cocos-engine/native/cocos/base/Map.h

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#pragma once

#define USE_STD_UNORDERED_MAP 1

#include <vector>

#if USE_STD_UNORDERED_MAP
    #include <unordered_map>
#else
    #include <map>
#endif

#include "base/Log.h"
#include "base/Random.h"
#include "base/Ref.h"

namespace cc {

/**
 * Similar to std::unordered_map, but it will manage reference count automatically internally.
 * Which means it will invoke Ref::retain() when adding an element, and invoke Ref::release() when removing an element.
 * @warning The element should be `Ref` or its sub-class.
 * @js NA
 * @lua NA
 */
template <class K, class V>
class Map {
public:
#if USE_STD_UNORDERED_MAP
    using RefMap = std::unordered_map<K, V>;
#else
    typedef std::map<K, V> RefMap;
#endif

    // ------------------------------------------
    // Iterators
    // ------------------------------------------

    /** Iterator, can be used to loop the Map. */
    using iterator = typename RefMap::iterator;
    /** Const iterator, can be used to loop the Map. */
    using const_iterator = typename RefMap::const_iterator;

    /** Return iterator to beginning. */
    iterator begin() { return _data.begin(); }
    /** Return const_iterator to beginning. */
    const_iterator begin() const { return _data.begin(); }

    /** Return iterator to end.*/
    iterator end() { return _data.end(); }
    /** Return const_iterator to end.*/
    const_iterator end() const { return _data.end(); }

    /** Return const_iterator to beginning.*/
    const_iterator cbegin() const { return _data.cbegin(); }
    /** Return const_iterator to end.*/
    const_iterator cend() const { return _data.cend(); }

    /** Default constructor */
    Map<K, V>()
    : _data() {
        static_assert(std::is_convertible<V, Ref *>::value, "Invalid Type for cc::Map<K, V>!");
    }

    /** Constructor with capacity. */
    explicit Map<K, V>(ssize_t capacity)
    : _data() {
        static_assert(std::is_convertible<V, Ref *>::value, "Invalid Type for cc::Map<K, V>!");
        _data.reserve(capacity);
    }

    /** Copy constructor. */
    Map<K, V>(const Map<K, V> &other) {
        static_assert(std::is_convertible<V, Ref *>::value, "Invalid Type for cc::Map<K, V>!");
        _data = other._data;
        addRefForAllObjects();
    }

    /** Move constructor. */
    Map<K, V>(Map<K, V> &&other) noexcept {
        static_assert(std::is_convertible<V, Ref *>::value, "Invalid Type for cc::Map<K, V>!");
        _data = std::move(other._data);
    }

    /**
     * Destructor.
     * It will release all objects in map.
     */
    ~Map<K, V>() {
        clear();
    }

    /** Sets capacity of the map. */
    void reserve(ssize_t capacity) {
#if USE_STD_UNORDERED_MAP
        _data.reserve(capacity);
#endif
    }

    /** Returns the number of buckets in the Map container. */
    ssize_t bucketCount() const {
#if USE_STD_UNORDERED_MAP
        return _data.bucket_count();
#else
        return 0;
#endif
    }

    /** Returns the number of elements in bucket n. */
    ssize_t bucketSize(ssize_t n) const {
#if USE_STD_UNORDERED_MAP
        return _data.bucket_size(n);
#else
        return 0;
#endif
    }

    /** Returns the bucket number where the element with key k is located. */
    ssize_t bucket(const K &k) const {
#if USE_STD_UNORDERED_MAP
        return _data.bucket(k);
#else
        return 0;
#endif
    }

    /** The number of elements in the map. */
    ssize_t size() const {
        return _data.size();
    }

    /**
     * Returns a bool value indicating whether the map container is empty, i.e. whether its size is 0.
     *  @note This function does not modify the content of the container in any way.
     *        To clear the content of an array object, member function unordered_map::clear exists.
     */
    bool empty() const {
        return _data.empty();
    }

    /** Returns all keys in the map. */
    std::vector<K> keys() const {
        std::vector<K> keys;

        if (!_data.empty()) {
            keys.reserve(_data.size());

            for (auto iter = _data.cbegin(); iter != _data.cend(); ++iter) {
                keys.push_back(iter->first);
            }
        }
        return keys;
    }

