//
// SJA1000 CAN 控制器外设实现（简化版，支持发送/接收队列，可配置长度）
// 仅支持 PeliCAN 模式的标准帧，不考虑 BasicCAN、扩展帧、错误处理、多帧、验收滤波和发送中断。
// 寄存器地址映射基于 PeliCAN 模式，包含 MOD, CMR, SR, IR, IER, BTR0, BTR1, OCR, RXERR, TXERR,
// 发送缓冲区（地址 16-26）、RBSA 和 CDR。命令寄存器位2=RRB，位3=CDO。
// 所有寄存器可随时读写，无复位模式限制。
//
// 队列长度可通过修改静态字段 MaxTxQueueSize 和 MaxRxQueueSize 调整。
// 发送队列满时，CPU 发送请求被忽略，并设置 TBS=0（发送缓冲区忙）；
// 接收队列满时，外部注入的新帧被丢弃。
//
// 日志开关：EnableVerboseLog = false 可关闭所有日志输出。
//

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

namespace Antmicro.Renode.Peripherals.CustomPeripherals
{
    /// <summary>
    /// 简化版 SJA1000 CAN 控制器（PeliCAN 模式，仅标准帧）
    /// </summary>
    public class SJA1000_CAN : IDoubleWordPeripheral, IBytePeripheral, IKnownSize
    {
        // 日志开关（设置为 false 可屏蔽所有日志）
        public static bool EnableVerboseLog = false;

        // 队列长度配置（可修改）
        public static int MaxTxQueueSize = 64;   // 发送队列最大帧数
        public static int MaxRxQueueSize = 64;   // 接收队列最大帧数

        public SJA1000_CAN(IMachine machine)
        {
            this.machine = machine;
            IRQ = new GPIO();

            txBuffer = new byte[11];
            rxBuffer = new byte[11];
            txFrameQueue = new Queue<byte[]>();  // 发送队列
            rxFrameQueue = new Queue<byte[]>();  // 接收队列

            Reset();
        }

        public void Reset()
        {
            mod = 0;
            ier = 0;
            btr0 = 0;
            btr1 = 0;
            ocr = 0;
            rxerr = 0;
            txerr = 0;
            rbsa = 0;
            cdr = 0;

            sr_tbs = 1;      // 发送缓冲区初始为空闲
            sr_rbs = 0;      // 接收缓冲区初始为空
            ir = 0;

            Array.Clear(txBuffer, 0, txBuffer.Length);
            Array.Clear(rxBuffer, 0, rxBuffer.Length);
            txFrameQueue.Clear();
            rxFrameQueue.Clear();

            lastInterruptState = false;   // 重置中断边沿状态
            UpdateInterrupts();

            if (EnableVerboseLog)
                this.Log(LogLevel.Info, $"SJA1000 CAN controller reset (txQueueMax={MaxTxQueueSize}, rxQueueMax={MaxRxQueueSize})");
        }

        // ================ IBusPeripheral 接口实现 ================

        public uint ReadDoubleWord(long offset)
        {
            return ReadByte(offset);
        }

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

        public byte ReadByte(long offset)
        {
            byte value = 0;
            lock (lockObject)
            {
                switch ((Registers)offset)
                {
                    case Registers.MOD:
                        value = mod;
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Read MOD: 0x{0:X2}", value);
                        break;

                    case Registers.CMR:
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Read CMR (always 0)");
                        value = 0;
                        break;

                    case Registers.SR:
                        value = (byte)((sr_tbs << 2) | sr_rbs);  // BS 恒为0
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Read SR: TBS={0}, RBS={1} -> 0x{2:X2}", sr_tbs, sr_rbs, value);
                        break;

                    case Registers.IR:
                        value = ir;
                        ir = 0;
                        UpdateIrFromRbs();
                        // 中断被软件清除，重置边沿检测状态，允许下次条件满足时再次触发中断
                        lastInterruptState = false;
                        UpdateInterrupts();
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Read IR: 0x{0:X2}, cleared", value);
                        break;

                    case Registers.IER:
                        value = ier;
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Read IER: 0x{0:X2}", value);
                        break;

                    case Registers.BTR0:
                        value = btr0;
                        break;
                    case Registers.BTR1:
                        value = btr1;
                        break;
                    case Registers.OCR:
                        value = ocr;
                        break;
                    case Registers.RXERR:
                        value = rxerr;
                        break;
                    case Registers.TXERR:
                        value = txerr;
                        break;
                    case Registers.RBSA:
                        value = rbsa;
                        break;
                    case Registers.CDR:
                        value = cdr;
                        break;

