main.rs

/// This file is currently missing logic. I will implement it soon.
use std::collections::{HashMap, VecDeque};
use std::fmt;
use std::fs::File;
use std::io::{self, Read, Write};
use std::sync::atomic::{AtomicU64, Ordering};
use std::time::{Duration, Instant};

#[derive(Debug, Clone, PartialEq)]
pub enum CPUError {
    MemoryAccessViolation { address: usize, access_type: AccessType },
    InvalidInstruction { opcode: u8, context: String },
    StackError(StackErrorType),
    DivisionByZero,
    InvalidInterrupt { vector: u8, reason: String },
    PipelineHazard(HazardType),
    CacheError(CacheErrorType),
    ProtectionFault { operation: String, privilege_level: u8 },
}

#[derive(Debug, Clone, PartialEq)]
pub enum AccessType {
    Read,
    Write,
    Execute,
}

#[derive(Debug, Clone, PartialEq)]
pub enum StackErrorType {
    Overflow,
    Underflow,
    InvalidAccess,
}

#[derive(Debug, Clone, PartialEq)]
pub enum HazardType {
    DataHazard,
    StructuralHazard,
    ControlHazard,
}

#[derive(Debug, Clone, PartialEq)]
pub enum CacheErrorType {
    InvalidAccess,
    Coherency,
    Replacement,
}

#[derive(Debug)]
struct MMU {
    page_table: HashMap<usize, PageTableEntry>,
    tlb: TLB,
}

#[derive(Debug, Clone)]
struct PageTableEntry {
    physical_address: usize,
    flags: PageFlags,
    last_access: Instant,
}

#[derive(Debug, Clone)]
struct PageFlags {
    readable: bool,
    writable: bool,
    executable: bool,
    cached: bool,
    dirty: bool,
}

#[derive(Debug)]
struct Pipeline {
    stages: VecDeque<PipelineStage>,
    hazard_unit: HazardUnit,
    branch_predictor: BranchPredictor,
}

#[derive(Debug)]
struct HazardUnit {
    forwarding_enabled: bool,
    stall_pipeline: bool,
    hazard_type: Option<HazardType>,
}

#[derive(Debug)]
struct BranchPredictor {
    branch_history_table: HashMap<usize, BranchHistory>,
    global_history_register: u16,
    prediction_accuracy: f64,
}

#[derive(Debug)]
struct BranchHistory {
    taken_count: u32,
    not_taken_count: u32,
    last_outcome: bool,
}

#[derive(Debug, Clone)]
enum PipelineStage {
    Fetch(u8),
    Decode(Instruction),
    Execute(ExecutionResult),
    MemoryAccess(MemoryOperation),
    WriteBack(WriteBackData),
}

#[derive(Debug, Clone)]
struct ExecutionResult {
    result: u16,
    flags: StatusFlags,
}

#[derive(Debug, Clone)]
struct MemoryOperation {
    address: usize,
    data: Option<u8>,
    is_read: bool,
}

#[derive(Debug, Clone)]
struct WriteBackData {
    register: String,
    value: u8,
}

#[derive(Debug, Clone)]
struct StatusFlags {
    zero: bool,
    carry: bool,
    overflow: bool,
    negative: bool,
    interrupt: bool,
}

#[derive(Debug, Clone)]
struct Cache {
    data_cache: HashMap<usize, CacheLine>,
    instruction_cache: HashMap<usize, CacheLine>,
    cache_stats: CacheStats,
    lines: Vec<CacheLine>,
    config: CacheConfig,
}

#[derive(Debug, Clone)]
struct CacheLine {
    data: Vec<u8>,
    valid: bool,
    dirty: bool,
    last_access: Instant,
}

#[derive(Debug, Clone)]
struct CacheStats {
    hits: usize,
    misses: usize,
    evictions: usize,
}

struct CacheHierarchy {
    l1_instruction: Cache,
    l1_data: Cache,
    l2_unified: Cache,
    statistics: CacheStatistics,
}

#[derive(Debug, Clone)]
struct CacheConfig {
    size: usize,
    line_size: usize,
    associativity: usize,
    write_policy: WritePolicy,
    replacement_policy: ReplacementPolicy,
}

