#include <errno.h>
#include <stdio.h>
#include <stdlib.h>

#include "stacks.h"

void add(STACK *st) {
  if ((st->cnt) > 1) {
    (st->cnt)--;
    st->st[(st->cnt) - 1] = st->st[(st->cnt) - 1] + st->st[st->cnt];
  } else {
    fprintf(stderr, "Not enough operands to add\n");
  }
}

void substract(STACK *st) {
  if ((st->cnt) > 1) {
    (st->cnt)--;
    st->st[(st->cnt) - 1] = st->st[(st->cnt) - 1] - st->st[st->cnt];
  } else {
    fprintf(stderr, "Not enough operands to substract\n");
  }
}

void multiply(STACK *st) {
  if ((st->cnt) > 1) {
    (st->cnt)--;
    st->st[(st->cnt) - 1] = st->st[(st->cnt) - 1] * st->st[st->cnt];
  } else {
    fprintf(stderr, "Not enough operands to multiply\n");
  }
}

void divide(STACK *st) {
  if ((st->cnt) > 1) {
    (st->cnt)--;
    st->st[(st->cnt) - 1] = st->st[(st->cnt) - 1] / st->st[st->cnt];
  } else {
    fprintf(stderr, "Not enough operands to divide\n");
  }
}

int parse(char *s, STACK *stack) {
  double operand = 0;
  char *endptr;
  if ((*s == '-') && (*(s + 1) == '\0')) {
    substract(stack);
    return 0;
  } else if (*s == '+') {
    add(stack);
    return 0;
  } else if (*s == '/') {
    if ((stack->st[(stack->cnt) - 1]) == 0) {
      return -2;
    }
    divide(stack);
    return 0;
  } else if (*s == 'x') {
    multiply(stack);
    return 0;
  }
  errno = 0;
  operand = strtod(s, &endptr);
  if (errno != 0 || *endptr != '\0')
    return -1;
  push(stack, operand);
  return 0;
}

int sorting_station(STACK *operands, CHAR_STACK *operators, char *token) {
  int error;
  if (((*token == '-') && (*(token + 1) == '\0')) || (*token == '+') ||
      (*token == 'x') || (*token == '/')) {
    if (char_top(operators) != NULL) {
      switch (*char_top(operators)) {
      case '[':
        char_push(operators, *token);
        break;
      case '+':
      case '-':
        if (*token == '/' || *token == 'x') {
          char_push(operators, *token);
          break;
        }
      case 'x':
      case '/':
        if (*token == '/' || *token == 'x') {
          while (char_top(operators) != NULL && (*char_top(operators) == '/' || *char_top(operators) == 'x')) {
            error = parse(char_top(operators), operands);
            if (error != 0) {
              return error;
            }
            char_pop(operators);
          }
          char_push(operators, *token);
          break;
        } else {
          while (char_top(operators) != NULL && *char_top(operators) != '[') {
            error = parse(char_top(operators), operands);
            if (error != 0) {
              return error;
            }
            char_pop(operators);
          }
          char_push(operators, *token);
          break;
        }
      }
      return (0);
    } else {
    char_push(operators, *token);
    return (0);
  } 
  }

  if (*token == '[') {
    char_push(operators, *token);
    return (0);
  }

  if (*token == ']') {
    while (char_top(operators) != NULL && *char_top(operators) != '[') {
      error = parse(char_top(operators), operands);
      if (error != 0) {
        return error;
      }
      char_pop(operators);
    }
    if (char_top(operators) == NULL) {
      fprintf(stderr, "Opening bracket not found!\n");
      return (-3);
    } else {
      char_pop(operators);
      return (0);
    }
  }

  error = parse(token, operands);
  return (error);
}

int main(int argc, char **argv) {
  STACK *operands = init_stack(argc);
  CHAR_STACK *operators = init_char_stack(argc);

  if (operands == NULL) {
    fprintf(stderr, "Error creating operand stack.\n");
    return (2);
  }
  if (operators == NULL) {
    fprintf(stderr, "Error creating operator stack.\n");
    return (2);
  }
  int error;
  while (*++argv) {
    error = sorting_station(operands, operators, *argv);
    if (error == -1) {
      fprintf(stderr, "Error parsing operand.\n");
      return (1);
    } else if (error == -2) {
      fprintf(stderr, "Division by zero!");
      return (2);
    } else if (error == -3) {
      return (3);
    }
  }

  while (char_top(operators) != NULL) {
    error = parse(char_top(operators), operands);
    if (error == -1) {
      fprintf(stderr, "Error parsing operand.\n");
      return (1);
    } else if (error == -2) {
      fprintf(stderr, "Division by zero!");
      return (2);
    }
    char_pop(operators);
  }

  int i;
  printf("Stack status:\n");
  for (i = (operands->cnt); i > 0; i--)
    printf("%f\n", pop(operands));
  destroy_stack(operands);
  destroy_char_stack(operators);
  return 0;
}