/*
 * This program source code file is part of KiCad, a free EDA CAD application.
 *
 * Copyright The KiCad Developers, see AUTHORS.txt for contributors.
 *
 * This program is free software: you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation, either version 3 of the License, or (at your
 * option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <text_eval/text_eval_parser.h>
#include <fmt/format.h>
#include <array>
#include <cctype>

namespace calc_parser
{
thread_local ERROR_COLLECTOR* g_errorCollector = nullptr;

class DATE_UTILS
{
private:
    static constexpr int epochYear = 1970;
    static constexpr std::array<int, 12> daysInMonth = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
    static constexpr std::array<const char*, 12> monthNames = {
        "January", "February", "March", "April", "May", "June",
        "July", "August", "September", "October", "November", "December"
    };
    static constexpr std::array<const char*, 12> monthAbbrev = {
        "Jan", "Feb", "Mar", "Apr", "May", "Jun",
        "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
    };
    static constexpr std::array<const char*, 7> weekdayNames = {
        "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"
    };

    static auto isLeapYear( int aYear ) -> bool
    {
        return ( aYear % 4 == 0 && aYear % 100 != 0 ) || ( aYear % 400 == 0 );
    }

    static auto daysInYear( int aYear ) -> int
    {
        return isLeapYear( aYear ) ? 366 : 365;
    }

    static auto daysInMonthForYear( int aMonth, int aYear ) -> int
    {
        if( aMonth == 2 && isLeapYear( aYear ) )
            return 29;

        return daysInMonth[aMonth - 1];
    }

public:
    static auto DaysToYmd( int aDaysSinceEpoch ) -> std::tuple<int, int, int>
    {
        int year = epochYear;
        int remainingDays = aDaysSinceEpoch;

        if( remainingDays >= 0 )
        {
            while( remainingDays >= daysInYear( year ) )
            {
                remainingDays -= daysInYear( year );
                year++;
            }
        }
        else
        {
            while( remainingDays < 0 )
            {
                year--;
                remainingDays += daysInYear( year );
            }
        }

        int month = 1;
        while( month <= 12 && remainingDays >= daysInMonthForYear( month, year ) )
        {
            remainingDays -= daysInMonthForYear( month, year );
            month++;
        }

        int day = remainingDays + 1;
        return {year, month, day};
    }

    static auto YmdToDays( int aYear, int aMonth, int aDay ) -> int
    {
        int totalDays = 0;

        if( aYear >= epochYear )
        {
            for( int y = epochYear; y < aYear; ++y )
                totalDays += daysInYear( y );
        }
        else
        {
            for( int y = aYear; y < epochYear; ++y )
                totalDays -= daysInYear( y );
        }

        for( int m = 1; m < aMonth; ++m )
            totalDays += daysInMonthForYear( m, aYear );

        totalDays += aDay - 1;
        return totalDays;
    }

    static auto ParseDate( const std::string& aDateStr ) -> std::optional<int>
    {
        std::istringstream iss( aDateStr );
        std::string token;
        std::vector<int> parts;

        char separator = 0;
        bool isCjkFormat = false;

        // Check for CJK date formats first (Chinese, Korean, or mixed)
        bool hasChineseYear = aDateStr.find( "年" ) != std::string::npos;
        bool hasChineseMonth = aDateStr.find( "月" ) != std::string::npos;
        bool hasChineseDay = aDateStr.find( "日" ) != std::string::npos;
        bool hasKoreanYear = aDateStr.find( "년" ) != std::string::npos;
        bool hasKoreanMonth = aDateStr.find( "월" ) != std::string::npos;
        bool hasKoreanDay = aDateStr.find( "일" ) != std::string::npos;

        // Check if we have any CJK date format (pure or mixed)
        if( (hasChineseYear || hasKoreanYear) &&
            (hasChineseMonth || hasKoreanMonth) &&
            (hasChineseDay || hasKoreanDay) )
        {
            // CJK format: Support pure Chinese, pure Korean, or mixed formats
            isCjkFormat = true;

            size_t yearPos, monthPos, dayPos;

            // Find year position and marker
            if( hasChineseYear )
                yearPos = aDateStr.find( "年" );
            else
                yearPos = aDateStr.find( "년" );