                    // 发送/接收缓冲区地址 16-26
                    case Registers.TX_FRAME_INFO:
                    case Registers.TX_ID1:
                    case Registers.TX_ID2:
                    case Registers.TX_DATA1:
                    case Registers.TX_DATA2:
                    case Registers.TX_DATA3:
                    case Registers.TX_DATA4:
                    case Registers.TX_DATA5:
                    case Registers.TX_DATA6:
                    case Registers.TX_DATA7:
                    case Registers.TX_DATA8:
                        int bufIndex = (int)(offset - (long)Registers.TX_FRAME_INFO) / 4;
                        if (sr_rbs == 1)
                        {
                            value = rxBuffer[bufIndex];
                            if (EnableVerboseLog) this.Log(LogLevel.Info, "Read RX buffer[{0}]: 0x{1:X2}", bufIndex, value);
                        }
                        else
                        {
                            value = txBuffer[bufIndex];
                            if (EnableVerboseLog) this.Log(LogLevel.Info, "Read TX buffer[{0}]: 0x{1:X2}", bufIndex, value);
                        }
                        break;

                    default:
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Read from unimplemented offset 0x{0:X}", offset);
                        value = 0;
                        break;
                }
            }
            return value;
        }

        public void WriteByte(long offset, byte value)
        {
            lock (lockObject)
            {
                switch ((Registers)offset)
                {
                    case Registers.MOD:
                        mod = value;
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Write MOD: 0x{0:X2}", value);
                        break;

                    case Registers.CMR:
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Write CMR: 0x{0:X2}", value);
                        if ((value & CMR_TR) != 0)
                        {
                            // 发送请求
                            if (sr_tbs == 1)
                            {
                                var frame = new byte[11];
                                
                                if (txFrameQueue.Count < (MaxTxQueueSize - 1))
                                {
                                    Array.Copy(txBuffer, frame, 11);
                                    txFrameQueue.Enqueue(frame);
                                    Array.Clear(txBuffer, 0, txBuffer.Length);
                                    sr_tbs = 1;
                                    if (EnableVerboseLog) this.Log(LogLevel.Info, "Frame enqueued for transmission, queue size: {0}", txFrameQueue.Count);
                                }
                                else if (txFrameQueue.Count == (MaxTxQueueSize - 1))
                                {
                                    Array.Copy(txBuffer, frame, 11);
                                    txFrameQueue.Enqueue(frame);
                                    Array.Clear(txBuffer, 0, txBuffer.Length);
                                    sr_tbs = 0;
                                    if (EnableVerboseLog) this.Log(LogLevel.Info, "Frame enqueued, TX queue now full, TBS cleared");
                                }
                                else
                                {
                                    sr_tbs = 0;
                                    if (EnableVerboseLog) this.Log(LogLevel.Warning, "Send request while TBS=0 ignored");
                                }
                            }
                            else
                            {
                                if (EnableVerboseLog) this.Log(LogLevel.Warning, "Send request while TBS=0 ignored");
                            }
                        }
                        if ((value & CMR_RRB) != 0)
                        {
                            LoadNextRxFrame();
                            if (EnableVerboseLog) this.Log(LogLevel.Info, "Receive buffer released");
                        }
                        if ((value & CMR_CDO) != 0)
                        {
                            // 清除数据溢出（无操作，但保留接口）
                            if (EnableVerboseLog) this.Log(LogLevel.Info, "Clear data overflow (no effect)");
                        }
                        break;

                    case Registers.SR:
                        if (EnableVerboseLog) this.Log(LogLevel.Warning, "Attempted write to read-only SR");
                        break;

                    case Registers.IR:
                        if (EnableVerboseLog) this.Log(LogLevel.Warning, "Attempted write to read-only IR");
                        break;

                    case Registers.IER:
                        ier = (byte)(value & 0x01);
                        UpdateIrFromRbs();
                        UpdateInterrupts();
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Write IER: 0x{0:X2}", ier);
                        break;

