#include <MCUFRIEND_kbv.h>
#include <Adafruit_GFX.h>
#include <TouchScreen.h>
#include <avr/wdt.h>

#define MINPRESSURE 200
#define MAXPRESSURE 1000

const int XP = 8, XM = A2, YP = A3, YM = 9;
const int TS_LEFT = 125, TS_RT = 920, TS_TOP = 948, TS_BOT = 97;

TouchScreen ts = TouchScreen(XP, YP, XM, YM, 300);
MCUFRIEND_kbv tft;

const char* button_labels[5][5] = {
  {"7", "8", "9", "/", "C"},
  {"4", "5", "6", "*", "<-"},
  {"1", "2", "3", "-", "("},
  {"0", ".", "=", "+", ")"},
  {"sqrt", "x^2", "1/x", "%", "+/-"}
};

#define ROWS 5
#define COLS 5
int pixel_x, pixel_y;

#define STACK_MAX 12
float numStack[STACK_MAX];
char opStack[STACK_MAX];
int ns = 0, os = 0;

#define INPUT_MAX 40  // auch für längere serielle Eingaben
char input[INPUT_MAX+1] = "0";
bool errorFlag = false;

void serialPrintInput() {
  Serial.print("Display: ");
  Serial.println(input);
}

// ---------- Sicherheitsprüfungen ----------
bool isSafeInput(const char* in) {
  int len = strlen(in);
  if (len == 0) return false;
  if (strchr("+-*/%", in[len-1])) return false;
  if (strchr("+*/%)", in[0])) return false;
  for (int i = 1; i < len; i++) {
    if (strchr("+-*/%", in[i]) && strchr("+-*/%", in[i-1])) return false;
  }
  int bal = 0;
  for (int i = 0; i < len; i++) {
    if (in[i] == '(') bal++;
    if (in[i] == ')') bal--;
    if (bal < 0) return false;
    if (in[i] == '(' && in[i+1] == ')') return false;
  }
  if (bal != 0) return false;
  for (int i = 1; i < len; i++) {
    if (in[i] == ')' && strchr("+-*/%(", in[i-1])) return false;
  }
  for (int i = 1; i < len; i++) {
    if (in[i] == '.' && (strchr("+-*/%()", in[i-1]) || in[i-1] == 0)) return false;
  }
  return true;
}

