//
// Created by stefan on 10.06.20.
//
#include "arena_list.h"

Node *listPopFront(List *list) {
    Node *front = list->first;
    if (front == NULL) {
        return NULL;
    }

    list->first = front->next;
    if (front == list->last) {
        // Only Node in the list
        list->last = NULL;
        return front;
    }

    if (front->next != NULL) {
        list->first->prev = NULL;
        front->next = NULL;
    }
    return front;
}

Node *listPopBack(List* list) { return NULL; }

void listPushFront(List *list, Node *new) {
    if (list->first == NULL) {
        // List was empty
        list->first = new;
        list->last = new;
        return;
    }
    new->prev = NULL;
    new->next = list->first;
    new->next->prev = new;
    list->first = new;
}

void listPushBack(List* list, Node *value) {}

ArenaList alInit(Node *arena, size_t size) {
    ArenaList al;
    al.activeList = (List){.first = NULL, .last = NULL};
    al.freeList = (List){.first = arena, .last = &arena[size - 1]};
    al.arena = arena;
    al.size = size;
    arena[0] = (Node){.value = NULL, .prev = NULL, .next = &arena[1]};
    for (size_t i = 1; i < size - 1; ++i) {
        arena[i] = (Node){.value = NULL, .prev = &arena[i - 1], .next = &arena[i + 1]};
    }
    arena[size - 1] = (Node){.value = NULL, .prev = &arena[size - 2], .next = NULL};
    return al;
}

int alPush(ArenaList* al, void *value) {
    Node *current = listPopFront(&al->freeList);
    // List is empty
    if (current == NULL) {
        return -1;
    }
    current->value = value;
    listPushFront(&al->activeList, current);
    return 0;
}



int alRemoveElem(ArenaList*  al, void * value){
    for(size_t i = 0; i < al->size; ++i) {
        if(al->arena[i].value == value) {
            return alRemove(al, &al->arena[i]);
        }
    }
    return -1;
}

int alRemove(ArenaList*  al, Node * node) {
    //TODO Should we check that the node is actually in the active list
    //Maybe as an assert that gets optimized out
    if(node == al->activeList.first) {
        listPopFront(&al->activeList);
        listPushFront(&al->freeList, node);
        return 0;
    }
    if(node == al->activeList.last) {
        listPopBack(&al->activeList);
        listPushFront(&al->freeList, node);
        return 0;
    }
    // The node is somewhere in the middle
    Node * prev = node ->prev;
    Node * next = node ->next;

    next->prev = prev;
    prev->next = next;

    listPushFront(&al->freeList, node);
    return 0;
}