/*
 * include/shard/ISAMTree.h
 *
 * Copyright (C) 2023 Douglas B. Rumbaugh <drumbaugh@psu.edu> 
 *                    Dong Xie <dongx@psu.edu>
 *
 * Distributed under the Modified BSD License.
 *
 * A shard shim around an in-memory ISAM tree.
 *
 */
#pragma once

#include <vector>
#include <cassert>

#include "framework/ShardRequirements.h"

#include "util/bf_config.h"
#include "psu-ds/BloomFilter.h"
#include "util/SortedMerge.h"

using psudb::CACHELINE_SIZE;
using psudb::BloomFilter;
using psudb::PriorityQueue;
using psudb::queue_record;
using psudb::byte;

namespace de {

template <KVPInterface R>
class ISAMTree {
private:

typedef decltype(R::key) K;
typedef decltype(R::value) V;

constexpr static size_t NODE_SZ = 256;
constexpr static size_t INTERNAL_FANOUT = NODE_SZ / (sizeof(K) + sizeof(byte*));

struct InternalNode {
    K keys[INTERNAL_FANOUT];
    byte* child[INTERNAL_FANOUT];
};

static_assert(sizeof(InternalNode) == NODE_SZ, "node size does not match");

constexpr static size_t LEAF_FANOUT = NODE_SZ / sizeof(R);


public:
    ISAMTree(BufferView<R> buffer)
        : m_bf(new BloomFilter<R>(BF_FPR, buffer.get_tombstone_count(), BF_HASH_FUNCS))
        , m_isam_nodes(nullptr)
        , m_root(nullptr)
        , m_reccnt(0)
        , m_tombstone_cnt(0)
        , m_internal_node_cnt(0)
        , m_deleted_cnt(0)
        , m_alloc_size(0)
        , m_data(nullptr)
    {
        m_alloc_size = psudb::sf_aligned_alloc(CACHELINE_SIZE, 
                                               buffer.get_record_count() * 
                                                 sizeof(Wrapped<R>), 
                                               (byte**) &m_data);

        auto res = sorted_array_from_bufferview(std::move(buffer), m_data, m_bf);
        m_reccnt = res.record_count;
        m_tombstone_cnt = res.tombstone_count;

        if (m_reccnt > 0) {
            build_internal_levels();
        }
    }

    ISAMTree(std::vector<ISAMTree*> &shards)
        : m_bf(nullptr) 
        , m_isam_nodes(nullptr)
        , m_root(nullptr)
        , m_reccnt(0)
        , m_tombstone_cnt(0)
        , m_internal_node_cnt(0)
        , m_deleted_cnt(0)
        , m_alloc_size(0)
        , m_data(nullptr)
    {
        size_t attemp_reccnt = 0;
        size_t tombstone_count = 0;
        auto cursors = build_cursor_vec<R, ISAMTree>(shards, &attemp_reccnt, &tombstone_count);

        m_bf = new BloomFilter<R>(BF_FPR, tombstone_count, BF_HASH_FUNCS);
        m_alloc_size = psudb::sf_aligned_alloc(CACHELINE_SIZE, 
                                               attemp_reccnt * sizeof(Wrapped<R>),
                                               (byte **) &m_data);

        auto res = sorted_array_merge<R>(cursors, m_data, m_bf);
        m_reccnt = res.record_count;
        m_tombstone_cnt = res.tombstone_count;

        if (m_reccnt > 0) {
            build_internal_levels();
        }
    }

    ~ISAMTree() {
        free(m_data);
        free(m_isam_nodes);
        delete m_bf;
    }

    Wrapped<R> *point_lookup(const R &rec, bool filter=false) {
        if (filter && !m_bf->lookup(rec)) {
            return nullptr;
        }

        size_t idx = get_lower_bound(rec.key);
        if (idx >= m_reccnt) {
            return nullptr;
        }

        while (idx < m_reccnt && m_data[idx].rec < rec) ++idx;

        if (m_data[idx].rec == rec) {
            return m_data + idx;
        }

        return nullptr;
    }

    Wrapped<R>* get_data() const {
        return m_data;
    }
    
    size_t get_record_count() const {
        return m_reccnt;
    }

    size_t get_tombstone_count() const {
        return m_tombstone_cnt;
    }


    size_t get_memory_usage() {
        return m_alloc_size + m_internal_node_cnt * NODE_SZ;
    }

    size_t get_aux_memory_usage() {
        return (m_bf) ? m_bf->memory_usage() : 0;
    }

