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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>
#include <assert.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, ptrdiff_t loc_next) {
    if (begin == NULL)
        return NULL;

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

    return last;
}

void cx_linked_list_add(void **begin, void **end, ptrdiff_t loc_prev, ptrdiff_t loc_next, void *new_node) {
    void *last;
    if (end == NULL) {
        assert(begin != NULL);
        last = cx_linked_list_last(*begin, loc_next);
    } else {
        last = *end;
    }
    if (last == NULL) {
        assert(begin != NULL);
        *begin = new_node;
    } else {
        // if there is a last node, update its next pointer
        CX_LL_PTR(last, loc_next) = new_node;
    }

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

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

size_t cx_linked_list_size(void *node, ptrdiff_t loc_next) {
    size_t size = 0;
    while (node != NULL) {
        node = CX_LL_PTR(node, loc_next);
        size++;
    }
    return size;
}

#define ll_prev(node) CX_LL_PTR(node, loc_prev)
#define ll_next(node) CX_LL_PTR(node, loc_next)
#define ll_data(node) (follow_ptr?CX_LL_PTR(node, loc_data):(((char*)node)+loc_data))

static void *cx_linked_list_sort_merge(ptrdiff_t loc_prev, ptrdiff_t loc_next,
                                       ptrdiff_t loc_data, int follow_ptr,
                                       size_t length, void *ls, void *le, void *re,
                                       CxListComparator cmp_func) {
    const size_t sbo_len = 1024;
    void *sbo[sbo_len];
    void **sorted = (length >= sbo_len) ? malloc(sizeof(void *) * length) : sbo;
    void *rc, *lc;

    lc = ls;
    rc = le;
    size_t n = 0;
    while (lc && lc != le && rc != re) {
        if (cmp_func(ll_data(lc), ll_data(rc)) <= 0) {
            sorted[n] = lc;
            lc = ll_next(lc);
        } else {
            sorted[n] = rc;
            rc = ll_next(rc);
        }
        n++;
    }
    while (lc && lc != le) {
        sorted[n] = lc;
        lc = ll_next(lc);
        n++;
    }
    while (rc && rc != re) {
        sorted[n] = rc;
        rc = ll_next(rc);
        n++;
    }

    // Update pointer
    if (loc_prev >= 0) ll_prev(sorted[0]) = NULL;
    for (size_t i = 0; i < length - 1; i++) {
        ll_next(sorted[i]) = sorted[i + 1];
        if (loc_prev >= 0) ll_prev(sorted[i + 1]) = sorted[i];
    }
    ll_next(sorted[length - 1]) = NULL;

    void *ret = sorted[0];
    if (sorted != sbo) {
        free(sorted);
    }
    return ret;
}

void cx_linked_list_sort(void **begin, void **end, ptrdiff_t loc_prev, ptrdiff_t loc_next,
                         ptrdiff_t loc_data, int follow_ptr, CxListComparator cmp_func) {
    assert(begin != NULL);

    void *lc, *ls, *le, *re;

    // set start node
    ls = *begin;

    // check how many elements are already sorted
    lc = ls;
    size_t ln = 1;
    while (ll_next(lc) != NULL && cmp_func(ll_data(ll_next(lc)), ll_data(lc)) > 0) {
        lc = ll_next(lc);
        ln++;
    }
    le = ll_next(lc);

    // if first unsorted node is NULL, the list is already completely sorted
    if (le != NULL) {
        void *rc;
        size_t rn = 1;
        rc = le;
        // skip already sorted elements
        while (ll_next(rc) != NULL && cmp_func(ll_data(ll_next(rc)), ll_data(rc)) > 0) {
            rc = ll_next(rc);
            rn++;
        }
        re = ll_next(rc);

        // {ls,...,le->prev} and {rs,...,re->prev} are sorted - merge them
        void *sorted = cx_linked_list_sort_merge(loc_prev, loc_next, loc_data, follow_ptr,
                                                 ln + rn, ls, le, re, cmp_func);

        // Something left? Sort it!
        size_t remainder_length = cx_linked_list_size(re, loc_next);
        if (remainder_length > 0) {
            void *remainder = re;
            cx_linked_list_sort(&remainder, NULL, loc_prev, loc_next, loc_data, follow_ptr, cmp_func);

            // merge sorted list with (also sorted) remainder
            *begin = cx_linked_list_sort_merge(loc_prev, loc_next, loc_data, follow_ptr,
                                               ln + rn + remainder_length,
                                               sorted, remainder, NULL, cmp_func);
        } else {
            // no remainder - we've got our sorted list
            *begin = sorted;
        }
        if (end) *end = cx_linked_list_last(sorted, loc_next);
    }
}

#undef ll_next
#undef ll_data

/* HIGH LEVEL LINKED LIST IMPLEMENTATION */

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

#define CX_LL_LOC_PREV offsetof(cx_linked_list_node, prev)
#define CX_LL_LOC_NEXT offsetof(cx_linked_list_node, next)
#define CX_LL_LOC_DATA offsetof(cx_linked_list_node, payload)

typedef struct {
    cx_list_s base;
    cx_linked_list_node *begin;
    cx_linked_list_node *end;
} cx_linked_list;

static cx_linked_list_node *cx_ll_node_at(cx_linked_list *list, size_t index) {
    if (index >= list->base.size) {
        return NULL;
    } else if (index > list->base.size / 2) {
        return cx_linked_list_at(list->end, list->base.size - 1, CX_LL_LOC_PREV, index);
    } else {
        return cx_linked_list_at(list->begin, 0, CX_LL_LOC_NEXT, index);
    }
}

static int cx_ll_insert(cx_list_s *list, size_t index, void *elem) {
    // out-of bounds check
    if (index > list->size) return 1;

