/*
 * 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.
 */

#include "fud_string_view.hpp"

#include "fud_string.hpp"

namespace fud {

StringView::StringView(const String& fudString) noexcept : StringView(fudString.length(), fudString.data())
{
}

bool StringView::nullTerminated() const
{
    return m_data != nullptr && m_data[m_length] == '\0';
}

bool StringView::utf8Valid() const
{
    if (m_data == nullptr) {
        return false;
    }

    for (size_t idx = 0; idx < m_length;) {
        if (Ascii::valid(m_data[idx])) {
            idx++;
        } else if (idx + 1 < m_length && Utf82Byte::valid(m_data[idx], m_data[idx + 1])) {
            idx += 2;
        } else if (idx + 2 < m_length && Utf83Byte::valid(m_data[idx], m_data[idx + 1], m_data[idx + 2])) {
            idx += 3;
        } else if (
            idx + 3 < m_length && Utf84Byte::valid(m_data[idx], m_data[idx + 1], m_data[idx + 2], m_data[idx + 3])) {
            idx += 4;
        } else {
            return false;
        }
    }

    return true;
}

Result<size_t, FudStatus> StringView::skipWhitespace()
{
    using RetType = Result<size_t, FudStatus>;
    if (m_data == nullptr) {
        return RetType::error(FudStatus::NullPointer);
    }
    size_t index = 0;
    while (m_length > 0 && classify::isSpace(static_cast<char>(m_data[0]))) {
        m_data++;
        m_length--;
        index++;
    }

    return RetType::okay(index);
}

Result<size_t, FudStatus> StringView::trimWhitespace()
{
    using RetType = Result<size_t, FudStatus>;
    if (m_data == nullptr) {
        return RetType::error(FudStatus::NullPointer);
    }

    size_t count = 0;
    while (m_length > 0 && classify::isSpace(static_cast<char>(m_data[m_length - 1]))) {
        m_length--;
        count++;
    }

    return RetType::okay(count);
}

bool StringView::advance()
{
    if (m_length < 1) {
        return false;
    }
    m_length--;
    m_data++;
    return true;
}

void StringView::advanceUnsafe()
{
    fudAssert(m_length > 0);
    m_length--;
    m_data++;
}

bool StringView::advance(size_t size)
{
    if (size > m_length) {
        return false;
    }
    m_length -= size;
    m_data += size;
    return true;
}

void StringView::advanceUnsafe(size_t size)
{
    fudAssert(size <= m_length);
    m_length -= size;
    m_data += size;
}

FudStatus skipWhitespace(StringView& view, size_t& skipIndex)
{
    auto skipResult = view.skipWhitespace();
    if (skipResult.isError()) {
        return skipResult.getError();
    }
    skipIndex = skipResult.getOkay();
    if (view.length() < 1) {
        return FudStatus::ArgumentInvalid;
    }
    return FudStatus::Success;
}

#if 0

FudStatus fud_string_truncate(ExtBasicString* source, ssize_t newLength)
{
    if (source == nullptr) {
        return FudStatus::NullPointer;
    }
    StringBorrow wrapper{*source};
    if (!wrapper.valid()) {
        return FudStatus::StringInvalid;
    }

    if ((newLength > 0 && static_cast<size_t>(newLength) > source->m_length) ||
        (static_cast<size_t>(-newLength) > source->m_length)) {
        return FudStatus::ArgumentInvalid;
    }

    if (newLength < 0) {
        source->m_length = source->m_length - static_cast<size_t>(-newLength);
    } else {
        source->m_length = static_cast<size_t>(newLength);
    }

    return wrapper.nullTerminate();
}

FudStatus fud_string_reverse(ExtBasicString* source)
{
    if (source == nullptr || source->m_data == nullptr) {
        return FudStatus::NullPointer;
    }
    return fud_string_reverse_substring(source, StringView{source->m_length, source->m_data});
}

FudStatus fud_string_reverse_substring(ExtBasicString* source, StringView subString)
{
    auto dataOffset = subString.data - source->m_data;
    if (dataOffset < 0 || static_cast<size_t>(dataOffset) > source->m_length) {
        return FudStatus::ArgumentInvalid;
    }
    if (static_cast<size_t>(dataOffset) + subString.length > source->m_length) {
        return FudStatus::ArgumentInvalid;
    }

    if (source == nullptr || source->m_data == nullptr) {
        return FudStatus::NullPointer;
    }

