#include "binary_table.h"
#include <algorithm>
#include <cstring>
#include <functional>
#include <filesystem>
#include <iostream>

namespace bt {

// FNV-1a hash implementation
int64_t BinaryTable::hashString(const std::string& str) const {
    uint64_t hash = 0xcbf29ce484222325ULL; // FNV offset basis
    for (char c : str) {
        hash ^= static_cast<uint8_t>(c);
        hash *= 0x100000001b3ULL; // FNV prime
    }
    return static_cast<int64_t>(hash);
}

// Value encoding implementations
std::vector<uint8_t> encodeValue(const int32_t& value) {
    std::vector<uint8_t> buffer;
    buffer.push_back(static_cast<uint8_t>(BT_Type::INTEGER));
    
    // Little endian encoding
    buffer.push_back(value & 0xFF);
    buffer.push_back((value >> 8) & 0xFF);
    buffer.push_back((value >> 16) & 0xFF);
    buffer.push_back((value >> 24) & 0xFF);
    
    return buffer;
}

std::vector<uint8_t> encodeValue(const float& value) {
    std::vector<uint8_t> buffer;
    buffer.push_back(static_cast<uint8_t>(BT_Type::FLOAT));
    
    // Convert float to bytes (little endian)
    uint32_t floatBits;
    std::memcpy(&floatBits, &value, sizeof(float));
    
    buffer.push_back(floatBits & 0xFF);
    buffer.push_back((floatBits >> 8) & 0xFF);
    buffer.push_back((floatBits >> 16) & 0xFF);
    buffer.push_back((floatBits >> 24) & 0xFF);
    
    return buffer;
}

std::vector<uint8_t> encodeValue(const std::string& value) {
    std::vector<uint8_t> buffer;
    buffer.push_back(static_cast<uint8_t>(BT_Type::STRING));
    
    // String length (little endian)
    int32_t length = static_cast<int32_t>(value.length());
    buffer.push_back(length & 0xFF);
    buffer.push_back((length >> 8) & 0xFF);
    buffer.push_back((length >> 16) & 0xFF);
    buffer.push_back((length >> 24) & 0xFF);
    
    // String bytes
    for (char c : value) {
        buffer.push_back(static_cast<uint8_t>(c));
    }
    
    return buffer;
}

std::vector<uint8_t> encodeValue(const std::vector<int32_t>& value) {
    std::vector<uint8_t> buffer;
    buffer.push_back(static_cast<uint8_t>(BT_Type::INTEGER_ARRAY));
    
    // Array length (little endian)
    int32_t length = static_cast<int32_t>(value.size());
    buffer.push_back(length & 0xFF);
    buffer.push_back((length >> 8) & 0xFF);
    buffer.push_back((length >> 16) & 0xFF);
    buffer.push_back((length >> 24) & 0xFF);
    
    // Array elements
    for (const auto& item : value) {
        auto itemBuffer = encodeValue(item);
        buffer.insert(buffer.end(), itemBuffer.begin(), itemBuffer.end());
    }
    
    return buffer;
}

std::vector<uint8_t> encodeValue(const std::vector<float>& value) {
    std::vector<uint8_t> buffer;
    buffer.push_back(static_cast<uint8_t>(BT_Type::FLOAT_ARRAY));
    
    // Array length (little endian)
    int32_t length = static_cast<int32_t>(value.size());
    buffer.push_back(length & 0xFF);
    buffer.push_back((length >> 8) & 0xFF);
    buffer.push_back((length >> 16) & 0xFF);
    buffer.push_back((length >> 24) & 0xFF);
    
    // Array elements
    for (const auto& item : value) {
        auto itemBuffer = encodeValue(item);
        buffer.insert(buffer.end(), itemBuffer.begin(), itemBuffer.end());
    }
    
    return buffer;
}

// BT_Reference implementation
BT_Reference::BT_Reference(BinaryTable* table, BT_Pointer pointer) 
    : table_(table), pointer_(pointer) {}

template<>
int32_t BT_Reference::decodeValue<int32_t>() {
    if (pointer_.isNull()) {
        throw std::runtime_error("Null pointer");
    }
    
    table_->setFilePosition(pointer_.address());
    uint8_t typeId = table_->readByte(pointer_.address());
    
    if (static_cast<BT_Type>(typeId) != BT_Type::INTEGER) {
        throw std::runtime_error("Type mismatch");
    }
    
