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

namespace Antmicro.Renode.Peripherals.Timers
{
    public class Custom_RTC_R17V1 : IDoubleWordPeripheral, IKnownSize
    {
        // 寄存器偏移地址定义
        private const uint CMD_ADDR_OFFSET = 0x00000000;    // 命令寄存器
        private const uint STATUS_ADDR_OFFSET = 0x00000004; // 状态寄存器
        private const uint US_LOW_ADDR_OFFSET = 0x00000008; // 微秒低位
        private const uint US_HIGH_ADDR_OFFSET = 0x0000000C; // 微秒高位
        private const uint SEC_LOW_ADDR_OFFSET = 0x00000010; // 秒低位
        private const uint SEC_HIGH_ADDR_OFFSET = 0x00000014; // 秒高位

        // 寄存器存储
        private readonly Dictionary<long, uint> registerMap;
        private readonly object lockObject = new object();
        private readonly uint baseAddress;
        
        // 时间相关变量
        private DateTime startTime;
        private ulong baseOffsetUs;
        private ulong baseOffsetSec;
        private bool isTimeLocked;
        private uint lockedUsLow;
        private uint lockedUsHigh;
        private uint lockedSecLow;
        private uint lockedSecHigh;

        public Custom_RTC_R17V1(IMachine machine)
        {
            baseAddress = 0x20800D80;
            registerMap = new Dictionary<long, uint>();
            
            // 设置启动时间对齐到整秒
            var now = DateTime.Now;
            startTime = new DateTime(now.Year, now.Month, now.Day,
                                     now.Hour, now.Minute, now.Second,
                                     DateTimeKind.Local);
            
            InitializeRegisters();
            LogInitializationInfo();
        }

        private void InitializeRegisters()
        {
            lock (lockObject)
            {
                // 初始化所有寄存器为0
                registerMap[CMD_ADDR_OFFSET] = 0x00000000;
                registerMap[STATUS_ADDR_OFFSET] = 0x00000000;
                registerMap[US_LOW_ADDR_OFFSET] = 0x00000000;
                registerMap[US_HIGH_ADDR_OFFSET] = 0x00000000;
                registerMap[SEC_LOW_ADDR_OFFSET] = 0x00000000;
                registerMap[SEC_HIGH_ADDR_OFFSET] = 0x00000000;
                
                baseOffsetUs = 0;
                baseOffsetSec = 0;
                isTimeLocked = false;
                lockedUsLow = 0;
                lockedUsHigh = 0;
                lockedSecLow = 0;
                lockedSecHigh = 0;
            }
        }

        private void LogInitializationInfo()
        {
            this.Log(LogLevel.Info, "==========================================");
            this.Log(LogLevel.Info, "RTC实时时钟初始化完成");
            this.Log(LogLevel.Info, "基地址: 0x{0:X8}", baseAddress);
            this.Log(LogLevel.Info, "6个寄存器，32位有效");
            this.Log(LogLevel.Info, "寄存器定义: CMD(写0xBB锁定时间), US_LOW+US_HIGH(微秒20位), SEC_LOW+SEC_HIGH(秒32位)");
            this.Log(LogLevel.Info, "启动时间已对齐到整秒: {0}", startTime.ToString("HH:mm:ss.fff"));
            this.Log(LogLevel.Info, "");
            this.Log(LogLevel.Info, "寄存器地址映射:");
            this.Log(LogLevel.Info, "  CMD寄存器    : 地址0x{0:X8} (偏移0x00), 写入0xBB锁定时间", baseAddress + CMD_ADDR_OFFSET);
            this.Log(LogLevel.Info, "  STATUS寄存器 : 地址0x{0:X8} (偏移0x04), 只读", baseAddress + STATUS_ADDR_OFFSET);
            this.Log(LogLevel.Info, "  US_LOW寄存器 : 地址0x{0:X8} (偏移0x08), 微秒低16位", baseAddress + US_LOW_ADDR_OFFSET);
            this.Log(LogLevel.Info, "  US_HIGH寄存器: 地址0x{0:X8} (偏移0x0C), 微秒高4位", baseAddress + US_HIGH_ADDR_OFFSET);
            this.Log(LogLevel.Info, "  SEC_LOW寄存器: 地址0x{0:X8} (偏移0x10), 秒低16位", baseAddress + SEC_LOW_ADDR_OFFSET);
            this.Log(LogLevel.Info, "  SEC_HIGH寄存器: 地址0x{0:X8} (偏移0x14), 秒高16位(读取后自动解锁)", baseAddress + SEC_HIGH_ADDR_OFFSET);
            this.Log(LogLevel.Info, "==========================================");
        }

        // 获取当前微秒值
        private uint GetCurrentMicrosecondsLow()
        {
            var elapsed = DateTime.Now - startTime;
            if (elapsed.TotalSeconds < 0)
            {
                this.Log(LogLevel.Error, "检测到系统时间回退！重置startTime");
                startTime = DateTime.Now;
                elapsed = TimeSpan.Zero;
            }

            double totalSeconds = elapsed.TotalSeconds + (double)baseOffsetSec;
            double fractionalSeconds = totalSeconds - Math.Floor(totalSeconds);
            ulong microseconds = (ulong)(fractionalSeconds * 1_000_000.0);

            if (microseconds >= 1_000_000)
            {
                microseconds = 999_999;
            }

            return (uint)(microseconds & 0xFFFF);
        }

        private uint GetCurrentMicrosecondsHigh()
        {
            var elapsed = DateTime.Now - startTime;
            if (elapsed.TotalSeconds < 0)
            {
                return 0;
            }

