rusty_emu/tests/intel_4002_state_machine_test.rs

//! Intel 4002 RAM Unified State Machine Diagnostic Test
//!
//! This test isolates Intel 4002 RAM unified state machine to verify that it correctly
//! progresses through all states: Idle → AddressPhase → WaitLatency → ReadData/WriteData/OutputPort → Idle
//!
//! The test focuses on unified state machine progression without involving other system components.

use std::thread;
use std::time::Duration;

use rusty_emu::component::Component;
use rusty_emu::components::common::intel_400x::{
    Intel400xTimingState, Intel400xUnifiedState, TimingState,
};
use rusty_emu::components::memory::intel_4002::{Intel4002, PendingOperation};
use rusty_emu::pin::PinValue;

/// Test helper to create a test RAM with minimal setup
fn create_test_ram() -> Intel4002 {
    // Create RAM with 1ns access time for fast testing
    let mut ram = Intel4002::new_with_access_time("TEST_RAM".to_string(), 1);

    // Initialize RAM with test data using write_ram_direct
    for (i, &value) in [0x0A, 0x0B, 0x0C, 0x0D, 0x0E].iter().enumerate() {
        ram.write_ram_direct(i as u8, value).unwrap();
    }

    // Start the component so it can process updates
    ram.base.set_running(true);

    // Initialize clock pins to Low to establish known state for edge detection
    let phi1_pin = ram.get_pin("PHI1").unwrap();
    let phi2_pin = ram.get_pin("PHI2").unwrap();
    {
        let mut phi1_guard = phi1_pin.lock().unwrap();
        let mut phi2_guard = phi2_pin.lock().unwrap();
        phi1_guard.set_driver(Some("TEST".to_string()), PinValue::Low);
        phi2_guard.set_driver(Some("TEST".to_string()), PinValue::Low);
    }

    // Process initial state (this initializes prev_phi1/prev_phi2 for edge detection)
    ram.update();

    ram
}

/// Test helper to wait for pin settlement time
fn wait_for_pin_settlement() {
    thread::sleep(Duration::from_nanos(10)); // 10ns settlement time
}

/// Test helper to set data bus value
fn set_data_bus(ram: &Intel4002, value: u8) {
    let nibble = value & 0x0F; // Only lower 4 bits

    for i in 0..4 {
        if let Ok(pin) = ram.get_pin(&format!("D{}", i)) {
            if let Ok(mut pin_guard) = pin.lock() {
                let bit_value = (nibble >> i) & 1;
                let pin_value = if bit_value == 1 {
                    PinValue::High
                } else {
                    PinValue::Low
                };
                pin_guard.set_driver(Some("TEST".to_string()), pin_value);
            }
        }
    }

    wait_for_pin_settlement();
}

/// Test helper to clear data bus drivers
fn clear_data_bus_drivers(ram: &Intel4002) {
    for i in 0..4 {
        if let Ok(pin) = ram.get_pin(&format!("D{}", i)) {
            if let Ok(mut pin_guard) = pin.lock() {
                pin_guard.remove_driver("TEST");
            }
        }
    }

    wait_for_pin_settlement();
}

/// Test helper to generate a clock edge
fn generate_clock_edge(ram: &mut Intel4002, phi1_high: bool, phi2_high: bool) {
    let phi1_pin = ram.get_pin("PHI1").unwrap();
    let phi2_pin = ram.get_pin("PHI2").unwrap();

    // Set clock pins
    {
        let mut phi1_guard = phi1_pin.lock().unwrap();
        let mut phi2_guard = phi2_pin.lock().unwrap();

        phi1_guard.set_driver(
            Some("TEST".to_string()),
            if phi1_high {
                PinValue::High
            } else {
                PinValue::Low
            },
        );
        phi2_guard.set_driver(
            Some("TEST".to_string()),
            if phi2_high {
                PinValue::High
            } else {
                PinValue::Low
            },
        );
    }

    wait_for_pin_settlement();

    // Update to process: edge
    ram.update();
}

/// Test helper to generate a complete clock cycle
fn generate_clock_cycle(ram: &mut Intel4002) {
    // Start with both clocks low
    generate_clock_edge(ram, false, false);

    // Φ1 rising edge
    generate_clock_edge(ram, true, false);

    // Φ1 falling edge
    generate_clock_edge(ram, false, false);

    // Φ2 rising edge
    generate_clock_edge(ram, false, true);

