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

/**
 * Prida vozen na koniec vlaku.
 */
struct car* add_car(struct car* first, const char* target) {
    // vytvorenie noveho vozna
    struct car* newcar = calloc(1, sizeof(struct car));
    if (newcar == NULL) {
        return first; // ak zlyha alokacia, vrat povodny zoznam
    }

    strcpy(newcar->value, target);
    newcar->next = NULL;

    // ak je vlak prazdny
    if (first == NULL) {
        return newcar;
    }

    // najdi posledny vozen
    struct car* this = first;
    while (this->next != NULL) {
        this = this->next;
    }

    // pripoj novy vozen
    this->next = newcar;
    return first;
}

/**
 * Vypise vsetky vozne vo vlaku.
 */
void print_train(struct car* first) {
    struct car* this = first;
    while (this != NULL) {
        printf("%s\n", this->value);
        this = this->next;
    }
}

/**
 * Zrusenie vsetkych voznov vo vlaku.
 */
void cancel_train(struct car* first) {
    if (first == NULL) return;

    // rekurzivne uvolnenie
    cancel_train(first->next);
    free(first);
}

/**
 * Vyradenie vsetkych voznov, ktorych cielova stanica je target.
 */
struct car* clear_train(struct car* first, const char* target) {
    struct car* current = first;
    struct car* prev = NULL;

    while (current != NULL) {
        if (strcmp(current->value, target) == 0) {
            // treba zmazat tento vozen
            struct car* to_delete = current;
            if (prev == NULL) {
                // mazeme prvy prvok
                first = current->next;
            } else {
                // mazeme stredny alebo posledny prvok
                prev->next = current->next;
            }
            current = current->next;
            free(to_delete);
        } else {
            // presun dalej
            prev = current;
            current = current->next;
        }
    }

    return first;
}