#include "lib/lib.h"
#include "lib/vec.h"
#include <ctype.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>

DECL_VEC(CharVec, char);

int priority(char x) {
    switch (x) {
    case '(':
        return 0;
        break;
    case '+':
    case '-':
        return 1;
    case '*':
    case '/':
        return 2;
    }
    return 0;
}

CharVec readStdinToNewline() {
    CharVec cvec = CharVec_new(2);
    int ch;
    while (EOF != (ch = fgetc(stdin)) && ch != '\n') {
        CharVec_push(&cvec, ch);
    }
    return cvec;
}

int main() {
    print_header();
    printf("Enter the Infix Expression:\n");
    CharVec stack = CharVec_new(2);
    CharVec input = readStdinToNewline();
    printf("The Postfix expression:\n ");
    while (input.elem_count != 0) {
        char ch = CharVec_first(&input);
        if (ch == ' ') {
            continue;
        } else if (isalnum(ch)) {
            printf("%c ", ch);
        } else if (ch == '(') {
            CharVec_push(&stack, ch);
        } else if (ch == ')') {
            char x;
            while ((x = CharVec_pop(&stack)) != '(') {
                printf("%c ", x);
            }
        } else {
            while (stack.elem_count != 0 && priority(*CharVec_peek(&stack)) >= priority(ch))
                printf("%c ", CharVec_pop(&stack));
            CharVec_push(&stack, ch);
        }
    }

    while (stack.elem_count != 0) {
        printf("%c ", CharVec_pop(&stack));
    }
    printf("\nEnd of Program\n");

    return EXIT_SUCCESS;
}