    // Φ2 falling edge
    generate_clock_edge(ram, false, false);
}

/// Test RAM read operation state progression
///
/// Note: This test verifies the state machine behavior through direct state manipulation
/// rather than through pin-based triggering. The Intel 4002 implementation processes
/// events through process_event_direct() which doesn't call handle_component_event(),
/// so chip select via pins doesn't work the same way as Intel 4001.
///
/// Address latching happens on Φ1 falling edge (after data is stable).
#[test]
fn test_ram_read_state_progression() {
    println!("=== Testing RAM Read Operation State Progression ===");

    let mut ram = create_test_ram();

    // Initially should be in idle state
    assert_eq!(ram.get_timing_state(), TimingState::Idle);
    println!("Initial state: {:?}", ram.get_timing_state());

    // Set operation type to Read
    ram.set_pending_operation(PendingOperation::Read);

    // Manually transition to AddressPhase (simulating chip select)
    ram.set_state_for_test(Intel400xUnifiedState::AddressPhase);

    // Set address high nibble (0x0) on data bus
    set_data_bus(&ram, 0x0);

    // Generate Φ1 rising edge (no latching yet, data may not be stable)
    generate_clock_edge(&mut ram, true, false);

    // Generate Φ1 falling edge - address latching happens here (data is now stable)
    generate_clock_edge(&mut ram, false, false);

    // Should have latched high nibble
    assert_eq!(ram.get_address_high_nibble(), Some(0x0));
    println!(
        "After high nibble: state={:?}, high_nibble={:?}",
        ram.get_timing_state(),
        ram.get_address_high_nibble()
    );

    // Set address low nibble (0x1) on data bus
    set_data_bus(&ram, 0x1);

    // Generate Φ1 rising edge (no latching yet)
    generate_clock_edge(&mut ram, true, false);

    // Generate Φ1 falling edge - low nibble latching happens here
    generate_clock_edge(&mut ram, false, false);

    // Should have latched low nibble and transitioned to WaitLatency
    assert_eq!(ram.get_address_low_nibble(), Some(0x1));
    println!(
        "After low nibble: high_nibble={:?}, low_nibble={:?}",
        ram.get_address_high_nibble(),
        ram.get_address_low_nibble()
    );

    // Wait for latency to elapse (with 1ns access time, it should elapse immediately)
    std::thread::sleep(std::time::Duration::from_millis(1));

    // Generate Φ2 rising edge to trigger latency check and data driving
    generate_clock_edge(&mut ram, false, true);

    // Should have transitioned to ReadData/DriveData state
    assert_eq!(ram.get_timing_state(), TimingState::DriveData);
    println!("After Φ2 rising: state={:?}", ram.get_timing_state());

    // Clear data bus drivers to prepare for reading
    clear_data_bus_drivers(&ram);

    // Execute state logic to drive data
    ram.update();

    // Check that RAM is driving data bus with correct data
    let d0_pin = ram.get_pin("D0").unwrap();
    let d1_pin = ram.get_pin("D1").unwrap();
    let d2_pin = ram.get_pin("D2").unwrap();
    let d3_pin = ram.get_pin("D3").unwrap();

    // Read data bus value
    let mut data_value = 0;
    if d0_pin.lock().unwrap().read() == PinValue::High {
        data_value |= 1 << 0;
    }
    if d1_pin.lock().unwrap().read() == PinValue::High {
        data_value |= 1 << 1;
    }
    if d2_pin.lock().unwrap().read() == PinValue::High {
        data_value |= 1 << 2;
    }
    if d3_pin.lock().unwrap().read() == PinValue::High {
        data_value |= 1 << 3;
    }

    // Should be reading value at address 0x01 (0x0B from our test data)
    assert_eq!(data_value, 0x0B);
    println!("Data bus value: 0x{:X} (expected: 0x0B)", data_value);

    // Generate Φ2 falling edge to complete operation
    generate_clock_edge(&mut ram, false, false);

    // Should have returned to idle state
    assert_eq!(ram.get_timing_state(), TimingState::Idle);
    println!("Final state: {:?}", ram.get_timing_state());

    println!("✅ RAM read operation state progression test passed!");
}

/// Test RAM write operation state progression
///
/// Note: This test verifies the state machine behavior through direct state manipulation
/// rather than through pin-based triggering. The Intel 4002 implementation processes
/// events through process_event_direct() which doesn't call handle_component_event(),
/// so chip select via pins doesn't work the same way as Intel 4001.
///
/// Address latching happens on Φ1 falling edge (after data is stable).
#[test]
fn test_ram_write_state_progression() {
    println!("=== Testing RAM Write Operation State Progression ===");

    let mut ram = create_test_ram();

