/*
 * Copyright (C) 2014 Pavel Kirienko <pavel.kirienko@gmail.com>
 */

#pragma once

#include <cassert>
#include <cstdlib>
#include <uavcan/linked_list.hpp>
#include <uavcan/impl_constants.hpp>
#include <uavcan/dynamic_memory.hpp>
#include <uavcan/util/compile_time.hpp>

namespace uavcan
{
/**
 * Slow but memory efficient KV container.
 * Type requirements:
 *  Both key and value must be copyable, assignable and default constructible.
 *  Key must implement a comparison operator.
 *  Key's default constructor must initialize the object into invalid state.
 *  Size of Key + Value + padding must not exceed MemPoolBlockSize.
 */
template <typename Key, typename Value, unsigned NumStaticEntries>
class UAVCAN_EXPORT Map : Noncopyable
{
    UAVCAN_PACKED_BEGIN
    struct KVPair
    {
        Key key;
        Value value;
        KVPair() { }
        KVPair(const Key& key, const Value& value)
            : key(key)
            , value(value)
        { }
        bool match(const Key& rhs) const { return rhs == key; }
    };

    struct KVGroup : LinkedListNode<KVGroup>
    {
        enum { NumKV = (MemPoolBlockSize - sizeof(LinkedListNode<KVGroup>)) / sizeof(KVPair) };
        KVPair kvs[NumKV];

        KVGroup()
        {
            StaticAssert<(NumKV > 0)>::check();
            IsDynamicallyAllocatable<KVGroup>::check();
        }

        static KVGroup* instantiate(IAllocator& allocator)
        {
            void* const praw = allocator.allocate(sizeof(KVGroup));
            if (praw == NULL)
            {
                return NULL;
            }
            return new (praw) KVGroup();
        }

        static void destroy(KVGroup*& obj, IAllocator& allocator)
        {
            if (obj != NULL)
            {
                obj->~KVGroup();
                allocator.deallocate(obj);
                obj = NULL;
            }
        }

        KVPair* find(const Key& key)
        {
            for (int i = 0; i < NumKV; i++)
            {
                if (kvs[i].match(key))
                {
                    return kvs + i;
                }
            }
            return NULL;
        }
    };
    UAVCAN_PACKED_END

    LinkedListRoot<KVGroup> list_;
    IAllocator& allocator_;
    KVPair static_[NumStaticEntries];

    KVPair* find(const Key& key);

    void optimizeStorage();

    void compact();

    struct YesPredicate
    {
        bool operator()(const Key& k, const Value& v) const { (void)k; (void)v; return true; }
    };

    // This container is not copyable
    Map(const Map&);
    bool operator=(const Map&);

public:
    Map(IAllocator& allocator)
        : allocator_(allocator)
    {
        assert(Key() == Key());
    }

    ~Map() { removeAll(); }

    Value* access(const Key& key);

    /// If entry with the same key already exists, it will be replaced
    Value* insert(const Key& key, const Value& value);

    void remove(const Key& key);

    /**
     * Remove entries where predicate returns true.
     * Predicate prototype:
     *  bool (const Key& key, const Value& value)
     */
    template <typename Predicate>
    void removeWhere(Predicate predicate);

    template <typename Predicate>
    const Key* findFirstKey(Predicate predicate) const;

    void removeAll();

    bool isEmpty() const;

    /// For testing
    unsigned getNumStaticPairs() const;

    /// For testing
    unsigned getNumDynamicPairs() const;
};

// ----------------------------------------------------------------------------

/*
 * Map<>
 */
template <typename Key, typename Value, unsigned NumStaticEntries>
typename Map<Key, Value, NumStaticEntries>::KVPair* Map<Key, Value, NumStaticEntries>::find(const Key& key)
{
    for (unsigned i = 0; i < NumStaticEntries; i++)
    {
        if (static_[i].match(key))
        {
            return static_ + i;
        }
    }

    KVGroup* p = list_.get();
    while (p)
    {
        KVPair* const kv = p->find(key);
        if (kv)
        {
            return kv;
        }
        p = p->getNextListNode();
    }
    return NULL;
}

template <typename Key, typename Value, unsigned NumStaticEntries>
void Map<Key, Value, NumStaticEntries>::optimizeStorage()
{
    while (true)
    {
        // Looking for first EMPTY static entry
        KVPair* stat = NULL;
        for (unsigned i = 0; i < NumStaticEntries; i++)
        {
            if (static_[i].match(Key()))
            {
                stat = static_ + i;
                break;
            }
        }
        if (stat == NULL)
        {
            break;
        }

        // Looking for the first NON-EMPTY dynamic entry, erasing immediately
        KVGroup* p = list_.get();
        KVPair dyn;
        while (p)
        {
            bool stop = false;
            for (int i = 0; i < KVGroup::NumKV; i++)
            {
                if (!p->kvs[i].match(Key())) // Non empty
                {
                    dyn = p->kvs[i];         // Copy by value
                    p->kvs[i] = KVPair();    // Erase immediately
                    stop = true;
                    break;
                }
            }
            if (stop)
            {
                break;
            }
            p = p->getNextListNode();
        }
        if (dyn.match(Key()))
        {
            break;
        }