                    case Registers.BTR0:
                        btr0 = value;
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Write BTR0: 0x{0:X2}", value);
                        break;
                    case Registers.BTR1:
                        btr1 = value;
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Write BTR1: 0x{0:X2}", value);
                        break;
                    case Registers.OCR:
                        ocr = value;
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Write OCR: 0x{0:X2}", value);
                        break;
                    case Registers.RXERR:
                        rxerr = value;
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Write RXERR: 0x{0:X2}", value);
                        break;
                    case Registers.TXERR:
                        txerr = value;
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Write TXERR: 0x{0:X2}", value);
                        break;
                    case Registers.RBSA:
                        rbsa = value;
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Write RBSA: 0x{0:X2}", value);
                        break;
                    case Registers.CDR:
                        cdr = value;
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Write CDR: 0x{0:X2}", value);
                        break;

                    // 发送缓冲区写入
                    case Registers.TX_FRAME_INFO:
                    case Registers.TX_ID1:
                    case Registers.TX_ID2:
                    case Registers.TX_DATA1:
                    case Registers.TX_DATA2:
                    case Registers.TX_DATA3:
                    case Registers.TX_DATA4:
                    case Registers.TX_DATA5:
                    case Registers.TX_DATA6:
                    case Registers.TX_DATA7:
                    case Registers.TX_DATA8:
                        int bufIndex = (int)(offset - (long)Registers.TX_FRAME_INFO) / 4;
                        if (sr_tbs == 1)
                        {
                            txBuffer[bufIndex] = value;
                            if (EnableVerboseLog) this.Log(LogLevel.Info, "Write TX buffer[{0}]: 0x{1:X2}", bufIndex, value);
                        }
                        else
                        {
                            if (EnableVerboseLog) this.Log(LogLevel.Warning, "Write to TX buffer while TBS=0 ignored");
                        }
                        break;

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

        // ================ 内部辅助方法 ================

        private void UpdateIrFromRbs()
        {
            if (sr_rbs == 1)
                ir |= IR_RI;
            else
                ir = (byte)(ir & ~IR_RI);
        }

        private void UpdateInterrupts()
        {
            bool currentInterrupt = ((ir & IR_RI) != 0) && ((ier & IER_RIE) != 0);
            if (currentInterrupt && !lastInterruptState)
            {
                IRQ.Set(true);
                machine.ScheduleAction(TimeInterval.FromMicroseconds(1), _ =>
                {
                    IRQ.Set(false);
                });
                if (EnableVerboseLog) this.Log(LogLevel.Info, "Interrupt pulse generated (RI)");
            }
            lastInterruptState = currentInterrupt;
        }

        private readonly object lockObject = new object();

        /// <summary>
        /// 获取发送队列中所有帧的字符串表示（每帧以空格分隔的十六进制字节，帧间用换行分隔）
        /// 调用后清空发送队列，并恢复发送缓冲区状态（如果之前因队列满被锁定）。
        /// </summary>
        public string GetTxBufferDataString()
        {
            lock (lockObject)
            {
                if (txFrameQueue.Count == 0)
                {
                    if (EnableVerboseLog) Console.WriteLine("GetTxBufferDataString: no frames in TX queue");
                    if (sr_tbs == 0) sr_tbs = 1;
                    return null;
                }
                var sb = new StringBuilder();
                while (txFrameQueue.Count > 0)
                {
                    var frame = txFrameQueue.Dequeue();
                    for (int i = 0; i < frame.Length; i++)
                    {
                        if (i > 0) sb.Append(" ");
                        sb.Append(frame[i].ToString("X2"));
                    }
                    sb.AppendLine();
                }
                string result = sb.ToString().TrimEnd();
                sr_tbs = 1;
                if (EnableVerboseLog) Console.WriteLine("GetTxBufferDataString returning: " + result);
                return result;
            }
        }

