/**
 * Element binary serialization for Implexus storage layer.
 *
 * Provides serialization and deserialization of Invercargill.Element
 * values to/from binary format for persistent storage.
 */

namespace Implexus.Storage {

    /**
     * Type codes for binary element serialization.
     */
    internal enum ElementTypeCode {
        NULL = 0x00,
        BOOL = 0x01,
        INT64 = 0x02,
        UINT64 = 0x03,
        DOUBLE = 0x04,
        STRING = 0x05,
        BINARY = 0x06,
        ARRAY = 0x07,
        DICTIONARY = 0x08;

        /**
         * Determines the type code from an Element's GLib.Type.
         */
        public static ElementTypeCode from_type(GLib.Type type) {
            if (type == typeof(bool)) {
                return BOOL;
            } else if (type == typeof(int64)) {
                return INT64;
            } else if (type == typeof(uint64)) {
                return UINT64;
            } else if (type == typeof(double)) {
                return DOUBLE;
            } else if (type == typeof(string)) {
                return STRING;
            } else if (type == typeof(Invercargill.BinaryData)) {
                return BINARY;
            } else if (type == typeof(Invercargill.Enumerable<Invercargill.Element>)) {
                return ARRAY;
            } else if (type == typeof(Invercargill.Properties)) {
                return DICTIONARY;
            } else {
                return NULL;
            }
        }
    }

    /**
     * Writes Element values to binary format.
     */
    public class ElementWriter : Object {
        private Invercargill.ByteComposition _buffer;

        /**
         * Creates a new ElementWriter.
         */
        public ElementWriter() {
            _buffer = new Invercargill.ByteComposition();
        }

        /**
         * Writes an element to the buffer.
         *
         * @param element The element to write
         */
        public void write_element(Invercargill.Element element) throws StorageError {
            // Check for null element
            if (element.is_null()) {
                write_null();
                return;
            }

            // Check the element's type and serialize accordingly
            var type = element.type();
            if (type == typeof(bool)) {
                _buffer.append_uint8(ElementTypeCode.BOOL);
                try {
                    write_bool(element.as<bool?>());
                } catch (Invercargill.ElementError e) {
                    throw new StorageError.CORRUPT_DATA("Failed to get bool value: %s".printf(e.message));
                }
            } else if (type == typeof(int64)) {
                _buffer.append_uint8(ElementTypeCode.INT64);
                try {
                    int64? val = element.as<int64?>();
                    write_int64(val == null ? 0 : (!) val);
                } catch (Invercargill.ElementError e) {
                    throw new StorageError.CORRUPT_DATA("Failed to get int64 value: %s".printf(e.message));
                }
            } else if (type == typeof(uint64)) {
                _buffer.append_uint8(ElementTypeCode.UINT64);
                try {
                    uint64? val = element.as<uint64?>();
                    write_uint64(val == null ? 0 : (!) val);
                } catch (Invercargill.ElementError e) {
                    throw new StorageError.CORRUPT_DATA("Failed to get uint64 value: %s".printf(e.message));
                }
            } else if (type == typeof(double)) {
                _buffer.append_uint8(ElementTypeCode.DOUBLE);
                try {
                    double? val = element.as<double?>();
                    write_double(val == null ? 0.0 : (!) val);
                } catch (Invercargill.ElementError e) {
                    throw new StorageError.CORRUPT_DATA("Failed to get double value: %s".printf(e.message));
                }
            } else if (type == typeof(string)) {
                _buffer.append_uint8(ElementTypeCode.STRING);
                try {
                    write_string(element.as<string>());
                } catch (Invercargill.ElementError e) {
                    throw new StorageError.CORRUPT_DATA("Failed to get string value: %s".printf(e.message));
                }
            } else if (type == typeof(Invercargill.BinaryData)) {
                _buffer.append_uint8(ElementTypeCode.BINARY);
                try {
                    write_binary(element.as<Invercargill.BinaryData>());
                } catch (Invercargill.ElementError e) {
                    throw new StorageError.CORRUPT_DATA("Failed to get binary value: %s".printf(e.message));
                }
            } else if (type == typeof(Invercargill.Enumerable<Invercargill.Element>)) {
                _buffer.append_uint8(ElementTypeCode.ARRAY);
                try {
                    write_array(element.as<Invercargill.Enumerable<Invercargill.Element>>());
                } catch (Invercargill.ElementError e) {
                    throw new StorageError.CORRUPT_DATA("Failed to get array value: %s".printf(e.message));
                }
            } else if (type == typeof(Invercargill.Properties)) {
                _buffer.append_uint8(ElementTypeCode.DICTIONARY);
                try {
                    write_dictionary(element.as<Invercargill.Properties>());
                } catch (Invercargill.ElementError e) {
                    throw new StorageError.CORRUPT_DATA("Failed to get dictionary value: %s".printf(e.message));
                }
            } else {
                // Unknown type - serialize as null
                write_null();
            }
        }