        // Migrating
        *stat = dyn;
    }
}

template <typename Key, typename Value, unsigned NumStaticEntries>
void Map<Key, Value, NumStaticEntries>::compact()
{
    KVGroup* p = list_.get();
    while (p)
    {
        KVGroup* const next = p->getNextListNode();
        bool remove_this = true;
        for (int i = 0; i < KVGroup::NumKV; i++)
        {
            if (!p->kvs[i].match(Key()))
            {
                remove_this = false;
                break;
            }
        }
        if (remove_this)
        {
            list_.remove(p);
            KVGroup::destroy(p, allocator_);
        }
        p = next;
    }
}

template <typename Key, typename Value, unsigned NumStaticEntries>
Value* Map<Key, Value, NumStaticEntries>::access(const Key& key)
{
    assert(!(key == Key()));
    KVPair* const kv = find(key);
    return kv ? &kv->value : NULL;
}

template <typename Key, typename Value, unsigned NumStaticEntries>
Value* Map<Key, Value, NumStaticEntries>::insert(const Key& key, const Value& value)
{
    assert(!(key == Key()));
    remove(key);

    KVPair* const kv = find(Key());
    if (kv)
    {
        *kv = KVPair(key, value);
        return &kv->value;
    }

    KVGroup* const kvg = KVGroup::instantiate(allocator_);
    if (kvg == NULL)
    {
        return NULL;
    }
    list_.insert(kvg);
    kvg->kvs[0] = KVPair(key, value);
    return &kvg->kvs[0].value;
}

template <typename Key, typename Value, unsigned NumStaticEntries>
void Map<Key, Value, NumStaticEntries>::remove(const Key& key)
{
    assert(!(key == Key()));
    KVPair* const kv = find(key);
    if (kv)
    {
        *kv = KVPair();
        optimizeStorage();
        compact();
    }
}

template <typename Key, typename Value, unsigned NumStaticEntries>
template <typename Predicate>
void Map<Key, Value, NumStaticEntries>::removeWhere(Predicate predicate)
{
    unsigned num_removed = 0;

    for (unsigned i = 0; i < NumStaticEntries; i++)
    {
        if (!static_[i].match(Key()))
        {
            if (predicate(static_[i].key, static_[i].value))
            {
                num_removed++;
                static_[i] = KVPair();
            }
        }
    }

    KVGroup* p = list_.get();
    while (p)
    {
        for (int i = 0; i < KVGroup::NumKV; i++)
        {
            const KVPair* const kv = p->kvs + i;
            if (!kv->match(Key()))
            {
                if (predicate(kv->key, kv->value))
                {
                    num_removed++;
                    p->kvs[i] = KVPair();
                }
            }
        }
        p = p->getNextListNode();
    }

    if (num_removed > 0)
    {
        optimizeStorage();
        compact();
    }
}

template <typename Key, typename Value, unsigned NumStaticEntries>
template <typename Predicate>
const Key* Map<Key, Value, NumStaticEntries>::findFirstKey(Predicate predicate) const
{
    for (unsigned i = 0; i < NumStaticEntries; i++)
    {
        if (!static_[i].match(Key()))
        {
            if (predicate(static_[i].key, static_[i].value))
            {
                return &static_[i].key;
            }
        }
    }

    KVGroup* p = list_.get();
    while (p)
    {
        for (int i = 0; i < KVGroup::NumKV; i++)
        {
            const KVPair* const kv = p->kvs + i;
            if (!kv->match(Key()))
            {
                if (predicate(kv->key, kv->value))
                {
                    return &p->kvs[i].key;
                }
            }
        }
        p = p->getNextListNode();
    }
    return NULL;
}

template <typename Key, typename Value, unsigned NumStaticEntries>
void Map<Key, Value, NumStaticEntries>::removeAll()
{
    removeWhere(YesPredicate());
}

template <typename Key, typename Value, unsigned NumStaticEntries>
bool Map<Key, Value, NumStaticEntries>::isEmpty() const
{
    return (getNumStaticPairs() == 0) && (getNumDynamicPairs() == 0);
}

template <typename Key, typename Value, unsigned NumStaticEntries>
unsigned Map<Key, Value, NumStaticEntries>::getNumStaticPairs() const
{
    unsigned num = 0;
    for (unsigned i = 0; i < NumStaticEntries; i++)
    {
        if (!static_[i].match(Key()))
        {
            num++;
        }
    }
    return num;
}

template <typename Key, typename Value, unsigned NumStaticEntries>
unsigned Map<Key, Value, NumStaticEntries>::getNumDynamicPairs() const
{
    unsigned num = 0;
    KVGroup* p = list_.get();
    while (p)
    {
        for (int i = 0; i < KVGroup::NumKV; i++)
        {
            const KVPair* const kv = p->kvs + i;
            if (!kv->match(Key()))
            {
                num++;
            }
        }
        p = p->getNextListNode();
    }
    return num;
}

}