anya-core 1.2.0

use bitcoin::{Transaction, Block, BlockHeader};
use thiserror::Error;
use std::collections::{HashMap, VecDeque};
use std::sync::{Arc, Mutex, RwLock};
use std::time::{SystemTime, UNIX_EPOCH, Duration};
use rand::{Rng, thread_rng};
use rand::distributions::Alphanumeric;
use rayon::prelude::*;

use crate::bitcoin::validation::{TransactionValidator, ValidationError, VerificationRecord};
use crate::bitcoin::protocol::{BitcoinProtocol, BPCLevel, BitcoinError};
use crate::hardware_optimization::{HardwareOptimizationManager, OptimizableOperation, HardwareType};

/// [CONSENSUS CRITICAL]: This struct represents a consensus violation 
/// found during differential validation testing
#[derive(Debug, Clone)]
pub struct ConsensusViolation {
    /// Transaction that caused the violation
    pub transaction: Transaction,
    
    /// Expected validation result from reference implementation
    pub expected_result: Result<(), ValidationError>,
    
    /// Actual result from our implementation
    pub actual_result: Result<(), ValidationError>,
    
    /// Timestamp when violation was detected
    pub timestamp: u64,
    
    /// Additional context about the violation
    pub context: HashMap<String, String>,
}

/// [SECURITY SENSITIVE]: Error types specific to differential fuzzing
#[derive(Debug, Error)]
pub enum DifferentialFuzzerError {
    #[error("Consensus violation detected: {0}")]
    ConsensusViolation(String),
    
    #[error("Reference client error: {0}")]
    ReferenceClientError(String),
    
    #[error("Test client error: {0}")]
    TestClientError(String),
    
    #[error("Mutation engine error: {0}")]
    MutationEngineError(String),
}

/// [SECURITY SENSITIVE]: Mutation engine for generating test transactions
pub struct MutationEngine {
    /// Base set of transactions to mutate
    base_transactions: Vec<Transaction>,
    
    /// Mutation rate (0.0-1.0)
    mutation_rate: f64,
    
    /// Maximum mutations per transaction
    max_mutations: usize,
}

impl MutationEngine {
    /// Create a new mutation engine with default settings
    pub fn new() -> Self {
        Self {
            base_transactions: Vec::new(),
            mutation_rate: 0.05,
            max_mutations: 5,
        }
    }
    
    /// Configure the mutation rate
    pub fn with_mutation_rate(mut self, rate: f64) -> Self {
        self.mutation_rate = rate.max(0.0).min(1.0);
        self
    }
    
    /// Configure maximum mutations per transaction
    pub fn with_max_mutations(mut self, max: usize) -> Self {
        self.max_mutations = max;
        self
    }
    
    /// Add base transactions for mutation
    pub fn with_base_transactions(mut self, transactions: Vec<Transaction>) -> Self {
        self.base_transactions = transactions;
        self
    }
    
    /// Generate a batch of mutated transactions for testing
    /// 
    /// # Security
    /// [VALIDATION IMPORTANT] This function generates transactions that may push
    /// consensus rules to their limits to detect implementation differences
    pub fn generate_test_batch(&self, count: usize) -> Vec<Transaction> {
        let mut rng = thread_rng();
        let mut result = Vec::with_capacity(count);
        
        // If we have base transactions, use them as templates
        if !self.base_transactions.is_empty() {
            for _ in 0..count {
                // Pick a random base transaction
                let base_idx = rng.gen_range(0..self.base_transactions.len());
                let mut tx = self.base_transactions[base_idx].clone();
                
                // Apply random mutations
                let mutations = rng.gen_range(1..=self.max_mutations);
                for _ in 0..mutations {
                    if rng.gen_bool(self.mutation_rate) {
                        self.mutate_transaction(&mut tx);
                    }
                }
                
                result.push(tx);
            }
        } else {
            // Generate completely random transactions if no base transactions
            for _ in 0..count {
                result.push(self.generate_random_transaction());
            }
        }
        
        result
    }
    
    // Apply a random mutation to a transaction
    fn mutate_transaction(&self, tx: &mut Transaction) {
        let mut rng = thread_rng();
        
        // Pick a random mutation type
        let mutation_type = rng.gen_range(0..5);
        
        match mutation_type {
            0 => {
                // Modify version
                tx.version = rng.gen_range(1..=4);
            },
            1 => {
                // Modify lock_time (potentially to trigger time-based validation differences)
                let new_locktime = rng.gen_range(0..=0xffffffff);
                tx.lock_time = bitcoin::LockTime::from_consensus(new_locktime);
            },
            2 => {
                // Modify input (if any)
                if !tx.input.is_empty() {
                    let input_idx = rng.gen_range(0..tx.input.len());
                    let sequence = rng.gen_range(0..=0xffffffff);
                    tx.input[input_idx].sequence = sequence;
                }
            },
            3 => {
                // Modify output (if any)
                if !tx.output.is_empty() {
                    let output_idx = rng.gen_range(0..tx.output.len());
                    let value = rng.gen_range(0..=21_000_000_00000000); // Random value up to 21M BTC
                    tx.output[output_idx].value = value;
                }
            },
            _ => {
                // Do nothing (equivalent to no mutation)
            }
        }
    }
    
