#include <Arduino.h>
#include <SoftwareSerial.h>
#include "lin_frame.h"

#define IR_ARDUINO_PIN PIN_PA0 // Digital pin 10
#define LED_PIN        PIN_PA7 // Digital pin 3
#define RPI_POWER_PIN  PIN_PA2 // GPIO 16 of the RPi is connected to PA2 of the ATtiny

#define RX_PIN         PIN_PB2 // Digital pin 2
#define TX_PIN         PIN_PB0 // Digital pin 0 (Unused dummy pin or LIN TX)
#define FAULT_PIN      PIN_PB1 // Digital pin 1
#define CS_PIN         PIN_PB3 // Digital pin 11

#define RTI_TX_PIN     PIN_PA5 // Digital pin 5

#define SYN_FIELD 0x55
#define SWM_ID 0x20

SoftwareSerial LINBusSerial(RX_PIN, TX_PIN);

void rti_write_byte(uint8_t data) {
  // Disable interrupts to ensure precise bit-banging timing
  uint8_t oldSREG = SREG;
  cli();

  // Start bit (LOW)
  digitalWrite(RTI_TX_PIN, LOW);
  delayMicroseconds(417); // 1 / 2400 baud ≈ 416.67 us

  // 8 Data bits (LSB first)
  for (uint8_t i = 0; i < 8; i++) {
    if (data & (1 << i)) {
      digitalWrite(RTI_TX_PIN, HIGH);
    } else {
      digitalWrite(RTI_TX_PIN, LOW);
    }
    delayMicroseconds(417);
  }

  // Stop bit (HIGH)
  digitalWrite(RTI_TX_PIN, HIGH);
  delayMicroseconds(417);

  // Restore interrupts
  SREG = oldSREG;
}

// RC-6 timing constants
// 1 time unit (1t) = 444us
static const uint16_t RC6_T = 444;

// Mark = LOW on wire (simulating TSOP receiving an IR burst)
void sendMark(uint16_t us) {
  digitalWrite(IR_ARDUINO_PIN, LOW);
  delayMicroseconds(us);
}

// Space = HIGH on wire (simulating TSOP idle)
void sendSpace(uint16_t us) {
  digitalWrite(IR_ARDUINO_PIN, HIGH);
  delayMicroseconds(us);
}

// Send a single RC-6 bit using Manchester encoding
void sendRC6Bit(uint8_t bit, uint8_t width) {
  if (bit) {
    sendMark(RC6_T * width);
    sendSpace(RC6_T * width);
  } else {
    sendSpace(RC6_T * width);
    sendMark(RC6_T * width);
  }
}

// Send RC-6 Mode 6A (MCE) frame
void sendRC6_MCE(uint32_t data, uint8_t toggle) {
  // Disable interrupts to ensure precise IR timing
  noInterrupts();

  // Leader: 6t mark + 2t space
  sendMark(RC6_T * 6);
  sendSpace(RC6_T * 2);

  // Start bit: always 1
  sendRC6Bit(1, 1);

  // Mode bits: 1, 1, 0 (mode 6)
  sendRC6Bit(1, 1);
  sendRC6Bit(1, 1);
  sendRC6Bit(0, 1);

  // Toggle bit (double width = 2t per half-bit)
  sendRC6Bit(toggle & 1, 2);

  // 32 data bits, MSB first
  for (int i = 31; i >= 0; i--) {
    sendRC6Bit((data >> i) & 1, 1);
  }

  // Final return to idle state (HIGH)
  sendSpace(1000); 

  // Re-enable interrupts
  interrupts();
  