            // Find month position and marker
            if( hasChineseMonth )
                monthPos = aDateStr.find( "月" );
            else
                monthPos = aDateStr.find( "월" );

            // Find day position and marker
            if( hasChineseDay )
                dayPos = aDateStr.find( "日" );
            else
                dayPos = aDateStr.find( "일" );

            try
            {
                int year = std::stoi( aDateStr.substr( 0, yearPos ) );
                int month = std::stoi( aDateStr.substr( yearPos + 3, monthPos - yearPos - 3 ) ); // 3 bytes for CJK year marker
                int day = std::stoi( aDateStr.substr( monthPos + 3, dayPos - monthPos - 3 ) ); // 3 bytes for CJK month marker

                parts = { year, month, day };
            }
            catch( ... )
            {
                return std::nullopt;
            }
        }
        else if( aDateStr.find( '-' ) != std::string::npos )
            separator = '-';
        else if( aDateStr.find( '/' ) != std::string::npos )
            separator = '/';
        else if( aDateStr.find( '.' ) != std::string::npos )
            separator = '.';

        if( separator )
        {
            while( std::getline( iss, token, separator ) )
            {
                try
                {
                    parts.push_back( std::stoi( token ) );
                }
                catch( ... )
                {
                    return std::nullopt;
                }
            }
        }
        else if( !isCjkFormat && aDateStr.length() == 8 )
        {
            try
            {
                int dateNum = std::stoi( aDateStr );
                int year = dateNum / 10000;
                int month = ( dateNum / 100 ) % 100;
                int day = dateNum % 100;
                return YmdToDays( year, month, day );
            }
            catch( ... )
            {
                return std::nullopt;
            }
        }
        else if( !isCjkFormat )
        {
            return std::nullopt;
        }

        if( parts.empty() || parts.size() > 3 )
            return std::nullopt;

        int year, month, day;

        if( parts.size() == 1 )
        {
            year = parts[0];
            month = 1;
            day = 1;
        }
        else if( parts.size() == 2 )
        {
            year = parts[0];
            month = parts[1];
            day = 1;
        }
        else
        {
            if( isCjkFormat )
            {
                // CJK formats are always in YYYY年MM月DD日 or YYYY년 MM월 DD일 order
                year = parts[0];
                month = parts[1];
                day = parts[2];
            }
            else if( separator == '/' && parts[0] <= 12 && parts[1] <= 31 )
            {
                month = parts[0];
                day = parts[1];
                year = parts[2];
            }
            else if( separator == '/' && parts[1] <= 12 )
            {
                day = parts[0];
                month = parts[1];
                year = parts[2];
            }
            else
            {
                year = parts[0];
                month = parts[1];
                day = parts[2];
            }
        }

        if( month < 1 || month > 12 )
            return std::nullopt;
        if( day < 1 || day > daysInMonthForYear( month, year ) )
            return std::nullopt;

        return YmdToDays( year, month, day );
    }

    static auto FormatDate( int aDaysSinceEpoch, const std::string& aFormat ) -> std::string
    {
        auto [year, month, day] = DaysToYmd( aDaysSinceEpoch );

        if( aFormat == "ISO" || aFormat == "iso" )
            return fmt::format( "{:04d}-{:02d}-{:02d}", year, month, day );
        else if( aFormat == "US" || aFormat == "us" )
            return fmt::format( "{:02d}/{:02d}/{:04d}", month, day, year );
        else if( aFormat == "EU" || aFormat == "european" )
            return fmt::format( "{:02d}/{:02d}/{:04d}", day, month, year );
        else if( aFormat == "long" )
            return fmt::format( "{} {}, {}", monthNames[month-1], day, year );
        else if( aFormat == "short" )
            return fmt::format( "{} {}, {}", monthAbbrev[month-1], day, year );
        else if( aFormat == "Chinese" || aFormat == "chinese" || aFormat == "CN" || aFormat == "cn" || aFormat == "中文" )
            return fmt::format( "{}年{:02d}月{:02d}日", year, month, day );
        else if( aFormat == "Japanese" || aFormat == "japanese" || aFormat == "JP" || aFormat == "jp" || aFormat == "日本語" )
            return fmt::format( "{}年{:02d}月{:02d}日", year, month, day );
        else if( aFormat == "Korean" || aFormat == "korean" || aFormat == "KR" || aFormat == "kr" || aFormat == "한국어" )
            return fmt::format( "{}년 {:02d}월 {:02d}일", year, month, day );
        else
            return fmt::format( "{:04d}-{:02d}-{:02d}", year, month, day );
    }

