//
// UART 外设实现
// 基于 UART 规格,包含完整的 FIFO、中断和调制解调器控制功能
//

using System;
using System.Collections.Generic;
using Antmicro.Renode.Core;
using Antmicro.Renode.Logging;
using Antmicro.Renode.Peripherals.Bus;
using Antmicro.Renode.Peripherals.UART;
using Antmicro.Renode.Utilities;

using Antmicro.Renode.Time;

namespace Antmicro.Renode.Peripherals.CustomPeripherals
{
    /// <summary>
    /// UART_771_RUHW_2CFG 控制器
    /// 接收缓存512B，发送缓存512B，时钟24MHz
    /// </summary>
    public class UART_771_RUHW_2CFG1 : IDoubleWordPeripheral, IBytePeripheral, IKnownSize
    {
        private readonly IMachine machine;      //TODO

        public UART_771_RUHW_2CFG1(IMachine machine)   
        {
            this.clockFrequency = 24000000;
            this.machine = machine;     //TODO

            // 创建 FIFO
            rxFifo = new Queue<byte>();
            txFifo = new Queue<byte>();

            // 创建中断线
            IRQ = new GPIO();

            // 初始化寄存器
            DefineRegisters();
            Reset();

            this.Log(LogLevel.Info, "771 UART initialized, clock: {0} Hz", clockFrequency);
        }


        public void Reset()
        {
            rxFifo.Clear();
            txFifo.Clear();

            ucr = 0x00;   // 控制寄存器
            usr = USR_TFE;// 状态寄存器
            mcr = 0x00;   // 调制控制寄存器：中断使能，接收使能
            brsr_l = 0x00;   // 波特率设置寄存器
            brsr_h = 0x00;
            fsta = (byte)(FSTA_TEMP | FSTA_REMP);   // FIFO状态寄存器
            tbr = 0;        // 发送FIFO剩余字节数 
            rbr = 0 ;   // 接收FIFO剩余字节数
            rstr = 0x00;   // 复位/使能寄存器

            ext_signal = 0x00;  // 向外部提供读写信号

            RxfifoEnabled = true;      //接收fifo使能
            TxfifoEnabled = true;       //发送fifo使能
            fifoTriggerLevel = 1;

            IRQ.Set(false);
            UpdateInterrupts();

            this.Log(LogLevel.Info, "UART reset");
        }

        
        private void DefineRegisters()
        {
            // 寄存器访问通过 ReadDoubleWord/WriteDoubleWord 实现

        }


        // ========================================
        // IBusPeripheral 接口实现
        // ========================================
        public uint ReadDoubleWord(long offset)
        {
            this.Log(LogLevel.Info, "entry ReadDoubleWord: 0x{0}", offset);
            return ReadRegisters(offset);
        }

        public void WriteDoubleWord(long offset, uint value)
        {
            WriteRegisters(offset, value);
        }


        // ========================================
        // 自定义
        // ========================================
        public uint ReadRegisters(long offset)
        {
            this.Log(LogLevel.Info, "entry ReadRegisters: 0x{0}", offset);

            uint value = 0;

            switch (offset)
            {
                case (long)Registers.TBR_RBR:   //接收FIFO，读操作
                    // 在接收FIFO寄存器中读取数据
                    value = ReadRBR();
                    this.Log(LogLevel.Info, "Read TBR_RBR: 0x{0:X2}", value);
                    break;

                case (long)Registers.UCR_USR:       //USR状态寄存器
                    value = (byte)(usr & 0xFF);
                    this.Log(LogLevel.Info, "Read USR: 0x{0:X2}", value);
                    // usr = (byte)(usr & (~USR_RBFI));       //usr寄存器，取消接收中断，与hw_uart_isr关联，暂定
                    break; 

                case (long)Registers.MCR:       //MCR调制控制寄存器
                    value = (byte)(mcr & 0xFF);
                    this.Log(LogLevel.Info, "Read MCR: 0x{0:X2}", value);
                    break; 

                case (long)Registers.BRSR:      //波特率寄存器，暂无读操作
                    value = (uint)((brsr_h << 8) + brsr_l);
                    this.Log(LogLevel.Info, "Read MCR: 0x{0}", value);
                    break;