    StringView view{subString};

    size_t index = 0;
    auto* data = source->m_data + dataOffset;
    while (index < subString.length) {
        if (fud_char_is_ascii(static_cast<char>(data[index]))) {
            index++;
            continue;
        }
        auto utf8 = FudUtf8::fromStringView(view, index);
        if (!utf8.valid()) {
            return ExtUtf8Invalid;
        }
        const auto* utf8Data = utf8.data();
        if (utf8Data == nullptr) {
            return ExtFailure;
        }
        auto utf8Size = utf8.size();
        switch (utf8Size) {
        case 2:
            data[index] = utf8Data[1];
            data[index + 1] = utf8Data[0];
            break;
        case 3:
            data[index] = utf8Data[2];
            data[index + 2] = utf8Data[0];
            break;
        case 4:
            data[index] = utf8Data[3];
            data[index + 1] = utf8Data[2];
            data[index + 2] = utf8Data[1];
            data[index + 3] = utf8Data[0];
            break;
        default:
            return ExtFailure;
        }
        index += utf8Size;
    }

    DataView<uint8_t> dataView{subString.length, data};
    reverse(dataView);

    return FudStatus::Success;
}

FudStatus fud_string_compare(StringView levo, StringView dextro, int* difference)
{
    if (anyAreNull(difference, levo.data, dextro.data)) {
        return FudStatus::NullPointer;
    }

    int diff = 0;
    size_t index = 0;
    while (diff == 0 && index < levo.length && index < dextro.length) {
        diff = levo.data[index] - dextro.data[index];
        index++;
    }

    if (diff != 0 || levo.length == dextro.length) {
        /* nothing to do */
    } else if (levo.length > dextro.length) {
        diff = static_cast<int>(levo.data[index]);
    } else {
        diff = -static_cast<int>(dextro.data[index]);
    }

    *difference = diff;
    return FudStatus::Success;
}

FudStatus fud_string_chr(StringView extStringView, char character, size_t* index)
{
    if (anyAreNull(extStringView.data, index)) {
        return FudStatus::NullPointer;
    }

    bool found = false;
    for (size_t localIndex = 0; localIndex < extStringView.length; ++localIndex) {
        if (extStringView.data[localIndex] == static_cast<uint8_t>(character)) {
            *index = localIndex;
            found = true;
            break;
        }
    }

    if (found) {
        return FudStatus::Success;
    }

    return ExtNotFound;
}

FudStatus fud_string_unicode_chr(StringView extString, const ExtUtf8* unicode, size_t* index)
{
    if (anyAreNull(extString.data, unicode, index)) {
        return FudStatus::NullPointer;
    }

    if (!unicode->valid()) {
        return ExtUtf8Invalid;
    }

    size_t charSize = unicode->size();
    ExtDebugAssert(charSize != 0);
    const uint8_t* dataMem = unicode->data();
    ExtDebugAssert(dataMem != nullptr);

    Array<uint8_t, 4> localData{};
    auto copyStatus = ExtCopyMem(localData.data(), localData.size(), dataMem, charSize);
    ExtDebugAssert(copyStatus == FudStatus::Success);

    for (size_t sIdx = 0; sIdx + charSize - 1 < extString.length;) {

        auto localChar = FudUtf8::fromStringView(extString, sIdx);

        if (!localChar.valid()) {
            return ExtUtf8Invalid;
        }

        if (localChar.m_variant == unicode->m_variant) {
            *index = sIdx;
            return FudStatus::Success;
        }

        sIdx += localChar.size();
    }

    return ExtNotFound;
}

FudStatus fud_string_span_c_api(
    const StringView& inputView,
    const StringView& characterSetString,
    StringView& result,
    bool inSet)
{
    size_t firstIndex = inputView.length;

    size_t sIdx = 0;
    while (sIdx < firstIndex) {
        auto stringChar = FudUtf8::fromStringView(inputView, sIdx);
        if (!stringChar.valid()) {
            return ExtUtf8Invalid;
        }

        size_t cIdx = 0;
        bool found = false;
        while (firstIndex > 0 && cIdx < firstIndex && cIdx < characterSetString.length) {
            auto setChar = FudUtf8::fromStringView(characterSetString, cIdx);
            if (!setChar.valid()) {
                return ExtUtf8Invalid;
            }

