/*
 * art.h
 *
 * This source file is part of the FoundationDB open source project
 *
 * Copyright 2013-2020 Apple Inc. and the FoundationDB project authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


#include <stdint.h>
#include "fdbclient/FDBTypes.h"
#include "flow/Arena.h"
#include "flow/Platform.h"

#ifndef ART_H
#define ART_H


struct art_iterator;

struct art_tree {
    enum ART_NODE_TYPE : uint8_t{
        ART_LEAF = 0, ART_NODE4 = 1, ART_NODE16 = 2, ART_NODE48 = 3, ART_NODE256 = 4,
        ART_NODE4_KV = 5, ART_NODE16_KV = 6, ART_NODE48_KV = 7, ART_NODE256_KV = 8
    };
#define ART_MIN_LEAF_UNSET 1UL
#define ART_LEAF_MATCH_KEY 1
#define ART_LEAF_SMALLER_KEY 2
#define ART_LEAF_LARGER_KEY 3
#define ART_I_FOUND 2
#define ART_I_DEPTH 3
#define ART_I_BACKTRACK 4

#define ART_NEXT 1
#define ART_PREV -1
#define ART_NEITHER 0


//#define ART_IS_LEAF(x) ( (*((ART_NODE_TYPE*)x) == ART_LEAF))
    template<class T>
    static inline bool ART_IS_LEAF(T const& x) {
        return *((ART_NODE_TYPE*)x) == ART_LEAF;
    }

#define ART_LEAF_RAW(x) ((art_leaf*)(x))

#define ART_LEAF_DISPL(x) fat_leaf_offset[(x)->type]
#define ART_FAT_NODE_LEAF(node_ptr) (*((art_leaf**) (((char*)(node_ptr))+ART_LEAF_DISPL(node_ptr))))

//In Bytes
//This is needed so that we can pre-allocate a static stack to perform efficient backtracking in iterative_bound
#define ART_MAX_KEY_LEN 10000

#define _mm_cmpge_epu8(a, b) \
        _mm_cmpeq_epi8(_mm_max_epu8(a, b), a)

#define _mm_cmple_epu8(a, b) _mm_cmpge_epu8(b, a)

#define _mm_cmpgt_epu8(a, b) \
        _mm_xor_si128(_mm_cmple_epu8(a, b), _mm_set1_epi8(-1))

#define _mm_cmplt_epu8(a, b) _mm_cmpgt_epu8(b, a)

#define ART_MAX_PREFIX_LEN 10


/**
 * This struct is included as part
 * of all the various node sizes
 */
    struct art_node {
        ART_NODE_TYPE type;
        uint8_t num_children;
        uint32_t partial_len;
        unsigned char partial[ART_MAX_PREFIX_LEN];
    };

/**
 * Represents a leaf. These are
 * of arbitrary size, as they include the key.
 * Note that the first two fields must be the same as in art_node
 */
    struct art_leaf {
        ART_NODE_TYPE type;
        void *value;
        art_leaf *prev = nullptr;
        art_leaf *next = nullptr;
        KeyRef key;

        art_leaf(const KeyRef &k, void *v) : type(ART_LEAF), value(v), key(k.begin(), k.size()) {
        }

        art_leaf(const uint8_t *ptr, int len, void *v) : type(ART_LEAF), value(v), key(ptr, len) {}

    };

/**
 * Small node with only 4 children
 */
    struct art_node4 {
        art_node n;
        unsigned char keys[4];
        art_node *children[4];
    };

/**
 * Node with 16 children
 */
    struct art_node16 {
        art_node n;
        unsigned char keys[16];
        art_node *children[16];
    };

/**
 * Node with 48 children, but
 * a full 256 byte field.
 */
    struct art_node48 {
        art_node n;
        unsigned char keys[256];
        art_node *children[48];
    };

/**
 * Full node with 256 children
 */
    struct art_node256 {
        art_node n;
        art_node *children[256];
    };

/**
 * Small node with only 4 children
 */
    struct art_node4_kv {
        art_node4 n;
        art_leaf *leaf;
    };

/**
 * Node with 16 children
 */
    struct art_node16_kv {
        art_node16 n;
        art_leaf *leaf;
    };

/**
 * Node with 48 children, but
 * a full 256 byte field.
 */
    struct art_node48_kv {
        art_node48 n;
        art_leaf *leaf;
    };

