// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you 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.

#pragma once

#include <hs/hs_common.h>
#include <hs/hs_runtime.h>
#include <re2/re2.h>

#include <algorithm>
#include <boost/iterator/iterator_facade.hpp>
#include <boost/regex.hpp>
#include <cstddef>
#include <cstdint>
#include <functional>
#include <memory>
#include <string>

#include "common/status.h"
#include "core/block/column_numbers.h"
#include "core/column/column_string.h"
#include "core/column/predicate_column.h"
#include "core/data_type/data_type_number.h"
#include "core/data_type/define_primitive_type.h"
#include "core/string_ref.h"
#include "core/types.h"
#include "exprs/aggregate/aggregate_function.h"
#include "exprs/function/function.h"
#include "exprs/function_context.h"
#include "util/string_search.hpp"

namespace doris {
class Block;

// FastPath types for LIKE pattern matching optimization
// This allows per-row pattern analysis to avoid regex when possible
enum class LikeFastPath {
    ALLPASS,     // Pattern is just '%' or '%%...' - matches everything
    EQUALS,      // No wildcards - exact string match
    STARTS_WITH, // Pattern ends with '%' only - prefix match
    ENDS_WITH,   // Pattern starts with '%' only - suffix match
    SUBSTRING,   // Pattern is '%xxx%' - substring search
    REGEX        // Contains '_' or multiple '%' - needs regex
};

// Lightweight pattern analysis without RE2
// Returns the fast path type and extracts the search string (without wildcards)
// Correctly handles escape sequences: backslash-% -> literal %, backslash-_ -> literal _
inline LikeFastPath extract_like_fast_path(const char* pattern, size_t len,
                                           std::string& search_string) {
    search_string.clear();
    if (len == 0) {
        return LikeFastPath::EQUALS;
    }

    // Returns true if the character is NOT escaped (even number of preceding backslashes)
    auto is_unescaped = [&pattern](size_t pos) -> bool {
        size_t backslash_count = 0;
        while (pos > 0 && pattern[pos - 1] == '\\') {
            backslash_count++;
            pos--;
        }
        return (backslash_count % 2 == 0);
    };

    bool starts_with_percent = (pattern[0] == '%');
    bool ends_with_percent = (pattern[len - 1] == '%' && is_unescaped(len - 1));

    // Quick check: if starts or ends with unescaped '_', need regex
    if (pattern[0] == '_') {
        return LikeFastPath::REGEX;
    }
    if (pattern[len - 1] == '_' && is_unescaped(len - 1)) {
        return LikeFastPath::REGEX;
    }

    // Helper lambda: check if character is a wildcard that needs escaping
    auto is_wildcard = [](char c) { return c == '%' || c == '_' || c == '\\'; };

    size_t i = 0;
    // Skip leading '%' characters (unescaped)
    while (i < len && pattern[i] == '%') {
        i++;
    }
    // If pattern is all '%', it's ALLPASS
    if (i >= len) {
        return LikeFastPath::ALLPASS;
    }

    search_string.reserve(len);
    while (i < len) {
        char c = pattern[i];
        // Escaped character - add the literal
        if (c == '\\' && i + 1 < len && is_wildcard(pattern[i + 1])) {
            search_string.push_back(pattern[i + 1]);
            i += 2;
            continue;
        }

        // Unescaped '_' requires regex
        if (c == '_') {
            return LikeFastPath::REGEX;
        }

        // Check for trailing '%' or middle '%' (which needs regex)
        if (c == '%') {
            // Check if this is a trailing '%' sequence
            size_t j = i;
            while (j < len && pattern[j] == '%') {
                j++;
            }
            if (j >= len) {
                // All remaining chars are '%', we're done parsing
                break;
            }
            // '%' in the middle with more content after - need regex
            return LikeFastPath::REGEX;
        }

        search_string.push_back(c);
        i++;
    }

    // Determine the pattern type based on '%' positions
    if (starts_with_percent && ends_with_percent) {
        return LikeFastPath::SUBSTRING;
    } else if (starts_with_percent) {
        return LikeFastPath::ENDS_WITH;
    } else if (ends_with_percent) {
        return LikeFastPath::STARTS_WITH;
    } else {
        return LikeFastPath::EQUALS;
    }
}

inline std::string replace_pattern_by_escape(const StringRef& pattern, char escape_char) {
    std::string result;
    result.reserve(pattern.size);
    for (size_t i = 0; i < pattern.size; ++i) {
        if (i + 1 < pattern.size && pattern.data[i] == escape_char &&
            (pattern.data[i + 1] == escape_char || pattern.data[i + 1] == '%' ||
             pattern.data[i + 1] == '_')) {
            // "^^" -> "^"
            // "^%" -> "\%"
            // "^_" -> "\_"
            if ((pattern.data[i + 1] == '%' || pattern.data[i + 1] == '_')) {
                result.push_back('\\');
            }
            result.push_back(pattern.data[i + 1]);
            ++i; // skip next char
        } else if (pattern.data[i] == '\\') {
            // "\" -> "\\"
            result.append("\\\\");
        } else {
            result.push_back(pattern.data[i]);
        }
    }
    return result;
}

