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/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright 2021 Mike Becker, Olaf Wintermann All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   1. Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *
 *   2. Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include "cx/linked_list.h"
#include <stdint.h>
#include <string.h>

/* LOW LEVEL LINKED LIST FUNCTIONS */

#define CX_LL_PTR(cur, off) ((void**)(((char*)cur)+off))

void *cx_linked_list_at(void *start, size_t start_index, ptrdiff_t loc_advance, size_t index) {
    size_t i = start_index;
    void* cur = start;
    while (i != index && cur != NULL) {
        cur = *CX_LL_PTR(cur, loc_advance);
        i < index ? i++ : i--;
    }
    return cur;
}

void *cx_linked_list_last(void **begin, void **end, ptrdiff_t loc_next) {
    if (end != NULL) {
        return *end;
    } else {
        if (begin == NULL || *begin == NULL)
            return NULL;

        void *cur = *begin;
        void *last;
        do {
            last = cur;
        } while ((cur = *CX_LL_PTR(cur, loc_next)) != NULL);

        return last;
    }
}

int cx_linked_list_add(void **begin, void **end, ptrdiff_t loc_prev, ptrdiff_t loc_next, void *new_node) {
    void *last = cx_linked_list_last(begin, end, loc_next);
    if (last == NULL) {
        if (begin == NULL) {
            // no current list and no begin ptr to write to - we don't find something to append to
            return 1;
        } else {
            // start fresh list
            *begin = new_node;
        }
    } else {
        // if there is a last node, update its next pointer
        void **next = CX_LL_PTR(last, loc_next);
        *next = new_node;
    }

    // if there is an end pointer, update it
    if (end != NULL) {
        *end = cx_linked_list_last(&new_node, NULL, loc_next);
    }

    // if the nodes use a prev pointer, update it
    if (loc_prev >= 0) {
        void **prev = CX_LL_PTR(new_node, loc_prev);
        *prev = last;
    }

    return 0;
}

/* HIGH LEVEL LINKED LIST IMPLEMENTATION */

struct cx_linked_list_node {
    void *prev;
    void *next;
    char payload[];
};

#define CX_LL_LOC_PREV offsetof(struct cx_linked_list_node, prev)
#define CX_LL_LOC_NEXT offsetof(struct cx_linked_list_node, next)

typedef struct {
    cx_list_s base;
    void *begin;
    void *end;
    ptrdiff_t loc_prev;
    ptrdiff_t loc_next;
} cx_linked_list;

static int cx_ll_add(cx_list_s *list, void *elem) {
    cx_linked_list *ll = (cx_linked_list *) list;

    struct cx_linked_list_node *node = cxMalloc(list->allocator,
                                                sizeof(struct cx_linked_list_node) + list->itemsize);
    if (node == NULL)
        return 1;

    node->next = node->prev = NULL;
    memcpy(node->payload, elem, list->itemsize);

    int ret = cx_linked_list_add(
            &ll->begin, &ll->end,
            CX_LL_LOC_PREV, CX_LL_LOC_NEXT,
            node
    );
    if (ret == 0) {
        list->size++;
        return 0;
    } else {
        return ret;
    }
}

static int cx_ll_insert(cx_list_s *list, size_t index, void *elem) {
    cx_linked_list *ll = (cx_linked_list *) list;
    // TODO: implement using low level API
    return 1;
}

static int cx_ll_remove(cx_list_s *list, size_t index) {
    if (index >= list->size) {
        return 1;
    }
    cx_linked_list *ll = (cx_linked_list *) list;
    // TODO: implement using low level API
    return 0;
}

static void *cx_ll_at(cx_list_s *list, size_t index) {
    cx_linked_list *ll = (cx_linked_list *) list;
    struct cx_linked_list_node *node;
    if (index >= list->size) {
        node = NULL;
    } else if (index > list->size / 2) {
        node = cx_linked_list_at(ll->end, list->size, CX_LL_LOC_PREV, index);
    } else {
        node = cx_linked_list_at(ll->begin, 0, CX_LL_LOC_NEXT, index);
    }
    return node == NULL ? NULL : &node->payload;
}

static size_t cx_ll_find(cx_list_s *list, void *elem) {
    CxListComparator cmp = list->cmpfunc;
    cx_linked_list *ll = (cx_linked_list *) list;

    size_t index;
    struct cx_linked_list_node* node = ll->begin;
    for (index = 0 ; index < list->size ; index++) {
        void* current = node->payload;
        if (cmp(current, elem) == 0) {
            return index;
        }
        node = node->next;
    }
    return index;
}

static void *cx_ll_last(cx_list_s *list) {
    cx_linked_list *ll = (cx_linked_list *) list;
    struct cx_linked_list_node *last = cx_linked_list_last(NULL, &ll->end, CX_LL_LOC_NEXT);
    return &last->payload;
}

cx_list_class cx_linked_list_class = {
        cx_ll_add,
        cx_ll_insert,
        cx_ll_remove,
        cx_ll_at,
        cx_ll_find,
        cx_ll_last
};

CxList cxLinkedListCreate(CxAllocator allocator, CxListComparator comparator, size_t item_size) {
    cx_linked_list* list = cxMalloc(allocator, sizeof(cx_linked_list));
    if (list == NULL)
        return NULL;

    list->base.cl = &cx_linked_list_class;
    list->base.allocator = allocator;
    list->base.cmpfunc = comparator;
    list->base.itemsize = item_size;
    list->base.capacity = SIZE_MAX;
    list->base.size = 0;

    list->begin = NULL;
    list->end = NULL;
    list->loc_prev = CX_LL_LOC_PREV;
    list->loc_next = CX_LL_LOC_NEXT;

    return (CxList) list;
}

void cxLinkedListDestroy(CxList list) {
    cx_linked_list* ll = (cx_linked_list*) list;

    struct cx_linked_list_node* node = ll->begin;
    while (node) {
        void* next = node->next;
        cxFree(list->allocator, node);
        node = next;
    }

    cxFree(list->allocator, list);
}

size_t cxLinkedListRecalculateSize(CxList list) {
    cx_linked_list *ll = (cx_linked_list *) list;

    if (ll->begin == NULL) {
        ll->base.size = 0;
        ll->end = NULL;
        return 0;
    } else {
        void *cur = ll->begin;
        void *last;
        size_t size = 0;
        do {
            last = cur;
            size++;
        } while ((cur = *CX_LL_PTR(cur, ll->loc_next)) != NULL);
        ll->end = last;
        ll->base.size = size;
        return size;
    }
}