#[derive(Debug)]
struct PerformanceMonitor {
    cycle_count: AtomicU64,
    instruction_count: AtomicU64,
    cache_stats: CacheStatistics,
    branch_stats: BranchStatistics,
    power_usage: PowerStatistics,
}

#[derive(Debug)]
struct TLB {
    entries: HashMap<usize, usize>,
    capacity: usize,
}

#[derive(Debug)]
struct CacheStatistics {
    hits: usize,
    misses: usize,
    evictions: usize,
    access_time: Duration,
}

#[derive(Debug)]
struct BranchStatistics {
    predictions: usize,
    correct_predictions: usize,
    mispredictions: usize,
}

#[derive(Debug)]
struct PowerStatistics {
    total_power: f64,
    instruction_power: f64,
    memory_power: f64,
    cache_power: f64,
}

#[derive(Debug, Clone)]
enum WritePolicy {
    WriteThrough,
    WriteBack,
}

#[derive(Debug, Clone)]
enum ReplacementPolicy {
    LRU,
    FIFO,
    Random,
}

#[derive(Debug, Clone)]
enum Instruction {
    Add(String, String, String), // <-- Arithmetic/Logic
    Sub(String, String, String),
    Mul(String, String, String),
    Div(String, String, String),
    And(String, String, String),
    Or(String, String, String),
    Xor(String, String, String),
    Not(String, String),
    Shl(String, String), // <-- Shifts and Rotates
    Shr(String, String),
    Rol(String, String),
    Ror(String, String),
    Jmp(usize), // <-- Control Flow
    Jz(usize),
    Jnz(usize),
    Jc(usize),
    Call(usize),
    Ret,
    Push(String), // <-- Stack Operations
    Pop(String),
    LoadMem(String, usize), // <-- Memory/IO Operations
    StoreMem(String, usize),
    LoadIO(String, usize),
    StoreIO(String, usize),
    Cmp(String, String), // <-- Special Operations
    Set(String, String),
    Int(u8),
    Iret,
    DmaTransfer(usize, usize, usize),
}

struct CPU {
    registers: HashMap<String, u8>,
    memory: Vec<u8>,
    rom: Vec<u8>,
    stack: Vec<u8>,
    pc: usize,
    flags: StatusFlags,
    pipeline: VecDeque<PipelineStage>,
    cache: Cache,
    interrupt_vector: Vec<u16>,
    protected_mode: bool,
    cycle_count: u64,
    power_consumption: f64,
    last_instruction_time: Instant,
    io_memory: Vec<u8>,
    dma_controller: DMAController,
}

struct DMAController {
    busy: bool,
    source: usize,
    destination: usize,
    size: usize,
}

impl TLB {
    fn new(capacity: usize) -> Self {
        TLB {
            entries: HashMap::new(),
            capacity,
        }
    }

    fn lookup(&self, virtual_addr: usize) -> Option<usize> {
        self.entries.get(&virtual_addr).copied()
    }

    fn insert(&mut self, virtual_addr: usize, physical_addr: usize) {
        if self.entries.len() >= self.capacity {
            // Simple FIFO replacement
            if let Some(key) = self.entries.keys().next().copied() {
                self.entries.remove(&key);
            }
        }
        self.entries.insert(virtual_addr, physical_addr);
    }
}

impl MMU {
    fn new(memory_size: usize) -> Self {
        MMU {
            page_table: HashMap::new(),
            tlb: TLB::new(64), // 64-entry TLB
        }
    }

    fn translate_address(&self, virtual_addr: usize) -> Result<usize, CPUError> {
        let page_number = virtual_addr / 4096; // 4KB pages
        let offset = virtual_addr % 4096;

        if let Some(entry) = self.page_table.get(&page_number) {
            Ok(entry.physical_address + offset)
        } else {
            Err(CPUError::MemoryAccessViolation {
                address: virtual_addr,
                access_type: AccessType::Read,
            })
        }
    }
}

impl CPU {
    pub fn new(config: CPUConfig) -> Self {
        let mut registers = HashMap::new();
        for i in 0..8 {
            registers.insert(format!("R{}", i), 0);
        }

        let mmu = MMU::new(config.memory_size);
        let cache_hierarchy = CacheHierarchy::new(&config.cache_config);
        let pipeline = Pipeline::new(&config.pipeline_config);
        let performance_monitor = PerformanceMonitor::new();