    // Initially should be in idle state
    assert_eq!(ram.get_timing_state(), TimingState::Idle);
    println!("Initial state: {:?}", ram.get_timing_state());

    // Set operation type to Write
    ram.set_pending_operation(PendingOperation::Write);

    // Manually transition to AddressPhase (simulating chip select)
    ram.set_state_for_test(Intel400xUnifiedState::AddressPhase);

    // Set address high nibble (0x0) on data bus
    set_data_bus(&ram, 0x0);

    // Generate Φ1 rising edge (no latching yet)
    generate_clock_edge(&mut ram, true, false);

    // Generate Φ1 falling edge - address latching happens here
    generate_clock_edge(&mut ram, false, false);

    // Should have latched high nibble
    assert_eq!(ram.get_address_high_nibble(), Some(0x0));
    println!(
        "After high nibble: state={:?}, high_nibble={:?}",
        ram.get_timing_state(),
        ram.get_address_high_nibble()
    );

    // Set address low nibble (0x2) on data bus
    set_data_bus(&ram, 0x2);

    // Generate Φ1 rising edge (no latching yet)
    generate_clock_edge(&mut ram, true, false);

    // Generate Φ1 falling edge - low nibble latching happens here
    generate_clock_edge(&mut ram, false, false);

    // Should have latched low nibble
    assert_eq!(ram.get_address_low_nibble(), Some(0x2));
    println!(
        "After low nibble: high_nibble={:?}, low_nibble={:?}",
        ram.get_address_high_nibble(),
        ram.get_address_low_nibble()
    );

    // Wait for latency to elapse (with 1ns access time, it should elapse immediately)
    std::thread::sleep(std::time::Duration::from_millis(1));

    // Set data to write (0x0F) on data bus
    set_data_bus(&ram, 0x0F);

    // Generate Φ2 rising edge to handle data operation
    generate_clock_edge(&mut ram, false, true);

    // Should have transitioned to WriteData/DriveData state
    assert_eq!(ram.get_timing_state(), TimingState::DriveData);
    println!("After Φ2 rising: state={:?}", ram.get_timing_state());

    // Generate Φ2 falling edge to complete operation
    generate_clock_edge(&mut ram, false, false);

    // Should have returned to idle state
    assert_eq!(ram.get_timing_state(), TimingState::Idle);
    println!("Final state: {:?}", ram.get_timing_state());

    // Verify that data was written correctly
    assert_eq!(ram.read_ram(0x02).unwrap(), 0x0F);
    println!("Written data verified: address 0x02 = 0x0F");

    println!("✅ RAM write operation state progression test passed!");
}

/// Test output port operation state progression
///
/// Note: This test verifies the state machine behavior through direct state manipulation
/// rather than through pin-based triggering. The Intel 4002 implementation processes
/// events through process_event_direct() which doesn't call handle_component_event(),
/// so chip select via pins doesn't work the same way as Intel 4001.
///
/// Address latching happens on Φ1 falling edge (after data is stable).
#[test]
fn test_output_port_state_progression() {
    println!("=== Testing Output Port Operation State Progression ===");

    let mut ram = create_test_ram();

    // Initially should be in idle state
    assert_eq!(ram.get_timing_state(), TimingState::Idle);
    println!("Initial state: {:?}", ram.get_timing_state());

    // Set operation type to OutputPort
    ram.set_pending_operation(PendingOperation::OutputPort);

    // Manually transition to AddressPhase (simulating chip select)
    ram.set_state_for_test(Intel400xUnifiedState::AddressPhase);

    // Set address high nibble (0x1) on data bus (for output port 0x14-0x17)
    set_data_bus(&ram, 0x1);

    // Generate Φ1 rising edge (no latching yet)
    generate_clock_edge(&mut ram, true, false);

    // Generate Φ1 falling edge - address latching happens here
    generate_clock_edge(&mut ram, false, false);

    // Should have latched high nibble
    assert_eq!(ram.get_address_high_nibble(), Some(0x1));
    println!(
        "After high nibble: state={:?}, high_nibble={:?}",
        ram.get_timing_state(),
        ram.get_address_high_nibble()
    );

    // Set address low nibble (0x4) on data bus (for output port 0 address 0x14)
    set_data_bus(&ram, 0x4);

    // Generate Φ1 rising edge (no latching yet)
    generate_clock_edge(&mut ram, true, false);

    // Generate Φ1 falling edge - low nibble latching happens here
    generate_clock_edge(&mut ram, false, false);