                case (long)Registers.FSTA:      // FIFO状态寄存器
                    value = (byte)(fsta & 0xFF);
                    this.Log(LogLevel.Info, "Read FSTA: 0x{0:X2}", value);
                    break; 

                case (long)Registers.TBR_FreeBytes:      //发送FIFO剩余字节数
                    tbr = (ushort)txFifo.Count; 
                    value = (uint)tbr;
                    this.Log(LogLevel.Info, "Read TBR_FreeBytes: {0}", value);
                    break;

                case (long)Registers.RBR_FreeBytes:      //接收FIFO剩余字节数
                    rbr = (ushort)rxFifo.Count;
                    value = (uint)rbr;
                    this.Log(LogLevel.Info, "Read RBR_FreeBytes: {0}", value);
                    break;                

                case (long)Registers.RSTR:      // 复位/使能,暂无读操作
                    value = (uint)rstr;
                    break;

                case (long)Registers.EXTI:      //自定义，向外部提供读写信号
                    value = (uint)(ext_signal & 0xFF);
                    break;

                default:
                    this.Log(LogLevel.Warning, "Read to unknown offset: 0x{0:X} = 0x{1:X2}", offset, value);
                    break;
            }
            
            return value;
        }


        public void WriteRegisters(long offset, uint value)
        {
            this.Log(LogLevel.Info, "entry WriteRegisters: 0x{0}, value: 0x{1}", offset, value);
            switch (offset)
            {
                case (long)Registers.TBR_RBR:
                    WriteTBR((byte)value);      
                    this.Log(LogLevel.Info, "Write TBR_RBR: 0x{0:X2}", value);  
                    break; 

                case (long)Registers.UCR_USR:       //控制寄存器
                    WriteByte(offset, (byte)value);
                    break;

                case (long)Registers.MCR:   //调制控制寄存器
                    WriteByte(offset, (byte)value);
                    break;

                case (long)Registers.BRSR:      //波特率寄存器
                    if(value != 0)
                    {
                        currentBaudRate = (uint)(clockFrequency / value);;
                        brsr_l = (byte)(value);
                        brsr_h = (byte)(value >> 8);
                        this.Log(LogLevel.Info, "Write BRSR: {0}", value);
                        WriteByte(offset, brsr_l);
                        WriteByte((offset + 0x01), brsr_h);
                    }
                    break;

                case (long)Registers.RSTR:      // 复位/使能
                    WriteByte(offset, (byte)value);
                    break;

                case (long)Registers.EXTI:      //向外部提供写RXFIFO寄存器
                    value = (uint)ext_signal;
                    break;

                default:
                    this.Log(LogLevel.Warning, "Write to unknown offset: 0x{0:X} = 0x{1:X2}", offset, value);
                    break;
            }
        }


        public byte ReadByte(long offset)
        {
            this.Log(LogLevel.Info, "entry ReadByte: 0x{0}", offset);
            return 0x00;
        }


        public void WriteByte(long offset, byte value)
        {
            this.Log(LogLevel.Info, "entry WriteByte: 0x{0}, value: 0x{1}", offset, value);
            switch(offset)
            {

                case (long)Registers.UCR_USR:       //控制寄存器
                    ucr = (byte)(value & 0xFF);
                    this.Log(LogLevel.Info, "Write UCR_USR: 0x{0:X2}", ucr);
                    break;

                case (long)Registers.MCR:   //调制控制寄存器
                    mcr = (byte)(value & 0xFF);
                    this.Log(LogLevel.Info, "Write MCR: 0x{0:X2}", mcr);
                    UpdateModemControl();
                    break;

                case (long)Registers.BRSR:      //波特率寄存器
                    if(value != 0)
                    {
                        brsr_l = value;
                        this.Log(LogLevel.Info, "Write BRSR: 0x{0:X2}", brsr_l);
                    }
                    break;


                case (long)Registers.BRSR_H:
                    if(value != 0)
                    {
                        brsr_h = value;
                        this.Log(LogLevel.Info, "Write BRSR: 0x{0:X2}", brsr_h);
                    }
                    break;


                case (long)Registers.RSTR:      // 复位/使能
                    rstr = (byte)(value & 0xFF);
                    this.Log(LogLevel.Info, "Write RSTR: 0x{0:X2}", rstr);
                    if ((rstr & 0XFF) == RSTR_RES)
                    {
                        Reset();
                    }
                    break;

                case (long)Registers.EXTI:      //向外部提供写RXFIFO寄存器
                    WriteRXFIFOData((byte)value);
                    break;

                default:
                    this.Log(LogLevel.Warning, "Write to unknown offset: 0x{0:X} = 0x{1:X2}", offset, value);
                    break;
            