  // Wait to let receiver process
  delay(40); 
}

uint32_t get_mce_code(uint8_t button) {
  switch (button) {
    case 1: return 0x800f041e; // UP
    case 2: return 0x800f041f; // DOWN
    case 3: return 0x800f0420; // LEFT
    case 4: return 0x800f0421; // RIGHT
    case 5: return 0x800f0422; // ENTER / OK
    case 6: return 0x800f0423; // BACK
    case 7: return 0x800f0410; // Volume Up (Shutdown)
    case 9: return 0x800f0411; // Volume Down (Sleep)
    default: return 0;
  }
}

void send_ir_for_button(uint8_t button, uint8_t toggle) {
  uint32_t code = get_mce_code(button);
  if (code == 0) return;
  
  digitalWrite(LED_PIN, HIGH); // Turn debug LED ON
  sendRC6_MCE(code, toggle);
  digitalWrite(LED_PIN, LOW);  // Turn debug LED OFF
}

byte b, n;
LinFrame frame;

unsigned long last_frame_time = 0;
uint8_t current_button = 0;
uint8_t toggle_bit = 0;
unsigned long last_ir_send_time = 0;
unsigned long last_lin_activity_time = 0;
bool is_car_on = false;

// RTI Screen variables
bool screen_open = true; // Screen should open at startup
unsigned long last_rti_send_time = 0;
uint8_t rti_byte_index = 0;

// Debouncing variables for combinations
bool combination_active = false;
uint8_t pending_button = 0;
unsigned long pending_button_time = 0;
bool button_triggered = false;

// RPi Power control variables and functions
bool power_button_active = false;
unsigned long power_button_start_time = 0;

void trigger_power_button() {
  if (!power_button_active) {
    pinMode(RPI_POWER_PIN, OUTPUT);
    digitalWrite(RPI_POWER_PIN, LOW);
    power_button_active = true;
    power_button_start_time = millis();
  }
}

void update_power_button() {
  if (power_button_active && (millis() - power_button_start_time >= 150)) {
    pinMode(RPI_POWER_PIN, INPUT);
    power_button_active = false;
  }
}

void process_button_state(uint8_t active_button) {
  unsigned long now = millis();
  
  if (active_button != 0) {
    if (active_button >= 8) {
      // Combinations trigger immediately without delay
      if (current_button != active_button) {
        current_button = active_button;
        pending_button = 0;
        button_triggered = true;
        
        if (current_button == 8) {
          screen_open = !screen_open;
          rti_byte_index = 0; // Reset byte index to send new sequence immediately
        } else if (current_button == 9) {
          trigger_power_button();
        }
      }
    } else {
      // Single buttons: delay by 80ms to check if a combination is being pressed
      if (pending_button != active_button) {
        pending_button = active_button;
        pending_button_time = now;
        button_triggered = false;
      } else if (!button_triggered) {
        if (now - pending_button_time >= 80) {
          current_button = active_button;
          button_triggered = true;
          toggle_bit ^= 1;
          send_ir_for_button(current_button, toggle_bit);
          last_ir_send_time = now;
        }
      } else {
        // Button was already triggered and is being held down
        if (now - last_ir_send_time >= 250) {
          send_ir_for_button(current_button, toggle_bit);
          last_ir_send_time = now;
        }
      }
    }
  } else {
    // Idle state
    current_button = 0;
    pending_button = 0;
    button_triggered = false;
  }
  
  last_frame_time = now;
}

void handle_frame() {
  if (frame.get_byte(0) != SWM_ID)
    return;

  if (!frame.isValid())
    return;

  // Extract the data bytes
  // SWM button frame has 4 data bytes
  uint8_t d0 = frame.get_byte(1);
  uint8_t d1 = frame.get_byte(2);

  bool enter_pressed = (d1 & 0x08) != 0;
  bool back_pressed = (d1 & 0x01) != 0;
  bool right_pressed = (d0 & 0x08) != 0;

  uint8_t active_button = 0;
  