    return table_->readInt32(pointer_.address() + 1);
}

template<>
float BT_Reference::decodeValue<float>() {
    if (pointer_.isNull()) {
        throw std::runtime_error("Null pointer");
    }
    
    table_->setFilePosition(pointer_.address());
    uint8_t typeId = table_->readByte(pointer_.address());
    
    if (static_cast<BT_Type>(typeId) != BT_Type::FLOAT) {
        throw std::runtime_error("Type mismatch");
    }
    
    return table_->readFloat32(pointer_.address() + 1);
}

template<>
std::string BT_Reference::decodeValue<std::string>() {
    if (pointer_.isNull()) {
        throw std::runtime_error("Null pointer");
    }
    
    table_->setFilePosition(pointer_.address());
    uint8_t typeId = table_->readByte(pointer_.address());
    
    if (static_cast<BT_Type>(typeId) != BT_Type::STRING) {
        throw std::runtime_error("Type mismatch");
    }
    
    int32_t length = table_->readInt32(pointer_.address() + 1);
    auto bytes = table_->readBytes(pointer_.address() + 5, length);
    
    return std::string(bytes.begin(), bytes.end());
}

template<>
BT_UniformArray<int32_t> BT_Reference::decodeValue<BT_UniformArray<int32_t>>() {
    return BT_UniformArray<int32_t>(table_, pointer_);
}

template<>
BT_UniformArray<float> BT_Reference::decodeValue<BT_UniformArray<float>>() {
    return BT_UniformArray<float>(table_, pointer_);
}

template<>
std::vector<int32_t> BT_Reference::decodeValue<std::vector<int32_t>>() {
    if (pointer_.isNull()) {
        return {};
    }
    
    uint8_t typeId = table_->readByte(pointer_.address());
    BT_Type type = static_cast<BT_Type>(typeId);
    
    if (type != BT_Type::INTEGER_ARRAY) {
        throw std::runtime_error("Type mismatch - expected integer array");
    }
    
    int32_t length = table_->readInt32(pointer_.address() + 1);
    std::vector<int32_t> result;
    result.reserve(length);
    
    // Each element is: type byte (1) + int32 data (4) = 5 bytes
    int64_t elementPos = pointer_.address() + 1 + 4; // Skip type and length
    
    for (int32_t i = 0; i < length; i++) {
        // Skip the type byte, read the int32 value
        int32_t value = table_->readInt32(elementPos + 1);
        result.push_back(value);
        elementPos += 5; // Move to next element
    }
    
    return result;
}

template<>
std::vector<float> BT_Reference::decodeValue<std::vector<float>>() {
    if (pointer_.isNull()) {
        return {};
    }
    
    uint8_t typeId = table_->readByte(pointer_.address());
    BT_Type type = static_cast<BT_Type>(typeId);
    
    if (type != BT_Type::FLOAT_ARRAY) {
        throw std::runtime_error("Type mismatch - expected float array");
    }
    
    int32_t length = table_->readInt32(pointer_.address() + 1);
    std::vector<float> result;
    result.reserve(length);
    
    // Each element is: type byte (1) + float data (4) = 5 bytes
    int64_t elementPos = pointer_.address() + 1 + 4; // Skip type and length
    
    for (int32_t i = 0; i < length; i++) {
        // Skip the type byte, read the float value
        float value = table_->readFloat32(elementPos + 1);
        result.push_back(value);
        elementPos += 5; // Move to next element
    }
    
    return result;
}

int32_t BT_Reference::size() const {
    if (pointer_.isNull()) {
        return 0;
    }
    
    uint8_t typeId = table_->readByte(pointer_.address());
    BT_Type type = static_cast<BT_Type>(typeId);
    
    switch (type) {
        case BT_Type::POINTER:
            return 1 + 8; // Type byte + pointer
        case BT_Type::INTEGER:
        case BT_Type::FLOAT:
            return 1 + 4; // Type byte + data
        case BT_Type::STRING: {
            int32_t length = table_->readInt32(pointer_.address() + 1);
            return 1 + 4 + length; // Type + length + string bytes
        }
        case BT_Type::ADDRESS_TABLE: {
            int32_t count = table_->readInt32(pointer_.address() + 1);
            return 1 + 4 + count * (8 + 8); // Type + count + entries
        }
        case BT_Type::INTEGER_ARRAY:
        case BT_Type::FLOAT_ARRAY: {
            int32_t length = table_->readInt32(pointer_.address() + 1);
            int32_t elementSize = (type == BT_Type::INTEGER_ARRAY) ? (1 + 4) : (1 + 4);
            return 1 + 4 + length * elementSize;
        }
    }
    return 0;
}