// TODO: replace with std::string_view when `LikeSearchState.substring_pattern` can
// construct from std::string_view.
struct LikeSearchState {
    static constexpr char escape_char = '\\';

    /// Holds the string the StringRef points to and is set any time StringRef is
    /// used.
    std::string search_string;

    std::string pattern_str;

    /// Used for LIKE predicates if the pattern is a constant argument, and is either a
    /// constant string or has a constant string at the beginning or end of the pattern.
    /// This will be set in order to check for that pattern in the corresponding part of
    /// the string.
    StringRef search_string_sv;

    /// Used for LIKE predicates if the pattern is a constant argument and has a constant
    /// string in the middle of it. This will be use in order to check for the substring
    /// in the value.
    doris::StringSearch substring_pattern;

    /// Used for RLIKE and REGEXP predicates if the pattern is a constant argument.
    std::unique_ptr<re2::RE2> regex;

    /// Used for REGEXP predicates when RE2 doesn't support the pattern (e.g., zero-width assertions like `?=`, `?!`, `?<=`, `?<!`)
    std::unique_ptr<boost::regex> boost_regex;

    template <typename Deleter, Deleter deleter>
    struct HyperscanDeleter {
        template <typename T>
        void operator()(T* ptr) const {
            deleter(ptr);
        }
    };

    // hyperscan compiled pattern database and scratch space, reused for performance
    std::unique_ptr<hs_database_t, HyperscanDeleter<decltype(&hs_free_database), &hs_free_database>>
            hs_database;
    std::unique_ptr<hs_scratch_t, HyperscanDeleter<decltype(&hs_free_scratch), &hs_free_scratch>>
            hs_scratch;

    // hyperscan match callback
    static int hs_match_handler(unsigned int /* from */,       // NOLINT
                                unsigned long long /* from */, // NOLINT
                                unsigned long long /* to */,   // NOLINT
                                unsigned int /* flags */, void* ctx) {
        // set result to 1 for matched row
        *((unsigned char*)ctx) = 1;
        /// return non-zero to indicate hyperscan stop after first matched
        return 1;
    }

    LikeSearchState() = default;

    Status clone(LikeSearchState& cloned);

    void set_search_string(const std::string& search_string_arg) {
        search_string = search_string_arg;
        search_string_sv = StringRef(search_string);
        substring_pattern.set_pattern(&search_string_sv);
    }
};

using LikeFn = std::function<doris::Status(const LikeSearchState*, const ColumnString&,
                                           const StringRef&, ColumnUInt8::Container&)>;

using ScalarLikeFn = std::function<doris::Status(const LikeSearchState*, const StringRef&,
                                                 const StringRef&, unsigned char*)>;

using VectorLikeFn = std::function<doris::Status(const ColumnString&, const ColumnString&,
                                                 ColumnUInt8::Container&)>;

struct LikeState {
    bool is_like_pattern;
    bool has_custom_escape = false;
    char escape_char = {};
    LikeSearchState search_state;
    LikeFn function;
    ScalarLikeFn scalar_function;
};

struct VectorPatternSearchState {
    MutableColumnPtr _search_strings;
    std::string _search_string;
    VectorLikeFn _vector_function;
    bool _pattern_matched;

    VectorPatternSearchState(VectorLikeFn vector_function)
            : _search_strings(ColumnString::create()),
              _vector_function(vector_function),
              _pattern_matched(true) {}

    virtual ~VectorPatternSearchState() = default;

    virtual void like_pattern_match(const std::string& pattern_str) = 0;

    virtual void regexp_pattern_match(const std::string& pattern_str) = 0;
};

using VPatternSearchStateSPtr = std::shared_ptr<VectorPatternSearchState>;

class FunctionLikeBase : public IFunction {
public:
    size_t get_number_of_arguments() const override { return 0; }
    bool is_variadic() const override { return true; }

    DataTypePtr get_return_type_impl(const DataTypes& /*arguments*/) const override {
        return std::make_shared<DataTypeUInt8>();
    }

    Status execute_impl(FunctionContext* context, Block& block, const ColumnNumbers& arguments,
                        uint32_t result, size_t /*input_rows_count*/) const override;

    friend struct VectorAllpassSearchState;
    friend struct VectorEqualSearchState;
    friend struct VectorSubStringSearchState;
    friend struct VectorStartsWithSearchState;
    friend struct VectorEndsWithSearchState;

protected:
    Status vector_const(const ColumnString& values, const StringRef* pattern_val,
                        ColumnUInt8::Container& result, const LikeFn& function,
                        LikeSearchState* search_state) const;

    Status vector_non_const(const ColumnString& values, const ColumnString& patterns,
                            ColumnUInt8::Container& result, LikeState* state,
                            size_t input_rows_count) const;

