#pragma once

#include <type_traits>
#include <base/types.h>
#include <Common/Volnitsky.h>
#include <Columns/ColumnString.h>
#include <Columns/ColumnsNumber.h>
#include <Core/ColumnNumbers.h>
#include <Functions/Regexps.h>

#include "config.h"
#include <re2_st/re2.h>


namespace DB
{

namespace ErrorCodes
{
    extern const int ILLEGAL_COLUMN;
}

namespace impl
{

/// Is the [I]LIKE expression equivalent to a substring search?
inline bool likePatternIsSubstring(std::string_view pattern, String & res)
{
    /// TODO: ignore multiple leading or trailing %
    if (pattern.size() < 2 || !pattern.starts_with('%') || !pattern.ends_with('%'))
        return false;

    res.clear();
    res.reserve(pattern.size() - 2);

    const char * pos = pattern.data() + 1;
    const char * const end = pattern.data() + pattern.size() - 1;

    while (pos < end)
    {
        switch (*pos)
        {
            case '%':
            case '_':
                return false;
            case '\\':
                ++pos;
                if (pos == end)
                    /// pattern ends with \% --> trailing % is to be taken literally and pattern doesn't qualify for substring search
                    return false;
                else
                {
                    switch (*pos)
                    {
                        /// Known LIKE escape sequences:
                        case '%':
                        case '_':
                        case '\\':
                            res += *pos;
                            break;
                        /// For all other escape sequences, the backslash loses its special meaning
                        default:
                            res += '\\';
                            res += *pos;
                            break;
                    }
                }
                break;
            default:
                res += *pos;
                break;
        }
        ++pos;
    }

    return true;
}

}

// For more readable instantiations of MatchImpl<>
struct MatchTraits
{
enum class Syntax
{
    Like,
    Re2
};

enum class Case
{
    Sensitive,
    Insensitive
};

enum class Result
{
    DontNegate,
    Negate
};
};

/**
 * NOTE: We want to run regexp search for whole columns by one call (as implemented in function 'position')
 *  but for that, regexp engine must support \0 bytes and their interpretation as string boundaries.
 */
template <typename Name, MatchTraits::Syntax syntax_, MatchTraits::Case case_, MatchTraits::Result result_>
struct MatchImpl
{
    static constexpr bool use_default_implementation_for_constants = true;
    static constexpr bool supports_start_pos = false;
    static constexpr auto name = Name::name;

    static ColumnNumbers getArgumentsThatAreAlwaysConstant() { return {2};}

    using ResultType = UInt8;

    static constexpr bool is_like = (syntax_ == MatchTraits::Syntax::Like);
    static constexpr bool case_insensitive = (case_ == MatchTraits::Case::Insensitive);
    static constexpr bool negate = (result_ == MatchTraits::Result::Negate);

    using Searcher = std::conditional_t<case_insensitive, VolnitskyCaseInsensitiveUTF8, VolnitskyUTF8>;

    static void vectorConstant(
        const ColumnString::Chars & haystack_data,
        const ColumnString::Offsets & haystack_offsets,
        const String & needle,
        [[maybe_unused]] const ColumnPtr & start_pos_,
        PaddedPODArray<UInt8> & res,
        [[maybe_unused]] ColumnUInt8 * res_null)
    {
        /// `res_null` serves as an output parameter for implementing an XYZOrNull variant.
        assert(!res_null);

        const size_t haystack_size = haystack_offsets.size();

        assert(haystack_size == res.size());
        assert(start_pos_ == nullptr);

        if (haystack_offsets.empty())
            return;

        /// Shortcut for the silly but practical case that the pattern matches everything/nothing independently of the haystack:
        /// - col [not] [i]like '%' / '%%'
        /// - match(col, '.*')
        if ((is_like && (needle == "%" or needle == "%%")) || (!is_like && (needle == ".*" || needle == ".*?")))
        {
            for (auto & x : res)
                x = !negate;
            return;
        }

        /// Special case that the [I]LIKE expression reduces to finding a substring in a string
        String strstr_pattern;
        if (is_like && impl::likePatternIsSubstring(needle, strstr_pattern))
        {
            const UInt8 * const begin = haystack_data.data();
            const UInt8 * const end = haystack_data.data() + haystack_data.size();
            const UInt8 * pos = begin;