        CPU {
            registers,
            memory: vec![0; config.memory_size],
            rom: vec![0; config.rom_size],
            stack: Vec::with_capacity(256),
            pc: 0,
            flags: StatusFlags {
                zero: false,
                carry: false,
                overflow: false,
                negative: false,
                interrupt: true,
            },
            pipeline: pipeline.stages,
            cache_hierarchy,
            mmu,
            performance_monitor,
            io_memory: vec![0; 256],
            dma_controller: DMAController {
                busy: false,
                source: 0,
                destination: 0,
                size: 0,
            },
            interrupt_vector: vec![0; 256],
            protected_mode: false,
            cycle_count: 0,
            power_consumption: 0.0,
            last_instruction_time: Instant::now(),
        }
    }

    fn execute(&mut self) -> Result<(), CPUError> {
        while let Some(instruction) = self.pipeline.next_instruction() {
            self.performance_monitor.start_instruction();
            
            // Check hazards before execution
            self.pipeline.hazard_unit.check_hazards()?;
            
            let result = self.execute_instruction(instruction);
            
            match result {
                Ok(_) => {
                    self.performance_monitor.complete_instruction();
                    self.pipeline.branch_predictor.update(self.pc);
                }
                Err(e) => {
                    self.handle_error(e)?;
                }
            }
            
            self.pipeline.advance();
            self.check_interrupts()?;
        }
        Ok(())
    }

    fn execute_instruction(&mut self, instruction: Instruction) -> Result<(), CPUError> {
        self.cycle_count += 1;
        let start_time = Instant::now();

        let result = match instruction {
            Instruction::Add(dest, src1, src2) => self.execute_add(&dest, &src1, &src2),
            Instruction::Mul(dest, src1, src2) => self.execute_mul(&dest, &src1, &src2),
            Instruction::Div(dest, src1, src2) => self.execute_div(&dest, &src1, &src2),
        }
        let result = match instruction {
            Instruction::Add(dest, src1, src2) => {
                let a = self.get_register(&src1)?;
                let b = self.get_register(&src2)?;
                let (result, carry) = a.overflowing_add(b);
                self.flags.carry = carry;
                self.flags.zero = result == 0;
                self.set_register(&dest, result)?;
                Ok(())
            }
            Instruction::Mul(dest, src1, src2) => {
                let a = self.get_register(&src1)? as u16;
                let b = self.get_register(&src2)? as u16;
                let result = a * b;
                self.flags.overflow = result > 255;
                self.set_register(&dest, (result & 0xFF) as u8)?;
                Ok(())
            }
            Instruction::Div(dest, src1, src2) => {
                let a = self.get_register(&src1)?;
                let b = self.get_register(&src2)?;
                if b == 0 {
                    return Err(CPUError::DivisionByZero);
                }
                let result = a / b;
                self.flags.zero = result == 0;
                self.set_register(&dest, result)?;
                Ok(())
            }
            Instruction::LoadMem(reg, addr) => {
                let value = self.read_memory(addr)?;
                self.set_register(&reg, value)?;
                Ok(())
            }
            Instruction::StoreMem(reg, addr) => {
                let value = self.get_register(&reg)?;
                self.write_memory(addr, value)?;
                Ok(())
            }
            Instruction::Jump(addr) => {
                self.pc = addr;
                Ok(())
            }
            Instruction::Call(addr) => {
                self.push_stack(self.pc as u8)?;
                self.pc = addr;
                Ok(())
            }
            Instruction::Return => {
                let addr = self.pop_stack()? as usize;
                self.pc = addr;
                Ok(())
            }
            Instruction::Interrupt(vector) => {
                if !self.flags.interrupt {
                    return Ok(());
                }
                self.push_stack(self.pc as u8)?;
                self.flags.interrupt = false;
                self.pc = self.interrupt_vector[vector as usize] as usize;
                Ok(())
            }
            // Logical Operations
            Instruction::And(dest, src1, src2) => {
                let a = self.get_register(&src1)?;
                let b = self.get_register(&src2)?;
                let result = a & b;
                self.flags.zero = result == 0;
                self.set_register(&dest, result)
            }
            Instruction::Or(dest, src1, src2) => {
                let a = self.get_register(&src1)?;
                let b = self.get_register(&src2)?;
                let result = a | b;
                self.flags.zero = result == 0;
                self.set_register(&dest, result)
            }
            Instruction::Xor(dest, src1, src2) => {
                let a = self.get_register(&src1)?;
                let b = self.get_register(&src2)?;
                let result = a ^ b;
                self.flags.zero = result == 0;
                self.set_register(&dest, result)
            }
            Instruction::Not(dest, src) => {
                let value = self.get_register(&src)?;
                let result = !value;
                self.flags.zero = result == 0;
                self.set_register(&dest, result)
            }

