#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include "calculator.h"

int precedence(char c){
    if (c == 's' || c == 'c' || c == 'l' || c == '^') return 3;
    if (c == '*' || c == '/') return 2;
    if (c == '+' || c == '-') return 1;
    return 0;
}

int is_operator(char c){
    if (c == '+' || c == '-' || c == '*' || c == '/' || c == '^')
        return 1;
    return 0;
}

void infix_to_postfix(const char *infix, char *postfix){
    char stack[MAX];
    int top = -1;
    int i = 0, k = 0;

    while (infix[i] != '\0') {

        if ((infix[i] >= '0' && infix[i] <= '9') || infix[i] == '.'){
            postfix[k++] = infix[i++];
        }
        else if (infix[i] == ' '){
            postfix[k++] = ' ';
            i++;
        }
        else if (strncmp(&infix[i], "sin", 3) == 0){
            stack[++top] = 's';
            i += 3;
        }
        else if (strncmp(&infix[i], "cos", 3) == 0){
            stack[++top] = 'c';
            i += 3;
        }
        else if (strncmp(&infix[i], "log", 3) == 0){
            stack[++top] = 'l';
            i += 3;
        }
        else if (infix[i] == '('){
            stack[++top] = '(';
            i++;
        }
        else if (infix[i] == ')'){
            while (top >= 0 && stack[top] != '('){
                postfix[k++] = ' ';
                postfix[k++] = stack[top--];
         }
            top--;
            if (top >= 0 && (stack[top] == 's' || stack[top] == 'c' || stack[top] == 'l')){
                postfix[k++] = ' ';
                postfix[k++] = stack[top--];
         }
            i++;
        }
        else if (is_operator(infix[i])){
            postfix[k++] = ' ';
            while (top >= 0 && precedence(stack[top]) >= precedence(infix[i])){
                postfix[k++] = stack[top--];
                postfix[k++] = ' ';
            }
            stack[++top] = infix[i++];
        }
        else {
            i++;
        }
    }

    while (top >= 0) {
        postfix[k++] = ' ';
        postfix[k++] = stack[top--];
    }

    postfix[k] = '\0';
}

double evaluate_postfix(const char *postfix) {
    double stack[MAX];
    int top = -1;
    int i = 0;
    char num[MAX];

    while (postfix[i] != '\0') {

        if (postfix[i] == ' ') {
            i++;
            continue;
        }

        if ((postfix[i] >= '0' && postfix[i] <= '9') || postfix[i] == '.') {
            int j = 0;
            while ((postfix[i] >= '0' && postfix[i] <= '9') || postfix[i] == '.') {
                num[j++] = postfix[i++];
            }
            num[j] = '\0';
            stack[++top] = atof(num);
        }
        else {
            if (postfix[i] == 's') {
                stack[top] = sin(stack[top]);
            }
            else if (postfix[i] == 'c') {
                stack[top] = cos(stack[top]);
            }
            else if (postfix[i] == 'l') {
                stack[top] = log(stack[top]);
            }
            else if (postfix[i] == '^'){
                stack[top] = stack[top] * stack[top];
         }
         else{
               double b = stack[top--];
               double a = stack[top--];

               if (postfix[i] == '+') stack[++top] = a + b;
               if (postfix[i] == '-') stack[++top] = a - b;
               if (postfix[i] == '*') stack[++top] = a * b;
               if (postfix[i] == '/') stack[++top] = a / b;
         }
         i++;
      }
   }
    return stack[top];
}