/*
 * Copyright (c) 2014, Cisco Systems, Inc. All rights reserved.
 *
 * This software is available to you under a choice of one of two
 * licenses.  You may choose to be licensed under the terms of the GNU
 * General Public License (GPL) Version 2, available from the file
 * COPYING in the main directory of this source tree, or the
 * BSD license below:
 *
 *     Redistribution and use in source and binary forms, with or
 *     without modification, are permitted provided that the following
 *     conditions are met:
 *
 *      - Redistributions of source code must retain the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer.
 *
 *      - 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.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 */

#include <linux/init.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/list_sort.h>

#include <linux/interval_tree_generic.h>
#include "usnic_uiom_interval_tree.h"

#define START(node) ((node)->start)
#define LAST(node) ((node)->last)

#define MAKE_NODE(node, start, end, ref_cnt, flags, err, err_out)       \
                do {                                                    \
                        node = usnic_uiom_interval_node_alloc(start,    \
                                        end, ref_cnt, flags);           \
                                if (!node) {                            \
                                        err = -ENOMEM;                  \
                                        goto err_out;                   \
                                }                                       \
                } while (0)

#define MARK_FOR_ADD(node, list) (list_add_tail(&node->link, list))

#define MAKE_NODE_AND_APPEND(node, start, end, ref_cnt, flags, err,     \
                                err_out, list)                          \
                                do {                                    \
                                        MAKE_NODE(node, start, end,     \
                                                ref_cnt, flags, err,    \
                                                err_out);               \
                                        MARK_FOR_ADD(node, list);       \
                                } while (0)

#define FLAGS_EQUAL(flags1, flags2, mask)                               \
                        (((flags1) & (mask)) == ((flags2) & (mask)))

static struct usnic_uiom_interval_node*
usnic_uiom_interval_node_alloc(long int start, long int last, int ref_cnt,
                                int flags)
{
        struct usnic_uiom_interval_node *interval = kzalloc_obj(*interval,
                                                                GFP_ATOMIC);
        if (!interval)
                return NULL;

        interval->start = start;
        interval->last = last;
        interval->flags = flags;
        interval->ref_cnt = ref_cnt;

        return interval;
}

static int interval_cmp(void *priv, const struct list_head *a,
                        const struct list_head *b)
{
        struct usnic_uiom_interval_node *node_a, *node_b;

        node_a = list_entry(a, struct usnic_uiom_interval_node, link);
        node_b = list_entry(b, struct usnic_uiom_interval_node, link);

        /* long to int */
        if (node_a->start < node_b->start)
                return -1;
        else if (node_a->start > node_b->start)
                return 1;

        return 0;
}

static void
find_intervals_intersection_sorted(struct rb_root_cached *root,
                                   unsigned long start, unsigned long last,
                                   struct list_head *list)
{
        struct usnic_uiom_interval_node *node;

        INIT_LIST_HEAD(list);

        for (node = usnic_uiom_interval_tree_iter_first(root, start, last);
                node;
                node = usnic_uiom_interval_tree_iter_next(node, start, last))
                list_add_tail(&node->link, list);

        list_sort(NULL, list, interval_cmp);
}

int usnic_uiom_get_intervals_diff(unsigned long start, unsigned long last,
                                        int flags, int flag_mask,
                                        struct rb_root_cached *root,
                                        struct list_head *diff_set)
{
        struct usnic_uiom_interval_node *interval, *tmp;
        int err = 0;
        long int pivot = start;
        LIST_HEAD(intersection_set);

        INIT_LIST_HEAD(diff_set);

        find_intervals_intersection_sorted(root, start, last,
                                                &intersection_set);

        list_for_each_entry(interval, &intersection_set, link) {
                if (pivot < interval->start) {
                        MAKE_NODE_AND_APPEND(tmp, pivot, interval->start - 1,
                                                1, flags, err, err_out,
                                                diff_set);
                        pivot = interval->start;
                }