            // Shift and Rotate Operations
            Instruction::Shl(dest, src) => {
                let value = self.get_register(&src)?;
                self.flags.carry = (value & 0x80) != 0;
                let result = value << 1;
                self.flags.zero = result == 0;
                self.set_register(&dest, result)
            }
            Instruction::Shr(dest, src) => {
                let value = self.get_register(&src)?;
                self.flags.carry = (value & 0x01) != 0;
                let result = value >> 1;
                self.flags.zero = result == 0;
                self.set_register(&dest, result)
            }
            Instruction::Rol(dest, src) => {
                let value = self.get_register(&src)?;
                let carry = (value & 0x80) != 0;
                let result = (value << 1) | (if carry { 1 } else { 0 });
                self.flags.carry = carry;
                self.flags.zero = result == 0;
                self.set_register(&dest, result)
            }
            Instruction::Ror(dest, src) => {
                let value = self.get_register(&src)?;
                let carry = (value & 0x01) != 0;
                let result = (value >> 1) | (if carry { 0x80 } else { 0 });
                self.flags.carry = carry;
                self.flags.zero = result == 0;
                self.set_register(&dest, result)
            }

            // Jump Operations
            Instruction::Jmp(addr) => {
                self.pc = addr;
                Ok(())
            }
            Instruction::Jz(addr) => {
                if self.flags.zero {
                    self.pc = addr;
                }
                Ok(())
            }
            Instruction::Jnz(addr) => {
                if !self.flags.zero {
                    self.pc = addr;
                }
                Ok(())
            }
            Instruction::Jc(addr) => {
                if self.flags.carry {
                    self.pc = addr;
                }
                Ok(())
            }

            // Compare and Set
            Instruction::Cmp(reg1, reg2) => {
                let a = self.get_register(&reg1)?;
                let b = self.get_register(&reg2)?;
                self.flags.zero = a == b;
                self.flags.carry = a < b;
                Ok(())
            }
            Instruction::Set(dest, src) => {
                let value = self.get_register(&src)?;
                self.set_register(&dest, value)
            }

            // I/O Operations
            Instruction::LoadIO(reg, addr) => {
                if addr >= self.io_memory.len() {
                    return Err(CPUError::MemoryAccessViolation(addr));
                }
                let value = self.io_memory[addr];
                self.set_register(&reg, value)
            }
            Instruction::StoreIO(reg, addr) => {
                if addr >= self.io_memory.len() {
                    return Err(CPUError::MemoryAccessViolation(addr));
                }
                let value = self.get_register(&reg)?;
                self.io_memory[addr] = value;
                Ok(())
            }
            // Add more instruction implementations...
            _ => Ok(()),
        };

        match instruction {
            Instruction::Arithmetic(op) => self.execute_arithmetic(op),
            Instruction::Memory(op) => self.execute_memory(op),
            Instruction::Branch(op) => self.execute_branch(op),
            Instruction::System(op) => self.execute_system(op),
        }

        // Update performance metrics
        let duration = start_time.elapsed();
        self.update_power_consumption(duration);
        self.last_instruction_time = Instant::now();

        result
    }

    fn execute_add(&mut self, dest: &str, src1: &str, src2: &str) -> Result<(), CPUError> {
        let a = self.get_register(src1)?;
        let b = self.get_register(src2)?;
        let (result, carry) = a.overflowing_add(b);
        self.flags.carry = carry;
        self.flags.zero = result == 0;
        self.set_register(dest, result)
    }

    fn access_memory(&mut self, address: usize, access_type: AccessType) -> Result<u8, CPUError> {
        // Check protection rings
        self.check_memory_protection(address, access_type)?;
        