    static auto GetWeekdayName( int aDaysSinceEpoch ) -> std::string
    {
        int weekday = ( ( aDaysSinceEpoch + 3 ) % 7 ); // +3 because epoch was Thursday (Monday = 0)

        if( weekday < 0 )
            weekday += 7;

        return std::string{ weekdayNames[weekday] };
    }

    static auto GetCurrentDays() -> int
    {
        auto now = std::chrono::system_clock::now();
        auto timeT = std::chrono::system_clock::to_time_t( now );
        return static_cast<int>( timeT / ( 24 * 3600 ) );
    }

    static auto GetCurrentTimestamp() -> double
    {
        auto now = std::chrono::system_clock::now();
        auto timeT = std::chrono::system_clock::to_time_t( now );
        return static_cast<double>( timeT );
    }
};

EVAL_VISITOR::EVAL_VISITOR( VariableCallback aVariableCallback, ERROR_COLLECTOR& aErrorCollector ) :
        m_variableCallback( std::move( aVariableCallback ) ),
        m_errors( aErrorCollector ),
        m_gen( m_rd() )
{}

auto EVAL_VISITOR::operator()( const NODE& aNode ) const -> Result<Value>
    {
        switch( aNode.type )
        {
        case NodeType::Number:
            return MakeValue<Value>( std::get<double>( aNode.data ) );

        case NodeType::String:
            return MakeValue<Value>( std::get<std::string>( aNode.data ) );

        case NodeType::Var:
        {
            const auto& varName = std::get<std::string>( aNode.data );

            // Use callback to resolve variable
            if( m_variableCallback )
                return m_variableCallback( varName );

            return MakeError<Value>( fmt::format( "No variable resolver configured for: {}", varName ) );
        }

        case NodeType::BinOp:
        {
            const auto& binop = std::get<BIN_OP_DATA>( aNode.data );
            auto leftResult = binop.left->Accept( *this );
            if( !leftResult )
                return leftResult;

            auto rightResult = binop.right ?
                binop.right->Accept( *this ) : MakeValue<Value>( 0.0 );
            if( !rightResult )
                return rightResult;

            // Special handling for string concatenation with +
            if( binop.op == '+' )
            {
                const auto& leftVal = leftResult.GetValue();
                const auto& rightVal = rightResult.GetValue();

                // If either operand is a string, concatenate
                if( std::holds_alternative<std::string>( leftVal ) ||
                    std::holds_alternative<std::string>( rightVal ) )
                {
                    return MakeValue<Value>( VALUE_UTILS::ConcatStrings( leftVal, rightVal ) );
                }
            }

            // Otherwise, perform arithmetic
            return VALUE_UTILS::ArithmeticOp( leftResult.GetValue(), rightResult.GetValue(), binop.op );
        }

        case NodeType::Function:
        {
            const auto& func = std::get<FUNC_DATA>( aNode.data );
            return evaluateFunction( func );
        }

        default:
            return MakeError<Value>( "Cannot evaluate this node type" );
        }
}

auto EVAL_VISITOR::evaluateFunction( const FUNC_DATA& aFunc ) const -> Result<Value>
{
        const auto& name = aFunc.name;
        const auto& args = aFunc.args;

        // Zero-argument functions
        if( args.empty() )
        {
            if( name == "today" )
                return MakeValue<Value>( static_cast<double>( DATE_UTILS::GetCurrentDays() ) );
            else if( name == "now" )
                return MakeValue<Value>( DATE_UTILS::GetCurrentTimestamp() );
            else if( name == "random" )
            {
                std::uniform_real_distribution<double> dis( 0.0, 1.0 );
                return MakeValue<Value>( dis( m_gen ) );
            }
        }