/**
 * Full node with 256 children
 */
    struct art_node256_kv {
        art_node256 n;
        art_leaf *leaf;
    };


private:
    art_node *root;
    uint64_t size;
    Arena *arena;
    static int fat_leaf_offset[9];
    static int node_sizes[9];

    static int check_bound_node(art_node *n, const KeyRef &k, int *depth_p, art_leaf **result, bool strict);

    static int art_bound_leaf(art_node *n, const KeyRef &k, int depth, art_leaf **result);

    static art_leaf *minimum(art_node *n);

    static art_leaf *maximum(art_node *n);

    static int leaf_matches_signed(art_leaf *n, const KeyRef &k, int depth);

    static int leaf_matches(const art_leaf *n, const KeyRef &k, int depth);

    static int signed_prefix_mismatch(art_node *n, const KeyRef &k, int depth, art_leaf **min_leaf, bool find_min);

    static int prefix_mismatch(art_node *n, KeyRef &k, int depth, art_leaf **minout);

    static art_leaf *minimum_kv(art_node *n);

    static art_node **find_child(art_node *n, unsigned char c);

    static void find_next(art_node *n, unsigned char c, art_node **out);

    static void find_prev(art_node *n, unsigned char c, art_node **out);

    static int art_next_prev(art_node *n, unsigned char c, art_node **out);

    void art_bound_iterative(art_node *n, const KeyRef &k, int depth, art_leaf **result, bool strict);

    static inline int min(int a, int b) {
        return (a < b) ? a : b;
    }

    static inline void *SET_LEAF(void *x) {
        (*((uint8_t *) x) = 0);
        return x;
    }

    static int check_prefix(const art_node *n, const KeyRef &k, int depth);

    void recursive_delete_binary(art_node *n, art_node **ref, const KeyRef &k, int depth);

    void remove_child(art_node *n, art_node **ref, unsigned char c, art_node **l, int depth);

    //needs this pointer to do allocation
    art_node *alloc_node(ART_NODE_TYPE type);

    art_node *alloc_kv_node(ART_NODE_TYPE type);

    art_leaf *make_leaf(const KeyRef &k, void *value);

    static void remove_fat_child(art_node *n, art_node **ref, int depth);

    static void remove_fat_child4(art_node4_kv *n, art_node **ref, int depth);

    static void remove_child4(art_node4 *n, art_node **ref, art_node **l, int depth);

    static void remove_fat_child16(art_node16_kv *n, art_node **ref);

    void remove_child16(art_node16 *n, art_node **ref, art_node **l);

    static void remove_fat_child48(art_node48_kv *n, art_node **ref);

    void remove_child48(art_node48 *n, art_node **ref, unsigned char c);

    static void remove_fat_child256(art_node256_kv *n, art_node **ref);

    void remove_child256(art_node256 *n, art_node **ref, unsigned char c);

    static void copy_header(art_node *dest, art_node *src);

    art_leaf *iterative_insert(art_node *root, art_node **root_ptr, KeyRef &k, void *value,
                               int depth, int *old, int replace_existing);

    art_leaf *insert_leaf(art_node *n, art_node **ref, const KeyRef &k, void *value, int depth,
                          int *old, int replace_existing);

    art_leaf *insert_fat_node(art_node *n, art_node **ref, const KeyRef &k, void *value, int depth,
                              int *old, art_leaf *min_of_n, int replace_existing);

    art_leaf *insert_internal_node(art_node *n, art_node **ref, const KeyRef &k, void *value, int depth,
                                   int *old, art_leaf *min_of_n, int prefix_diff, int replace_existing);

    art_leaf *insert_child(art_node *n, art_node **ref, const KeyRef &k, void *value, int depth,
                           int *old, int replace_existing);

    static inline int longest_common_prefix(const KeyRef &k1, const KeyRef &k2, int depth);

    static void insert_after(art_leaf *l_new, art_leaf *l_existing);

    static void insert_before(art_leaf *l_new, art_leaf *l_existing);

    void add_child(art_node *n, art_node **ref, unsigned char c, void *child);

    void add_child256(art_node256 *n, art_node **ref, unsigned char c, void *child);

    void add_child48(art_node48 *n, art_node **ref, unsigned char c, void *child);

    void add_child16(art_node16 *n, art_node **ref, unsigned char c, void *child);

    void add_child4(art_node4 *n, art_node **ref, unsigned char c, void *child);

public:
    art_tree(Arena &a) {
        this->arena = &a;
        this->root = alloc_node(ART_NODE4); //Sentinel node. Also needed for empty key
        this->size = 0;
    }

    art_iterator lower_bound(const KeyRef &k);

    art_iterator upper_bound(const KeyRef &k);

    art_iterator insert(KeyRef &key, void *value);

    art_iterator insert_if_absent(KeyRef &key, void *value, int *replaced);

    void erase(const art_iterator &it);

    uint64_t count() {
        return size;
    }


}; //art_tree

struct art_iterator {

private:
    art_tree::art_leaf *leaf;

public:
    art_iterator(art_tree::art_leaf *l) {
        leaf = l;
    }

    art_iterator(const art_iterator &i) {
        leaf = i.leaf;
    }

    art_iterator() {
        leaf = nullptr;
    }

    art_iterator &operator++() {
        leaf = leaf->next;
        return (*this);
    }

    art_iterator &operator--() {
        leaf = leaf->prev;
        return (*this);
    }

    bool operator==(const art_iterator &other) const {
        return leaf == other.leaf;
    }

    bool operator!=(const art_iterator &other) const {
        return leaf != other.leaf;
    }

    const KeyRef &key() const {
        return leaf->key;
    }

    void *value() const {
        return leaf->value;
    }

    void **value_ptr() {
        return &(leaf->value);
    }
};


#endif  //ART_H