        // Try TLB first
        if let Some(physical_address) = self.mmu.tlb.lookup(address) {
            return self.access_physical_memory(physical_address, access_type);
        }
        
        // TLB miss, check page table
        let physical_address = self.mmu.translate_address(address)?;
        self.mmu.tlb.insert(address, physical_address);
        
        self.access_physical_memory(physical_address, access_type)
    }

    fn read_memory(&mut self, addr: usize) -> Result<u8, CPUError> {
        // Check cache first
        if let Some(cache_line) = self.cache.data_cache.get(&(addr / 16)) {
            if cache_line.valid {
                self.cache.cache_stats.hits += 1;
                return Ok(cache_line.data[addr % 16]);
            }
        }

        self.cache.cache_stats.misses += 1;
        
        // Cache miss - read from memory
        if addr >= self.memory.len() {
            return Err(CPUError::MemoryAccessViolation(addr));
        }
        
        // Load into cache
        self.update_cache(addr, self.memory[addr]);
        
        Ok(self.memory[addr])
    }

    fn write_memory(&mut self, addr: usize, value: u8) -> Result<(), CPUError> {
        if addr >= self.memory.len() {
            return Err(CPUError::MemoryAccessViolation(addr));
        }

        // Update cache if present
        if let Some(cache_line) = self.cache.data_cache.get_mut(&(addr / 16)) {
            if cache_line.valid {
                cache_line.data[addr % 16] = value;
                cache_line.dirty = true;
                self.cache.cache_stats.hits += 1;
            }
        }

        self.memory[addr] = value;
        Ok(())
    }

    fn update_cache(&mut self, addr: usize, value: u8) {
        let cache_line = CacheLine {
            data: vec![0; 16],
            valid: true,
            dirty: false,
            last_access: Instant::now(),
        };

        // Simple LRU implementation
        if self.cache.data_cache.len() >= 256 {
            if let Some((oldest_addr, _)) = self.cache.data_cache
                .iter()
                .min_by_key(|(_, line)| line.last_access) {
                let oldest_addr = *oldest_addr;
                self.cache.data_cache.remove(&oldest_addr);
                self.cache.cache_stats.evictions += 1;
            }
        }

        self.cache.data_cache.insert(addr / 16, cache_line);
    }

    fn update_power_consumption(&mut self, duration: Duration) {
        // Simple power consumption model
        let instruction_power = 0.1; // Base power per instruction
        let memory_power = 0.05; // Additional power for memory access
        let cache_power = 0.02; // Additional power for cache access

        let total_power = instruction_power
            + (self.cache.cache_stats.hits as f64 * cache_power)
            + (self.cache.cache_stats.misses as f64 * memory_power);

        self.power_consumption += total_power * duration.as_secs_f64();
    }

    fn push_stack(&mut self, value: u8) -> Result<(), CPUError> {
        if self.stack.len() >= 256 {
            return Err(CPUError::StackOverflow);
        }
        self.stack.push(value);
        Ok(())
    }

    fn pop_stack(&mut self) -> Result<u8, CPUError> {
        self.stack.pop().ok_or(CPUError::StackOverflow)
    }

    fn get_register(&self, reg: &str) -> Result<u8, CPUError> {
        self.registers
            .get(reg)
            .copied()
            .ok_or(CPUError::InvalidInstruction(0))
    }

    fn set_register(&mut self, reg: &str, value: u8) -> Result<(), CPUError> {
        if let Some(r) = self.registers.get_mut(reg) {
            *r = value;
            Ok(())
        } else {
            Err(CPUError::InvalidInstruction(0))
        }
    }
}

// Assembler implementation
struct Assembler {
    labels: HashMap<String, usize>,
    instructions: HashMap<String, u8>,
}