BT_Type BT_Reference::getType() const {
    if (pointer_.isNull()) {
        throw std::runtime_error("Null pointer");
    }
    
    uint8_t typeId = table_->readByte(pointer_.address());
    return static_cast<BT_Type>(typeId);
}

// BT_UniformArray template implementations
template<typename T>
int32_t BT_UniformArray<T>::length() const {
    if (this->pointer_.isNull()) {
        return 0;
    }
    
    try {
        uint8_t typeId = this->table_->readByte(this->pointer_.address());
        BT_Type type = static_cast<BT_Type>(typeId);
        
        if (!isArrayType(type)) {
            return 0; // Treat non-array as empty array instead of throwing
        }
        
        return this->table_->readInt32(this->pointer_.address() + 1);
    } catch (...) {
        return 0; // If we can't read, treat as empty
    }
}

template<typename T>
T BT_UniformArray<T>::operator[](int32_t index) const {
    if (this->pointer_.isNull()) {
        throw std::runtime_error("Null pointer");
    }
    
    int32_t len = length();
    if (index < 0 || index >= len) {
        throw std::out_of_range("Index out of range");
    }
    
    // Determine element type and size
    uint8_t elementTypeId = this->table_->readByte(this->pointer_.address() + 1 + 4);
    BT_Type elementType = static_cast<BT_Type>(elementTypeId);
    int32_t elementSize = 1 + getTypeSize(elementType);
    
    int64_t itemAddress = this->pointer_.address() + 1 + 4 + index * elementSize;
    BT_Reference itemRef(this->table_, BT_Pointer(itemAddress));
    
    return itemRef.decodeValue<T>();
}

template<typename T>
void BT_UniformArray<T>::set(int32_t index, const T& value) {
    if (this->pointer_.isNull()) {
        throw std::runtime_error("Null pointer");
    }
    
    int32_t len = length();
    if (index < 0 || index >= len) {
        throw std::out_of_range("Index out of range");
    }
    
    // Validate type compatibility
    BT_Type expectedType = getTypeFromValue<T>();
    uint8_t elementTypeId = this->table_->readByte(this->pointer_.address() + 1 + 4);
    BT_Type elementType = static_cast<BT_Type>(elementTypeId);
    
    if (expectedType != elementType) {
        throw std::runtime_error("Type mismatch");
    }
    
    // Encode and write value
    auto valueBuffer = encodeValue(value);
    int32_t elementSize = 1 + getTypeSize(elementType);
    int64_t itemAddress = this->pointer_.address() + 1 + 4 + index * elementSize;
    
    this->table_->writeBytes(itemAddress, valueBuffer);
}

template<typename T>
void BT_UniformArray<T>::add(const T& value) {
    addAll({value});
}

template<typename T>
void BT_UniformArray<T>::addAll(const std::vector<T>& values) {
    this->table_->antiFreeListScope([&]() {
        // Get current element type or determine from new values
        BT_Type elementType = getTypeFromValue<T>();
        
        if (length() > 0) {
            uint8_t existingTypeId = this->table_->readByte(this->pointer_.address() + 1 + 4);
            BT_Type existingType = static_cast<BT_Type>(existingTypeId);
            if (existingType != elementType) {
                throw std::runtime_error("Type mismatch");
            }
        }
        
        // Validate all values are compatible
        for (const auto& value : values) {
            (void)value; // Suppress unused variable warning
            BT_Type valueType = getTypeFromValue<T>();
            if (valueType != elementType) {
                throw std::runtime_error("Type mismatch in values");
            }
            if (getTypeSize(elementType) == -1) {
                throw std::runtime_error("Variable size types not supported in uniform arrays");
            }
        }
        
        // Read current array buffer
        int32_t currentLength = length();
        int32_t elementSize = 1 + getTypeSize(elementType);
        int32_t currentBufferSize = 1 + 4 + currentLength * elementSize;
        
        std::vector<uint8_t> fullBuffer;
        if (currentLength > 0) {
            fullBuffer = this->table_->readBytes(this->pointer_.address(), currentBufferSize);
        } else {
            // Empty array, create initial buffer
            fullBuffer.push_back(static_cast<uint8_t>(elementType == BT_Type::INTEGER ? BT_Type::INTEGER_ARRAY : BT_Type::FLOAT_ARRAY));
            fullBuffer.push_back(0); // Length will be updated
            fullBuffer.push_back(0);
            fullBuffer.push_back(0);
            fullBuffer.push_back(0);
        }
        