        // Evaluate arguments to mixed types
        std::vector<Value> argValues;
        argValues.reserve( args.size() );

        for( const auto& arg : args )
        {
            auto result = arg->Accept( *this );
            if( !result )
                return result;

            argValues.push_back( result.GetValue() );
        }

        const auto argc = argValues.size();

        // String formatting functions (return strings!)
        if( name == "format" && argc >= 1 )
        {
            auto numResult = VALUE_UTILS::ToDouble( argValues[0] );
            if( !numResult )
                return MakeError<Value>( numResult.GetError() );

            const auto value = numResult.GetValue();
            int decimals = 2;
            if( argc > 1 )
            {
                auto decResult = VALUE_UTILS::ToDouble( argValues[1] );
                if( decResult )
                    decimals = static_cast<int>( decResult.GetValue() );
            }

            return MakeValue<Value>( fmt::format( "{:.{}f}", value, decimals ) );
        }
        else if( name == "currency" && argc >= 1 )
        {
            auto numResult = VALUE_UTILS::ToDouble( argValues[0] );
            if( !numResult )
                return MakeError<Value>( numResult.GetError() );

            const auto amount = numResult.GetValue();
            const auto symbol = argc > 1 ? VALUE_UTILS::ToString( argValues[1] ) : "$";

            return MakeValue<Value>( fmt::format( "{}{:.2f}", symbol, amount ) );
        }
        else if( name == "fixed" && argc >= 1 )
        {
            auto numResult = VALUE_UTILS::ToDouble( argValues[0] );
            if( !numResult )
                return MakeError<Value>( numResult.GetError() );

            const auto value = numResult.GetValue();
            int decimals = 2;
            if( argc > 1 )
            {
                auto decResult = VALUE_UTILS::ToDouble( argValues[1] );
                if( decResult )
                    decimals = static_cast<int>( decResult.GetValue() );
            }

            return MakeValue<Value>( fmt::format( "{:.{}f}", value, decimals ) );
        }

        // Date formatting functions (return strings!)
        else if( name == "dateformat" && argc >= 1 )
        {
            auto dateResult = VALUE_UTILS::ToDouble( argValues[0] );
            if( !dateResult )
                return MakeError<Value>( dateResult.GetError() );

            const auto days = static_cast<int>( dateResult.GetValue() );
            const auto format = argc > 1 ? VALUE_UTILS::ToString( argValues[1] ) : "ISO";

            return MakeValue<Value>( DATE_UTILS::FormatDate( days, format ) );
        }
        else if( name == "datestring" && argc == 1 )
        {
            auto dateStr = VALUE_UTILS::ToString( argValues[0] );
            auto daysResult = DATE_UTILS::ParseDate( dateStr );

            if( !daysResult )
                return MakeError<Value>( "Invalid date format: " + dateStr );

            return MakeValue<Value>( static_cast<double>( daysResult.value() ) );
        }
        else if( name == "weekdayname" && argc == 1 )
        {
            auto dateResult = VALUE_UTILS::ToDouble( argValues[0] );
            if( !dateResult )
                return MakeError<Value>( dateResult.GetError() );

            const auto days = static_cast<int>( dateResult.GetValue() );
            return MakeValue<Value>( DATE_UTILS::GetWeekdayName( days ) );
        }

        // String functions (return strings!)
        else if( name == "upper" && argc == 1 )
        {
            auto str = VALUE_UTILS::ToString( argValues[0] );
            std::transform( str.begin(), str.end(), str.begin(), ::toupper );
            return MakeValue<Value>( str );
        }
        else if( name == "lower" && argc == 1 )
        {
            auto str = VALUE_UTILS::ToString( argValues[0] );
            std::transform( str.begin(), str.end(), str.begin(), ::tolower );
            return MakeValue<Value>( str );
        }
        else if( name == "concat" && argc >= 2 )
        {
            std::string result;
            for( const auto& val : argValues )
                result += VALUE_UTILS::ToString( val );

            return MakeValue<Value>( result );
        }

        // Conditional functions (handle mixed types)
        if( name == "if" && argc == 3 )
        {
            // Convert only the condition to a number
            auto conditionResult = VALUE_UTILS::ToDouble( argValues[0] );
            if( !conditionResult )
                return MakeError<Value>( conditionResult.GetError() );

            const auto condition = conditionResult.GetValue() != 0.0;
            return MakeValue<Value>( condition ? argValues[1] : argValues[2] );
        }