            if (stringChar == setChar) {
                found = true;
            }

            cIdx += setChar.size();
        }

        if (!inSet && found) {
            firstIndex = sIdx;
        } else if (inSet && !found) {
            if (sIdx > 0) {
                firstIndex = sIdx;
            }
            break;
        }

        sIdx += stringChar.size();
    }

    if (firstIndex < inputView.length) {
        result.length = inputView.length - firstIndex;
        result.data = inputView.data + firstIndex;
        return FudStatus::Success;
    }

    return ExtNotFound;
}

FudStatus fud_string_span_set(StringView inputView, const ExtUtf8Set* characterSet, StringView* stringView, bool inSet)
{
    if (anyAreNull(inputView.data, characterSet, stringView)) {
        return FudStatus::NullPointer;
    }

    if (!characterSet->valid()) {
        return ExtUtf8Invalid;
    }

    size_t firstIndex = inputView.length;
    size_t sIdx = 0;
    while (sIdx < firstIndex) {
        auto localChar = FudUtf8::fromStringView(inputView, sIdx);
        if (!localChar.valid()) {
            return ExtUtf8Invalid;
        }

        bool found = characterSet->contains(localChar);

        if (!inSet && found) {
            firstIndex = sIdx;
        } else if (inSet && !found) {
            if (sIdx > 0) {
                firstIndex = sIdx;
            }
            break;
        }

        sIdx += localChar.size();
    }

    if (firstIndex < inputView.length) {
        stringView->length = inputView.length - firstIndex;
        stringView->data = inputView.data + firstIndex;
        return FudStatus::Success;
    }

    return ExtNotFound;
}

FudStatus fud_string_span(StringView extString, StringView characterSetString, StringView* result)
{
    if (result == nullptr) {
        return FudStatus::NullPointer;
    }

    const StringView inputView{extString};
    const StringView characterSet{characterSetString};

    return fud_string_span_c_api(inputView, characterSet, *result, true);
}

FudStatus fud_string_c_span(StringView extString, StringView characterSetString, StringView* result)
{
    if (result == nullptr) {
        return FudStatus::NullPointer;
    }

    const StringView inputView{extString};
    const StringView characterSet{characterSetString};

    return fud_string_span_c_api(inputView, characterSet, *result, false);
}

FudStatus fud_string_span_set(StringView extString, const ExtUtf8Set* characterSet, StringView* stringView)
{
    return fud_string_span_set(extString, characterSet, stringView, true);
}

FudStatus fud_string_c_span_set(StringView extString, const ExtUtf8Set* characterSet, StringView* stringView)
{
    return fud_string_span_set(extString, characterSet, stringView, false);
}

FudStatus fud_string_find_substring(StringView haystack, StringView needle, StringView* stringView)
{
    if (anyAreNull(haystack.data, needle.data, stringView)) {
        return FudStatus::NullPointer;
    }

    if (needle.length > haystack.length) {
        return ExtNotFound;
    }

    if (needle.length == 1) {
        size_t index = 0;
        auto chrFindStatus = fud_string_chr(haystack, static_cast<char>(needle.data[0]), &index);
        if (chrFindStatus == FudStatus::Success) {
            stringView->data = haystack.data + index;
            stringView->length = 1;
        }
        return chrFindStatus;
    }

    size_t haystackIdx = 0;
    while (haystackIdx < haystack.length - needle.length) {
        StringView lhs;
        lhs.data = haystack.data + haystackIdx;
        lhs.length = haystack.length - haystackIdx;
        size_t lhsIndex = 0;
        auto chrFindStatus = fud_string_chr(lhs, static_cast<char>(needle.data[0]), &lhsIndex);
        if (chrFindStatus != FudStatus::Success) {
            return chrFindStatus;
        }
        haystackIdx += lhsIndex;
        // GE or GT?
        if (haystackIdx + needle.length >= haystack.length) {
            break;
        }
        lhs.data = haystack.data + haystackIdx;
        lhs.length = needle.length;

        int difference = -1;
        auto cmpStatus = fud_string_compare(lhs, needle, &difference);
        ExtDebugAssert(cmpStatus == FudStatus::Success);
        if (difference == 0) {
            stringView->data = lhs.data;
            stringView->length = lhs.length;
            return FudStatus::Success;
        }
        haystackIdx++;
    }

    return ExtNotFound;
}

#endif

} // namespace fud