// ---------- Parser ----------
int precedence(char op) {
  if (op == '+' || op == '-') return 1;
  if (op == '*' || op == '/' || op == '%') return 2;
  return 0;
}
bool applyOp() {
  if (ns < 2) return false;
  float b = numStack[--ns], a = numStack[--ns];
  char op = opStack[--os];
  switch(op) {
    case '+': numStack[ns++] = a + b; break;
    case '-': numStack[ns++] = a - b; break;
    case '*': numStack[ns++] = a * b; break;
    case '/': if (b == 0) return false; numStack[ns++] = a / b; break;
    case '%': if (b == 0) return false; numStack[ns++] = fmod(a, b); break;
  }
  return true;
}
float evalExpr(const char* expr, bool& error) {
  ns = os = 0;
  int i = 0;
  while (expr[i]) {
    if (expr[i] == ' ') { i++; continue; }
    // Sonderfunktionen für serielle Eingabe: sqrt(), sq(), inv()
    if (!strncmp(&expr[i], "sqrt(", 5)) {
      i += 5;
      int start = i;
      int par = 1;
      while (expr[i] && par > 0) {
        if (expr[i] == '(') par++;
        if (expr[i] == ')') par--;
        i++;
      }
      char inner[INPUT_MAX+1]; strncpy(inner, &expr[start], i-start-1); inner[i-start-1] = 0;
      bool err = false;
      float x = evalExpr(inner, err);
      if (err || x < 0) { error = true; return 0; }
      if (ns >= STACK_MAX) { error = true; return 0; }
      numStack[ns++] = sqrt(x);
      continue;
    }
    if (!strncmp(&expr[i], "sq(", 3)) {
      i += 3;
      int start = i;
      int par = 1;
      while (expr[i] && par > 0) {
        if (expr[i] == '(') par++;
        if (expr[i] == ')') par--;
        i++;
      }
      char inner[INPUT_MAX+1]; strncpy(inner, &expr[start], i-start-1); inner[i-start-1] = 0;
      bool err = false;
      float x = evalExpr(inner, err);
      if (err) { error = true; return 0; }
      if (ns >= STACK_MAX) { error = true; return 0; }
      numStack[ns++] = x * x;
      continue;
    }
    if (!strncmp(&expr[i], "inv(", 4)) {
      i += 4;
      int start = i;
      int par = 1;
      while (expr[i] && par > 0) {
        if (expr[i] == '(') par++;
        if (expr[i] == ')') par--;
        i++;
      }
      char inner[INPUT_MAX+1]; strncpy(inner, &expr[start], i-start-1); inner[i-start-1] = 0;
      bool err = false;
      float x = evalExpr(inner, err);
      if (err || x == 0) { error = true; return 0; }
      if (ns >= STACK_MAX) { error = true; return 0; }
      numStack[ns++] = 1.0 / x;
      continue;
    }
    if (isdigit(expr[i]) || expr[i] == '.' || (expr[i] == '-' && (i == 0 || expr[i-1] == '('))) {
      char buf[16]; int bi=0;
      if (expr[i] == '-') buf[bi++] = expr[i++];
      while (isdigit(expr[i]) || expr[i] == '.') buf[bi++] = expr[i++];
      buf[bi]=0;
      if (ns >= STACK_MAX) { error = true; return 0; }
      numStack[ns++] = atof(buf);
    }
    else if (expr[i] == '(') { opStack[os++] = '('; i++; }
    else if (expr[i] == ')') {
      while (os > 0 && opStack[os-1] != '(') {
        if (!applyOp()) { error = true; return 0; }
      }
      if (os == 0) { error = true; return 0; }
      os--; i++;
    }
    else if (strchr("+-*/%", expr[i])) {
      char currOp = expr[i];
      while (os > 0 && precedence(opStack[os-1]) >= precedence(currOp)) {
        if (!applyOp()) { error = true; return 0; }
      }
      opStack[os++] = currOp;
      i++;
    }
    else { error = true; return 0; }
  }
  while (os > 0) {
    if (!applyOp()) { error = true; return 0; }
  }
  if (ns != 1) { error = true; return 0; }
  return numStack[0];
}

// ---------- Anzeige & Eingabe ----------
#define BTN_W  62
#define BTN_H  56
#define BTN_SX  3
#define BTN_SY  8
#define BTN_X0  5
#define BTN_Y0  140

void drawButtons() {
  tft.setTextSize(2);
  for (int row = 0; row < ROWS; row++) {
    for (int col = 0; col < COLS; col++) {
      int x = BTN_X0 + col * (BTN_W + BTN_SX);
      int y = BTN_Y0 + row * (BTN_H + BTN_SY);
      tft.fillRoundRect(x, y, BTN_W, BTN_H, 14, 0xC618);
      tft.drawRoundRect(x, y, BTN_W, BTN_H, 14, TFT_BLACK);
      int labelLen = strlen(button_labels[row][col]);
      int fontW = 12;
      int fontH = 16;
      int xOffset = BTN_W/2 - (labelLen*fontW)/2;
      int yOffset = BTN_H/2 - fontH/2;
      tft.setTextColor(TFT_BLACK);
      tft.setCursor(x + xOffset, y + yOffset);
      tft.print(button_labels[row][col]);
    }
  }
  tft.setTextSize(2);
}
void handleTouch(int px, int py) {
  for (int row = 0; row < ROWS; row++)
    for (int col = 0; col < COLS; col++) {
      int x = BTN_X0 + col * (BTN_W + BTN_SX);
      int y = BTN_Y0 + row * (BTN_H + BTN_SY);
      if (px >= x && px < x + BTN_W && py >= y && py < y + BTN_H) {
        handleButton(button_labels[row][col]);
        serialPrintInput();
      }
    }
}
void drawScreen() {
  tft.fillScreen(TFT_WHITE);
  tft.fillRoundRect(10, 40, 300, 65, 8, 0xFFFF);
  tft.drawRoundRect(10, 40, 300, 65, 8, 0x0000);
  drawButtons();
}
void showInput() {
  tft.fillRoundRect(15, 50, 280, 55, 6, 0xFFFF);
  tft.setTextColor(TFT_BLACK);
  tft.setTextSize(3);
  tft.setCursor(22, 67);
  int len = strlen(input);
  if (len > 12) tft.print("..." + String(&input[len-12]));
  else tft.print(input);
  serialPrintInput();
}
void resetCalc() {
  strcpy(input, "0");
  errorFlag = false;
  serialPrintInput();
}