    // Generate a completely random transaction
    fn generate_random_transaction(&self) -> Transaction {
        let mut rng = thread_rng();
        
        // Generate random transaction with minimal valid structure
        let version = rng.gen_range(1..=4);
        let lock_time = bitcoin::LockTime::from_consensus(rng.gen_range(0..=0xffffffff));
        
        // Empty inputs/outputs - this is just a placeholder for testing
        // In a real implementation, these would be more realistic
        
        Transaction {
            version,
            lock_time,
            input: vec![],
            output: vec![],
        }
    }
}

/// [CONSENSUS CRITICAL]: A mock Bitcoin reference client for consensus testing
/// In production, this would connect to an actual Bitcoin Core node
pub struct BitcoinReferenceClient {
    /// Connection details to Bitcoin Core
    endpoint: String,
    
    /// Cache of validation results to reduce external calls
    validation_cache: RwLock<HashMap<String, bool>>,
}

impl BitcoinReferenceClient {
    /// Create a new reference client connected to Bitcoin Core
    pub fn new(endpoint: &str) -> Self {
        Self {
            endpoint: endpoint.to_string(),
            validation_cache: RwLock::new(HashMap::new()),
        }
    }
    
    /// Validate a transaction using the reference client
    /// 
    /// # Security
    /// [CONSENSUS CRITICAL] This function must return exactly what Bitcoin Core would return
    /// for the same transaction to ensure consensus compatibility
    pub fn validate_transaction(&self, tx: &Transaction) -> Result<(), ValidationError> {
        // In a real implementation, this would call Bitcoin Core
        // For this demo, we'll simulate a response
        
        let tx_hash = tx.txid().to_string();
        
        // Check cache first
        if let Ok(cache) = self.validation_cache.read() {
            if let Some(result) = cache.get(&tx_hash) {
                return if *result {
                    Ok(())
                } else {
                    Err(ValidationError::InvalidTransaction("Cached invalid transaction".into()))
                };
            }
        }
        
        // Simulate a call to Bitcoin Core
        // In reality, this would use Bitcoin Core's JSON-RPC API
        
        // For simplicity in this demo, always return valid for standard transactions
        // and invalid for specific edge cases
        
        // Simple validation: in a real implementation this would be much more comprehensive
        let result = if tx.version < 1 || tx.version > 2 {
            Err(ValidationError::InvalidTransaction("Invalid version".into()))
        } else {
            Ok(())
        };
        
        // Cache the result
        if let Ok(mut cache) = self.validation_cache.write() {
            cache.insert(tx_hash, result.is_ok());
        }
        
        result
    }
}

/// [CONSENSUS CRITICAL]: Differential fuzzer for validating consensus between 
/// our implementation and the Bitcoin Core reference implementation
pub struct DifferentialFuzzer {
    /// Reference Bitcoin client (Bitcoin Core)
    reference_client: Arc<BitcoinReferenceClient>,
    
    /// Our transaction validator to test
    test_client: Arc<TransactionValidator>,
    
    /// Engine for generating test transactions
    mutation_engine: MutationEngine,
    
    /// Record of consensus violations found
    consensus_violations: RwLock<Vec<ConsensusViolation>>,
    
    /// Configuration
    config: DifferentialFuzzerConfig,
}

/// Configuration for the differential fuzzer
#[derive(Debug, Clone)]
pub struct DifferentialFuzzerConfig {
    /// Number of test iterations to run
    pub iterations: usize,
    
    /// Number of transactions to test per iteration
    pub batch_size: usize,
    
    /// Whether to run tests in parallel
    pub parallel: bool,
    
    /// Whether to stop on first violation
    pub fail_fast: bool,
}

impl Default for DifferentialFuzzerConfig {
    fn default() -> Self {
        Self {
            iterations: 100,
            batch_size: 100,
            parallel: true,
            fail_fast: false,
        }
    }
}

impl DifferentialFuzzer {
    /// Create a new differential fuzzer
    pub fn new(
        reference_client: Arc<BitcoinReferenceClient>,
        test_client: Arc<TransactionValidator>,
    ) -> Self {
        Self {
            reference_client,
            test_client,
            mutation_engine: MutationEngine::new(),
            consensus_violations: RwLock::new(Vec::new()),
            config: DifferentialFuzzerConfig::default(),
        }
    }
    
    /// Configure the mutation engine
    pub fn with_mutation_engine(mut self, engine: MutationEngine) -> Self {
        self.mutation_engine = engine;
        self
    }
    