        /**
         * Writes a null value.
         */
        public void write_null() {
            _buffer.append_uint8(ElementTypeCode.NULL);
        }

        /**
         * Writes a boolean value.
         */
        public void write_bool(bool value) {
            _buffer.append_uint8(value ? (uint8) 1 : (uint8) 0);
        }

        /**
         * Writes an int64 value (big-endian).
         */
        public void write_int64(int64 value) {
            _buffer.append_uint8((uint8) ((value >> 56) & 0xFF));
            _buffer.append_uint8((uint8) ((value >> 48) & 0xFF));
            _buffer.append_uint8((uint8) ((value >> 40) & 0xFF));
            _buffer.append_uint8((uint8) ((value >> 32) & 0xFF));
            _buffer.append_uint8((uint8) ((value >> 24) & 0xFF));
            _buffer.append_uint8((uint8) ((value >> 16) & 0xFF));
            _buffer.append_uint8((uint8) ((value >> 8) & 0xFF));
            _buffer.append_uint8((uint8) (value & 0xFF));
        }

        /**
         * Writes a uint64 value (big-endian).
         */
        public void write_uint64(uint64 value) {
            _buffer.append_uint8((uint8) ((value >> 56) & 0xFF));
            _buffer.append_uint8((uint8) ((value >> 48) & 0xFF));
            _buffer.append_uint8((uint8) ((value >> 40) & 0xFF));
            _buffer.append_uint8((uint8) ((value >> 32) & 0xFF));
            _buffer.append_uint8((uint8) ((value >> 24) & 0xFF));
            _buffer.append_uint8((uint8) ((value >> 16) & 0xFF));
            _buffer.append_uint8((uint8) ((value >> 8) & 0xFF));
            _buffer.append_uint8((uint8) (value & 0xFF));
        }

        /**
         * Writes a double value.
         */
        public void write_double(double value) {
            int64 bits = (int64) *(uint64*) &value;
            write_int64(bits);
        }

        /**
         * Writes a length value (int64).
         */
        public void write_length(int64 length) {
            write_int64(length);
        }

        /**
         * Writes a string value.
         */
        public void write_string(string value) {
            int64 len = value.length;
            write_length(len);
            _buffer.append_string(value);
        }

        /**
         * Writes binary data.
         */
        public void write_binary(Invercargill.BinaryData value) {
            var bytes = value.to_bytes();
            int64 len = (int64) bytes.length;
            write_length(len);
            _buffer.append_bytes(bytes);
        }

        /**
         * Writes an array of elements.
         */
        public void write_array(Invercargill.Enumerable<Invercargill.Element> collection) {
            uint count = collection.count();
            write_length((int64) count);
            foreach (var item in collection) {
                try {
                    write_element(item);
                } catch (StorageError e) {
                    // Skip invalid elements - write null
                    write_null();
                }
            }
        }

        /**
         * Writes a dictionary of elements.
         */
        public void write_dictionary(Invercargill.Properties props) {
            uint count = props.count();
            write_length((int64) count);
            foreach (var kvp in props) {
                write_string(kvp.key);
                try {
                    write_element(kvp.value);
                } catch (StorageError e) {
                    // Write null for invalid elements
                    write_null();
                }
            }
        }

