////////////////////////////////
//~ Hash types

#define Fnv64Basis 0xCBF29CE484222325

////////////////////////////////
//~ Mergesort types

/* Compare functions should
 * return a positive value if a should go before b
 * return a negative value if a should go after b
 * return 0 otherwise
 */
#define MergesortCompareFuncDef(name, arg_a, arg_b, arg_udata) i32 name(void *arg_a, void *arg_b, void *arg_udata)
typedef MergesortCompareFuncDef(MergesortCompareFunc, a, b, udata);

////////////////////////////////
//~ Dict types

Struct(DictEntry)
{
    u64 hash;
    u64 value;
    DictEntry *prev_in_bin;
    DictEntry *next_in_bin;
    DictEntry *prev;
    DictEntry *next;
};

Struct(DictBin)
{
    DictEntry *first;
    DictEntry *last;
};

Struct(Dict)
{
    u64 bins_count;
    DictBin *bins;
    DictEntry *first_free;
    DictEntry *first;
    DictEntry *last;
};

////////////////////////////////
//~ Hash utils

/* FNV-1a parameters for different hash sizes:
 * https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function#FNV_hash_parameters
 */
Inline u64 HashFnv64(u64 seed, String s)
{
    u64 hash = seed;
    for (u64 i = 0; i < s.len; ++i)
    {
        hash ^= (u8)s.text[i];
        hash *= 0x100000001B3;
    }
    return hash;
}

////////////////////////////////
//~ Mergesort utils

Inline void MergesortInternal(u8 *left, u8 *right, u8 *items, u64 left_count, u64 right_count, u64 item_size, MergesortCompareFunc *callback, void *udata)
{
    /* Sort */
    u64 i = 0;
    u64 l = 0;
    u64 r = 0;
    while (l < left_count && r < right_count)
    {
        u8 *dst = items + (i * item_size);
        u8 *left_item = left + (l * item_size);
        u8 *right_item = right + (r * item_size);
        ++i;
        if (callback(left_item, right_item, udata) > 0)
        {
            CopyBytes(dst, left_item, item_size);
            ++l;
        }
        else
        {
            CopyBytes(dst, right_item, item_size);
            ++r;
        }
    }
    /* Copy remaining */
    if (l != left_count)
    {
        u64 remaining_count = left_count - l;
        u64 remaining_bytes = remaining_count * item_size;
        u8 *dst = items + (i * item_size);
        u8 *src = left + (l * item_size);
        CopyBytes(dst, src, remaining_bytes);
    }
    else if (r != right_count)
    {
        u64 remaining_count = right_count - r;
        u64 remaining_bytes = remaining_count * item_size;
        u8 *dst = items + (i * item_size);
        u8 *src = right + (r * item_size);
        CopyBytes(dst, src, remaining_bytes);
    }
}

Inline void Mergesort(void *items, u64 item_count, u64 item_size, MergesortCompareFunc *callback, void *udata)
{
    if (item_count > 1)
    {
        TempArena scratch = BeginScratchNoConflict();
        u64 left_count = item_count / 2;
        u64 right_count = item_count - left_count;

        u64 left_size = left_count * item_size;
        u64 right_size = right_count * item_size;

        u8 *left = PushStructsNoZero(scratch.arena, u8, left_size);
        u8 *right = PushStructsNoZero(scratch.arena, u8, right_size);
        CopyBytes(left, items, left_size);
        CopyBytes(right, (u8 *)items + left_size, right_size);

        Mergesort(left, left_count, item_size, callback, udata);
        Mergesort(right, right_count, item_size, callback, udata);
        MergesortInternal(left, right, (u8 *)items, left_count, right_count, item_size, callback, udata);
        EndScratch(scratch);
    }
}

////////////////////////////////
//~ Dict utils

//- Dict init

Inline Dict *InitDict(Arena *arena, u64 bins_count)
{
    __prof;
    Dict *dict = PushStruct(arena, Dict);
    dict->bins_count = MaxU64(bins_count, 1);  /* Ensure at least 1 bin */
    dict->bins = PushStructs(arena, DictBin, dict->bins_count);
    return dict;
}

Inline void ResetDict(Dict *dict)
{
    ZeroBytes(dict->bins, sizeof(*dict->bins) * dict->bins_count);
    if (dict->first)
    {
        dict->last->next = dict->first_free;
        dict->first_free = dict->first;
    }
}

//- Dict set

Inline DictEntry *EnsureDictEntry(Arena *arena, Dict *dict, u64 hash)
{
    __prof;
    DictBin *bin = &dict->bins[hash % dict->bins_count];

    DictEntry *entry = bin->first;
    while (entry)
    {
        if (hash == entry->hash)
        {
            /* Existing match found */
            break;
        }
        entry = entry->next_in_bin;
    }

    /* No match found, create new entry */
    if (!entry)
    {
        if (dict->first_free)
        {
            entry = dict->first_free;
            dict->first_free = entry->next;
        }
        else
        {
            entry = PushStructNoZero(arena, DictEntry);
        }
        ZeroStruct(entry);
        entry->hash = hash;
        if (bin->last)
        {
            bin->last->next_in_bin = entry;
            entry->prev_in_bin = bin->last;
        }
        else
        {
            bin->first = entry;
        }
        bin->last = entry;
        if (dict->last)
        {
            dict->last->next = entry;
            entry->prev = dict->last;
        }
        else
        {
            dict->first = entry;
        }
        dict->last = entry;
    }

    return entry;
}

Inline void SetDictValue(Arena *arena, Dict *dict, u64 hash, u64 value)
{
    __prof;
    DictEntry *entry = EnsureDictEntry(arena, dict, hash);
    entry->value = value;
}

//- Dict remove

Inline void RemoveDictEntry(Dict *dict, DictEntry *entry)
{
    /* Remove from bin */
    {
        DictBin *bin = &dict->bins[entry->hash % dict->bins_count];
        DictEntry *prev_in_bin = entry->prev_in_bin;
        DictEntry *next_in_bin = entry->next_in_bin;
        if (prev_in_bin)
        {
            prev_in_bin->next_in_bin = next_in_bin;
        }
        else
        {
            bin->first = next_in_bin;
        }
        if (next_in_bin)
        {
            next_in_bin->prev_in_bin = prev_in_bin;
        }
        else
        {
            bin->last = prev_in_bin;
        }
    }
    /* Remove from list */
    {
        DictEntry *prev = entry->prev;
        DictEntry *next = entry->next;
        if (prev)
        {
            prev->next = next;
        }
        else
        {
            dict->first = next;
        }
        if (next)
        {
            next->prev = prev;
        }
        else
        {
            dict->last = prev;
        }
    }
    /* Insert into free list */
    {
        entry->next = dict->first_free;
        dict->first_free = entry;
    }
}

//- Dict index

Inline DictEntry *DictEntryFromHash(Dict *dict, u64 hash)
{
    __prof;
    DictEntry *result = 0;
    DictBin *bin = &dict->bins[hash % dict->bins_count];
    for (DictEntry *entry = bin->first; entry; entry = entry->next_in_bin)
    {
        if (hash == entry->hash)
        {
            /* Match found */
            result = entry;
            break;
        }
    }
    return result;
}

Inline u64 DictValueFromHash(Dict *dict, u64 hash)
{
    __prof;
    DictEntry *entry = DictEntryFromHash(dict, hash);
    return entry ? entry->value : 0;
}