// Licensed to the Apache Software Foundation (ASF) under one

// or more contributor license agreements.  See the NOTICE file

// distributed with this work for additional information

// regarding copyright ownership.  The ASF licenses this file

// to you 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 <fmt/core.h>

#include <parallel_hashmap/phmap.h>

#include <algorithm>

#include <memory>

#include <mutex>

#include <type_traits>

#include <vector>

#include "common/logging.h"

#include "olap/iterators.h"

#include "olap/olap_common.h"

#include "olap/schema.h"

#include "olap/tablet.h"

#include "olap/tablet_schema.h"

#include "util/time.h"

namespace doris {

namespace segment_v2 {

class Segment;

class SegmentIterator;

using SegmentIteratorUPtr = std::unique_ptr<SegmentIterator>;

} // namespace segment_v2

// The SchemaCache is utilized to cache pre-allocated data structures,

// eliminating the need for frequent allocation and deallocation during usage.

// This caching mechanism proves immensely advantageous, particularly in scenarios

// with high concurrency, where queries are executed simultaneously.

class SchemaCache : public LRUCachePolicy {

public:

    static SchemaCache* instance() { return _s_instance; }

    static void create_global_instance(size_t capacity);

    static std::string get_schema_key(int64_t tablet_id, const std::vector<TColumn>& columns,

                                      int32_t version);

    // Get a shared cached schema from cache, schema_key is a subset of column unique ids

    TabletSchemaSPtr get_schema(const std::string& schema_key) {

        if (!_s_instance || schema_key.empty()) {

            return {};

        }

        auto lru_handle = _cache->lookup(schema_key);

        if (lru_handle) {

            Defer release([cache = _cache.get(), lru_handle] { cache->release(lru_handle); });

            auto value = (CacheValue*)_cache->value(lru_handle);

            value->last_visit_time = UnixMillis();

            VLOG_DEBUG << "use cache schema";

            return value->tablet_schema;

        }

        return {};

    }

    // Insert a shared Schema into cache, schema_key is full column unique ids

    void insert_schema(const std::string& key, TabletSchemaSPtr schema) {

        if (!_s_instance || key.empty()) {

            return;

        }

        CacheValue* value = new CacheValue;

        value->last_visit_time = UnixMillis();

        value->tablet_schema = schema;

        auto deleter = [](const doris::CacheKey& key, void* value) {

            CacheValue* cache_value = (CacheValue*)value;

            delete cache_value;

        };

        auto lru_handle = _cache->insert(key, value, sizeof(CacheValue), deleter,

                                         CachePriority::NORMAL, schema->mem_size());

        _cache->release(lru_handle);

    }

    // Try to prune the cache if expired.

    Status prune();

    struct CacheValue : public LRUCacheValueBase {

        TabletSchemaSPtr tablet_schema = nullptr;

    };

private:

    SchemaCache(size_t capacity)

            : LRUCachePolicy("SchemaCache", capacity, LRUCacheType::NUMBER,

                             config::schema_cache_sweep_time_sec) {}

    static constexpr char SCHEMA_DELIMITER = '-';

    static SchemaCache* _s_instance;

};

} // namespace doris