    /** Returns all keys that matches the object. */
    std::vector<K> keys(V object) const {
        std::vector<K> keys;

        if (!_data.empty()) {
            keys.reserve(_data.size() / 10);

            for (auto iter = _data.cbegin(); iter != _data.cend(); ++iter) {
                if (iter->second == object) {
                    keys.push_back(iter->first);
                }
            }
        }

        keys.shrink_to_fit();

        return keys;
    }

    /**
     * Returns a reference to the mapped value of the element with key k in the map.
     *
     *  @note If key does not match the key of any element in the container, the function return nullptr.
     *  @param key Key value of the element whose mapped value is accessed.
     *       Member type K is the keys for the elements in the container. defined in Map<K, V> as an alias of its first template parameter (Key).
     */
    V at(const K &key) {
        auto iter = _data.find(key);
        if (iter != _data.end()) {
            return iter->second;
        }
        return nullptr;
    }

    /**
     * Searches the container for an element with 'key' as key and returns an iterator to it if found,
     *         otherwise it returns an iterator to Map<K, V>::end (the element past the end of the container).
     *
     * @param key Key to be searched for.
     *        Member type 'K' is the type of the keys for the elements in the container,
     *        defined in Map<K, V> as an alias of its first template parameter (Key).
     */
    const_iterator find(const K &key) const {
        return _data.find(key);
    }

    iterator find(const K &key) {
        return _data.find(key);
    }

    /**
     * Inserts new elements in the map.
     *
     * @note If the container has already contained the key, this function will erase the old pair(key, object)  and insert the new pair.
     * @param key The key to be inserted.
     * @param object The object to be inserted.
     */
    void insert(const K &key, V object) {
        CCASSERT(object != nullptr, "Object is nullptr!");
        object->retain();
        erase(key);
        _data.insert(std::make_pair(key, object));
    }

    /**
     * Removes an element with an iterator from the Map<K, V> container.
     *
     * @param position Iterator pointing to a single element to be removed from the Map<K, V>.
     *        Member type const_iterator is a forward iterator type.
     */
    iterator erase(const_iterator position) {
        CCASSERT(position != _data.cend(), "Invalid iterator!");
        position->second->release();
        return _data.erase(position);
    }

    /**
     * Removes an element with an iterator from the Map<K, V> container.
     *
     * @param k Key of the element to be erased.
     *        Member type 'K' is the type of the keys for the elements in the container,
     *        defined in Map<K, V> as an alias of its first template parameter (Key).
     */
    size_t erase(const K &k) {
        auto iter = _data.find(k);
        if (iter != _data.end()) {
            iter->second->release();
            _data.erase(iter);
            return 1;
        }
        return 0;
    }

    /**
     * Removes some elements with a vector which contains keys in the map.
     *
     * @param keys Keys of elements to be erased.
     */
    void erase(const std::vector<K> &keys) {
        for (const auto &key : keys) {
            this->erase(key);
        }
    }

    /**
     * All the elements in the Map<K,V> container are dropped:
     *  their reference count will be decreased, and they are removed from the container,
     *  leaving it with a size of 0.
     */
    void clear() {
        for (auto iter = _data.cbegin(); iter != _data.cend(); ++iter) {
            iter->second->release();
        }

        _data.clear();
    }

    /**
     * Gets a random object in the map.
     * @return Returns the random object if the map isn't empty, otherwise it returns nullptr.
     */
    V getRandomObject() const {
        if (!_data.empty()) {
            auto           randIdx  = RandomHelper::randomInt<int>(0, static_cast<int>(_data.size()) - 1);
            const_iterator randIter = _data.begin();
            std::advance(randIter, randIdx);
            return randIter->second;
        }
        return nullptr;
    }

    /** Copy assignment operator. */
    Map<K, V> &operator=(const Map<K, V> &other) {
        if (this != &other) {
            clear();
            _data = other._data;
            addRefForAllObjects();
        }
        return *this;
    }

    /** Move assignment operator. */
    Map<K, V> &operator=(Map<K, V> &&other) noexcept {
        if (this != &other) {
            clear();
            _data = std::move(other._data);
        }
        return *this;
    }

protected:
    /** Retains all the objects in the map */
    void addRefForAllObjects() {
        for (auto iter = _data.begin(); iter != _data.end(); ++iter) {
            iter->second->retain();
        }
    }

    RefMap _data;
};

} // namespace cc