                /*
                 * Invariant: Set [start, pivot] is either in diff_set or root,
                 * but not in both.
                 */

                if (pivot > interval->last) {
                        continue;
                } else if (pivot <= interval->last &&
                                FLAGS_EQUAL(interval->flags, flags,
                                flag_mask)) {
                        pivot = interval->last + 1;
                }
        }

        if (pivot <= last)
                MAKE_NODE_AND_APPEND(tmp, pivot, last, 1, flags, err, err_out,
                                        diff_set);

        return 0;

err_out:
        list_for_each_entry_safe(interval, tmp, diff_set, link) {
                list_del(&interval->link);
                kfree(interval);
        }

        return err;
}

void usnic_uiom_put_interval_set(struct list_head *intervals)
{
        struct usnic_uiom_interval_node *interval, *tmp;
        list_for_each_entry_safe(interval, tmp, intervals, link)
                kfree(interval);
}

int usnic_uiom_insert_interval(struct rb_root_cached *root, unsigned long start,
                                unsigned long last, int flags)
{
        struct usnic_uiom_interval_node *interval, *tmp;
        unsigned long istart, ilast;
        int iref_cnt, iflags;
        unsigned long lpivot = start;
        int err = 0;
        LIST_HEAD(to_add);
        LIST_HEAD(intersection_set);

        find_intervals_intersection_sorted(root, start, last,
                                                &intersection_set);

        list_for_each_entry(interval, &intersection_set, link) {
                /*
                 * Invariant - lpivot is the left edge of next interval to be
                 * inserted
                 */
                istart = interval->start;
                ilast = interval->last;
                iref_cnt = interval->ref_cnt;
                iflags = interval->flags;

                if (istart < lpivot) {
                        MAKE_NODE_AND_APPEND(tmp, istart, lpivot - 1, iref_cnt,
                                                iflags, err, err_out, &to_add);
                } else if (istart > lpivot) {
                        MAKE_NODE_AND_APPEND(tmp, lpivot, istart - 1, 1, flags,
                                                err, err_out, &to_add);
                        lpivot = istart;
                } else {
                        lpivot = istart;
                }

                if (ilast > last) {
                        MAKE_NODE_AND_APPEND(tmp, lpivot, last, iref_cnt + 1,
                                                iflags | flags, err, err_out,
                                                &to_add);
                        MAKE_NODE_AND_APPEND(tmp, last + 1, ilast, iref_cnt,
                                                iflags, err, err_out, &to_add);
                } else {
                        MAKE_NODE_AND_APPEND(tmp, lpivot, ilast, iref_cnt + 1,
                                                iflags | flags, err, err_out,
                                                &to_add);
                }

                lpivot = ilast + 1;
        }

        if (lpivot <= last)
                MAKE_NODE_AND_APPEND(tmp, lpivot, last, 1, flags, err, err_out,
                                        &to_add);

        list_for_each_entry_safe(interval, tmp, &intersection_set, link) {
                usnic_uiom_interval_tree_remove(interval, root);
                kfree(interval);
        }

        list_for_each_entry(interval, &to_add, link)
                usnic_uiom_interval_tree_insert(interval, root);

        return 0;

err_out:
        list_for_each_entry_safe(interval, tmp, &to_add, link)
                kfree(interval);

        return err;
}

void usnic_uiom_remove_interval(struct rb_root_cached *root,
                                unsigned long start, unsigned long last,
                                struct list_head *removed)
{
        struct usnic_uiom_interval_node *interval;

        for (interval = usnic_uiom_interval_tree_iter_first(root, start, last);
                        interval;
                        interval = usnic_uiom_interval_tree_iter_next(interval,
                                                                        start,
                                                                        last)) {
                if (--interval->ref_cnt == 0)
                        list_add_tail(&interval->link, removed);
        }

        list_for_each_entry(interval, removed, link)
                usnic_uiom_interval_tree_remove(interval, root);
}

INTERVAL_TREE_DEFINE(struct usnic_uiom_interval_node, rb,
                        unsigned long, __subtree_last,
                        START, LAST, , usnic_uiom_interval_tree)