-4s | %-10s | %-30s | %-20s\n", "ID", "Status", "Titel", "Erstellt");
+    printf("-----+------------+--------------------------------+--------------------\n");
+    
+    for (int i = 0; i < list->count; i++) {
+        const Todo* todo = &list->items[i];
+        char date_str[26];
+        ctime_r(&todo->created_at, date_str);
+        date_str[24] = '\0';  // Remove newline
+        
+        const char* status = todo->completed ? "[✓] Done   " : "[ ] Open   ";
+        printf("%-4d | %s | %-30s | %.20s\n", 
+               todo->id, status, todo->title, date_str);
+        
+        if (strlen(todo->description) > 0) {
+            printf("     |            | %s\n", todo->description);
+        }
+    }
+    printf("\n");
+}
+
+void todo_complete(TodoList* list, int id) {
+    for (int i = 0; i < list->count; i++) {
+        if (list->items[i].id == id) {
+            list->items[i].completed = !list->items[i].completed;
+            printf("Todo #%d %s!\n", id, 
+                   list->items[i].completed ? "abgeschlossen" : "wieder geöffnet");
+            return;
+        }
+    }
+    printf("Fehler: Todo #%d nicht gefunden!\n", id);
+}
+
+void todo_delete(TodoList* list, int id) {
+    int found_index = -1;
+    
+    for (int i = 0; i < list->count; i++) {
+        if (list->items[i].id == id) {
+            found_index = i;
+            break;
+        }
+    }
+    
+    if (found_index == -1) {
+        printf("Fehler: Todo #%d nicht gefunden!\n", id);
+        return;
+    }
+    
+    // Array komprimieren
+    for (int i = found_index; i < list->count - 1; i++) {
+        list->items[i] = list->items[i + 1];
+        list->items[i].id = i + 1;  // ID neu zuweisen
+    }
+    
+    list->count--;
+    printf("Todo #%d gelöscht!\n", id);
+}
+
+void todo_save(const TodoList* list) {
+    FILE* file = fopen(DATA_FILE, "wb");
+    if (!file) {
+        printf("Fehler: Konnte Datei nicht öffnen!\n");
+        return;
+    }
+    
+    fwrite(&list->count, sizeof(int), 1, file);
+    fwrite(list->items, sizeof(Todo), list->count, file);
+    
+    fclose(file);
+    printf("Todos gespeichert!\n");
+}
+
+void todo_load(TodoList* list) {
+    FILE* file = fopen(DATA_FILE, "rb");
+    if (!file) {
+        printf("Keine gespeicherte Daten gefunden. Starte neu...\n");
+        return;
+    }
+    
+    fread(&list->count, sizeof(int), 1, file);
+    fread(list->items, sizeof(Todo), list->count, file);
+    
+    fclose(file);
+    printf("%d Todos geladen!\n", list->count);
+}
+
+void print_menu(void) {
+    printf("\n=== TODO-APP ===\n");
+    printf("1. Todo hinzufügen\n");
+    printf("2. Todos anzeigen\n");
+    printf("3. Todo abschließen/öffnen\n");
+    printf("4. Todo löschen\n");
+    printf("5. Speichern\n");
+    printf("6. Beenden\n");
+    printf("Wahl: ");
+}
+
+void clear_input_buffer(void) {
+    int c;
+    while ((c = getchar()) != '\n' && c != EOF);
+}
+
+// ============================================
+// HAUPTPROGRAMM
+// ============================================
+int main(void) {
+    TodoList list;
+    todo_init(&list);
+    todo_load(&list);
+    
+    int choice;
+    char title[MAX_TITLE];
+    char description[MAX_DESC];
+    int id;
+    
+    printf("\n📝 Willkommen zur Todo-App!\n");
+    
+    while (true) {
+        print_menu();
+        
+        if (scanf("%d", &choice) != 1) {
+            clear_input_buffer();
+            printf("Ungültige Eingabe!\n");
+            continue;
+        }
+        clear_input_buffer();
+        
+        switch (choice) {
+            case 1:
+                printf("Titel: ");
+                fgets(title, MAX_TITLE, stdin);
+                title[strcspn(title, "\n")] = '\0';  // Remove newline
+                
+                printf("Beschreibung (optional): ");
+                fgets(description, MAX_DESC, stdin);
+                description[strcspn(description, "\n")] = '\0';
+                
+                todo_add(&list, title, description);
+                break;
+                
+            case 2:
+                todo_list(&list);
+                break;
+                
+            case 3:
+                printf("Todo-ID: ");
+                if (scanf("%d", &id) == 1) {
+                    todo_complete(&list, id);
+                }
+                clear_input_buffer();
+                break;
+                
+            case 4:
+                printf("Todo-ID: ");
+                if (scanf("%d", &id) == 1) {
+                    todo_delete(&list, id);
+                }
+                clear_input_buffer();
+                break;
+                
+            case 5:
+                todo_save(&list);
+                break;
+                
+            case 6:
+                printf("Speichern vor Beenden? (j/n): ");
+                char save_choice;
+                scanf(" %c", &save_choice);
+                if (save_choice == 'j' || save_choice == 'J') {
+                    todo_save(&list);
+                }
+                printf("Auf Wiedersehen!\n");
+                return 0;
+                
+            default:
+                printf("Ungültige Wahl!\n");
+        }
+    }
+    
+    return 0;
+}