void setup() {
  Serial.begin(115200);
  wdt_enable(WDTO_2S);
  uint16_t ID = tft.readID();
  tft.begin(ID);
  tft.setRotation(0);
  drawScreen();
  resetCalc();
  showInput();
  Serial.println("Touch-Taschenrechner bereit! Eingabe per Touch ODER Serial Monitor.");
  Serial.println("Beispiele:");
  Serial.println("1+2*3  -> 7");
  Serial.println("sqrt(9) -> 3");
  Serial.println("inv(2) -> 0.5");
  Serial.println("sq(5)  -> 25");
  Serial.println("C      -> Reset");
}

void handleButton(const char* btn) {
  int len = strlen(input);
  if (errorFlag && strcmp(btn,"C") && !(isdigit(btn[0]) && strlen(btn)==1)) return;
  if (!strcmp(btn,"C")) {
    resetCalc();
  }
  else if (!strcmp(btn,"<-")) {
    if (len > 1) { input[len-1]=0; }
    else strcpy(input, "0");
  }
  else if (!strcmp(btn,"=")) {
    if (!isSafeInput(input)) {
      strcpy(input, "ERR");
      errorFlag = true;
      Serial.println("ERR");
      return;
    }
    bool error = false;
    float res = evalExpr(input, error);
    if (error || isinf(res) || isnan(res) || fabs(res) > 999999999) {
      strcpy(input, "ERR");
      errorFlag = true;
      Serial.println("ERR");
      return;
    }
    if (fabs(res - (long)res) < 1e-6) sprintf(input, "%ld", (long)res);
    else {
      dtostrf(res, 1, 6, input);
      char* p = input+strlen(input)-1;
      while (*p == '0' && p > input && *(p-1) != '.') *p-- = 0;
      if (*p == '.') *p = 0;
    }
    Serial.println(input);
  }
  else if (!strcmp(btn,"+/-")) {
    if (strcmp(input, "0") && strcmp(input, "ERR")) {
      if (input[0]=='-') memmove(input, input+1, strlen(input));
      else if (len < INPUT_MAX) { memmove(input+1, input, len+1); input[0]='-'; }
    }
  }
  else if (!strcmp(btn,"sqrt")) {
    float val = atof(input);
    if (val<0) { strcpy(input, "ERR"); errorFlag=true; Serial.println("ERR"); return; }
    val = sqrt(val);
    if (fabs(val - (long)val) < 1e-6) sprintf(input, "%ld", (long)val);
    else dtostrf(val, 1, 6, input);
    Serial.println(input);
  }
  else if (!strcmp(btn,"x^2")) {
    float val = atof(input); val *= val;
    if (fabs(val - (long)val) < 1e-6) sprintf(input, "%ld", (long)val);
    else dtostrf(val, 1, 6, input);
    Serial.println(input);
  }
  else if (!strcmp(btn,"1/x")) {
    float val = atof(input);
    if (val==0) { strcpy(input, "ERR"); errorFlag=true; Serial.println("ERR"); return; }
    val = 1.0/val;
    if (fabs(val - (long)val) < 1e-6) sprintf(input, "%ld", (long)val);
    else dtostrf(val, 1, 6, input);
    Serial.println(input);
  }
  else if (!strcmp(btn,"%")) {
    float val = atof(input);
    val = val / 100.0;
    if (fabs(val - (long)val) < 1e-6) sprintf(input, "%ld", (long)val);
    else dtostrf(val, 1, 6, input);
    Serial.println(input);
  }
  else if (!strcmp(btn,".") && !strchr(input, '.') && len < INPUT_MAX-1) {
    input[len] = '.'; input[len+1]=0;
  }
  else if (strlen(btn)==1 && isdigit(btn[0])) {
    if (!strcmp(input,"0") || !strcmp(input,"ERR")) { input[0]=btn[0]; input[1]=0; }
    else if (len < INPUT_MAX-1) { input[len]=btn[0]; input[len+1]=0; }
  }
  else if (strchr("+-*/()", btn[0]) && len < INPUT_MAX-1) {
    char last = (len>0) ? input[len-1] : 0;
    if ((strchr("+-*/%", last) && btn[0] != '(' && btn[0] != ')') ||
        (len == 0 && btn[0]!='(' && btn[0]!='-') ||
        (last == '(' && strchr("*/%)", btn[0]))) {
      return;
    }
    input[len]=btn[0]; input[len+1]=0;
  }
}