            /// The current index in the array of strings.
            size_t i = 0;

            /// TODO You need to make that `searcher` is common to all the calls of the function.
            Searcher searcher(strstr_pattern.data(), strstr_pattern.size(), end - pos);

            /// We will search for the next occurrence in all rows at once.
            while (pos < end && end != (pos = searcher.search(pos, end - pos)))
            {
                /// Let's determine which index it refers to.
                while (begin + haystack_offsets[i] <= pos)
                {
                    res[i] = negate;
                    ++i;
                }

                /// We check that the entry does not pass through the boundaries of strings.
                if (pos + strstr_pattern.size() < begin + haystack_offsets[i])
                    res[i] = !negate;
                else
                    res[i] = negate;

                pos = begin + haystack_offsets[i];
                ++i;
            }

            /// Tail, in which there can be no substring.
            if (i < res.size())
                memset(&res[i], negate, (res.size() - i) * sizeof(res[0]));

            return;
        }

        const auto & regexp = Regexps::Regexp(Regexps::createRegexp<is_like, /*no_capture*/ true, case_insensitive>(needle));

        String required_substring;
        bool is_trivial;
        bool required_substring_is_prefix; /// for `anchored` execution of the regexp.

        regexp.getAnalyzeResult(required_substring, is_trivial, required_substring_is_prefix);

        if (required_substring.empty())
        {
            if (!regexp.getRE2()) /// An empty regexp. Always matches.
                memset(res.data(), !negate, haystack_size * sizeof(res[0]));
            else
            {
                size_t prev_offset = 0;
                for (size_t i = 0; i < haystack_size; ++i)
                {
                    const bool match = regexp.getRE2()->Match(
                            {reinterpret_cast<const char *>(&haystack_data[prev_offset]), haystack_offsets[i] - prev_offset - 1},
                            0,
                            haystack_offsets[i] - prev_offset - 1,
                            re2_st::RE2::UNANCHORED,
                            nullptr,
                            0);
                    res[i] = negate ^ match;

                    prev_offset = haystack_offsets[i];
                }
            }
        }
        else
        {
            /// NOTE This almost matches with the case of impl::likePatternIsSubstring.

            const UInt8 * const begin = haystack_data.data();
            const UInt8 * const end = haystack_data.begin() + haystack_data.size();
            const UInt8 * pos = begin;

            /// The current index in the array of strings.
            size_t i = 0;

            Searcher searcher(required_substring.data(), required_substring.size(), end - pos);

            /// We will search for the next occurrence in all rows at once.
            while (pos < end && end != (pos = searcher.search(pos, end - pos)))
            {
                /// Determine which index it refers to.
                while (begin + haystack_offsets[i] <= pos)
                {
                    res[i] = negate;
                    ++i;
                }

                /// We check that the entry does not pass through the boundaries of strings.
                if (pos + required_substring.size() < begin + haystack_offsets[i])
                {
                    /// And if it does not, if necessary, we check the regexp.
                    if (is_trivial)
                        res[i] = !negate;
                    else
                    {
                        const char * str_data = reinterpret_cast<const char *>(&haystack_data[haystack_offsets[i - 1]]);
                        size_t str_size = haystack_offsets[i] - haystack_offsets[i - 1] - 1;

                        /** Even in the case of `required_substring_is_prefix` use UNANCHORED check for regexp,
                          *  so that it can match when `required_substring` occurs into the string several times,
                          *  and at the first occurrence, the regexp is not a match.
                          */
                        const size_t start_pos = (required_substring_is_prefix) ? (reinterpret_cast<const char *>(pos) - str_data) : 0;
                        const size_t end_pos = str_size;

                        const bool match = regexp.getRE2()->Match(
                                {str_data, str_size},
                                start_pos,
                                end_pos,
                                re2_st::RE2::UNANCHORED,
                                nullptr,
                                0);
                        res[i] = negate ^ match;
                    }
                }
                else
                    res[i] = negate;

                pos = begin + haystack_offsets[i];
                ++i;
            }

            /// Tail, in which there can be no substring.
            if (i < res.size())
                memset(&res[i], negate, (res.size() - i) * sizeof(res[0]));
        }
    }