        // Add new values to buffer
        for (const auto& value : values) {
            auto valueBuffer = encodeValue(value);
            fullBuffer.insert(fullBuffer.end(), valueBuffer.begin(), valueBuffer.end());
        }
        
        // Update length in buffer
        int32_t newLength = currentLength + static_cast<int32_t>(values.size());
        fullBuffer[1] = newLength & 0xFF;
        fullBuffer[2] = (newLength >> 8) & 0xFF;
        fullBuffer[3] = (newLength >> 16) & 0xFF;
        fullBuffer[4] = (newLength >> 24) & 0xFF;
        
        // Free old array if it exists
        if (!this->pointer_.isNull()) {
            this->table_->free(this->pointer_, currentBufferSize);
        }
        
        // Allocate new space
        BT_Pointer newPointer = this->table_->alloc(static_cast<int32_t>(fullBuffer.size()));
        
        // Update any references in address table
        auto addressTable = this->table_->getAddressTable();
        for (auto& [key, value] : addressTable) {
            if (value == this->pointer_) {
                value = newPointer;
            }
        }
        this->table_->setAddressTable(addressTable);
        this->pointer_ = newPointer;
        
        // Write updated buffer
        this->table_->writeBytes(newPointer.address(), fullBuffer);
    });
}

template<typename T>
std::vector<T> BT_UniformArray<T>::fetchSublist(int32_t start, int32_t end) {
    int32_t len = length();
    if (len == 0) {
        return {};
    }
    
    if (end == -1) {
        end = len;
    }
    
    if (start < 0 || start >= len || end < start || end > len) {
        throw std::out_of_range("Invalid range");
    }
    
    uint8_t elementTypeId = this->table_->readByte(this->pointer_.address() + 1 + 4);
    BT_Type elementType = static_cast<BT_Type>(elementTypeId);
    int32_t elementSize = 1 + getTypeSize(elementType);
    
    if (getTypeSize(elementType) == -1) {
        throw std::runtime_error("Variable size types not supported in uniform arrays");
    }
    
    std::vector<T> result;
    for (int32_t i = start; i < end; i++) {
        int64_t itemAddress = this->pointer_.address() + 1 + 4 + i * elementSize;
        BT_Reference itemRef(this->table_, BT_Pointer(itemAddress));
        result.push_back(itemRef.decodeValue<T>());
    }
    
    return result;
}

// Explicit template instantiations
template class BT_UniformArray<int32_t>;
template class BT_UniformArray<float>;

// BinaryTable implementation
BinaryTable::BinaryTable(const std::string& path) 
    : filePath_(path), freeListLifted_(false) {
    file_.open(path, std::ios::binary | std::ios::in | std::ios::out);
    if (!file_) {
        // File doesn't exist, create it
        file_.open(path, std::ios::binary | std::ios::out);
        file_.close();
        file_.open(path, std::ios::binary | std::ios::in | std::ios::out);
    }
}

BinaryTable::~BinaryTable() {
    if (file_.is_open()) {
        file_.close();
    }
}

void BinaryTable::initialize() {
    file_.seekp(0);
    writeInt64(0, BT_Null.address()); // Address table pointer (8 bytes)
    writeInt32(8, 0); // Free list entry count (4 bytes)
    file_.flush();
}

// File I/O helper implementations
int32_t BinaryTable::readInt32(int64_t position) {
    file_.seekg(position);
    uint8_t bytes[4];
    file_.read(reinterpret_cast<char*>(bytes), 4);
    
    return static_cast<int32_t>(bytes[0]) |
           (static_cast<int32_t>(bytes[1]) << 8) |
           (static_cast<int32_t>(bytes[2]) << 16) |
           (static_cast<int32_t>(bytes[3]) << 24);
}

float BinaryTable::readFloat32(int64_t position) {
    file_.seekg(position);
    uint8_t bytes[4];
    file_.read(reinterpret_cast<char*>(bytes), 4);
    
    uint32_t floatBits = static_cast<uint32_t>(bytes[0]) |
                        (static_cast<uint32_t>(bytes[1]) << 8) |
                        (static_cast<uint32_t>(bytes[2]) << 16) |
                        (static_cast<uint32_t>(bytes[3]) << 24);
    
