/*
 * libfud
 * Copyright 2025 Dominick Allen
 *
 * Licensed 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 "fud_hash.hpp"

namespace fud::detail {

size_t djb2(const utf8* data, size_t length)
{
    /* Allegedly djb chose 5381 after testing showed fewer collisions and better avalanching: see
     * https://stackoverflow.com/questions/10696223/reason-for-the-number-5381-in-the-djb-hash-function */
    constexpr size_t hashInit = 5381;
    constexpr size_t mulBy = 33;
    size_t hash = hashInit;
    if (data == nullptr) {
        return hash;
    }

    for (size_t index = 0; index < length; ++index) {
        hash = (hash * mulBy) ^ data[index];
    }

    return hash;
}


size_t DefaultHash<String>::operator()(const String& value, size_t seed) const
{
        static_cast<void>(seed);
        return djb2(value.data(), value.length());
}

size_t DefaultHash<StringView>::operator()(const StringView& value, size_t seed) const
{
        static_cast<void>(seed);
        return djb2(value.data(), value.length());
}

}