    /// Very carefully crafted copy-paste.
    static void vectorFixedConstant(
        const ColumnString::Chars & haystack,
        size_t N,
        const String & needle,
        PaddedPODArray<UInt8> & res,
        [[maybe_unused]] ColumnUInt8 * res_null)
    {
        /// `res_null` serves as an output parameter for implementing an XYZOrNull variant.
        assert(!res_null);

        const size_t haystack_size = haystack.size() / N;

        assert(haystack_size == res.size());

        if (haystack.empty())
            return;

        /// Shortcut for the silly but practical case that the pattern matches everything/nothing independently of the haystack:
        /// - col [not] [i]like '%' / '%%'
        /// - match(col, '.*')
        if ((is_like && (needle == "%" or needle == "%%")) || (!is_like && (needle == ".*" || needle == ".*?")))
        {
            for (auto & x : res)
                x = !negate;
            return;
        }

        /// Special case that the [I]LIKE expression reduces to finding a substring in a string
        String strstr_pattern;
        if (is_like && impl::likePatternIsSubstring(needle, strstr_pattern))
        {
            const UInt8 * const begin = haystack.data();
            const UInt8 * const end = haystack.data() + haystack.size();
            const UInt8 * pos = begin;

            size_t i = 0;
            const UInt8 * next_pos = begin;

            /// If needle is larger than string size - it cannot be found.
            if (strstr_pattern.size() <= N)
            {
                Searcher searcher(strstr_pattern.data(), strstr_pattern.size(), end - pos);

                /// We will search for the next occurrence in all rows at once.
                while (pos < end && end != (pos = searcher.search(pos, end - pos)))
                {
                    /// Let's determine which index it refers to.
                    while (next_pos + N <= pos)
                    {
                        res[i] = negate;
                        next_pos += N;
                        ++i;
                    }
                    next_pos += N;

                    /// We check that the entry does not pass through the boundaries of strings.
                    if (pos + strstr_pattern.size() <= next_pos)
                        res[i] = !negate;
                    else
                        res[i] = negate;

                    pos = next_pos;
                    ++i;
                }
            }

            /// Tail, in which there can be no substring.
            if (i < res.size())
                memset(&res[i], negate, (res.size() - i) * sizeof(res[0]));

            return;
        }

        const auto & regexp = Regexps::Regexp(Regexps::createRegexp<is_like, /*no_capture*/ true, case_insensitive>(needle));

        String required_substring;
        bool is_trivial;
        bool required_substring_is_prefix; /// for `anchored` execution of the regexp.

        regexp.getAnalyzeResult(required_substring, is_trivial, required_substring_is_prefix);

        if (required_substring.empty())
        {
            if (!regexp.getRE2()) /// An empty regexp. Always matches.
                memset(res.data(), !negate, haystack_size * sizeof(res[0]));
            else
            {
                size_t offset = 0;
                for (size_t i = 0; i < haystack_size; ++i)
                {
                    const bool match = regexp.getRE2()->Match(
                            {reinterpret_cast<const char *>(&haystack[offset]), N},
                            0,
                            N,
                            re2_st::RE2::UNANCHORED,
                            nullptr,
                            0);
                    res[i] = negate ^ match;

                    offset += N;
                }
            }
        }
        else
        {
            /// NOTE This almost matches with the case of likePatternIsSubstring.

            const UInt8 * const begin = haystack.data();
            const UInt8 * const end = haystack.data() + haystack.size();
            const UInt8 * pos = begin;

            size_t i = 0;
            const UInt8 * next_pos = begin;

            /// If required substring is larger than string size - it cannot be found.
            if (required_substring.size() <= N)
            {
                Searcher searcher(required_substring.data(), required_substring.size(), end - pos);

                /// We will search for the next occurrence in all rows at once.
                while (pos < end && end != (pos = searcher.search(pos, end - pos)))
                {
                    /// Let's determine which index it refers to.
                    while (next_pos + N <= pos)
                    {
                        res[i] = negate;
                        next_pos += N;
                        ++i;
                    }
                    next_pos += N;

                    if (pos + required_substring.size() <= next_pos)
                    {
                        /// And if it does not, if necessary, we check the regexp.
                        if (is_trivial)
                            res[i] = !negate;
                        else
                        {
                            const char * str_data = reinterpret_cast<const char *>(next_pos - N);