    // cast a linked list pointer
    cx_linked_list *ll = (cx_linked_list *) list;

    // create the new node
    cx_linked_list_node *node = cxMalloc(list->allocator,
                                         sizeof(cx_linked_list_node) + list->itemsize);

    // sortir if failed
    if (node == NULL) return 1;

    // copy payload to the new node
    memcpy(node->payload, elem, list->itemsize);

    // check if this is the first node
    if (ll->begin == NULL) {
        node->prev = node->next = NULL;
        ll->begin = ll->end = node;
    } else {
        // check if this shall be the new end node
        if (index == list->size) {
            ll->end->next = node;
            node->prev = ll->end;
            node->next = NULL;
            ll->end = node;
        }
            // check if this shall be the new start node
        else if (index == 0) {
            ll->begin->prev = node;
            node->next = ll->begin;
            node->prev = NULL;
            ll->begin = node;
        } else {
            // find the node at the current index
            cx_linked_list_node *cur = cx_ll_node_at(ll, index);

            // insert before that node
            // (we know all ptr are non-null because we handled all other cases before)
            node->next = cur;
            node->prev = cur->prev;
            cur->prev = node;
            node->prev->next = node;
        }
    }

    // increase the size and return
    list->size++;
    return 0;
}

static int cx_ll_add(cx_list_s *list, void *elem) {
    return cx_ll_insert(list, list->size, elem);
}

static int cx_pll_insert(cx_list_s *list, size_t index, void *elem) {
    return cx_ll_insert(list, index, &elem);
}

static int cx_pll_add(cx_list_s *list, void *elem) {
    return cx_ll_insert(list, list->size, &elem);
}

static int cx_ll_remove(cx_list_s *list, size_t index) {
    cx_linked_list *ll = (cx_linked_list *) list;
    cx_linked_list_node *node = cx_ll_node_at(ll, index);

    // out-of-bounds check
    if (node == NULL) return 1;

    // change left side connection
    if (node->prev == NULL) {
        ll->begin = node->next;
    } else {
        node->prev->next = node->next;
    }

    // change right side connection
    if (node->next == NULL) {
        ll->end = node->prev;
    } else {
        node->next->prev = node->prev;
    }

    // adjust size
    list->size--;

    // free and return
    cxFree(list->allocator, node);

    return 0;
}

static void *cx_ll_at(cx_list_s *list, size_t index) {
    cx_linked_list *ll = (cx_linked_list *) list;
    cx_linked_list_node *node = cx_ll_node_at(ll, index);
    return node == NULL ? NULL : node->payload;
}

static void *cx_pll_at(cx_list_s *list, size_t index) {
    cx_linked_list *ll = (cx_linked_list *) list;
    cx_linked_list_node *node = cx_ll_node_at(ll, index);
    return node == NULL ? NULL : *(void **) 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;
    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 size_t cx_pll_find(cx_list_s *list, void *elem) {
    CxListComparator cmp = list->cmpfunc;
    cx_linked_list *ll = (cx_linked_list *) list;

    size_t index;
    cx_linked_list_node *node = ll->begin;
    for (index = 0; index < list->size; index++) {
        void *current = *(void **) 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;
    cx_linked_list_node *last = ll->end;
    return last == NULL ? NULL : last->payload;
}

static void *cx_pll_last(cx_list_s *list) {
    cx_linked_list *ll = (cx_linked_list *) list;
    cx_linked_list_node *last = ll->end;
    return last == NULL ? NULL : *(void **) last->payload;
}

static void cx_ll_sort(cx_list_s *list) {
    cx_linked_list *ll = (cx_linked_list *) list;
    cx_linked_list_sort((void **) &ll->begin, (void **) &ll->end,
                        CX_LL_LOC_PREV, CX_LL_LOC_NEXT, CX_LL_LOC_DATA,
                        0, list->cmpfunc);
}

static void cx_pll_sort(cx_list_s *list) {
    cx_linked_list *ll = (cx_linked_list *) list;
    cx_linked_list_sort((void **) &ll->begin, (void **) &ll->end,
                        CX_LL_LOC_PREV, CX_LL_LOC_NEXT, CX_LL_LOC_DATA,
                        1, list->cmpfunc);
}

static 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,
        cx_ll_sort
};

static cx_list_class cx_pointer_linked_list_class = {
        cx_pll_add,
        cx_pll_insert,
        cx_ll_remove,
        cx_pll_at,
        cx_pll_find,
        cx_pll_last,
        cx_pll_sort
};

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;

    return (CxList) list;
}

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

    list->base.cl = &cx_pointer_linked_list_class;
    list->base.allocator = allocator;
    list->base.cmpfunc = comparator;
    list->base.itemsize = sizeof(void *);
    list->base.capacity = SIZE_MAX;
    list->base.size = 0;

    list->begin = NULL;
    list->end = NULL;

    return (CxList) list;
}

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

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

    cxFree(list->allocator, list);
}