        /**
         * Gets the written data as BinaryData.
         *
         * @return The binary data
         */
        public Invercargill.BinaryData to_binary_data() {
            return _buffer;
        }

        /**
         * Clears the buffer for reuse.
         */
        public void clear() {
            _buffer.clear();
        }
    }

    /**
     * Reads Element values from binary format.
     */
    public class ElementReader : Object {
        private Invercargill.BinaryData _data;
        private Invercargill.ReadOnlyAddressable<uint8> _buffer;
        private uint _position;
        private uint _size;

        /**
         * Creates a new ElementReader with the given data.
         *
         * @param data The binary data to read
         */
        public ElementReader(Invercargill.BinaryData data) {
            _data = data;
            _buffer = data.to_byte_buffer();
            _position = 0;
            _size = data.count();
        }

        /**
         * Current position in the data.
         */
        public uint position {
            get { return _position; }
        }

        /**
         * Size of the data.
         */
        public uint size {
            get { return _size; }
        }

        /**
         * Whether there is more data to read.
         */
        public bool has_more {
            get { return _position < _size; }
        }

        /**
         * Reads a single byte.
         */
        private uint8 read_byte() throws StorageError {
            if (_position >= _size) {
                throw new StorageError.CORRUPT_DATA("Unexpected end of data");
            }
            try {
                var byte_val = _buffer.get(_position);
                _position++;
                return byte_val;
            } catch (Invercargill.IndexError e) {
                throw new StorageError.CORRUPT_DATA("Failed to read byte: %s".printf(e.message));
            }
        }

        /**
         * Reads bytes from the data.
         *
         * @param length Number of bytes to read
         * @return The bytes read
         */
        private uint8[] read_bytes(uint length) throws StorageError {
            if (_position + length > _size) {
                throw new StorageError.CORRUPT_DATA("Unexpected end of data");
            }

            var bytes = new uint8[length];
            var slice = _data.slice(_position, _position + length);
            var slice_bytes = slice.to_bytes();
            Memory.copy(bytes, slice_bytes.get_data(), length);
            _position += length;
            return bytes;
        }

        /**
         * Reads an element from the data.
         *
         * @return The element read
         */
        public Invercargill.Element read_element() throws StorageError {
            if (_position >= _size) {
                throw new StorageError.CORRUPT_DATA("Unexpected end of data");
            }

            var type_code = (ElementTypeCode) read_byte();

            switch (type_code) {
                case ElementTypeCode.NULL:
                    return new Invercargill.NullElement();
                case ElementTypeCode.BOOL:
                    return new Invercargill.NativeElement<bool?>(read_bool());
                case ElementTypeCode.INT64:
                    return new Invercargill.NativeElement<int64?>(read_int64());
                case ElementTypeCode.UINT64:
                    return new Invercargill.NativeElement<uint64?>(read_uint64());
                case ElementTypeCode.DOUBLE:
                    return new Invercargill.NativeElement<double?>(read_double());
                case ElementTypeCode.STRING:
                    return new Invercargill.NativeElement<string>(read_string());
                case ElementTypeCode.BINARY:
                    return new Invercargill.NativeElement<Invercargill.BinaryData>(read_binary());
                case ElementTypeCode.ARRAY:
                    return read_array();
                case ElementTypeCode.DICTIONARY:
                    return read_dictionary();
                default:
                    throw new StorageError.CORRUPT_DATA("Unknown type code: %d".printf((int) type_code));
            }
        }

        /**
         * Reads a boolean value.
         */
        public bool read_bool() throws StorageError {
            return read_byte() != 0;
        }

