#pragma once
#include "types.h"

constexpr size_t strlen(const char *str) {
  int len = 0;
  while (str[len])
    ++len;
  return len;
}

/* reverse:  reverse string s in place */
constexpr void reverse(char s[]) {
  int i, j;
  char c;

  for (i = 0, j = strlen(s) - 1; i < j; i++, j--) {
    c = s[i];
    s[i] = s[j];
    s[j] = c;
  }
}

/* itoa:  convert n to characters in s */
template <int base = 10> constexpr void itoa(int n, char s[]) {
  int i, sign;

  if ((sign = n) < 0) /* record sign */
    n = -n;           /* make n positive */

  i = 0;
  do { /* generate digits in reverse order */
    s[i++] = "0123456789abcdef"[n % base]; /* get next digit */
  } while ((n /= base) > 0);               /* delete it */

  if (sign < 0)
    s[i++] = '-';

  s[i] = '\0';

  reverse(s);
}

class String {
public:
  class Iterator {
    friend class String;

  public:
    char next() { return p->buffer[pos++]; }
    operator bool() const { return (pos < p->m_length); }

  private:
    Iterator(const String *s) : p(s) {}

    size_t pos = 0;
    const String *p;
  };

  friend class Iterator;

  String(const char *d) : buffer{d}, m_length{strlen(d)} {}
  String(const char *d, size_t l) : buffer{d}, m_length{l} {}

  Iterator begin() const { return Iterator(this); }

private:
  const char *const buffer;
  const size_t m_length;
};