    /// Configure the fuzzer
    pub fn with_config(mut self, config: DifferentialFuzzerConfig) -> Self {
        self.config = config;
        self
    }
    
    /// Run the differential fuzzer and return consensus violations
    /// 
    /// # Security
    /// [CONSENSUS CRITICAL] This function verifies that our implementation
    /// matches Bitcoin Core's validation decisions exactly across many test cases
    pub fn run(&self) -> Result<Vec<ConsensusViolation>, DifferentialFuzzerError> {
        println!("Starting differential fuzzing with {} iterations of {} transactions each",
                 self.config.iterations, self.config.batch_size);
        
        let start_time = SystemTime::now();
        let mut violation_count = 0;
        
        for i in 0..self.config.iterations {
            // Generate test transactions
            let test_batch = self.mutation_engine.generate_test_batch(self.config.batch_size);
            
            // Process batch based on configuration
            if self.config.parallel {
                self.process_batch_parallel(&test_batch)?;
            } else {
                self.process_batch_sequential(&test_batch)?;
            }
            
            // Check if we found any violations
            let current_violations = self.consensus_violations.read().unwrap().len();
            let new_violations = current_violations - violation_count;
            violation_count = current_violations;
            
            // Log progress
            if i % 10 == 0 || new_violations > 0 {
                println!("Iteration {}/{}: {} transactions processed, {} violations found",
                         i+1, self.config.iterations, (i+1) * self.config.batch_size, violation_count);
            }
            
            // Stop if needed
            if self.config.fail_fast && violation_count > 0 {
                println!("Stopping early due to consensus violations (fail_fast=true)");
                break;
            }
        }
        
        // Collect final results
        let violations = self.consensus_violations.read().unwrap().clone();
        let elapsed = start_time.elapsed().unwrap_or(Duration::from_secs(0));
        
        println!("Differential fuzzing completed in {:.2}s", elapsed.as_secs_f64());
        println!("Processed {} transactions, found {} consensus violations",
                 self.config.iterations * self.config.batch_size, violations.len());
        
        Ok(violations)
    }
    
    // Process a batch of transactions sequentially
    fn process_batch_sequential(&self, batch: &[Transaction]) -> Result<(), DifferentialFuzzerError> {
        for tx in batch {
            self.compare_transaction(tx)?;
        }
        Ok(())
    }
    
    // Process a batch of transactions in parallel
    fn process_batch_parallel(&self, batch: &[Transaction]) -> Result<(), DifferentialFuzzerError> {
        batch.par_iter().try_for_each(|tx| {
            self.compare_transaction(tx)
        })
    }
    
    // Compare validation results between reference and test client for a single transaction
    fn compare_transaction(&self, tx: &Transaction) -> Result<(), DifferentialFuzzerError> {
        // Get validation result from reference client
        let reference_result = self.reference_client.validate_transaction(tx);
        
        // Get validation result from our implementation
        let test_result = self.test_client.validate(tx);
        
        // Compare results
        let reference_ok = reference_result.is_ok();
        let test_ok = test_result.is_ok();
        
        if reference_ok != test_ok {
            // Consensus violation detected!
            let violation = ConsensusViolation {
                transaction: tx.clone(),
                expected_result: reference_result.clone(),
                actual_result: test_result.clone(),
                timestamp: SystemTime::now()
                    .duration_since(UNIX_EPOCH)
                    .unwrap_or_default()
                    .as_secs(),
                context: HashMap::new(),
            };
            
            // Record the violation
            if let Ok(mut violations) = self.consensus_violations.write() {
                violations.push(violation);
            }
            
            // Return error if fail_fast is enabled
            if self.config.fail_fast {
                return Err(DifferentialFuzzerError::ConsensusViolation(
                    format!("Transaction {} validation mismatch: reference={}, test={}",
                            tx.txid(), reference_ok, test_ok)
                ));
            }
        }
        
        Ok(())
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    
    /// [SECURITY SENSITIVE] Test the basic functionality of the differential fuzzer
    #[test]
    fn test_differential_fuzzer_basic() {
        // Create reference client
        let reference_client = Arc::new(BitcoinReferenceClient::new("http://localhost:8332"));
        
        // Create our validator
        let validator = Arc::new(TransactionValidator::new());
        
        // Create fuzzer with minimal settings for quick test
        let fuzzer = DifferentialFuzzer::new(reference_client, validator)
            .with_config(DifferentialFuzzerConfig {
                iterations: 10,
                batch_size: 10,
                parallel: false,
                fail_fast: false,
            });
        
        // Run the fuzzer
        let violations = fuzzer.run().expect("Fuzzer should complete without errors");
        
        // In our test environment, we expect no violations since our implementation
        // should match the reference implementation
        assert!(violations.is_empty(), "Expected no consensus violations");
    }
}