#include <stdio.h>
#include <string.h>
#include <windows.h>
//#include "math_graphics.h"
#include <math.h>
#include <setjmp.h>
#include "m_string.h"


enum TokenKind {
	ENDOFINPUT, INTEGER, KOMMA, PLUS, MINUS, MUL, DIV, MODULO, LPAREN, RPAREN, POW, SQRT, SIN, COS, TAN, ATAN, ATAN2, ANS
};


//Definition Token
struct Token {
	TokenKind kind = ENDOFINPUT;
	double floatValue;
	long intValue;
};

//Erkennen ob Leerzeichen, Zeilenumbruch, Tabulator etc. 
bool isWhitespace(char c) {
	if (c == ' ' || c == '\n' || c == '\t' || c == '\r') {
		return true;
	}
	return false;
}

//Wenn Whitsepace weitergehen
void eatWhitespace(String &s) {
	while (isWhitespace(s[0])) {
		advance(s);
	}
}

bool isNumber(char c) {
	if ('0' <= c && c <= '9') {
		return true;
	}
	return false;
}

long parseInteger(String inputString) {
	long integerValue = 0;
	for (int currentPosition = 0; currentPosition < inputString.length; currentPosition++) {
		integerValue = integerValue * 10 + inputString[currentPosition] - '0';
	}
	return integerValue;
}

double parseFloat(String inputString) {
	double floatValue = 0.0;
	int currentPosition = 0;
	for (; currentPosition < inputString.length; currentPosition++) {
		if (inputString[currentPosition] == '.') {
			currentPosition++;
			break;
		}

		floatValue = floatValue * 10.0 + (inputString[currentPosition] - '0');
	}

	double floatValue2 = 0.0;
	for (int currentPosition2 = inputString.length - 1; currentPosition2 >= currentPosition; currentPosition2--) {
		floatValue2 = floatValue2 / 10.0 + (inputString[currentPosition2] - '0');
	}

	return floatValue + (floatValue2 / 10);
}

//Funktion zur Erkennung neuer Token
Token getNextToken(String &inputString) {
	Token token = {}; 

	eatWhitespace(inputString);
	if (!inputString.length) {
		return token;
	}

	if (isNumber(inputString[0])) {
		String start = inputString;
		advance(inputString);

		while (isNumber(inputString[0])) {
			advance(inputString);
		}

		if (inputString[0] == '.') {
			token.kind = KOMMA;
			advance(inputString);

			while (isNumber(inputString[0])) {
				advance(inputString);
			}

			start.length = inputString.data - start.data;
			token.floatValue = parseFloat(start);

		} else {
			start.length = inputString.data - start.data;
			token.kind = INTEGER;
			token.intValue = parseInteger(start);
		}
	//Token für mathematische Operatoren
	//ergänzt werden müssen: "atan2"
	} else if (inputString[0] == '+') {
		token.kind = PLUS;
		advance(inputString);
	} else if (inputString[0] == '-') {
		token.kind = MINUS;
		advance(inputString);
	} else if (inputString[0] == '*') {
		token.kind = MUL;
		advance(inputString);
	} else if (inputString[0] == '/') {
		token.kind = DIV;
		advance(inputString);
	} else if (inputString[0] == '%') {
		token.kind = MODULO;
		advance(inputString);
	} else if (inputString[0] == '(') {
		token.kind = LPAREN;
		advance(inputString);
	} else if (inputString[0] == ')') {
		token.kind = RPAREN;
		advance(inputString);
	} else if (inputString[0] == '^') {
		token.kind = POW;
		advance(inputString);
	} else if (starts_with(inputString, "atan2"_str)) {
		token.kind = ATAN2;
		advance(inputString, 5);
	} else if (starts_with(inputString, "atan"_str)) {
		token.kind = ATAN;
		advance(inputString, 4);
	} else if (starts_with(inputString, "sqrt"_str)) {
		token.kind = SQRT;
		advance(inputString, 4);
	} else if (starts_with(inputString, "sin"_str)) {
		token.kind = SIN;
		advance(inputString, 3);
	} else if (starts_with(inputString, "cos"_str)) {
		token.kind = COS;
		advance(inputString, 3);
	} else if (starts_with(inputString, "tan"_str)) {
		token.kind = TAN;
		advance(inputString, 3);
	} else if (starts_with(inputString, "ans"_str)) {
		token.kind = ANS;
		advance(inputString, 3);
	}
	return token;

}

double parseExpression(String &string);
Token token = {};
double ans = 0;

jmp_buf Rechner;