                
            }
        }

        private void UpdateInterrupts()
        {
            bool interrupt = false;

            // D2中断使能 必须置位才能产生中断
            if ((mcr & MCR_BEN) != 0)
            {
                // 检查各种中断条件
                if ((usr & USR_TCMP) != 0 )     //发送完成，发送FIFO空（发送中断）
                    interrupt = true;
                else if ((usr & USR_RBFI) != 0 )        //接收FIFO中有数据后，延迟10ms产生一次（接收中断）
                    interrupt = true;
                else if ((usr & (USR_PE | USR_FE | USR_OE | USR_BI)) != 0 )     //校验错、帧错、溢出错、接收碎片
                    interrupt = true;
            }

            IRQ.Set(interrupt);

            if (interrupt)
            {
                this.Log(LogLevel.Info, "Interrupt asserted");
                machine.ScheduleAction(TimeInterval.FromMicroseconds(1),
                    _ => {
                        IRQ.Set(false);
                        this.Log(LogLevel.Info, "Interrupt deasserted");
                    });
            }
        }


        private void UpdateModemControl()
        {
            if( (mcr & MCR_REN) == 0)
            {
                RxfifoEnabled = false;      //待定
            }
            this.Log(LogLevel.Info, "Modem control: MCR_BEN={0}, MCR_REN={1}",
                (mcr & MCR_BEN) != 0, (mcr & MCR_REN) != 0);

            UpdateInterrupts();
        }


        public void WriteTBR(byte value)
        {
            // 从星务接收数据 ，操作txFifo
            this.Log(LogLevel.Info, "Write TBR: 0x{0:X2} ('{1}')", value,
                (value >= 32 && value < 127) ? (char)value : '.');

            if (TxfifoEnabled)
            {
                if (txFifo.Count < TX_FIFO_SIZE)
                {
                    txFifo.Enqueue(value);
                    fsta = (byte)(fsta & (~FSTA_TEMP));     // 发送缓冲区不为空，D0置0
                    usr = (byte)(usr & (~USR_TFE));     //发送FIFO不为空，D6置0
                }
                else
                {
                    fsta = (byte)(fsta | FSTA_TFUL);     // 发送FIFO满
                    this.Log(LogLevel.Warning, "TX FIFO overflow");
                }
            }
            else
            {
                // 非 FIFO 模式，待定
                txFifo.Clear();
                txFifo.Enqueue(value);
                fsta = (byte)(fsta & (~FSTA_TEMP));     // 发送缓冲区不为空，D0置0              
            }

            // 暂时不发送数据，由中间层自取            
        }


        public uint GetTXFIFOData()
        {
            uint data = 0x00;

            // 从 TX FIFO 发送数据，中间层获取txfifo接口
            if (txFifo.Count > 0)
            {
                data = txFifo.Dequeue();

                // 调用基类的 TransmitCharacter 发送数据
                // TransmitCharacter(data);

                this.Log(LogLevel.Info, "Transmitted: 0x{0:X2} ('{1}')", data,
                    (data >= 32 && data < 127) ? (char)data : '.');
            }
            else 
            {
                this.Log(LogLevel.Info, "TXFIFO Null ");
            }

            // 更新状态       
            if (txFifo.Count == 0)
            {
                fsta = (byte)((fsta &0xF0) | FSTA_TEMP);     // 发送缓冲区为空，D0置0
                usr = (byte)(usr | USR_TFE);       // 发送FIFO空
                usr = (byte)(usr | USR_TCMP);       // 发送完成（发送中断）            
            }

            UpdateInterrupts();      

            return data;
        }

        public string GetTXFIFODataString()
        {
            string data = "0x";
            byte tmp;

