#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <math.h>

typedef struct Stack{ //stack for characters
	double data[255]; //char* array to serve as stack
	int top; //marks where the head is
}stack;

void create(stack * s); //initializes stack
int empty(stack * s); //checks if the stack is empty
int full(stack * s); //checks if the stack is full
double pop(stack * s); //pops a double from the stack
void push(stack * s, double c); //gets a double then places them into the stack
void process(stack* s, char* postfix);
double solve(char c, double x, double y);
double convert(char c); //convert the value from char to double

int main(){
	int choice; //open a file or not
	stack s; //stack for double inputs
	printf("Open a file? 1/0 ");
	scanf("%d", &choice);
	if(choice == 0){
		int count = 1; //to determine if the user will continue giving statements
		char* postfix;
		create(&s);

		while(count != 0){
			printf("Enter postfix: ");
			scanf("%s", postfix);

			process(&s, postfix);

			printf("Continue? 1/0");
			scanf("%d", &count);
		}
	}
	else if(choice == 1){
		char fn[255]; //file name array
		char buffer[255]; //temporary array for reading lines in the text file to be given
		printf("Input file name: ");
		scanf("%s", fn);
		create(&s);
		FILE *fp;
		fp = fopen(fn, "r"); //opens file that contains multiple postfix commands
		while(!(feof(fp))){ //while not end of file, read contents
			FILE* w;
			w = fopen("output.txt", "w"); //creates an empty txt file
			fclose(w);

			fgets(buffer, sizeof(buffer), (FILE*)fp); //gets the current line (aka the postfix command) and adds to buffer
			process(&s, buffer); //gets the file name of the current loop, the stack, the buffer (postfix), and the number of the current loop
		}
		fclose(fp); //closes the postfix txt
	}
	else
		printf("Give a valid choice.");
}

void create(stack * s){
	s -> top = -1; //sets the stack head at -1 thus makes the array inaccessible
}

int empty(stack * s){
	if(s->top==-1)
        return 1; //stack is empty
    return 0; //stack is not empty
}

int full(stack * s){
	if(s->top==254)//since the data array is only 255 big
        return 1;//stack is full
    return 0;
}

double pop(stack * s){
	double x;
    x=s->data[s->top];//gets the value of the data at the current top and assign to x
    s->top=s->top-1; //reduces the current value of top
    return(x);
}

void push(stack * s, double c){
	s->top=s->top+1; //moves the top amount to move array position
    s->data[s->top]=c; //assigns the top to the value of c
}

void process(stack* s, char* postfix){
	//stuff here
	double x, y;
	double total;
	int i;
	FILE* fp;
	fp = fopen("output.txt", "a");
	fprintf(fp, "%s\n", postfix);
	fclose(fp);

	for(i = 0; i < strlen(postfix); i++){
		if(isalnum(postfix[i])){ //checks if the current postfix character is a number or a letter
			push(s, convert(postfix[i])); //pushes to stack the converted value of the operand
		}
		else{ //if the postfix character is an operand
			if(empty(s)==0){ //checks if the stack is empty
				x = pop(s); //pops the value
			}
			else{ //it means there are no operands anymore to compute
				printf("Form invalid.\n");
				exit(0);
			}
			if(empty(s)==0){ //a repetition of the earlier process but assigned to y
				y = pop(s);
			}
			else{
				printf("Form invalid.\n");
				exit(0);
			}

			total = solve(postfix[i], x, y);
			push(s, total);
		}
	}

	fp = fopen("output.txt", "a");
	total = pop(s); //pops the final pushed value
	if(empty(s)==1){ //if no more operands is left in the stack
		fprintf(fp, "Total is %lf\n", total);
	}
	else{ //something is still in the stack
		fprintf(fp, "Form invalid.\n");
		exit(0);
	}
	fclose(fp);
}

double solve(char c, double x, double y){
	FILE* fp;
	fp = fopen("output.txt", "a"); //opens the current loop filename and appends the commands

	char* s;
	switch(c){
		case '+':
			fprintf(fp, "LD %lf\nAD %lf\n", y, x);
			fclose(fp);
			return(y+x);
		break;
		case '-':
			fprintf(fp, "LD %lf\nSB %lf\n", y, x);
			fclose(fp);
			return(y-x);
		break;
		case '*':
			fprintf(fp, "LD %lf\nML %lf\n", y, x);
			fclose(fp);
			return(y*x);
		break;
		case '/':
			fprintf(fp, "LD %lf\nDV %lf\n", y, x);
			fclose(fp);
			return(y/x);
		break;
		case '^':
			fprintf(fp, "LD %lf\nPR %lf\n", x, y);
			fclose(fp);
			return pow(x, y);
		break;
	}
}

double convert(char c){ //converts characters to double values
	switch(c){
		case 'A':
		return 1.0;
		break;
		case 'B':
		return 2.0;
		break;
		case 'C':
		return 3.0;
		break;
		case 'D':
		return 4.0;
		break;
		case 'E':
		return 5.0;
		break;
		case 'F':
		return 6.0;
		break;
		case 'G':
		return 7.0;
		break;
		case 'H':
		return 8.0;
		break;
		case 'I':
		return 9.0;
		break;
		case 'J':
		return 10.0;
		break;
		case 'K':
		return 11.0;
		break;
		case 'L':
		return 12.0;
		break;
		case 'M':
		return 13.0;
		break;
		case 'N':
		return 14.0;
		break;
		case 'O':
		return 15.0;
		break;
		case 'P':
		return 16.0;
		break;
		case 'Q':
		return 17.0;
		break;
		case 'R':
		return 18.0;
		break;
		case 'S':
		return 19.0;
		break;
		case 'T':
		return 20.0;
		break;
		case 'U':
		return 21.0;
		break;
		case 'V':
		return 22.0;
		break;
		case 'W':
		return 23.0;
		break;
		case 'X':
		return 24.0;
		break;
		case 'Y':
		return 25.0;
		break;
		case 'Z':
		return 26.0;
		break;
		case 'a':
		return -1.0;
		break;
		case 'b':
		return -2.0;
		break;
		case 'c':
		return -3.0;
		break;
		case 'd':
		return -4.0;
		break;
		case 'e':
		return -5.0;
		break;
		case 'f':
		return -6.0;
		break;
		case 'g':
		return -7.0;
		break;
		case 'h':
		return -8.0;
		break;
		case 'i':
		return -9.0;
		break;
		case 'j':
		return -10.0;
		break;
		case 'k':
		return -11.0;
		break;
		case 'l':
		return -12.0;
		break;
		case 'm':
		return -13.0;
		break;
		case 'n':
		return -14.0;
		break;
		case 'o':
		return -15.0;
		break;
		case 'p':
		return -16.0;
		break;
		case 'q':
		return -17.0;
		break;
		case 'r':
		return -18.0;
		break;
		case 's':
		return -19.0;
		break;
		case 't':
		return -20.0;
		break;
		case 'u':
		return -21.0;
		break;
		case 'v':
		return -22.0;
		break;
		case 'w':
		return -23.0;
		break;
		case 'x':
		return -24.0;
		break;
		case 'y':
		return -25.0;
		break;
		case 'z':
		return -26.0;
		break;
		case '1':
		return 1.0;
		break;
		case '2':
		return 2.0;
		break;
		case '3':
		return 3.0;
		break;
		case '4':
		return 4.0;
		break;
		case '5':
		return 5.0;
		break;
		case '6':
		return 6.0;
		break;
		case '7':
		return 7.0;
		break;
		case '8':
		return 8.0;
		break;
		case '9':
		return 9.0;
		break;
		case '0':
		return 0.0;
	}
}