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

void *cx_linked_list_at(
        void *start,
        size_t start_index,
        ptrdiff_t loc_advance,
        size_t index
) {
    assert(start != NULL);
    assert(loc_advance >= 0);
    size_t i = start_index;
    void *cur = start;
    while (i != index && cur != NULL) {
        cur = ll_advance(cur);
        i < index ? i++ : i--;
    }
    return cur;
}

size_t cx_linked_list_find(
        void *start,
        ptrdiff_t loc_advance,
        ptrdiff_t loc_data,
        int follow_ptr,
        CxListComparator cmp_func,
        void *elem
) {
    assert(start != NULL);
    assert(loc_advance >= 0);
    assert(loc_data >= 0);
    assert(cmp_func);

    void *node = start;
    size_t index = 0;
    do {
        void *current = ll_data(node);
        if (cmp_func(current, elem) == 0) {
            return index;
        }
        node = ll_advance(node);
        index++;
    } while (node != NULL);
    return index;
}

void *cx_linked_list_first(
        void *node,
        ptrdiff_t loc_prev
) {
    return cx_linked_list_last(node, loc_prev);
}

void *cx_linked_list_last(
        void *node,
        ptrdiff_t loc_next
) {
    assert(node != NULL);
    assert(loc_next >= 0);

    void *cur = node;
    void *last;
    do {
        last = cur;
    } while ((cur = ll_next(cur)) != NULL);

    return last;
}

void *cx_linked_list_prev(
        void *begin,
        ptrdiff_t loc_next,
        void *node
) {
    assert(begin != NULL);
    assert(node != NULL);
    assert(loc_next >= 0);
    if (begin == node) return NULL;
    void *cur = begin;
    void *next;
    while (1) {
        next = ll_next(cur);
        if (next == node) return cur;
        cur = next;
    }
}

void cx_linked_list_link(
        void *left,
        void *right,
        ptrdiff_t loc_prev,
        ptrdiff_t loc_next
) {
    assert(loc_next >= 0);
    ll_next(left) = right;
    if (loc_prev >= 0) {
        ll_prev(right) = left;
    }
}

void cx_linked_list_unlink(
        void *left,
        void *right,
        ptrdiff_t loc_prev,
        ptrdiff_t loc_next
) {
    assert (loc_next >= 0);
    assert(ll_next(left) == right);
    ll_next(left) = NULL;
    if (loc_prev >= 0) {
        assert(ll_prev(right) == left);
        ll_prev(right) = NULL;
    }
}

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 = *begin == NULL ? NULL : cx_linked_list_last(*begin, loc_next);
    } else {
        last = *end;
    }
    cx_linked_list_insert_chain(begin, end, loc_prev, loc_next, last, new_node, new_node);
}

void cx_linked_list_prepend(
        void **begin,
        void **end,
        ptrdiff_t loc_prev,
        ptrdiff_t loc_next,
        void *new_node
) {
    cx_linked_list_insert_chain(begin, end, loc_prev, loc_next, NULL, new_node, new_node);
}

void cx_linked_list_insert(
        void **begin,
        void **end,
        ptrdiff_t loc_prev,
        ptrdiff_t loc_next,
        void *node,
        void *new_node
) {
    cx_linked_list_insert_chain(begin, end, loc_prev, loc_next, node, new_node, new_node);
}

void cx_linked_list_insert_chain(
        void **begin,
        void **end,
        ptrdiff_t loc_prev,
        ptrdiff_t loc_next,
        void *node,
        void *insert_begin,
        void *insert_end
) {
    // find the end of the chain, if not specified
    if (insert_end == NULL) {
        insert_end = cx_linked_list_last(insert_begin, loc_next);
    }

    // determine the successor
    void *successor;
    if (node == NULL) {
        assert(begin != NULL || (end != NULL && loc_prev >= 0));
        if (begin != NULL) {
            successor = *begin;
            *begin = insert_begin;
        } else {
            successor = *end == NULL ? NULL : cx_linked_list_first(*end, loc_prev);
        }
    } else {
        successor = ll_next(node);
        cx_linked_list_link(node, insert_begin, loc_prev, loc_next);
    }

    if (successor == NULL) {
        // the list ends with the new chain
        if (end != NULL) {
            *end = insert_end;
        }
    } else {
        cx_linked_list_link(insert_end, successor, loc_prev, loc_next);
    }
}

void cx_linked_list_remove(
        void **begin,
        void **end,
        ptrdiff_t loc_prev,
        ptrdiff_t loc_next,
        void *node
) {
    assert(node != NULL);
    assert(loc_next >= 0);
    assert(loc_prev >= 0 || begin != NULL);

    // find adjacent nodes
    void *next = ll_next(node);
    void *prev;
    if (loc_prev >= 0) {
        prev = ll_prev(node);
    } else {
        prev = cx_linked_list_prev(*begin, loc_next, node);
    }

    // update next pointer of prev node, or set begin
    if (prev == NULL) {
        if (begin != NULL) {
            *begin = next;
        }
    } else {
        ll_next(prev) = next;
    }

    // update prev pointer of next node, or set end
    if (next == NULL) {
        if (end != NULL) {
            *end = prev;
        }
    } else if (loc_prev >= 0) {
        ll_prev(next) = prev;
    }
}

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

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++) {
        cx_linked_list_link(sorted[i], sorted[i + 1], loc_prev, loc_next);
    }
    ll_next(sorted[length - 1]) = NULL;

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

void cx_linked_list_sort( /* NOLINT(misc-no-recursion) - purposely recursive function */
        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);
    assert(loc_next >= 0);
    assert(loc_data >= 0);
    assert(cmp_func);

    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);
    }
}

void cx_linked_list_reverse(
        void **begin,
        void **end,
        ptrdiff_t loc_prev,
        ptrdiff_t loc_next
) {
    assert(begin != NULL);
    assert(loc_next >= 0);

    // swap all links
    void *prev = NULL;
    void *cur = *begin;
    while (cur != NULL) {
        void *next = ll_next(cur);

        ll_next(cur) = prev;
        if (loc_prev >= 0) {
            ll_prev(cur) = next;
        }

        prev = cur;
        cur = next;
    }

    // update begin and end
    if (end != NULL) {
        *end = *begin;
    }
    *begin = prev;
}

/* 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 new_node
    cx_linked_list_node *new_node = cxMalloc(list->allocator,
                                             sizeof(cx_linked_list_node) + list->itemsize);

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

    // initialize new new_node
    new_node->prev = new_node->next = NULL;
    memcpy(new_node->payload, elem, list->itemsize);

    // find position efficiently
    cx_linked_list_node *node = index == 0 ? NULL : cx_ll_node_at(ll, index - 1);

    // insert
    cx_linked_list_insert_chain(
            (void **) &ll->begin, (void **) &ll->end,
            CX_LL_LOC_PREV, CX_LL_LOC_NEXT,
            node, new_node, new_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;

    // remove
    cx_linked_list_remove((void **) &ll->begin, (void **) &ll->end,
                          CX_LL_LOC_PREV, CX_LL_LOC_NEXT, node);

    // 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
) {
    return cx_linked_list_find(((cx_linked_list *) list)->begin,
                               CX_LL_LOC_NEXT, CX_LL_LOC_DATA,
                               0, list->cmpfunc, elem);
}

static size_t cx_pll_find(
        cx_list_s *list,
        void *elem
) {
    return cx_linked_list_find(((cx_linked_list *) list)->begin,
                               CX_LL_LOC_NEXT, CX_LL_LOC_DATA,
                               1, list->cmpfunc, elem);
}

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_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_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);
}