            // 从 TX FIFO 发送数据，中间层获取txfifo接口

            if(txFifo.Count == 0)
            {
                this.Log(LogLevel.Info, "TXFIFO Null");
                return "0x00";
            }

            while (txFifo.Count > 0)
            {
                tmp = txFifo.Dequeue();
                data += tmp.ToString("X2");  // 转换为16进制字符串                
            }

            this.Log(LogLevel.Info, "Transmitted: 0x{0}, TXFIFO Null", data);
            ext_signal = (byte)(ext_signal & (~EXT_SIGNAL_READ));     // 通知外部不可读


            // 更新状态       
            if (txFifo.Count == 0)
            {
                fsta = (byte)((fsta &0xF0) | FSTA_TEMP);     // 发送缓冲区为空，D0置0
                usr = (byte)(usr | USR_TFE);       // 发送FIFO空
                usr = (byte)(usr | USR_TCMP);       // 发送完成（发送中断）            
            }

            UpdateInterrupts();      

            return data;
        }


        public byte ReadRBR()
        {

            byte value = 0;

            if (rxFifo.Count > 0)
            {
                value = rxFifo.Dequeue();
                this.Log(LogLevel.Info, "Read: 0x{0:X2} ('{1}')", value,
                    (value >= 32 && value < 127) ? (char)value : '.');

            }
            else
            {
                this.Log(LogLevel.Warning, "Read from empty RBR");
            }

            // 更新状态
            if (rxFifo.Count == 0)
            {
                fsta = (byte)(fsta | FSTA_REMP);  // 接收FIFO空
                usr = (byte)(usr & (~USR_OE));  // 清除溢出错误
                ext_signal = (byte)(ext_signal | EXT_SIGNAL_WRITE);     // 通知外部可写
            }

            UpdateInterrupts();
            return value;            
        }        

        public void WriteRXFIFOData(byte value)   
        {
            // 向外部网络提供RXFIFO数据写入功能

            if(RxfifoEnabled)
            {
                if(rxFifo.Count < RX_FIFO_SIZE)
                {
                    rxFifo.Enqueue(value);
                    fsta = (byte)(fsta & (~FSTA_REMP));      //接收FIFO非空
                    this.Log(LogLevel.Info, "External Write RXFIFO: 0x{0:X2} ('{1}')", value,
                        (value >= 32 && value < 127) ? (char)value : '.');
                }
                else
                {
                    //待定
                    fsta = (byte)(fsta | FSTA_RFUL);      //接收FIFO满
                    this.Log(LogLevel.Warning, "RX FIFO Already Full");
                }
            }

            // this.Wait(TimeInterval.FromMilliseconds(10)); 无法实现等待10ms，暂不实现
            usr = (byte)(usr | USR_RBFI);       //usr寄存器，置接收中断
            UpdateInterrupts();

        }


        public void WriteRXFIFODataString(string value)   
        {
            // 向外部网络提供RXFIFO数据写入功能，value=0xAABB...
            string data = value.StartsWith("0x",StringComparison.OrdinalIgnoreCase) ?  value.Substring(2) : value;
            this.Log(LogLevel.Info, "External Write RXFIFO: {0} ", value);

            string tmpString;
            byte tmpHex;
            int i;

            if(RxfifoEnabled)
            {
                if(data.Length % 2 != 0)
                {
                     data = "0" + data;     // 前面补0
                }

                if((data.Length/2) > (RX_FIFO_SIZE - rxFifo.Count))    //value超出fifo剩余
                {
                    this.Log(LogLevel.Warning, "Data too long");
                    return;
                }
                
                for(i = 0; i < data.Length ; i+=2)
                {
                    tmpString = data.Substring(i, 2);
                    tmpHex = Convert.ToByte(tmpString, 16);
                    rxFifo.Enqueue(tmpHex);
                }

                ext_signal = (byte)(ext_signal & (~EXT_SIGNAL_WRITE));     // 通知外部不可写
                fsta = (byte)(fsta & (~FSTA_REMP));      //接收FIFO非空

                if(rxFifo.Count == RX_FIFO_SIZE)
                {
                    fsta = (byte)(fsta | FSTA_RFUL);      //接收FIFO满
                    this.Log(LogLevel.Warning, "RX FIFO Already Full");
                }

                usr = (byte)(usr | USR_RBFI);       //usr寄存器，置接收中断
                machine.ScheduleAction(TimeInterval.FromMicroseconds(10000),    
                    _ => {
                        UpdateInterrupts();     //等待10ms
                    });
            }
            else
            {