        /**
         * Reads an int64 value (big-endian).
         */
        public int64 read_int64() throws StorageError {
            if (_position + 8 > _size) {
                throw new StorageError.CORRUPT_DATA("Unexpected end of data reading int64");
            }
            try {
                int64 result = (int64) (
                    ((int64) _buffer.get(_position) << 56) |
                    ((int64) _buffer.get(_position + 1) << 48) |
                    ((int64) _buffer.get(_position + 2) << 40) |
                    ((int64) _buffer.get(_position + 3) << 32) |
                    ((int64) _buffer.get(_position + 4) << 24) |
                    ((int64) _buffer.get(_position + 5) << 16) |
                    ((int64) _buffer.get(_position + 6) << 8) |
                    ((int64) _buffer.get(_position + 7))
                );
                _position += 8;
                return result;
            } catch (Invercargill.IndexError e) {
                throw new StorageError.CORRUPT_DATA("Failed to read int64: %s".printf(e.message));
            }
        }

        /**
         * Reads a uint64 value (big-endian).
         */
        public uint64 read_uint64() throws StorageError {
            if (_position + 8 > _size) {
                throw new StorageError.CORRUPT_DATA("Unexpected end of data reading uint64");
            }
            try {
                uint64 result = (uint64) (
                    ((uint64) _buffer.get(_position) << 56) |
                    ((uint64) _buffer.get(_position + 1) << 48) |
                    ((uint64) _buffer.get(_position + 2) << 40) |
                    ((uint64) _buffer.get(_position + 3) << 32) |
                    ((uint64) _buffer.get(_position + 4) << 24) |
                    ((uint64) _buffer.get(_position + 5) << 16) |
                    ((uint64) _buffer.get(_position + 6) << 8) |
                    ((uint64) _buffer.get(_position + 7))
                );
                _position += 8;
                return result;
            } catch (Invercargill.IndexError e) {
                throw new StorageError.CORRUPT_DATA("Failed to read uint64: %s".printf(e.message));
            }
        }

        /**
         * Reads a double value.
         */
        public double read_double() throws StorageError {
            int64 bits = read_int64();
            return *(double*) &bits;
        }

        /**
         * Reads a length value.
         */
        public int64 read_length() throws StorageError {
            return read_int64();
        }

        /**
         * Reads a string value.
         */
        public string read_string() throws StorageError {
            int64 len = read_length();
            if (len < 0) {
                throw new StorageError.CORRUPT_DATA("Negative string length");
            }
            var bytes = read_bytes((uint) len);
            // Create a properly null-terminated string from the bytes
            // We need to copy the data and add a null terminator
            var str_builder = new StringBuilder.sized((size_t)(len + 1));
            for (int64 i = 0; i < len; i++) {
                str_builder.append_c((char) bytes[i]);
            }
            return str_builder.str;
        }

        /**
         * Reads binary data.
         */
        public Invercargill.BinaryData read_binary() throws StorageError {
            int64 len = read_length();
            if (len < 0) {
                throw new StorageError.CORRUPT_DATA("Negative binary length");
            }
            var bytes = read_bytes((uint) len);
            return new Invercargill.DataStructures.ByteBuffer.from_byte_array(bytes);
        }

        /**
         * Reads an array of elements.
         */
        public Invercargill.NativeElement<Invercargill.Enumerable<Invercargill.Element>> read_array() throws StorageError {
            int64 count = read_length();
            if (count < 0) {
                throw new StorageError.CORRUPT_DATA("Negative array count");
            }

            var array = new Invercargill.DataStructures.Vector<Invercargill.Element>();
            for (int64 i = 0; i < count; i++) {
                var element = read_element();
                array.add(element);
            }

            return new Invercargill.NativeElement<Invercargill.Enumerable<Invercargill.Element>>(array);
        }

        /**
         * Reads a dictionary of elements.
         */
        public Invercargill.NativeElement<Invercargill.Properties> read_dictionary() throws StorageError {
            int64 count = read_length();
            if (count < 0) {
                throw new StorageError.CORRUPT_DATA("Negative dictionary count");
            }

            var props = new Invercargill.DataStructures.PropertyDictionary();
            for (int64 i = 0; i < count; i++) {
                string key = read_string();
                var value = read_element();
                try {
                    props.set(key, value);
                } catch (Invercargill.IndexError e) {
                    throw new StorageError.CORRUPT_DATA("Failed to set dictionary key: %s".printf(e.message));
                }
            }

            return new Invercargill.NativeElement<Invercargill.Properties>(props);
        }
    }
}