    Status execute_substring(const ColumnString::Chars& values,
                             const ColumnString::Offsets& value_offsets,
                             ColumnUInt8::Container& result, LikeSearchState* search_state) const;

    template <bool LIKE_PATTERN>
    static VPatternSearchStateSPtr pattern_type_recognition(const ColumnString& patterns);

    static Status constant_allpass_fn(const LikeSearchState* state, const ColumnString& val,
                                      const StringRef& pattern, ColumnUInt8::Container& result);

    static Status constant_allpass_fn_scalar(const LikeSearchState* state, const StringRef& val,
                                             const StringRef& pattern, unsigned char* result);

    static Status vector_allpass_fn(const ColumnString& vals, const ColumnString& search_strings,
                                    ColumnUInt8::Container& result);

    static Status constant_starts_with_fn(const LikeSearchState* state, const ColumnString& val,
                                          const StringRef& pattern, ColumnUInt8::Container& result);

    static Status constant_starts_with_fn_scalar(const LikeSearchState* state, const StringRef& val,
                                                 const StringRef& pattern, unsigned char* result);

    static Status vector_starts_with_fn(const ColumnString& vals,
                                        const ColumnString& search_strings,
                                        ColumnUInt8::Container& result);

    static Status constant_ends_with_fn(const LikeSearchState* state, const ColumnString& val,
                                        const StringRef& pattern, ColumnUInt8::Container& result);

    static Status constant_ends_with_fn_scalar(const LikeSearchState* state, const StringRef& val,
                                               const StringRef& pattern, unsigned char* result);

    static Status vector_ends_with_fn(const ColumnString& vals, const ColumnString& search_strings,
                                      ColumnUInt8::Container& result);

    static Status constant_equals_fn(const LikeSearchState* state, const ColumnString& val,
                                     const StringRef& pattern, ColumnUInt8::Container& result);

    static Status constant_equals_fn_scalar(const LikeSearchState* state, const StringRef& val,
                                            const StringRef& pattern, unsigned char* result);

    static Status vector_equals_fn(const ColumnString& vals, const ColumnString& search_strings,
                                   ColumnUInt8::Container& result);

    static Status constant_substring_fn(const LikeSearchState* state, const ColumnString& val,
                                        const StringRef& pattern, ColumnUInt8::Container& result);

    static Status constant_substring_fn_scalar(const LikeSearchState* state, const StringRef& val,
                                               const StringRef& pattern, unsigned char* result);

    static Status vector_substring_fn(const ColumnString& vals, const ColumnString& search_strings,
                                      ColumnUInt8::Container& result);

    static Status constant_regex_fn(const LikeSearchState* state, const ColumnString& val,
                                    const StringRef& pattern, ColumnUInt8::Container& result);

    static Status constant_regex_fn_scalar(const LikeSearchState* state, const StringRef& val,
                                           const StringRef& pattern, unsigned char* result);

    static Status regexp_fn(const LikeSearchState* state, const ColumnString& val,
                            const StringRef& pattern, ColumnUInt8::Container& result);

    static Status regexp_fn_scalar(const LikeSearchState* state, const StringRef& val,
                                   const StringRef& pattern, unsigned char* result);

    // hyperscan compile expression to database and allocate scratch space
    static Status hs_prepare(FunctionContext* context, const char* expression,
                             hs_database_t** database, hs_scratch_t** scratch);
};

class FunctionLike : public FunctionLikeBase {
public:
    static constexpr auto name = "like";

    static FunctionPtr create() { return std::make_shared<FunctionLike>(); }

    String get_name() const override { return name; }

    Status open(FunctionContext* context, FunctionContext::FunctionStateScope scope) override;

    static Status construct_like_const_state(FunctionContext* ctx, const StringRef& pattern,
                                             std::shared_ptr<LikeState>& state,
                                             bool try_hyperscan = true);

    friend struct LikeSearchState;
    friend struct VectorAllpassSearchState;
    friend struct VectorEqualSearchState;
    friend struct VectorSubStringSearchState;
    friend struct VectorStartsWithSearchState;
    friend struct VectorEndsWithSearchState;

private:
    static Status like_fn(const LikeSearchState* state, const ColumnString& val,
                          const StringRef& pattern, ColumnUInt8::Container& result);

    static Status like_fn_scalar(const LikeSearchState* state, const StringRef& val,
                                 const StringRef& pattern, unsigned char* result);

    static void convert_like_pattern(const LikeSearchState* state, const std::string& pattern,
                                     std::string* re_pattern);

    static void remove_escape_character(std::string* search_string);
};

class FunctionRegexpLike : public FunctionLikeBase {
public:
    static constexpr auto name = "regexp";
    static constexpr auto alias = "rlike";

    static FunctionPtr create() { return std::make_shared<FunctionRegexpLike>(); }

    String get_name() const override { return name; }

    Status open(FunctionContext* context, FunctionContext::FunctionStateScope scope) override;
};

} // namespace doris