#define expect(k) if(token.kind != (k)) { printf("Unexpected Token"); exit(0); } token = getNextToken(input);

double parseExpressionOperand(String& input) {
	if (token.kind == INTEGER) {
		long value = token.intValue;
		token = getNextToken(input);
		return value;
	} else if (token.kind == KOMMA) {
		double value = token.floatValue;
		token = getNextToken(input);
		return value;
	} else if (token.kind == LPAREN) {
		token = getNextToken(input);
		double expression = parseExpression(input);
		expect(RPAREN);
		return expression;
	} else if (token.kind == SQRT) {
		token = getNextToken(input);
		return sqrt(parseExpressionOperand(input));
	} else if (token.kind == SIN) {
		token = getNextToken(input);
		return sin(parseExpressionOperand(input));
	} else if (token.kind == COS) {
		token = getNextToken(input);
		return cos(parseExpressionOperand(input));
	} else if (token.kind == TAN) {
		token = getNextToken(input);
		return tan(parseExpressionOperand(input));
	} else if (token.kind == ATAN) {
		token = getNextToken(input);
		return atan(parseExpressionOperand(input));
	} else if (token.kind == ATAN2) {
		printf("Coming soon!");
		return 0;
	} else if (token.kind == ANS) {
		token = getNextToken(input);
		return ans;
	}
	printf("Unexpected Token.\n");
	longjmp(Rechner, 0);
	return 0;
}

double parseExpressionUnary(String& input) {
	if (token.kind == MINUS) {
		token = getNextToken(input);
		return -parseExpressionUnary(input);
	}
	return parseExpressionOperand(input);
}

double parseExpressionPower(String& input) {
	double expression = parseExpressionUnary(input);

	while (token.kind == POW) {
		token = getNextToken(input);
		expression = pow(expression, parseExpressionUnary(input));
	}
	return expression;
}

double parseExpressionMultiplicative(String& input) {
	double expression = parseExpressionPower(input);

	while (token.kind == MUL || token.kind == DIV) {
		if (token.kind == MUL) {
			token = getNextToken(input);
			expression = expression * parseExpressionPower(input);
		} else if (token.kind == DIV) {
			token = getNextToken(input);
			expression = expression / parseExpressionPower(input);
		}
	}
	return expression;
}
double parseExpressionAdditive(String& input) {
	double expression = parseExpressionMultiplicative(input);

	while (token.kind == PLUS || token.kind == MINUS) {
		if (token.kind == PLUS) {
			token = getNextToken(input);
			expression = expression + parseExpressionMultiplicative(input);
		} else if (token.kind == MINUS) {
			token = getNextToken(input);
			expression = expression - parseExpressionMultiplicative(input);
		}
	}
	return expression;
}

double parseExpression(String &input) {
	return parseExpressionAdditive(input);
}

void write_entire_file(const char* filename, String s){

	FILE* file = fopen(filename, "w");
	fwrite(s.data, s.length, 1, file);
	fclose(file);
}

String helpstring = R"(
Taschenrechner --- Help

Operator:
- Addition                  'Ausdruck' + 'Ausdruck'
- Subtraktion               'Ausdruck' - 'Ausdruck'
- Multiplikation            'Ausdruck' * 'Ausdruck'
- Division                  'Ausdruck' / 'Ausdruck'
- Potenzen                  'Ausdruck' ^ 'Ausdruck'

Klammern:
('Ausdruck' + 'Ausdruck') * 'Ausdruck'
('Ausdruck' + 'Ausdruck') * ('Ausdruck' - 'Ausdruck')
'Ausdruck' - (('Ausdruck' + 'Ausdruck') * 'Ausdruck') / 'Ausdruck'

Trigonometrie:
- Wurzel                    sqrt 'Ausdruck' ODER sqrt('Ausdruck')
- Sinus/Cosinus/Tangens     sin/cos/tan 'Ausdruck' ODER sin('Ausdruck')

Letzte Antwort kann mittels 'ans' genutzt werden. Beispiel:
- 4 + 5
  9
- ans * 2
  18

)"_str;

int main() {
	SetConsoleOutputCP(65001);
	write_entire_file("Help.txt", helpstring);


	while (true) {
		setjmp(Rechner);
		printf("Was möchten Sie berechnen? Für Hilfe 'help' eingeben!\n");

		char buffer[1024];
		String input = { 1024, buffer };
		fgets(buffer, 1024, stdin);
		input.length = strlen(buffer);

		if (starts_with(input, "help"_str) || starts_with(input, "Help"_str)) {
			printf("%s", helpstring.data);
			continue;
		}

		token = getNextToken(input);
		ans = parseExpression(input);
		printf("%g\n", ans);
	}

	return 0;
}