#include <SPI.h>
#include <SD.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 96
#define SCREEN_HEIGHT 16

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

// ---------------- PINS ----------------
const int SD_CS = 53;
const int CD_PIN = 2;

// Buttons
const int R1 = 23;
const int R2 = 24;
const int R3 = 25;
const int C1 = 26;

// ---------------- FILES ----------------
char files[50][32];
int fileCount = 0;

// ---------------- UI ----------------
int cursor = 0;
int scroll = 0;
int selected = -1;

// ---------------- CARD STATE ----------------
bool lastCardState = false;

// CD is inverted in your module
bool cardInserted() {
  return digitalRead(CD_PIN) == HIGH;
}

// ---------------- OLED ----------------
void msg(const char* text) {
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0, 4);
  display.println(text);
  display.display();
}

void drawMenu() {
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);

  for (int i = 0; i < 2; i++) {
    int idx = scroll + i;
    if (idx >= fileCount) break;

    display.setCursor(0, i * 8);

    if (idx == selected) display.print("*");   // selected
    else if (idx == cursor) display.print(">"); // cursor
    else display.print(" ");

    String name = files[idx];
    if (name.length() > 12) name = name.substring(0, 12);

    display.print(name);
  }

  display.display();
}

// ---------------- SD SCAN ----------------
void scanSD() {
  fileCount = 0;

  File root = SD.open("/");
  if (!root) return;

  while (true) {
    File entry = root.openNextFile();
    if (!entry) break;

    if (!entry.isDirectory()) {
      String name = entry.name();

      if (name.endsWith(".GCO") || name.endsWith(".GCODE")) {
        if (fileCount < 50) {
          name.toCharArray(files[fileCount], 32);
          fileCount++;
        }
      }
    }

    entry.close();
  }

  root.close();
}

// ---------------- BUTTONS ----------------
int readButton() {
  digitalWrite(C1, LOW);
  delayMicroseconds(5);

  if (digitalRead(R1) == LOW) return 1;
  if (digitalRead(R2) == LOW) return 2;
  if (digitalRead(R3) == LOW) return 3;

  return 0;
}

void waitRelease() {
  while (readButton() != 0) delay(10);
}

// ---------------- SETUP ----------------
void setup() {
  Serial.begin(115200);

  pinMode(R1, INPUT_PULLUP);
  pinMode(R2, INPUT_PULLUP);
  pinMode(R3, INPUT_PULLUP);

  pinMode(C1, OUTPUT);
  digitalWrite(C1, HIGH);

  pinMode(CD_PIN, INPUT_PULLUP);

  display.begin(SSD1306_SWITCHCAPVCC, 0x3C);

  lastCardState = cardInserted();

  if (lastCardState) {
    msg("SD inserted");
    SD.begin(SD_CS);
    scanSD();
    delay(1000);
  } else {
    msg("No SD card");
    delay(1000);
  }

  drawMenu();
}

// ---------------- LOOP ----------------
void loop() {

  bool current = cardInserted();

  // ---------------- INSERT EVENT ----------------
  if (current && !lastCardState) {
    msg("Card inserted");
    delay(1000);

    if (SD.begin(SD_CS)) {
      scanSD();
      cursor = 0;
      scroll = 0;
    }

    drawMenu();
  }

  // ---------------- REMOVE EVENT ----------------
  if (!current && lastCardState) {
    msg("Card removed");
    delay(1000);

    fileCount = 0;
    cursor = 0;
    scroll = 0;
    selected = -1;
  }

  lastCardState = current;

  // ---------------- NO CARD ----------------
  if (!current) {
    msg("NO SD CARD");
    delay(200);
    return;
  }

  // ---------------- BUTTONS ----------------
  int btn = readButton();
  if (btn == 0) return;

  if (btn == 1 && cursor > 0) cursor--;
  if (btn == 2 && cursor < fileCount - 1) cursor++;
  if (btn == 3) {
    selected = cursor;

    Serial.print("Selected: ");
    Serial.println(files[selected]);
  }

  if (cursor < scroll) scroll = cursor;
  if (cursor > scroll + 1) scroll = cursor - 1;

  waitRelease();
  drawMenu();
}