    float result;
    std::memcpy(&result, &floatBits, sizeof(float));
    return result;
}

int64_t BinaryTable::readInt64(int64_t position) {
    file_.seekg(position);
    uint8_t bytes[8];
    file_.read(reinterpret_cast<char*>(bytes), 8);
    
    int64_t result = 0;
    for (int i = 0; i < 8; i++) {
        result |= static_cast<int64_t>(bytes[i]) << (i * 8);
    }
    
    return result;
}

uint8_t BinaryTable::readByte(int64_t position) {
    file_.seekg(position);
    uint8_t byte;
    file_.read(reinterpret_cast<char*>(&byte), 1);
    return byte;
}

std::vector<uint8_t> BinaryTable::readBytes(int64_t position, int32_t count) {
    file_.seekg(position);
    std::vector<uint8_t> bytes(count);
    file_.read(reinterpret_cast<char*>(bytes.data()), count);
    return bytes;
}

void BinaryTable::writeInt32(int64_t position, int32_t value) {
    file_.seekp(position);
    uint8_t bytes[4] = {
        static_cast<uint8_t>(value & 0xFF),
        static_cast<uint8_t>((value >> 8) & 0xFF),
        static_cast<uint8_t>((value >> 16) & 0xFF),
        static_cast<uint8_t>((value >> 24) & 0xFF)
    };
    file_.write(reinterpret_cast<const char*>(bytes), 4);
}

void BinaryTable::writeFloat32(int64_t position, float value) {
    file_.seekp(position);
    uint32_t floatBits;
    std::memcpy(&floatBits, &value, sizeof(float));
    
    uint8_t bytes[4] = {
        static_cast<uint8_t>(floatBits & 0xFF),
        static_cast<uint8_t>((floatBits >> 8) & 0xFF),
        static_cast<uint8_t>((floatBits >> 16) & 0xFF),
        static_cast<uint8_t>((floatBits >> 24) & 0xFF)
    };
    file_.write(reinterpret_cast<const char*>(bytes), 4);
}

void BinaryTable::writeInt64(int64_t position, int64_t value) {
    file_.seekp(position);
    uint8_t bytes[8];
    for (int i = 0; i < 8; i++) {
        bytes[i] = static_cast<uint8_t>((value >> (i * 8)) & 0xFF);
    }
    file_.write(reinterpret_cast<const char*>(bytes), 8);
}

void BinaryTable::writeByte(int64_t position, uint8_t value) {
    file_.seekp(position);
    file_.write(reinterpret_cast<const char*>(&value), 1);
}

void BinaryTable::writeBytes(int64_t position, const std::vector<uint8_t>& data) {
    file_.seekp(position);
    file_.write(reinterpret_cast<const char*>(data.data()), data.size());
}

int64_t BinaryTable::getFileLength() {
    file_.seekg(0, std::ios::end);
    return file_.tellg();
}

void BinaryTable::setFilePosition(int64_t position) {
    file_.seekg(position);
    file_.seekp(position);
}

// Address table management
std::unordered_map<int64_t, BT_Pointer> BinaryTable::getAddressTable() {
    file_.seekg(0);
    int64_t tableAddress = readInt64(0);
    
    if (tableAddress == -1) { // Null pointer
        return {};
    }
    
    try {
        uint8_t typeId = readByte(tableAddress);
        
        if (static_cast<BT_Type>(typeId) != BT_Type::ADDRESS_TABLE) {
            // Address table might not be valid yet, return empty
            return {};
        }
        
        int32_t tableCount = readInt32(tableAddress + 1);
        std::unordered_map<int64_t, BT_Pointer> addressTable;
        
        for (int32_t i = 0; i < tableCount; i++) {
            int64_t offset = tableAddress + 1 + 4 + i * (8 + 8);
            int64_t keyHash = readInt64(offset);
            int64_t valueAddress = readInt64(offset + 8);
            addressTable[keyHash] = BT_Pointer(valueAddress);
        }
        
        return addressTable;
    } catch (...) {
        // If we can't read the address table, return empty
        return {};
    }
}

void BinaryTable::setAddressTable(const std::unordered_map<int64_t, BT_Pointer>& table) {
    // Build buffer manually (matching Dart implementation exactly)
    std::vector<uint8_t> buffer;
    
    // Type byte
    buffer.push_back(static_cast<uint8_t>(BT_Type::ADDRESS_TABLE));
    
