package udptcp;

import java.util.ArrayList;
import java.util.List;

// ÖØÃüÃûΪPacketParser£¬±íʾÊý¾Ý°ü½âÎöÆ÷
public class PacketParser {
	// Ìí¼ÓÊ®Áù½øÖÆ×Ö·ûÊý×é³£Á¿
    private static final char[] HEX_ARRAY = "0123456789ABCDEF".toCharArray();
    // »º³åÇø×Ö½ÚÊý×é
    private byte[] buffer = new byte[4096];
    // µ±Ç°»º³åÇøÓÐЧÊý¾Ý³¤¶È
    private int bufferLength = 0;

    // ×·¼ÓÐÂÊý¾Ýµ½»º³åÇø
    public void appendData(byte[] newData, int length) {
        // ¼ì²é»º³åÇøÊÇ·ñ×ã¹»
        if (bufferLength + length > buffer.length) {
            // ´´½¨Ðµĸü´ó»º³åÇø
            byte[] newBuffer = new byte[bufferLength + length];
            // ¸´ÖÆÔ­ÓÐÊý¾Ý
            System.arraycopy(buffer, 0, newBuffer, 0, bufferLength);
            buffer = newBuffer;
        }
        // ×·¼ÓÐÂÊý¾Ý
        System.arraycopy(newData, 0, buffer, bufferLength, length);
        // ¸üлº³åÇø³¤¶È
        bufferLength += length;
    }
    
 // ÐÂÔö·½·¨£º×Ö½ÚÊý×éתʮÁù½øÖÆ×Ö·û´®
    public static String bytesToHexString(byte[] bytes) {
        if (bytes == null) return "";
        char[] hexChars = new char[bytes.length * 2];
        for (int j = 0; j < bytes.length; j++) {
            int v = bytes[j] & 0xFF;
            hexChars[j * 2] = HEX_ARRAY[v >>> 4];
            hexChars[j * 2 + 1] = HEX_ARRAY[v & 0x0F];
        }
        return new String(hexChars);
    }

    // ½âÎö»º³åÇøÖеÄËùÓÐÍêÕûÊý¾Ý°ü
    public List<DataPacket> parsePackets() {
        List<DataPacket> packets = new ArrayList<>();
        int index = 0;  // µ±Ç°½âÎöλÖÃË÷Òý
        
        // ±éÀú»º³åÇø²éÕÒÍêÕûÊý¾Ý°ü
        while (index <= bufferLength - 4) { // È·±£ÓÐ×ã¹»Êý¾Ý¼ì²é°üÍ·
            // ¼ì²é°üÍ·±êʶ 0x55 0xAA
            if (buffer[index] == 0x55 && (buffer[index + 1] & 0xFF) == 0xAA) {
                // »ñÈ¡°üÀàÐÍ£¨µÚ3×Ö½Ú£©
                int packetType = buffer[index + 2] & 0xFF;
                // »ñÈ¡Êý¾Ý³¤¶È£¨µÚ4×Ö½Ú£©
                int dataLenField = buffer[index + 3] & 0xFF;
                // ¼ÆËãÍêÕû°ü³¤¶È£¨°üÍ·+Êý¾Ý+УÑ飩
                int totalPacketLen = 4 + dataLenField + 2;  // Ôö¼Ó2×Ö½ÚУÑéλ
                
                // ¼ì²éÊÇ·ñÓÐ×ã¹»Êý¾Ý¹¹³ÉÍêÕû°ü
                if (index + totalPacketLen > bufferLength) {
                    break; // Êý¾Ý²»×㣬µÈ´ý¸ü¶àÊý¾Ý
                }
                
                // ÌáÈ¡ÍêÕûÊý¾Ý°ü
                byte[] packetData = new byte[totalPacketLen];
                System.arraycopy(buffer, index, packetData, 0, totalPacketLen);
                
                // Ñé֤УÑéºÍ
                if (verifyChecksum(packetData)) {
                    // ½âÎöµ¥¸öÊý¾Ý°ü
                    DataPacket packet = parseSinglePacket(packetType, packetData);
                    if (packet != null) {
                        packets.add(packet); // Ìí¼Óµ½½á¹ûÁбí
                    }
                    index += totalPacketLen; // Òƶ¯µ½ÏÂÒ»¸ö°ü
                } else {
                    index++; // УÑéʧ°Ü£¬Ìø¹ýµ±Ç°×Ö½Ú
                }
            } else {
                index++; // ·Ç°üÍ·±êʶ£¬¼ÌÐø²éÕÒ
            }
        }
        
        // ÇåÀíÒÑ´¦ÀíÊý¾Ý
        if (index > 0) {
            int remaining = bufferLength - index;
            if (remaining > 0) {
                // Òƶ¯Ê£ÓàÊý¾Ýµ½»º³åÇø¿ªÍ·
                System.arraycopy(buffer, index, buffer, 0, remaining);
            }
            bufferLength = remaining; // ¸üлº³åÇø³¤¶È
        }
        
        return packets;
    }

    // УÑéÊý¾Ý°üÍêÕûÐÔ
    private boolean verifyChecksum(byte[] packet) {
        int len = packet.length;
        if (len < 4) return false; // ³¤¶È²»×ã
        
        int sum = 0;
        // ¼ÆËã´ÓµÚ3×Ö½Úµ½µ¹ÊýµÚ3×ֽڵĺͣ¨Ìø¹ý°üÍ·ºÍУÑé룩
        for (int i = 2; i < len - 2; i++) {
            sum += packet[i] & 0xFF;
        }
        // È¡·´µÃµ½16λУÑéºÍ
        sum = ~sum & 0xFFFF;
        
        // ÌáÈ¡°üÖеÄУÑéºÍ£¨Ð¡¶Ë¸ñʽ£©
        int receivedChecksum = ((packet[len - 1] & 0xFF) << 8) | (packet[len - 2] & 0xFF);
        
        // ±È½ÏУÑéºÍ
        return sum == receivedChecksum;
    }

    // ½âÎöµ¥¸öÊý¾Ý°ü
    private DataPacket parseSinglePacket(int packetType, byte[] packet) {        
        
        // ´´½¨Êý¾Ý°ü¶ÔÏ󣨰üº¬°üÀàÐÍ£©
        return new DataPacket(packetType, packet);
    }

    // Êý¾Ý°üÄÚ²¿Àà
    public static class DataPacket {
        private final int packetType;  // °üÀàÐÍ
        private final byte[] packet;//°üÊý¾Ý

        public DataPacket(int packetType, byte[] packet) {
            this.packetType = packetType;
            this.packet = packet;
        }
        
        // »ñÈ¡°üÀàÐÍ
        public int getPacketType() {
            return packetType;
        }
        
        // °üÊý¾Ý
        public byte[] getPacket() {
            return packet;
        }
        
    }

    // HEX×Ö·û´®×ª×Ö½ÚÊý×é
    public static byte[] hexStringToBytes(String hex) {
        // ÒƳý¿Õ¸ñ
        hex = hex.replaceAll("\\s", "");
        int len = hex.length();
        // ´´½¨½á¹ûÊý×é
        byte[] data = new byte[len / 2];
        // ÿÁ½¸ö×Ö·ûת»»Ò»¸ö×Ö½Ú
        for (int i = 0; i < len; i += 2) {
            // ¸ßλת»»
            int high = Character.digit(hex.charAt(i), 16) << 4;
            // µÍλת»»
            int low = Character.digit(hex.charAt(i + 1), 16);
            data[i / 2] = (byte) (high | low);
        }
        return data;
    }
}