//
//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：高速通信HSP
    /// 接收缓存0B，发送缓存512B，时钟25MHz
    /// </summary>
    public class UART_771_RUHW_2CFG2 : IDoubleWordPeripheral, IKnownSize
    {
        private readonly IMachine machine;      //TODO

        public UART_771_RUHW_2CFG2(IMachine machine)    
        {
            this.clockFrequency = 25000000;
            this.machine = machine;     //TODO

            // 创建 FIFO
            rxFifo = 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();

            ucr = 0x00;   // 控制寄存器(默认0x02)
            usr = 0x00;   // 状态寄存器
            mcr = MCR_REN;   // 调制控制寄存器：中断使能，接收使能
            brsr = 0x43;   // 波特率设置寄存器
            fsta = 0x00;   // FIFO状态寄存器 
            rstr = 0x00;   // 复位/使能寄存器

            RxfifoEnabled = true;      //接收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)
        {
            return ReadRegisters(offset);
        }

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


        // ========================================
        // 自定义
        // ========================================
        public uint ReadRegisters(long offset)
        {
            uint value = 0;

            switch (offset)
            {
                case (long)Registers.RBR:   //接收FIFO，读操作
                    // 在接收FIFO寄存器中读取数据，高速数据串口为双字节读取，暂定小端TODO
                    value = (uint)(ReadRBR() << 8) + (uint)ReadRBR();        
                    this.Log(LogLevel.Info, "Read TBR_RBR: 0x{0:X8}", 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 = 0x00;     // 高速上行：读取该寄存器后，自动清寄存器（来自需求）
                    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;
                    this.Log(LogLevel.Info, "Read FSTA: 0x{0:X2}", 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.RSTR:      // 复位/使能,暂无读操作
                    value = (byte)(rstr & 0xFF);
                    this.Log(LogLevel.Info, "Read RSTR: 0x{0:X2}", value);                
                    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)
        {

            switch (offset)
            {
                case (long)Registers.UCR_USR:       //控制寄存器UCR
                    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)
                    {
                        currentBaudRate = (uint)(clockFrequency / value);
                        brsr = (ushort)value;
                        this.Log(LogLevel.Info, "Write BRSR: {0}", brsr);
                    }
                    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(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_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;
            }
            this.Log(LogLevel.Info, "Modem control: MCR_BEN={0}, MCR_REN={1}",
                (mcr & MCR_BEN) != 0, (mcr & MCR_REN) != 0);

            UpdateInterrupts();
        }



        public byte ReadRBR()
        {
            //单字节读取
            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
            }

            UpdateInterrupts();
            return value;            
        }        


        public void WriteRXFIFOData(uint value)   
        {
            // 向外部网络提供RXFIFO数据写入功能,value低16位有效

            if(RxfifoEnabled)
            {
                if(rxFifo.Count < RX_FIFO_SIZE)
                {
                    byte tmp = (byte)(value >> 8);
                    rxFifo.Enqueue(tmp);
                    tmp = (byte)value;
                    rxFifo.Enqueue(tmp);
                    fsta = (byte)(fsta & (~FSTA_REMP));      //接收FIFO非空
                    this.Log(LogLevel.Info, "External Write RXFIFO: 0x{0:X4} ('{1}')", (ushort)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);
                }

                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");
                }

                // 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();
            }
            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
        {
            RBR = 0x00,           // RBR接收FIFO，无发送操作
            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
            RSTR = 0x10,          /// 复位/使能 x55复位；其他使能
            FSTA = 0x14,          // FIFO状态寄存器
            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_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
        

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

        // 常量
        private const int RX_FIFO_SIZE = 2048;        // 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 ushort brsr;   // 波特率设置寄存器
        private byte fsta;   // FIFO状态寄存器
        private byte rstr;   // 复位/使能寄存器
        

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