    // Should have latched low nibble
    assert_eq!(ram.get_address_low_nibble(), Some(0x4));
    println!(
        "After low nibble: high_nibble={:?}, low_nibble={:?}",
        ram.get_address_high_nibble(),
        ram.get_address_low_nibble()
    );

    // Wait for latency to elapse (with 1ns access time, it should elapse immediately)
    std::thread::sleep(std::time::Duration::from_millis(1));

    // Set data to write (0x05) on data bus
    set_data_bus(&ram, 0x05);

    // Generate Φ2 rising edge to handle data operation
    generate_clock_edge(&mut ram, false, true);

    // Should have transitioned to OutputPort/DriveData state
    assert_eq!(ram.get_timing_state(), TimingState::DriveData);
    println!("After Φ2 rising: state={:?}", ram.get_timing_state());

    // Generate Φ2 falling edge to complete operation
    generate_clock_edge(&mut ram, false, false);

    // Should have returned to idle state
    assert_eq!(ram.get_timing_state(), TimingState::Idle);
    println!("Final state: {:?}", ram.get_timing_state());

    // Verify that output port was set correctly
    assert_eq!(ram.get_io_port(0).unwrap(), 0x05);
    println!("Output port 0 set to: 0x05");

    println!("✅ Output port operation state progression test passed!");
}

/// Test that unified state machine doesn't progress without proper signals
#[test]
fn test_no_progression_without_signals() {
    println!("=== Testing No State Progression Without Proper Signals ===");

    let mut ram = create_test_ram();

    // Initially should be in idle state
    assert_eq!(ram.get_timing_state(), TimingState::Idle);

    // Generate clock cycles without proper control signals
    for i in 0..5 {
        generate_clock_cycle(&mut ram);
        println!("Cycle {}: state={:?}", i + 1, ram.get_timing_state());

        // Should remain in idle state
        assert_eq!(ram.get_timing_state(), TimingState::Idle);
    }

    println!("✅ No progression without signals test passed!");
}

/// Test reset functionality
///
/// Note: This test verifies the state machine behavior through direct state manipulation
/// rather than through pin-based triggering. The Intel 4002 implementation processes
/// events through process_event_direct() which doesn't call handle_component_event(),
/// so chip select via pins doesn't work the same way as Intel 4001.
///
/// Address latching happens on Φ1 falling edge (after data is stable).
#[test]
fn test_reset_functionality() {
    println!("=== Testing Reset Functionality ===");

    let mut ram = create_test_ram();

    // Manually transition to AddressPhase and set up some state
    ram.set_state_for_test(Intel400xUnifiedState::AddressPhase);
    set_data_bus(&ram, 0x0);

    // Generate Φ1 rising edge (no latching yet)
    generate_clock_edge(&mut ram, true, false);

    // Generate Φ1 falling edge - address latching happens here
    generate_clock_edge(&mut ram, false, false);

    // Should have latched high nibble
    assert_eq!(ram.get_address_high_nibble(), Some(0x0));
    println!(
        "Before reset: high_nibble={:?}",
        ram.get_address_high_nibble()
    );

    // Assert RESET (active low)
    let reset_pin = ram.get_pin("RESET").unwrap();
    {
        let mut reset_guard = reset_pin.lock().unwrap();
        reset_guard.set_driver(Some("TEST".to_string()), PinValue::Low);
    }
    wait_for_pin_settlement();

    // Update with RESET low - should clear all state
    ram.update();

    // Should have returned to idle state
    assert_eq!(ram.get_timing_state(), TimingState::Idle);
    println!("After reset: state={:?}", ram.get_timing_state());

    // Verify address state is cleared
    assert_eq!(ram.get_address_high_nibble(), None);
    assert_eq!(ram.get_address_low_nibble(), None);
    assert_eq!(ram.get_full_address_ready(), false);

    println!("✅ Reset functionality test passed!");
}

/// Test complete unified state machine progression for all operations
///
/// Note: This test verifies the state machine behavior through direct state manipulation
/// rather than through pin-based triggering. The Intel 4002 implementation processes
/// events through process_event_direct() which doesn't call handle_component_event(),
/// so chip select via pins doesn't work the same way as Intel 4001.
///
/// Address latching happens on Φ1 falling edge (after data is stable).
#[test]
fn test_complete_state_machine_progression() {
    println!("=== Testing Complete Unified State Machine Progression ===");

    let mut ram = create_test_ram();