                            /** Even in the case of `required_substring_is_prefix` use UNANCHORED check for regexp,
                            *  so that it can match when `required_substring` occurs into the string several times,
                            *  and at the first occurrence, the regexp is not a match.
                            */
                            const size_t start_pos = (required_substring_is_prefix) ? (reinterpret_cast<const char *>(pos) - str_data) : 0;
                            const size_t end_pos = N;

                            const bool match = regexp.getRE2()->Match(
                                    {str_data, N},
                                    start_pos,
                                    end_pos,
                                    re2_st::RE2::UNANCHORED,
                                    nullptr,
                                    0);
                            res[i] = negate ^ match;
                        }
                    }
                    else
                        res[i] = negate;

                    pos = next_pos;
                    ++i;
                }
            }

            /// Tail, in which there can be no substring.
            if (i < res.size())
                memset(&res[i], negate, (res.size() - i) * sizeof(res[0]));
        }
    }

    static void vectorVector(
        const ColumnString::Chars & haystack_data,
        const ColumnString::Offsets & haystack_offsets,
        const ColumnString::Chars & needle_data,
        const ColumnString::Offsets & needle_offset,
        [[maybe_unused]] const ColumnPtr & start_pos_,
        PaddedPODArray<UInt8> & res,
        [[maybe_unused]] ColumnUInt8 * res_null)
    {
        /// `res_null` serves as an output parameter for implementing an XYZOrNull variant.
        assert(!res_null);

        const size_t haystack_size = haystack_offsets.size();

        assert(haystack_size == needle_offset.size());
        assert(haystack_size == res.size());
        assert(start_pos_ == nullptr);

        if (haystack_offsets.empty())
            return;

        String required_substr;
        bool is_trivial;
        bool required_substring_is_prefix; /// for `anchored` execution of the regexp.

        size_t prev_haystack_offset = 0;
        size_t prev_needle_offset = 0;

        Regexps::LocalCacheTable cache;
        Regexps::RegexpPtr regexp;

        for (size_t i = 0; i < haystack_size; ++i)
        {
            const auto * const cur_haystack_data = &haystack_data[prev_haystack_offset];
            const size_t cur_haystack_length = haystack_offsets[i] - prev_haystack_offset - 1;

            const auto * const cur_needle_data = &needle_data[prev_needle_offset];
            const size_t cur_needle_length = needle_offset[i] - prev_needle_offset - 1;

            const auto & needle = String(
                    reinterpret_cast<const char *>(cur_needle_data),
                    cur_needle_length);

            if (is_like && impl::likePatternIsSubstring(needle, required_substr))
            {
                if (required_substr.size() > cur_haystack_length)
                    res[i] = negate;
                else
                {
                    Searcher searcher(required_substr.data(), required_substr.size(), cur_haystack_length);
                    const auto * match = searcher.search(cur_haystack_data, cur_haystack_length);
                    res[i] = negate ^ (match != cur_haystack_data + cur_haystack_length);
                }
            }
            else
            {
                regexp = cache.getOrSet<is_like, /*no_capture*/ true, case_insensitive>(needle);
                regexp->getAnalyzeResult(required_substr, is_trivial, required_substring_is_prefix);

                if (required_substr.empty())
                {
                    if (!regexp->getRE2()) /// An empty regexp. Always matches.
                        res[i] = !negate;
                    else
                    {
                        const bool match = regexp->getRE2()->Match(
                                {reinterpret_cast<const char *>(cur_haystack_data), cur_haystack_length},
                                0,
                                cur_haystack_length,
                                re2_st::RE2::UNANCHORED,
                                nullptr,
                                0);
                        res[i] = negate ^ match;
                    }
                }
                else
                {
                    Searcher searcher(required_substr.data(), required_substr.size(), cur_haystack_length);
                    const auto * match = searcher.search(cur_haystack_data, cur_haystack_length);

                    if (match == cur_haystack_data + cur_haystack_length)
                        res[i] = negate; // no match
                    else
                    {
                        if (is_trivial)
                            res[i] = !negate; // no wildcards in pattern
                        else
                        {
                            const size_t start_pos = (required_substring_is_prefix) ? (match - cur_haystack_data) : 0;
                            const size_t end_pos = cur_haystack_length;