bool Touch_getXY(void)
{
  TSPoint p = ts.getPoint();
  pinMode(YP, OUTPUT);
  pinMode(XM, OUTPUT);
  digitalWrite(YP, HIGH);
  digitalWrite(XM, HIGH);
  bool pressed = (p.z > MINPRESSURE && p.z < MAXPRESSURE);
  if (pressed) {
    pixel_x = map(p.x, TS_LEFT, TS_RT, 0, tft.width());
    pixel_y = map(p.y, TS_TOP, TS_BOT, 0, tft.height());
  }
  return pressed;
}

// ---- Serieller Interpreter ----
void interpretSerial(char* buf) {
  // Remove newline
  int l = strlen(buf);
  while (l > 0 && (buf[l-1]=='\n'||buf[l-1]=='\r')) buf[--l]=0;

  if (l==0) return;
  if (!strcmp(buf, "C")) { resetCalc(); showInput(); return; }
  if (!strcmp(buf, "exit")) { asm volatile ("jmp 0"); return; }

  if (!isSafeInput(buf)) {
    strcpy(input, "ERR"); errorFlag = true;
    showInput();
    Serial.println("ERR");
    return;
  }
  bool error = false;
  float res = evalExpr(buf, error);
  if (error || isinf(res) || isnan(res) || fabs(res) > 999999999) {
    strcpy(input, "ERR"); errorFlag = true;
    showInput();
    Serial.println("ERR");
    return;
  }
  // Ausgabeformat wie im Taschenrechner
  if (fabs(res - (long)res) < 1e-6)
    sprintf(input, "%ld", (long)res);
  else {
    dtostrf(res, 1, 6, input);
    char* p = input+strlen(input)-1;
    while (*p == '0' && p > input && *(p-1) != '.') *p-- = 0;
        if (*p == '.') *p = 0;
  }
  showInput();
  Serial.println(input);
}

void loop() {
  wdt_reset();
  static bool prevTouch = false;
  bool currTouch = Touch_getXY();
  if (prevTouch && !currTouch) {
    handleTouch(pixel_x, pixel_y);
    showInput();
  }
  prevTouch = currTouch;

  // Serielle Eingabe verarbeiten
  static char serBuf[INPUT_MAX + 1];
  static uint8_t serIdx = 0;
  while (Serial.available()) {
    char c = Serial.read();
    if (c == '\r' || c == '\n') {
      serBuf[serIdx] = 0;
      if (serIdx > 0) {
        interpretSerial(serBuf);
        serIdx = 0;
      }
    } else if (serIdx < INPUT_MAX && (isprint(c) || c == '\t')) {
      serBuf[serIdx++] = c;
    }
  }
}