    /* SortedShardInterface methods */
    size_t get_lower_bound(const K& key) const {
        const InternalNode* now = m_root;
        while (!is_leaf(reinterpret_cast<const byte*>(now))) {
            const InternalNode* next = nullptr;
            for (size_t i = 0; i < INTERNAL_FANOUT - 1; ++i) {
                if (now->child[i + 1] == nullptr || key <= now->keys[i]) {
                    next = reinterpret_cast<InternalNode*>(now->child[i]);
                    break;
                }
            }

            now = next ? next : reinterpret_cast<const InternalNode*>(now->child[INTERNAL_FANOUT - 1]);
        }

        const Wrapped<R>* pos = reinterpret_cast<const Wrapped<R>*>(now);
        while (pos < m_data + m_reccnt && pos->rec.key < key) pos++;

        return pos - m_data;
    }

    size_t get_upper_bound(const K& key) const {
        const InternalNode* now = m_root;
        while (!is_leaf(reinterpret_cast<const byte*>(now))) {
            const InternalNode* next = nullptr;
            for (size_t i = 0; i < INTERNAL_FANOUT - 1; ++i) {
                if (now->child[i + 1] == nullptr || key < now->keys[i]) {
                    next = reinterpret_cast<InternalNode*>(now->child[i]);
                    break;
                }
            }

            now = next ? next : reinterpret_cast<const InternalNode*>(now->child[INTERNAL_FANOUT - 1]);
        }

        const Wrapped<R>* pos = reinterpret_cast<const Wrapped<R>*>(now);
        while (pos < m_data + m_reccnt && pos->rec.key <= key) pos++;

        return pos - m_data;
    }

    const Wrapped<R>* get_record_at(size_t idx) const {
        return (idx < m_reccnt) ? m_data + idx : nullptr;
    }

private:
    void build_internal_levels() {
        size_t n_leaf_nodes = m_reccnt / LEAF_FANOUT + (m_reccnt % LEAF_FANOUT != 0);

        size_t level_node_cnt = n_leaf_nodes;
        size_t node_cnt = 0;
        do {
            level_node_cnt = level_node_cnt / INTERNAL_FANOUT + (level_node_cnt % INTERNAL_FANOUT != 0);
            node_cnt += level_node_cnt;
        } while (level_node_cnt > 1);

        m_alloc_size += psudb::sf_aligned_calloc(CACHELINE_SIZE, node_cnt, NODE_SZ, (byte**) &m_isam_nodes);
        m_internal_node_cnt = node_cnt;

        InternalNode* current_node = m_isam_nodes;

        const Wrapped<R>* leaf_base = m_data;
        const Wrapped<R>* leaf_stop = m_data + m_reccnt;
        while (leaf_base < leaf_stop) {
            size_t fanout = 0;
            for (size_t i = 0; i < INTERNAL_FANOUT; ++i) {
                auto rec_ptr = leaf_base + LEAF_FANOUT * i;
                if (rec_ptr >= leaf_stop) break;
                const Wrapped<R>* sep_key = std::min(rec_ptr + LEAF_FANOUT - 1, leaf_stop - 1);
                current_node->keys[i] = sep_key->rec.key;
                current_node->child[i] = (byte*)rec_ptr;
                ++fanout;
            }
            current_node++;
            leaf_base += fanout * LEAF_FANOUT;
        }

        auto level_start = m_isam_nodes;
        auto level_stop = current_node;
        auto current_level_node_cnt = level_stop - level_start;
        while (current_level_node_cnt > 1) {
            auto now = level_start;
            while (now < level_stop) {
                size_t child_cnt = 0;
                for (size_t i = 0; i < INTERNAL_FANOUT; ++i) {
                    auto node_ptr = now + i;
                    ++child_cnt;
                    if (node_ptr >= level_stop) break;
                    current_node->keys[i] = node_ptr->keys[INTERNAL_FANOUT - 1];
                    current_node->child[i] = (byte*)node_ptr;
                }
                now += child_cnt;
                current_node++;
            }
            level_start = level_stop;
            level_stop = current_node;
            current_level_node_cnt = level_stop - level_start;
        }
        
        assert(current_level_node_cnt == 1);
        m_root = level_start;
    }

    bool is_leaf(const byte* ptr) const {
        return ptr >= (const byte*)m_data && ptr < (const byte*)(m_data + m_reccnt);
    }

    psudb::BloomFilter<R> *m_bf;
    InternalNode* m_isam_nodes;
    InternalNode* m_root;
    size_t m_reccnt;
    size_t m_tombstone_cnt;
    size_t m_internal_node_cnt;
    size_t m_deleted_cnt;
    size_t m_alloc_size;

    Wrapped<R>* m_data;
};
}