            double totalSeconds = elapsed.TotalSeconds + (double)baseOffsetSec;
            double fractionalSeconds = totalSeconds - Math.Floor(totalSeconds);
            ulong microseconds = (ulong)(fractionalSeconds * 1_000_000.0);

            if (microseconds >= 1_000_000)
            {
                microseconds = 999_999;
            }

            return (uint)((microseconds >> 16) & 0xF);
        }

        // 获取当前秒值
        private uint GetCurrentSecondsLow()
        {
            var elapsed = DateTime.Now - startTime;
            if (elapsed.TotalSeconds < 0)
            {
                return (uint)(baseOffsetSec & 0xFFFF);
            }
            ulong seconds = baseOffsetSec + (ulong)elapsed.TotalSeconds;
            return (uint)(seconds & 0xFFFF);
        }

        private uint GetCurrentSecondsHigh()
        {
            var elapsed = DateTime.Now - startTime;
            if (elapsed.TotalSeconds < 0)
            {
                return (uint)((baseOffsetSec >> 16) & 0xFFFF);
            }
            ulong seconds = baseOffsetSec + (ulong)elapsed.TotalSeconds;
            return (uint)((seconds >> 16) & 0xFFFF);
        }

        // 锁定时间
        private void LockTime()
        {
            lockedUsLow = GetCurrentMicrosecondsLow();
            lockedUsHigh = GetCurrentMicrosecondsHigh();
            lockedSecLow = GetCurrentSecondsLow();
            lockedSecHigh = GetCurrentSecondsHigh();
            isTimeLocked = true;
            
            this.Log(LogLevel.Debug, "时间已锁定: 微秒=0x{0:X4}{1:X4}, 秒=0x{2:X4}{3:X4}", 
                lockedUsHigh, lockedUsLow, lockedSecHigh, lockedSecLow);
        }

        public uint ReadDoubleWord(long offset)
        {
            lock (lockObject)
            {
                uint fullAddress = baseAddress + (uint)offset;
                
                // 处理各个寄存器的读取
                if (offset == US_LOW_ADDR_OFFSET)
                {
                    uint value = isTimeLocked ? lockedUsLow : GetCurrentMicrosecondsLow();
                    this.Log(LogLevel.Info, "US_LOW读取: 地址0x{0:X8} (偏移0x08), 值0x{1:X4}", 
                        fullAddress, value);
                    return value;
                }
                else if (offset == US_HIGH_ADDR_OFFSET)
                {
                    uint value = isTimeLocked ? lockedUsHigh : GetCurrentMicrosecondsHigh();
                    this.Log(LogLevel.Info, "US_HIGH读取: 地址0x{0:X8} (偏移0x0C), 值0x{1:X4}", 
                        fullAddress, value);
                    return value;
                }
                else if (offset == SEC_LOW_ADDR_OFFSET)
                {
                    uint value = isTimeLocked ? lockedSecLow : GetCurrentSecondsLow();
                    this.Log(LogLevel.Info, "SEC_LOW读取: 地址0x{0:X8} (偏移0x10), 值0x{1:X4}", 
                        fullAddress, value);
                    return value;
                }
                else if (offset == SEC_HIGH_ADDR_OFFSET)
                {
                    uint value = isTimeLocked ? lockedSecHigh : GetCurrentSecondsHigh();
                    this.Log(LogLevel.Info, "SEC_HIGH读取: 地址0x{0:X8} (偏移0x14), 值0x{1:X4}", 
                        fullAddress, value);
                    
                    // 读取SEC_HIGH后自动解锁
                    if (isTimeLocked)
                    {
                        isTimeLocked = false;
                        this.Log(LogLevel.Debug, "时间自动解锁（读取SEC_HIGH后）");
                    }
                    
                    return value;
                }
                else if (offset == STATUS_ADDR_OFFSET)
                {
                    uint value = 0;  // 状态寄存器始终返回0
                    this.Log(LogLevel.Info, "STATUS读取: 地址0x{0:X8} (偏移0x04), 值0x{1:X4}", 
                        fullAddress, value);
                    return value;
                }
                
                this.Log(LogLevel.Warning, "尝试读取未定义的寄存器偏移: 0x{0:X8} (地址0x{1:X8})", 
                    offset, fullAddress);
                return 0;
            }
        }

        public void WriteDoubleWord(long offset, uint value)
        {
            lock (lockObject)
            {
                uint fullAddress = baseAddress + (uint)offset;
                
                // 只允许写入CMD寄存器
                if (offset == CMD_ADDR_OFFSET)
                {
                    this.Log(LogLevel.Info, "CMD写入: 地址0x{0:X8} (偏移0x00), 值0x{1:X8}", 
                        fullAddress, value);
                    
                    if (value == 0xBB)
                    {
                        LockTime();
                        this.Log(LogLevel.Info, "时间锁定命令已执行");
                    }
                    else
                    {
                        this.Log(LogLevel.Warning, "未知的CMD命令: 0x{0:X8}", value);
                    }
                }
                else
                {
                    this.Log(LogLevel.Warning, "尝试写入未定义的寄存器偏移: 0x{0:X8} (地址0x{1:X8}), 值0x{2:X8}", 
                        offset, fullAddress, value);
                }
            }
        }

        public void Reset()
        {
            lock (lockObject)
            {
                registerMap.Clear();
                InitializeRegisters();
                
                // 重置启动时间
                var now = DateTime.Now;
                startTime = new DateTime(now.Year, now.Month, now.Day,
                                         now.Hour, now.Minute, now.Second,
                                         DateTimeKind.Local);
            }
            this.Log(LogLevel.Info, "RTC (基地址0x{0:X8}) 已复位，时间重置", baseAddress);
        }

        public long Size => 0x80;  // 4KB地址空间
    }
}