        /// <summary>
        /// 外部接口注入一帧接收数据（11字节的十六进制字符串，空格分隔）
        /// 可多次调用以注入多帧，帧将存入接收队列。
        /// 若接收队列已满，则新帧被丢弃。
        /// </summary>
        public void SendRxBufferDataString(string frameString)
        {
            lock (lockObject)
            {
                if (string.IsNullOrWhiteSpace(frameString))
                {
                    if (EnableVerboseLog) Console.WriteLine("SendRxBufferDataString: empty string, ignored");
                    return;
                }
                string[] parts = frameString.Split(new[] { ' ', '\t' }, StringSplitOptions.RemoveEmptyEntries);
                if (parts.Length != 11)
                {
                    if (EnableVerboseLog) Console.WriteLine($"SendRxBufferDataString: expected 11 bytes, got {parts.Length}, ignored");
                    return;
                }
                byte[] frame = new byte[11];
                for (int i = 0; i < 11; i++)
                {
                    string part = parts[i].Trim();
                    if (!byte.TryParse(part, System.Globalization.NumberStyles.HexNumber,
                        System.Globalization.CultureInfo.InvariantCulture, out byte b))
                    {
                        if (EnableVerboseLog) Console.WriteLine($"SendRxBufferDataString: invalid hex byte '{part}' at index {i}, set to 0");
                        b = 0;
                    }
                    frame[i] = b;
                }

                if (rxFrameQueue.Count >= MaxRxQueueSize)
                {
                    if (EnableVerboseLog) Console.WriteLine($"SendRxBufferDataString: RX queue full (max={MaxRxQueueSize}), frame dropped");
                    return;
                }

                rxFrameQueue.Enqueue(frame);
                if (EnableVerboseLog) Console.WriteLine($"Frame enqueued to RX queue, size: {rxFrameQueue.Count}");

                if (sr_rbs == 0)
                {
                    LoadNextRxFrame();
                }
            }
        }

        private void LoadNextRxFrame()
        {
            if (rxFrameQueue.Count > 0)
            {
                var frame = rxFrameQueue.Dequeue();
                Array.Copy(frame, rxBuffer, 11);
                sr_rbs = 1;
                UpdateIrFromRbs();
                UpdateInterrupts();
                if (EnableVerboseLog) Console.WriteLine("Loaded next RX frame into buffer, queue remaining: {0}", rxFrameQueue.Count);
            }
            else
            {
                sr_rbs = 0;
                UpdateIrFromRbs();
                UpdateInterrupts();
                if (EnableVerboseLog) Console.WriteLine("RX queue empty, buffer cleared");
            }
        }

        // ================ 属性 ================

        public long Size => 0x80;

        public GPIO IRQ { get; }

        // ================ 寄存器枚举 ================

        private enum Registers : long
        {
            MOD = 0x00,
            CMR = 0x04,
            SR = 0x08,
            IR = 0x0C,
            IER = 0x10,
            BTR0 = 0x18,
            BTR1 = 0x1C,
            OCR = 0x20,
            RXERR = 0x38,
            TXERR = 0x3C,
            TX_FRAME_INFO = 0x40,
            TX_ID1 = 0x44,
            TX_ID2 = 0x48,
            TX_DATA1 = 0x4C,
            TX_DATA2 = 0x50,
            TX_DATA3 = 0x54,
            TX_DATA4 = 0x58,
            TX_DATA5 = 0x5C,
            TX_DATA6 = 0x60,
            TX_DATA7 = 0x64,
            TX_DATA8 = 0x68,
            RBSA = 0x78,
            CDR = 0x7C,
        }

        // ================ 常量位定义 ================

        private const byte CMR_TR = 0x01;
        private const byte CMR_RRB = 0x04;
        private const byte CMR_CDO = 0x08;

        private const byte SR_BS = 0x80;
        private const byte SR_TBS = 0x04;
        private const byte SR_RBS = 0x01;

        private const byte IR_RI = 0x01;
        private const byte IER_RIE = 0x01;

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

        private readonly IMachine machine;

        private byte mod;
        private byte ier;
        private byte btr0, btr1;
        private byte ocr;
        private byte rxerr, txerr;
        private byte rbsa;
        private byte cdr;

        private byte sr_tbs;
        private byte sr_rbs;
        private byte ir;

        private bool lastInterruptState;   // 用于中断边沿检测

        private readonly byte[] txBuffer;
        private readonly byte[] rxBuffer;

        private readonly Queue<byte[]> txFrameQueue;
        private readonly Queue<byte[]> rxFrameQueue;
    }
}