// Public domain / CC0. Use freely for any purpose. RoyR 2026
// linkedlist.cm - Linked list implementation
// Demonstrates: structs simulated with arrays, complex pointer manipulation, memory layout

void printf(uint8 *fmt);
void *malloc(uint32 size);
void free(void *ptr);

// Node structure simulated as:
// [0] = data (int32)
// [4] = next pointer (int32*)
// Total size: 8 bytes per node

int32 *create_node(int32 value) {
    int32 *node = (int32*)malloc(8);
    node[0] = value;        // data
    node[1] = 0;            // next = NULL
    return node;
}

void insert_front(int32 **head, int32 value) {
    int32 *new_node = create_node(value);
    new_node[1] = (int32)(*head);  // new->next = head
    *head = new_node;               // head = new_node
}

void insert_back(int32 **head, int32 value) {
    int32 *new_node = create_node(value);
    
    if (*head == 0) {
        *head = new_node;
        return;
    }
    
    int32 *current = *head;
    while (current[1] != 0) {
        current = (int32*)current[1];
    }
    current[1] = (int32)new_node;
}

int32 list_length(int32 *head) {
    int32 count = 0;
    int32 *current = head;
    while (current != 0) {
        count = count + 1;
        current = (int32*)current[1];
    }
    return count;
}

void print_list(int32 *head) {
    int32 *current = head;
    printf("[");
    while (current != 0) {
        printf("%d", current[0]);
        current = (int32*)current[1];
        if (current != 0) printf(", ");
    }
    printf("]\n");
}

int32 find_value(int32 *head, int32 value) {
    int32 *current = head;
    int32 index = 0;
    while (current != 0) {
        if (current[0] == value) {
            return index;
        }
        current = (int32*)current[1];
        index = index + 1;
    }
    return -1;
}

void delete_value(int32 **head, int32 value) {
    if (*head == 0) return;
    
    // Check if head node contains the value
    if ((*head)[0] == value) {
        int32 *temp = *head;
        *head = (int32*)(*head)[1];
        free(temp);
        return;
    }
    
    // Search for the value in remaining nodes
    int32 *current = *head;
    while (current[1] != 0) {
        int32 *next = (int32*)current[1];
        if (next[0] == value) {
            current[1] = next[1];  // current->next = next->next
            free(next);
            return;
        }
        current = next;
    }
}

void free_list(int32 *head) {
    int32 *current = head;
    while (current != 0) {
        int32 *next = (int32*)current[1];
        free(current);
        current = next;
    }
}

int32 main(void) {
    int32 *list = 0;  // Empty list (NULL)
    
    printf("Linked List Demo\n");
    printf("================\n\n");
    
    printf("Inserting at front: 3, 2, 1\n");
    insert_front(&list, 3);
    insert_front(&list, 2);
    insert_front(&list, 1);
    print_list(list);
    
    printf("\nInserting at back: 4, 5, 6\n");
    insert_back(&list, 4);
    insert_back(&list, 5);
    insert_back(&list, 6);
    print_list(list);
    
    printf("\nList length: %d\n", list_length(list));
    
    printf("\nSearching for values:\n");
    int32 search_vals[4] = { 1, 4, 7, 5 };
    for (int32 i = 0; i < 4; i = i + 1) {
        int32 val = search_vals[i];
        int32 pos = find_value(list, val);
        if (pos >= 0) {
            printf("  %d found at position %d\n", val, pos);
        } else {
            printf("  %d not found\n", val);
        }
    }
    
    printf("\nDeleting value 3\n");
    delete_value(&list, 3);
    print_list(list);
    
    printf("\nDeleting value 1 (head)\n");
    delete_value(&list, 1);
    print_list(list);
    
    printf("\nDeleting value 6 (tail)\n");
    delete_value(&list, 6);
    print_list(list);
    
    printf("\nFinal list length: %d\n", list_length(list));
    
    free_list(list);
    printf("\nList freed\n");
    
    return 0;
}