            }

        }


        public long Size => 0x28;   //uart地址长度总空间

        public GPIO IRQ { get; }

        // ========================================
        // 寄存器定义
        // ========================================

        private enum Registers : long
        {
            TBR_RBR = 0x00,      // TBR发送FIFO，RBR接收FIFO
            UCR_USR = 0x04,      // UCR控制寄存器,USR状态寄存器
            MCR = 0x08,          // 调制控制寄存器
            BRSR = 0x0C,         // 波特率设置寄存器
            BRSR_H = 0x0D,          // 波特率设置寄存器-高位
            FSTA = 0x10,          // FIFO状态寄存器
            TBR_FreeBytes = 0x14,          // 发送FIFO剩余字节数
            RBR_FreeBytes = 0x18,          // 接收FIFO剩余字节数
            RSTR = 0x20,          // 复位/使能 x55复位；其他使能
            EXTI = 0x24            // 向外部提供读写FIFO接口
        }

        // UCR控制寄存器 位定义
        private const byte UCR_STB = 0x01;    // 停止位1位
        private const byte UCR_PB = 0x0E;    // 奇偶校验3位

        private const byte USR_PE = 0x01;    // 校验错
        private const byte USR_FE = 0x02;    // 帧错
        private const byte USR_OE = 0x04;   // 溢出错
        private const byte USR_BI = 0x08;    // 接收碎片
        private const byte USR_TCMP = 0x20;   // 发送完成（发送中断）
        private const byte USR_TFE = 0x40;   // 发送FIFO空
        private const byte USR_RBFI = 0x80;   // 接收中断

        // MCR 调制控制寄存器
        private const byte MCR_BEN = 0x04;     // 中断使能
        private const byte MCR_REN = 0x20;     // 接收使能

        // FSTA FIFO状态寄存器
        private const byte FSTA_TEMP = 0x01;  // 发送FIFO空
        private const byte FSTA_TLHF= 0x02;  // 发送FIFO低阈值半满
        private const byte FSTA_TFUL = 0x04;  // 发送FIFO满
        private const byte FSTA_THHF = 0x08;  // 发送FIFO高阈值半满
        private const byte FSTA_REMP = 0x10;  // 接收FIFO空
        private const byte FSTA_RLHF = 0x20;  // 接收FIFO低阈值半满
        private const byte FSTA_RFUL = 0x40;  // 接收FIFO满
        private const byte FSTA_RHHF = 0x80;  // 接收FIFO 高阈值半满
        

        // RSTR 复位/使能寄存器
        private const byte RSTR_RES = 0x55;  // 复位
        private const byte RSTR_EN = 0xAA;   // 使能

        private const byte EXT_SIGNAL_WRITE = 0x0F; //0x0F表示外部可写
        private const byte EXT_SIGNAL_READ = 0xF0;  //0xF0表示外部可读

        // 常量
        private const int RX_FIFO_SIZE = 512;        // 接收FIFO_SIZE
        private const int TX_FIFO_SIZE = 512;        // 发送FIFO_SIZE

        // ========================================
        // 私有字段
        // ========================================

        private readonly uint clockFrequency;
        private uint currentBaudRate;
      

        // 寄存器
        private byte ucr;   // 控制寄存器
        private byte usr;   // 状态寄存器
        private byte mcr;   // 调制控制寄存器
        private byte brsr_l;   // 波特率设置寄存器
        private byte brsr_h;   // 波特率设置寄存器
        private byte fsta;   // FIFO状态寄存器
        private ushort tbr;   // 发送FIFO剩余字节数
        private ushort rbr;   // 接收FIFO剩余字节数
        private byte rstr;   // 复位/使能寄存器

        private byte ext_signal;    //外部提供读写信号，读信号待确定
        

        // FIFO
        private readonly Queue<byte> rxFifo;
        private readonly Queue<byte> txFifo;
        private bool RxfifoEnabled;
        private bool TxfifoEnabled;
        private int fifoTriggerLevel;
    }
}