    // Test 1: RAM Read Operation
    println!("Test 1: RAM Read Operation");
    ram.set_pending_operation(PendingOperation::Read);
    ram.set_state_for_test(Intel400xUnifiedState::AddressPhase);
    set_data_bus(&ram, 0x0);
    generate_clock_edge(&mut ram, true, false); // Φ1 rising (no latching yet)
    generate_clock_edge(&mut ram, false, false); // Φ1 falling - latch high nibble
    set_data_bus(&ram, 0x1);
    generate_clock_edge(&mut ram, true, false); // Φ1 rising (no latching yet)
    generate_clock_edge(&mut ram, false, false); // Φ1 falling - latch low nibble
    clear_data_bus_drivers(&ram);
    std::thread::sleep(std::time::Duration::from_millis(1)); // Wait for latency
    generate_clock_edge(&mut ram, false, true); // Φ2 rising - read data
    generate_clock_edge(&mut ram, false, false); // Φ2 falling - return to idle
    assert_eq!(ram.get_timing_state(), TimingState::Idle);
    println!("✅ RAM Read Operation completed");

    // Test 2: RAM Write Operation
    println!("Test 2: RAM Write Operation");
    ram.set_pending_operation(PendingOperation::Write);
    ram.set_state_for_test(Intel400xUnifiedState::AddressPhase);
    println!(
        "Test 2: After set_state_for_test - nibbles: high={:?}, low={:?}",
        ram.get_address_high_nibble(),
        ram.get_address_low_nibble()
    );
    set_data_bus(&ram, 0x0);
    generate_clock_edge(&mut ram, true, false); // Φ1 rising (no latching yet)
    generate_clock_edge(&mut ram, false, false); // Φ1 falling - latch high nibble
    println!(
        "Test 2: After first Φ1 falling - nibbles: high={:?}, low={:?}",
        ram.get_address_high_nibble(),
        ram.get_address_low_nibble()
    );
    set_data_bus(&ram, 0x2);
    generate_clock_edge(&mut ram, true, false); // Φ1 rising (no latching yet)
    generate_clock_edge(&mut ram, false, false); // Φ1 falling - latch low nibble
    println!(
        "Test 2: After second Φ1 falling - nibbles: high={:?}, low={:?}, full_address_ready={}",
        ram.get_address_high_nibble(),
        ram.get_address_low_nibble(),
        ram.get_full_address_ready()
    );
    set_data_bus(&ram, 0x0F);
    println!("Test 2: Data bus set to 0x0F");
    std::thread::sleep(std::time::Duration::from_millis(1)); // Wait for latency
    println!(
        "Test 2: Before Φ2 rising - state={:?}",
        ram.get_timing_state()
    );
    generate_clock_edge(&mut ram, false, true); // Φ2 rising - write data
    println!(
        "Test 2: After Φ2 rising - state={:?}",
        ram.get_timing_state()
    );
    generate_clock_edge(&mut ram, false, false); // Φ2 falling - return to idle
    println!(
        "Test 2: After Φ2 falling - state={:?}",
        ram.get_timing_state()
    );
    println!(
        "Test 2: RAM[0x02]={:02X}, expected=0x0F",
        ram.read_ram(0x02).unwrap()
    );
    assert_eq!(ram.get_timing_state(), TimingState::Idle);
    assert_eq!(ram.read_ram(0x02).unwrap(), 0x0F);
    println!("✅ RAM Write Operation completed");

    // Test 3: Output Port Operation
    println!("Test 3: Output Port Operation");
    ram.set_pending_operation(PendingOperation::OutputPort);
    ram.set_state_for_test(Intel400xUnifiedState::AddressPhase);
    set_data_bus(&ram, 0x1);
    generate_clock_edge(&mut ram, true, false); // Φ1 rising (no latching yet)
    generate_clock_edge(&mut ram, false, false); // Φ1 falling - latch high nibble
    set_data_bus(&ram, 0x4);
    generate_clock_edge(&mut ram, true, false); // Φ1 rising (no latching yet)
    generate_clock_edge(&mut ram, false, false); // Φ1 falling - latch low nibble
    set_data_bus(&ram, 0x05);
    std::thread::sleep(std::time::Duration::from_millis(1)); // Wait for latency
    generate_clock_edge(&mut ram, false, true); // Φ2 rising - write to output port
    generate_clock_edge(&mut ram, false, false); // Φ2 falling - return to idle
    assert_eq!(ram.get_timing_state(), TimingState::Idle);
    assert_eq!(ram.get_io_port(0).unwrap(), 0x05);
    println!("✅ Output Port Operation completed");

    println!("✅ Complete unified state machine progression test passed!");
}