impl Assembler {
    fn new() -> Self {
        let mut instructions = HashMap::new();
        instructions.insert("AND".to_string(), 0x01);
        instructions.insert("OR".to_string(), 0x02);
        instructions.insert("XOR".to_string(), 0x03);
        instructions.insert("NOT".to_string(), 0x04);
        instructions.insert("SHL".to_string(), 0x05);
        instructions.insert("SHR".to_string(), 0x06);
        instructions.insert("ROL".to_string(), 0x07);
        instructions.insert("ROR".to_string(), 0x08);
        instructions.insert("JMP".to_string(), 0x09);
        instructions.insert("JZ".to_string(), 0x0A);
        instructions.insert("JNZ".to_string(), 0x0B);
        instructions.insert("JC".to_string(), 0x0C);
        instructions.insert("CMP".to_string(), 0x0D);
        instructions.insert("SET".to_string(), 0x0E);
        instructions.insert("PUSH".to_string(), 0x0F);
        instructions.insert("POP".to_string(), 0x10);
        instructions.insert("CALL".to_string(), 0x11);
        instructions.insert("RET".to_string(), 0x12);
        instructions.insert("MUL".to_string(), 0x13);
        instructions.insert("DIV".to_string(), 0x14);
        instructions.insert("INT".to_string(), 0x15);
        instructions.insert("IRET".to_string(), 0x16);
        instructions.insert("LOADM".to_string(), 0x17);
        instructions.insert("STOREM".to_string(), 0x18);
        instructions.insert("LOADIO".to_string(), 0x19);
        instructions.insert("STOREIO".to_string(), 0x1A);
        instructions.insert("DMA".to_string(), 0x1B);

        Assembler {
            labels: HashMap::new(),
            instructions,
        }
    }

    fn assemble(&mut self, source: &str) -> Result<Vec<u8>, String> {
        let mut binary = Vec::new();
        let mut current_address = 0;

        // First pass: collect labels
        for line in source.lines() {
            let line = line.trim();
            if line.is_empty() || line.starts_with(';') {
                continue;
            }

            if line.ends_with(':') {
                let label = line[..line.len() - 1].to_string();
                self.labels.insert(label, current_address);
            } else {
                current_address += self.instruction_size(line);
            }
        }

        // Second pass: generate binary
        for line in source.lines() {
            let line = line.trim();
            if line.is_empty() || line.starts_with(';') || line.ends_with(':') {
                continue;
            }

            let tokens: Vec<&str> = line.split_whitespace().collect();
            if let Some(&opcode) = self.instructions.get(tokens[0]) {
                binary.push(opcode);
                
                // Process operands
                for token in &tokens[1..] {
                    if let Ok(value) = token.parse::<u8>() {
                        binary.push(value);
                    } else if let Some(&addr) = self.labels.get(*token) {
                        binary.push(addr as u8);
                    } else {
                        return Err(format!("Invalid operand: {}", token));
                    }
                }
            }
        }

        Ok(binary)
    }

    fn instruction_size(&self, instruction: &str) -> usize {
        let tokens: Vec<&str> = instruction.split_whitespace().collect();
        if tokens.is_empty() {
            return 0;
        }
        
        // Basic size calculation - 1 byte for opcode + 1 byte per operand
        1 + tokens.len() - 1
    }
}

// Debugger implementation
struct Debugger {
    breakpoints: HashMap<usize, bool>,
    cpu: CPU,
}

impl Debugger {
    fn new(cpu: CPU) -> Self {
        Debugger {
            breakpoints: HashMap::new(),
            cpu,
        }
    }

    fn set_breakpoint(&mut self, address: usize) {
        self.breakpoints.insert(address, true);
    }

    fn clear_breakpoint(&mut self, address: usize) {
        self.breakpoints.remove(&address);
    }

    fn step(&mut self) -> Result<(), CPUError> {
        // Execute one instruction
        if let Some(instruction) = self.cpu.pipeline.pop_front() {
            match instruction {
                PipelineStage::Execute(result) => {
                    self.cpu.execute_instruction(result.into())?;
                }
                _ => {}
            }
        }
        Ok(())
    }

    fn run(&mut self) -> Result<(), CPUError> {
        while self.cpu.pc < self.cpu.memory.len() {
            if self.breakpoints.contains_key(&self.cpu.pc) {
                println!("Breakpoint hit at {:#04x}", self.cpu.pc);
                return Ok(());
            }
            self.step()?;
        }
        Ok(())
    }

    fn print_state(&self) {
        println!("CPU State:");
        println!("PC: {:#04x}", self.cpu.pc);
        println!("Flags: {:?}", self.cpu.flags);
        println!("Registers:");
        for (reg, value) in &self.cpu.registers {
            println!("{}: {:#04x}", reg, value);