    // Table count (little endian, 4 bytes)
    int32_t count = static_cast<int32_t>(table.size());
    for (int i = 0; i < 4; i++) {
        buffer.push_back(static_cast<uint8_t>((count >> (i * 8)) & 0xFF));
    }
    
    // Table entries
    for (const auto& [key, value] : table) {
        // Key hash (little endian, 8 bytes)
        for (int i = 0; i < 8; i++) {
            buffer.push_back(static_cast<uint8_t>((key >> (i * 8)) & 0xFF));
        }
        // Value address (little endian, 8 bytes)
        int64_t addr = value.address();
        for (int i = 0; i < 8; i++) {
            buffer.push_back(static_cast<uint8_t>((addr >> (i * 8)) & 0xFF));
        }
    }
    
    // Write new address table at end of file
    BT_Pointer tableAddress = alloc(static_cast<int32_t>(buffer.size()));
    file_.seekp(tableAddress.address());
    file_.write(reinterpret_cast<const char*>(buffer.data()), buffer.size());
    
    // Read old table pointer before updating
    file_.seekg(0);
    int64_t oldTablePointerAddress = readInt64(0);
    BT_Pointer oldTablePtr(oldTablePointerAddress);
    
    // Update header to point to new table  
    file_.seekp(0);
    writeInt64(0, tableAddress.address());
    file_.flush();
    
    // Now free the old table if it exists and is not the same as the new one
    if (!oldTablePtr.isNull() && oldTablePtr != tableAddress) {
        BT_Reference oldTableRef(this, oldTablePtr);
        free(oldTablePtr, oldTableRef.size());
    }
}

// Free list management
std::vector<BT_FreeListEntry> BinaryTable::getFreeList() {
    if (freeListLifted_) {
        return freeListCache_;
    }
    
    int64_t fileLength = getFileLength();
    if (fileLength < 4) {
        return {};
    }
    
    int32_t entryCount = readInt32(fileLength - 4);
    if (entryCount == 0) {
        return {};
    }
    
    int32_t entrySize = 8 + 4; // Pointer + Size
    int32_t freeListSize = entryCount * entrySize;
    int64_t freeListStart = fileLength - 4 - freeListSize;
    
    std::vector<BT_FreeListEntry> freeList;
    for (int32_t i = 0; i < entryCount; i++) {
        int64_t offset = freeListStart + i * entrySize;
        int64_t pointerAddress = readInt64(offset);
        int32_t size = readInt32(offset + 8);
        freeList.emplace_back(BT_Pointer(pointerAddress), size);
    }
    
    return freeList;
}

void BinaryTable::setFreeList(const std::vector<BT_FreeListEntry>& list) {
    if (freeListLifted_) {
        freeListCache_ = list;
        return;
    }
    
    std::cout << "DEBUG: setFreeList called with " << list.size() << " entries" << std::endl;
    
    // Read old entry count from last 4 bytes (matching Dart exactly)
    int64_t fileLength = getFileLength();
    std::cout << "DEBUG: File length: " << fileLength << std::endl;
    
    file_.seekg(fileLength - 4);
    int32_t oldEntryCount = readInt32(fileLength - 4);
    int32_t oldListSize = (oldEntryCount * (8 + 4)) + 4; // Entries + Count
    std::cout << "DEBUG: Old entry count: " << oldEntryCount << ", old list size: " << oldListSize << std::endl;
    
    // Truncate file to remove old free list (Dart does _file.truncateSync)
    int64_t newFileLength = fileLength - oldListSize;
    std::cout << "DEBUG: New file length after truncation: " << newFileLength << std::endl;
    // Skip actual truncation for now, just use logical position
    
    // Encode new free list (matching Dart bt_encode exactly)
    std::vector<uint8_t> buffer;
    
    // Entries
    for (const auto& entry : list) {
        std::cout << "DEBUG: Encoding entry - address: " << entry.pointer.address() << ", size: " << entry.size << std::endl;
        // Pointer (8 bytes, little endian)
        int64_t addr = entry.pointer.address();
        for (int i = 0; i < 8; i++) {
            buffer.push_back(static_cast<uint8_t>((addr >> (i * 8)) & 0xFF));
        }
        // Size (4 bytes, little endian)
        int32_t size = entry.size;
        for (int i = 0; i < 4; i++) {
            buffer.push_back(static_cast<uint8_t>((size >> (i * 8)) & 0xFF));
        }
    }
    
