/*
 * libfud
 * Copyright 2024 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.
 */

#ifndef FUD_STRING_HPP
#define FUD_STRING_HPP

#include "fud_allocator.hpp"
#include "fud_assert.hpp"
#include "fud_result.hpp"
#include "fud_status.hpp"
#include "fud_string_view.hpp"
#include "fud_c_string.hpp"
#include "fud_utf8.hpp"

#include <climits>
#include <cstddef>

static_assert(CHAR_BIT == 8);

namespace fud {

constexpr size_t SSO_BUF_LENGTH = 15;
constexpr size_t SSO_BUF_SIZE = SSO_BUF_LENGTH + 1;

using StringResult = Result<String, FudStatus>;

struct DrainResult {
    size_t bytesWritten;
    FudStatus status;
};

class String {
  public:
    static StringResult makeFromCString(const char* cString);

    static StringResult makeFromCString(const char* cString, Allocator* allocator);

    template <typename... CStrings>
    static StringResult makeFromCStrings(CStrings... cStrings)
    {
        return makeFromCStringsAlloc(&globalFudAllocator, cStrings...);
    }

    template <typename... CStrings>
    static StringResult makeFromCStringsAlloc(Allocator* allocator, CStrings... cStrings)
    {
        if (allocator == nullptr) {
            return StringResult::error(FudStatus::NullPointer);
        }
        size_t totalLength = 0;
        Array<size_t, sizeof...(cStrings)> lengths{};
        Array<const char*, sizeof...(cStrings)> strPointers{};
        size_t index = 0;
        for (const auto* cStringItem: {cStrings...}) {
            const char* cString = nullptr;
            if constexpr (std::is_same_v<decltype(cStringItem), const char*>) {
                cString = cStringItem;
            } else if constexpr (std::is_same_v<decltype(cStringItem), const utf8*>) {
                cString = reinterpret_cast<const char*>(cStringItem);
            } else {
                static_assert(!std::is_same_v<decltype(cStringItem), const char*>);
            }
            strPointers[index] = cString;

            auto lengthResult = cStringLength(cString);
            if (lengthResult < 0 || lengthResult >= SSIZE_MAX) {
                return StringResult::error(FudStatus::ArgumentInvalid);
            }
            auto stringLength = static_cast<size_t>(lengthResult);
            if (SIZE_MAX - totalLength < stringLength) {
                return StringResult::error(FudStatus::Failure);
            }
            totalLength += stringLength;
            lengths[index] = stringLength;
            index++;
        }

        String output{};
        output.m_length = totalLength;
        output.m_allocator = allocator;
        if (output.m_length >= output.m_capacity) {
            output.m_capacity = output.m_length + 1;
            /* Avoid using compiler expansions in headers */
            auto dataResult = output.m_allocator->allocate(output.m_capacity);
            if (dataResult.isError()) {
                return StringResult::error(dataResult.getError());
            }
            output.m_data = static_cast<utf8*>(dataResult.getOkay());
        }

        auto* data = output.data();
        size_t cumulativeLength = 0;
        for (size_t idx = 0; idx < strPointers.size(); ++idx) {
            const auto* cString = strPointers[idx];
            auto copyStatus = copyMem(data + cumulativeLength, output.m_capacity - cumulativeLength, cString, lengths[idx]);
            fudAssert(copyStatus == FudStatus::Success);
            cumulativeLength += lengths[idx];
        }

        auto terminateStatus = output.nullTerminate();
        fudAssert(terminateStatus == FudStatus::Success);

        return StringResult::okay(std::move(output));
    }

    String() noexcept = default;

    String(const String& rhs) = delete;

    String(String&& rhs) noexcept;

    ~String();

    String& operator=(const String& rhs) = delete;

    String& operator=(String&& rhs) noexcept;

    static StringResult from(const String& rhs);

    static StringResult from(StringView view, Allocator* allocator = &globalFudAllocator);

    FudStatus copy(const String& rhs);

    [[nodiscard]] constexpr size_t length() const
    {
        return m_length;
    }

    [[nodiscard]] constexpr bool empty() const
    {
        return m_length == 0;
    }

    [[nodiscard]] constexpr size_t size() const
    {
        return m_length + 1;
    }

    [[nodiscard]] constexpr size_t capacity() const
    {
        return m_capacity - 1;
    }

    /** \brier The underlying data, guaranteed to have c string representation. */
    [[nodiscard]] constexpr const utf8* data() const
    {
        return isLarge() ? m_data : m_buffer.data();
    }

    /** \brier The underlying data as an explicit c string. */
    [[nodiscard]] inline const char* c_str() const
    {
        return isLarge() ? reinterpret_cast<const char*>(m_data) : reinterpret_cast<const char*>(m_buffer.data());
    }

    /** \brier The underlying data, guaranteed to have c string representation. */
    [[nodiscard]] constexpr utf8* data()
    {
        return isLarge() ? m_data : m_buffer.data();
    }

    /** \brier The underlying data as an explicit c string. */
    [[nodiscard]] inline char* c_str()
    {
        return isLarge() ? reinterpret_cast<char*>(m_data) : reinterpret_cast<char*>(m_buffer.data());
    }

    [[nodiscard]] bool nullTerminated() const;

    [[nodiscard]] bool valid() const;

    [[nodiscard]] bool utf8Valid() const;

    FudStatus nullTerminate();

    FudStatus reserve(size_t newCapacity);

    [[nodiscard]] std::optional<utf8> back();

    [[nodiscard]] constexpr size_t remainingLength() const
    {
        if (m_length >= m_capacity) {
            return 0;
        }

        return m_capacity - 1U - m_length;
    }

    [[nodiscard]] inline StringView asView() const
    {
        return StringView(*this);
    }

    FudStatus pushBack(char letter);

    FudStatus pushBack(utf8 letter);

    FudStatus pushBack(const FudUtf8& letter);

    std::optional<utf8> pop();

    FudStatus append(const char* source);

    FudStatus append(const String& source);

    FudStatus append(StringView source);

    DrainResult drain(const char* source);

    DrainResult drain(const String& source);

    DrainResult drain(StringView source);

    [[nodiscard]] StringResult catenate(const String& rhs) const;

    [[nodiscard]] StringResult catenate(const char* rhs) const;

    [[nodiscard]] bool compare(const String& rhs) const;

    FudStatus clear();

    const utf8* begin() const;

    const utf8* end() const;

  private:
    void cleanup();

    FudStatus resize(size_t newCapacity);

    using BufType = Array<utf8, SSO_BUF_SIZE>;
    union {
        BufType m_buffer{BufType::constFill(0)};
        utf8* m_data;
    };

    size_t m_length{0};

    size_t m_capacity{SSO_BUF_SIZE};

    [[nodiscard]] constexpr bool isLarge() const
    {
        return m_capacity > SSO_BUF_SIZE;
    }

    Allocator* m_allocator{&globalFudAllocator};
};

} // namespace fud

#endif