package com.narutohuo.xindazhou.ble.util

/**
 * BLE分包处理器
 * 
 * 处理数据包的分包和组包
 * 根据新大洲本田蓝牙协议文档的分包协议
 */
class BLEPacketSplitter {
    
    /**
     * 分包数据
     * 
     * @param data 原始数据
     * @param mtu MTU大小（最大传输单元）
     * @param businessId 业务ID（4字节）
     * @return 分包后的数据包列表
     */
    fun splitPacket(data: ByteArray, mtu: Int, businessId: Int): List<ByteArray> {
        val packets = mutableListOf<ByteArray>()
        val totalPackets = (data.size + mtu - 1) / mtu
        
        for (i in 0 until totalPackets) {
            val start = i * mtu
            val end = minOf(start + mtu, data.size)
            val packetData = data.sliceArray(start until end)
            
            val packet = buildSplitPacket(
                businessId = businessId,
                totalPackets = totalPackets,
                packetIndex = i,
                data = packetData
            )
            
            packets.add(packet)
        }
        
        return packets
    }
    
    /**
     * 构建分包数据包
     */
    private fun buildSplitPacket(
        businessId: Int,
        totalPackets: Int,
        packetIndex: Int,
        data: ByteArray
    ): ByteArray {
        val packet = mutableListOf<Byte>()
        
        // 包头（0x0A）
        packet.add(0x0A.toByte())
        
        // 业务ID（4字节，小端序）
        packet.add((businessId and 0xFF).toByte())
        packet.add(((businessId shr 8) and 0xFF).toByte())
        packet.add(((businessId shr 16) and 0xFF).toByte())
        packet.add(((businessId shr 24) and 0xFF).toByte())
        
        // 总包数（2字节，小端序）
        packet.add((totalPackets and 0xFF).toByte())
        packet.add(((totalPackets shr 8) and 0xFF).toByte())
        
        // 包序号（2字节，小端序）
        packet.add((packetIndex and 0xFF).toByte())
        packet.add(((packetIndex shr 8) and 0xFF).toByte())
        
        // 数据长度（2字节，小端序）
        val dataLength = data.size
        packet.add((dataLength and 0xFF).toByte())
        packet.add(((dataLength shr 8) and 0xFF).toByte())
        
        // 数据区
        packet.addAll(data.toList())
        
        // 应答状态（0x01=ACK）
        packet.add(0x01.toByte())
        
        // 包校验（异或校验）
        var checksum = 0x00
        for (i in 1 until packet.size) {
            checksum = checksum xor packet[i].toInt()
        }
        packet.add(checksum.toByte())
        
        // 包尾（0x0D）
        packet.add(0x0D.toByte())
        
        return packet.toByteArray()
    }
    
    /**
     * 组包数据
     * 
     * @param packets 接收到的分包数据（Map<包序号, 数据>）
     * @return 组包后的完整数据
     */
    fun combinePackets(packets: Map<Int, ByteArray>): ByteArray {
        val sortedPackets = packets.toSortedMap()
        val result = mutableListOf<Byte>()
        
        sortedPackets.values.forEach { packetData ->
            result.addAll(packetData.toList())
        }
        
        return result.toByteArray()
    }
}