    // Entry count (4 bytes, little endian)
    int32_t count = static_cast<int32_t>(list.size());
    for (int i = 0; i < 4; i++) {
        buffer.push_back(static_cast<uint8_t>((count >> (i * 8)) & 0xFF));
    }
    
    std::cout << "DEBUG: Buffer size: " << buffer.size() << " bytes" << std::endl;
    std::cout << "DEBUG: Writing free list at position: " << newFileLength << std::endl;
    
    // Write at end of (truncated) file - seek to end of logical file, not physical file
    file_.seekp(0, std::ios::end);
    int64_t actualFileLength = file_.tellp();
    std::cout << "DEBUG: Actual file length: " << actualFileLength << std::endl;
    
    // Write at the calculated position (after logical truncation)
    file_.seekp(newFileLength);
    file_.write(reinterpret_cast<const char*>(buffer.data()), buffer.size());
    file_.flush();
    std::cout << "DEBUG: setFreeList completed" << std::endl;
}

void BinaryTable::truncateFile(int64_t newSize) {
    // Actually truncate the file (matching Dart behavior)
    file_.close();
    std::filesystem::resize_file(filePath_, newSize);
    file_.open(filePath_, std::ios::binary | std::ios::in | std::ios::out);
}

void BinaryTable::liftFreeList() {
    if (freeListLifted_) {
        throw std::runtime_error("Free list is already lifted");
    }
    
    freeListCache_ = getFreeList();
    
    int64_t fileLength = getFileLength();
    int32_t oldEntryCount = (fileLength >= 4) ? readInt32(fileLength - 4) : 0;
    int32_t oldEntrySize = 8 + 4;
    int32_t oldFreeListSize = oldEntryCount * oldEntrySize + 4;
    
    // Truncate file to remove free list
    truncateFile(fileLength - oldFreeListSize);
    
    freeListLifted_ = true;
}

void BinaryTable::dropFreeList() {
    if (!freeListLifted_) {
        throw std::runtime_error("Free list is not lifted");
    }
    
    std::cout << "DEBUG: dropFreeList - seeking to end" << std::endl;
    file_.seekp(0, std::ios::end);
    
    std::cout << "DEBUG: dropFreeList - about to call setFreeList with " << freeListCache_.size() << " entries" << std::endl;
    freeListLifted_ = false;
    setFreeList(freeListCache_);
    std::cout << "DEBUG: dropFreeList - setFreeList completed" << std::endl;
    freeListCache_.clear();
}

void BinaryTable::antiFreeListScope(std::function<void()> fn) {
    std::cout << "DEBUG: antiFreeListScope START" << std::endl;
    liftFreeList();
    std::cout << "DEBUG: After liftFreeList" << std::endl;
    try {
        fn();
        std::cout << "DEBUG: After fn() execution" << std::endl;
    } catch (...) {
        std::cout << "DEBUG: Exception caught, dropping free list" << std::endl;
        dropFreeList();
        throw;
    }
    std::cout << "DEBUG: About to dropFreeList" << std::endl;
    dropFreeList();
    std::cout << "DEBUG: antiFreeListScope END" << std::endl;
}

// Memory management
void BinaryTable::free(BT_Pointer pointer, int32_t size) {
    if (!freeListLifted_) {
        throw std::runtime_error("Free list must be lifted before freeing memory");
    }
    
    if (pointer.isNull() || size <= 0) {
        throw std::invalid_argument("Cannot free null pointer or zero size");
    }
    
    // Fetch current free list (matching Dart exactly)
    std::vector<BT_FreeListEntry> freeList = freeListCache_;
    
    // Add new free entry
    freeList.emplace_back(pointer, size);
    
    // Merge contiguous free entries (matching Dart logic exactly)
    auto mergeContiguousFreeBlocks = [](std::vector<BT_FreeListEntry> freeList) -> std::vector<BT_FreeListEntry> {
        if (freeList.empty()) return {};
        
        // Create a copy and sort by address to check for contiguous blocks
        std::vector<BT_FreeListEntry> sorted = freeList;
        std::sort(sorted.begin(), sorted.end(), 
                  [](const BT_FreeListEntry& a, const BT_FreeListEntry& b) {
                      return a.pointer.address() < b.pointer.address();
                  });
        
        std::vector<BT_FreeListEntry> merged;
        
        for (const auto& entry : sorted) {
            if (merged.empty()) {
                // First entry, just add it
                merged.emplace_back(entry.pointer, entry.size);
            } else {
                auto& last = merged.back();
                