        // Mathematical functions (return numbers) - convert args to doubles first
        std::vector<double> numArgs;
        for( const auto& val : argValues )
        {
            auto numResult = VALUE_UTILS::ToDouble( val );
            if( !numResult )
                return MakeError<Value>( numResult.GetError() );

            numArgs.push_back( numResult.GetValue() );
        }

        // Mathematical function implementations
        if( name == "abs" && argc == 1 )
            return MakeValue<Value>( std::abs( numArgs[0] ) );
        else if( name == "sum" && argc >= 1 )
            return MakeValue<Value>( std::accumulate( numArgs.begin(), numArgs.end(), 0.0 ) );
        else if( name == "round" && argc >= 1 )
        {
            const auto value = numArgs[0];
            const auto precision = argc > 1 ? static_cast<int>( numArgs[1] ) : 0;
            const auto multiplier = std::pow( 10.0, precision );
            return MakeValue<Value>( std::round( value * multiplier ) / multiplier );
        }
        else if( name == "sqrt" && argc == 1 )
        {
            if( numArgs[0] < 0 )
                return MakeError<Value>( "Square root of negative number" );

            return MakeValue<Value>( std::sqrt( numArgs[0] ) );
        }
        else if( name == "pow" && argc == 2 )
            return MakeValue<Value>( std::pow( numArgs[0], numArgs[1] ) );
        else if( name == "floor" && argc == 1 )
            return MakeValue<Value>( std::floor( numArgs[0] ) );
        else if( name == "ceil" && argc == 1 )
            return MakeValue<Value>( std::ceil( numArgs[0] ) );
        else if( name == "min" && argc >= 1 )
            return MakeValue<Value>( *std::min_element( numArgs.begin(), numArgs.end() ) );
        else if( name == "max" && argc >= 1 )
            return MakeValue<Value>( *std::max_element( numArgs.begin(), numArgs.end() ) );
        else if( name == "avg" && argc >= 1 )
        {
            const auto sum = std::accumulate( numArgs.begin(), numArgs.end(), 0.0 );
            return MakeValue<Value>( sum / static_cast<double>( argc ) );
        }

        return MakeError<Value>( fmt::format( "Unknown function: {} with {} arguments", name, argc ) );
}

auto DOC_PROCESSOR::Process( const DOC& aDoc, VariableCallback aVariableCallback )
                        -> std::pair<std::string, bool>
    {
        std::string result;
        auto localErrors = ERROR_COLLECTOR{};
        EVAL_VISITOR evaluator{ std::move( aVariableCallback ), localErrors };
        bool hadErrors = aDoc.HasErrors();

        for( const auto& node : aDoc.GetNodes() )
        {
            switch( node->type )
            {
            case NodeType::Text:
                result += std::get<std::string>( node->data );
                break;

            case NodeType::Calc:
            {
                const auto& calcData = std::get<BIN_OP_DATA>( node->data );
                auto evalResult = calcData.left->Accept( evaluator );

                if( evalResult )
                    result += VALUE_UTILS::ToString( evalResult.GetValue() );
                else
                {
                    // Don't add error formatting to result - errors go to error vector only
                    // The higher level will return original input unchanged if there are errors
                    hadErrors = true;
                }
                break;
            }

            default:
                result += "[Unknown node type]";
                hadErrors = true;
                break;
            }
        }

        return { std::move( result ), hadErrors || localErrors.HasErrors() };
}

auto DOC_PROCESSOR::ProcessWithDetails( const DOC& aDoc, VariableCallback aVariableCallback )
                                   -> std::tuple<std::string, std::vector<std::string>, bool>
{
    auto [result, hadErrors] = Process( aDoc, std::move( aVariableCallback ) );
    auto allErrors = aDoc.GetErrors();

    return { std::move( result ), std::move( allErrors ), hadErrors };
}

} // namespace calc_parser