                            const bool match2 = regexp->getRE2()->Match(
                                    {reinterpret_cast<const char *>(cur_haystack_data), cur_haystack_length},
                                    start_pos,
                                    end_pos,
                                    re2_st::RE2::UNANCHORED,
                                    nullptr,
                                    0);
                            res[i] = negate ^ match2;
                        }
                    }
                }
            }

            prev_haystack_offset = haystack_offsets[i];
            prev_needle_offset = needle_offset[i];
        }
    }

    static void vectorFixedVector(
        const ColumnString::Chars & haystack,
        size_t N,
        const ColumnString::Chars & needle_data,
        const ColumnString::Offsets & needle_offset,
        [[maybe_unused]] const ColumnPtr & start_pos_,
        PaddedPODArray<UInt8> & res,
        [[maybe_unused]] ColumnUInt8 * res_null)
    {
        /// `res_null` serves as an output parameter for implementing an XYZOrNull variant.
        assert(!res_null);

        const size_t haystack_size = haystack.size()/N;

        assert(haystack_size == needle_offset.size());
        assert(haystack_size == res.size());
        assert(start_pos_ == nullptr);

        if (haystack.empty())
            return;

        String required_substr;
        bool is_trivial;
        bool required_substring_is_prefix; // for `anchored` execution of the regexp.

        size_t prev_haystack_offset = 0;
        size_t prev_needle_offset = 0;

        Regexps::LocalCacheTable cache;
        Regexps::RegexpPtr regexp;

        for (size_t i = 0; i < haystack_size; ++i)
        {
            const auto * const cur_haystack_data = &haystack[prev_haystack_offset];
            const size_t cur_haystack_length = N;

            const auto * const cur_needle_data = &needle_data[prev_needle_offset];
            const size_t cur_needle_length = needle_offset[i] - prev_needle_offset - 1;

            const auto & needle = String(
                    reinterpret_cast<const char *>(cur_needle_data),
                    cur_needle_length);

            if (is_like && impl::likePatternIsSubstring(needle, required_substr))
            {
                if (required_substr.size() > cur_haystack_length)
                    res[i] = negate;
                else
                {
                    Searcher searcher(required_substr.data(), required_substr.size(), cur_haystack_length);
                    const auto * match = searcher.search(cur_haystack_data, cur_haystack_length);
                    res[i] = negate ^ (match != cur_haystack_data + cur_haystack_length);
                }
            }
            else
            {
                regexp = cache.getOrSet<is_like, /*no_capture*/ true, case_insensitive>(needle);
                regexp->getAnalyzeResult(required_substr, is_trivial, required_substring_is_prefix);

                if (required_substr.empty())
                {
                    if (!regexp->getRE2()) /// An empty regexp. Always matches.
                        res[i] = !negate;
                    else
                    {
                        const bool match = regexp->getRE2()->Match(
                                {reinterpret_cast<const char *>(cur_haystack_data), cur_haystack_length},
                                0,
                                cur_haystack_length,
                                re2_st::RE2::UNANCHORED,
                                nullptr,
                                0);
                        res[i] = negate ^ match;
                    }
                }
                else
                {
                    Searcher searcher(required_substr.data(), required_substr.size(), cur_haystack_length);
                    const auto * match = searcher.search(cur_haystack_data, cur_haystack_length);

                    if (match == cur_haystack_data + cur_haystack_length)
                        res[i] = negate; // no match
                    else
                    {
                        if (is_trivial)
                            res[i] = !negate; // no wildcards in pattern
                        else
                        {
                            const size_t start_pos = (required_substring_is_prefix) ? (match - cur_haystack_data) : 0;
                            const size_t end_pos = cur_haystack_length;

                            const bool match2 = regexp->getRE2()->Match(
                                    {reinterpret_cast<const char *>(cur_haystack_data), cur_haystack_length},
                                    start_pos,
                                    end_pos,
                                    re2_st::RE2::UNANCHORED,
                                    nullptr,
                                    0);
                            res[i] = negate ^ match2;
                        }
                    }
                }
            }
            prev_haystack_offset += N;
            prev_needle_offset = needle_offset[i];
        }
    }

    template <typename... Args>
    static void constantVector(Args &&...)
    {
        throw Exception(ErrorCodes::ILLEGAL_COLUMN, "Function '{}' doesn't support search with non-constant needles in constant haystack", name);
    }
};

}