  if (back_pressed && enter_pressed) {
    active_button = 8; // Special combination: BACK + ENTER (Toggle Screen)
    combination_active = true;
  } else if (right_pressed && enter_pressed) {
    active_button = 9; // Special combination: RIGHT + ENTER (Sleep Raspberry)
    combination_active = true;
  } else if (combination_active) {
    // A combination was active, but it's no longer detected as a combination.
    // If any buttons are still pressed, ignore them to prevent false single button triggering.
    if (enter_pressed || back_pressed || right_pressed || (d0 & 0x01) || (d0 & 0x02) || (d0 & 0x04)) {
      active_button = 0; // Ignore
    } else {
      combination_active = false; // All buttons released, clear flag
      active_button = 0;
    }
  } else {
    // Normal single button decoding
    if (d0 & 0x01) active_button = 1;      // UP
    else if (d0 & 0x02) active_button = 2; // DOWN
    else if (d0 & 0x04) active_button = 3; // LEFT
    else if (d0 & 0x08) active_button = 4; // RIGHT
    else if (d1 & 0x08) active_button = 5; // ENTER / OK
    else if (d1 & 0x01) active_button = 6; // BACK
  }

  process_button_state(active_button);
}

void setup() {
  pinMode(IR_ARDUINO_PIN, OUTPUT);
  digitalWrite(IR_ARDUINO_PIN, HIGH); // Idle state (HIGH)

  pinMode(LED_PIN, OUTPUT);
  digitalWrite(LED_PIN, LOW); // LED OFF

  // Configure RPi power pin (High-Z input initially)
  pinMode(RPI_POWER_PIN, INPUT);

  // Configure RTI TX pin
  pinMode(RTI_TX_PIN, OUTPUT);
  digitalWrite(RTI_TX_PIN, HIGH); // Serial idle is HIGH

  // Enable MCP2004
  pinMode(CS_PIN, OUTPUT);
  digitalWrite(CS_PIN, HIGH);

  pinMode(FAULT_PIN, OUTPUT);
  digitalWrite(FAULT_PIN, HIGH);

  LINBusSerial.begin(9600);

  // No timer initialization needed for bit-banging

  frame = LinFrame();
  last_frame_time = millis();
  last_lin_activity_time = millis();
  last_rti_send_time = millis();
}

void loop() {
  update_power_button();

  if (LINBusSerial.available()) {
    last_lin_activity_time = millis();
    if (!is_car_on) {
      is_car_on = true;
      screen_open = true; // Automatically open screen when car turns back on
    }
    b = LINBusSerial.read();
    n = frame.num_bytes();

    if (b == SYN_FIELD && n > 2 && frame.get_byte(n - 1) == 0) {
      frame.pop_byte();
      handle_frame();
      frame.reset();
    } else if (n == LinFrame::kMaxBytes) {
      frame.reset();
    } else {
      frame.append_byte(b);
    }
  }

  // Timeout: if no LIN frames received for 200ms, assume no button is pressed
  if (millis() - last_frame_time > 200) {
    if (pending_button == 0) {
      current_button = 0;
      button_triggered = false;
    }
  }

  // Car off detection: if no LIN activity for 5 seconds, send Volume Up to trigger shutdown
  if (is_car_on && (millis() - last_lin_activity_time > 5000)) {
    is_car_on = false;
    screen_open = false; // Close screen when car is off
    for (int i = 0; i < 3; i++) {
      send_ir_for_button(7, i & 1);
      delay(100);
    }
  }

  // Send RTI screen serial command byte every 100ms (non-blocking)
  unsigned long now = millis();
  if (now - last_rti_send_time >= 100) {
    last_rti_send_time = now;
    
    if (screen_open) {
      uint8_t byte_to_send = 0;
      // ON sequence: 0x4C (NTSC), 0x2F (max brightness), 0x83 (execute)
      if (rti_byte_index == 0) byte_to_send = 0x4C;
      else if (rti_byte_index == 1) byte_to_send = 0x2F;
      else byte_to_send = 0x83;
      
      rti_write_byte(byte_to_send);
      rti_byte_index = (rti_byte_index + 1) % 3;
    } else {
      // Stay completely silent on serial when screen is closed to let it retract/close
      rti_byte_index = 0;
    }
  }
}