// Auto_Seat
// EEPROM-backed automatic seat controller.
#include <EEPROM.h>

#define seatRelayD8 8
#define seatRelayD9 9
#define parkingPin A0
#define ignitionPin 7

const uint16_t SEAT_HARD_LIMIT_UP_MS = 6000;
const int PARKING_ON_THRESHOLD = 950;
const int PARKING_OFF_THRESHOLD = 940;
const int DOWN_SPEED_NUM = 11;
const int DOWN_SPEED_DEN = 10;
const unsigned long DRIVE_CONFIRM_MS = 80UL;
const unsigned long PARK_CONFIRM_MS = 250UL;
const int EEPROM_MAGIC_ADDR = 0;
const byte EEPROM_MAGIC_VALUE = 0x64;
const int EEPROM_SEAT_POSITION_ADDR = 2;

boolean ignitionState = LOW;
boolean parkingState = LOW;
boolean confirmedDriveMode = LOW;
boolean pendingDriveMode = LOW;
int parkingRawValue = 0;
uint16_t storedSeatPositionMs = 0;
long currentPosMs = 0;
long targetPosMs = 0;
long downSpeedRemainder = 0;
unsigned long lastTime = 0;
unsigned long pendingDriveModeStartTime = 0;
int seatAction = 0;

void setup() {
  pinMode(parkingPin, INPUT);
  pinMode(ignitionPin, INPUT);
  pinMode(seatRelayD8, OUTPUT);
  pinMode(seatRelayD9, OUTPUT);
  applySeatAction(0);
  loadSettings();
  measurement();
  confirmedDriveMode = getRawDriveMode();
  pendingDriveMode = confirmedDriveMode;
  targetPosMs = getTargetForConfirmedMode();
  lastTime = millis();
}

void loop() {
  measurement();
  unsigned long now = millis();
  unsigned long deltaTime = now - lastTime;
  lastTime = now;
  updateConfirmedDriveMode(now);
  targetPosMs = getTargetForConfirmedMode();
  updateMovement(deltaTime);
  applySeatAction(seatAction);
}

void measurement() {
  ignitionState = digitalRead(ignitionPin);
  parkingRawValue = analogRead(parkingPin);
  if (parkingState == LOW && parkingRawValue >= PARKING_ON_THRESHOLD) parkingState = HIGH;
  else if (parkingState == HIGH && parkingRawValue <= PARKING_OFF_THRESHOLD) parkingState = LOW;
}

boolean getRawDriveMode() { return ignitionState == HIGH && parkingState == LOW; }
long getTargetForConfirmedMode() { return confirmedDriveMode == HIGH ? storedSeatPositionMs : 0; }

void updateConfirmedDriveMode(unsigned long now) {
  boolean rawDriveMode = getRawDriveMode();
  if (rawDriveMode != pendingDriveMode) {
    pendingDriveMode = rawDriveMode;
    pendingDriveModeStartTime = now;
  }
  unsigned long confirmMs = pendingDriveMode == HIGH ? DRIVE_CONFIRM_MS : PARK_CONFIRM_MS;
  if (pendingDriveMode != confirmedDriveMode && now - pendingDriveModeStartTime >= confirmMs) {
    confirmedDriveMode = pendingDriveMode;
  }
}

void updateMovement(unsigned long deltaTime) {
  if (currentPosMs < targetPosMs) {
    seatAction = 1;
    currentPosMs += deltaTime;
    if (currentPosMs >= targetPosMs) { currentPosMs = targetPosMs; seatAction = 0; }
  } else if (currentPosMs > targetPosMs) {
    seatAction = -1;
    long scaled = deltaTime * DOWN_SPEED_NUM + downSpeedRemainder;
    currentPosMs -= scaled / DOWN_SPEED_DEN;
    downSpeedRemainder = scaled % DOWN_SPEED_DEN;
    if (currentPosMs <= targetPosMs) { currentPosMs = targetPosMs; downSpeedRemainder = 0; seatAction = 0; }
  } else {
    seatAction = 0;
  }
}

void loadSettings() {
  if (EEPROM.read(EEPROM_MAGIC_ADDR) != EEPROM_MAGIC_VALUE) {
    EEPROM.update(EEPROM_MAGIC_ADDR, EEPROM_MAGIC_VALUE);
    writeUint16(EEPROM_SEAT_POSITION_ADDR, SEAT_HARD_LIMIT_UP_MS);
  }
  storedSeatPositionMs = readUint16(EEPROM_SEAT_POSITION_ADDR);
  if (storedSeatPositionMs > SEAT_HARD_LIMIT_UP_MS) {
    storedSeatPositionMs = SEAT_HARD_LIMIT_UP_MS;
    writeUint16(EEPROM_SEAT_POSITION_ADDR, storedSeatPositionMs);
  }
}

uint16_t readUint16(int addr) { return (uint16_t)EEPROM.read(addr) | ((uint16_t)EEPROM.read(addr + 1) << 8); }
void writeUint16(int addr, uint16_t value) { EEPROM.update(addr, value & 0xFF); EEPROM.update(addr + 1, (value >> 8) & 0xFF); }
void setRelay(int relayPin, boolean state) { digitalWrite(relayPin, state ? LOW : HIGH); }
void applySeatAction(int action) {
  if (action == 1) { setRelay(seatRelayD8, 1); setRelay(seatRelayD9, 0); }
  else if (action == -1) { setRelay(seatRelayD8, 0); setRelay(seatRelayD9, 1); }
  else { setRelay(seatRelayD8, 0); setRelay(seatRelayD9, 0); }
}