                // Check if current entry is contiguous with the last merged entry
                if (last.pointer.address() + last.size == entry.pointer.address()) {
                    // Merge: extend the size of the last entry
                    last.size += entry.size;
                } else {
                    // Not contiguous, add as separate entry
                    merged.emplace_back(entry.pointer, entry.size);
                }
            }
        }
        
        return merged;
    };
    
    freeList = mergeContiguousFreeBlocks(freeList);
    
    // Update free list
    freeListCache_ = freeList;
}

BT_Pointer BinaryTable::alloc(int32_t size) {
    if (!freeListLifted_) {
        throw std::runtime_error("Free list must be lifted before allocation");
    }
    
    // Find suitable free block
    auto it = std::find_if(freeListCache_.begin(), freeListCache_.end(),
                          [size](const BT_FreeListEntry& entry) {
                              return entry.size >= size;
                          });
    
    if (it == freeListCache_.end()) {
        // No suitable block, allocate at end of file
        return BT_Pointer(getFileLength());
    }
    
    BT_Pointer result = it->pointer;
    
    if (it->size == size) {
        // Exact fit, remove block
        freeListCache_.erase(it);
    } else {
        // Split block
        it->pointer = BT_Pointer(it->pointer.address() + size);
        it->size -= size;
    }
    
    return result;
}

// Data operations
BT_Reference BinaryTable::getReference(const std::string& key) {
    auto addressTable = getAddressTable();
    int64_t keyHash = hashString(key);
    
    auto it = addressTable.find(keyHash);
    if (it == addressTable.end()) {
        throw std::runtime_error("Key does not exist");
    }
    
    return BT_Reference(this, it->second);
}

void BinaryTable::remove(const std::string& key) {
    antiFreeListScope([&]() {
        auto addressTable = getAddressTable();
        int64_t keyHash = hashString(key);
        
        auto it = addressTable.find(keyHash);
        if (it == addressTable.end()) {
            throw std::runtime_error("Key does not exist");
        }
        
        BT_Reference valueRef(this, it->second);
        free(it->second, valueRef.size());
        
        addressTable.erase(it);
        setAddressTable(addressTable);
    });
}

void BinaryTable::truncate() {
    antiFreeListScope([&]() {
        // Relocate address table
        setAddressTable(getAddressTable());
        
        // Check if last free block is at end of file
        auto freeList = getFreeList();
        if (freeList.empty()) {
            return;
        }
        
        std::sort(freeList.begin(), freeList.end(),
                 [](const BT_FreeListEntry& a, const BT_FreeListEntry& b) {
                     return a.pointer.address() < b.pointer.address();
                 });
        
        const auto& lastEntry = freeList.back();
        int64_t fileEnd = getFileLength();
        int64_t expectedEnd = lastEntry.pointer.address() + lastEntry.size;
        
        if (expectedEnd == fileEnd) {
            freeList.pop_back();
            setFreeList(freeList);
            
            // Truncate file
            file_.close();
            file_.open(filePath_, std::ios::binary | std::ios::in | std::ios::out);
        }
    });
}

// Debug methods
void BinaryTable::debugAddressTable(const std::string& context) {
    std::cout << "\n=== DEBUG ADDRESS TABLE";
    if (!context.empty()) {
        std::cout << " (" << context << ")";
    }
    std::cout << " ===" << std::endl;
    
    auto addressTable = getAddressTable();
    std::cout << "Address table has " << addressTable.size() << " entries" << std::endl;
    
    for (const auto& [hash, pointer] : addressTable) {
        std::cout << "  Hash " << hash << " -> Address " << pointer.address() << std::endl;
        
        if (!pointer.isNull()) {
            try {
                uint8_t typeByte = readByte(pointer.address());
                std::cout << "    Type byte: " << (int)typeByte << std::endl;
                
                if (typeByte == 2) { // INTEGER
                    int32_t value = readInt32(pointer.address() + 1);
                    std::cout << "    Value: " << value << std::endl;
                } else {
                    std::cout << "    Raw bytes: ";
                    for (int i = 0; i < 8; i++) {
                        uint8_t byte = readByte(pointer.address() + i);
                        std::cout << std::hex << (int)byte << " ";
                    }
                    std::cout << std::dec << std::endl;
                }
            } catch (const std::exception& e) {
                std::cout << "    Error reading data: " << e.what() << std::endl;
            }
        }
    }
    std::cout << "=========================" << std::endl;
}

} // namespace bt