/**
 * util.h: Various utility functions.
 *
 * Copyright © 2007 Pippijn van Steenhoven / The Ermyth Team
 * Rights to this code are as documented in doc/pod/gplicense.pod.
 *
 * $Id: util.h,v 1.8 2007/09/22 14:27:26 pippijn dead $
 */

#ifndef UTIL_H
#define UTIL_H

#include <sysconf.h>

#include <climits>
#include <cstddef>
#include <vector>

#include <ermyth/exception.h>

#include <sys/time.h>

/**
 * Mostly the same as std::vector, but erase can reorder
 * the elements, making insert/remove O(1) instead of O(n).
 *
 * NOTE: only some forms of erase are available
 * (Taken from Crossfire TRT http://cf.schmorp.de/)
 */
template<typename T, typename Alloc = std::allocator<T> >
struct unordered_vector : std::vector<T, Alloc>
{
  typedef typename unordered_vector::iterator iterator;

  void erase (unsigned pos)
  {
    if (pos < this->size () - 1)
      (*this)[pos] = (*this)[this->size () - 1];

    this->pop_back ();
  }

  void erase (iterator pos)
  {
    erase ((unsigned)(pos - this->begin ()));
  }

  void insert (T const &val)
  {
    push_back (val);
  }
};

/**
 * The following templates find a sufficiently large integer type to contain
 * the given number of bits.
 *
 * Usage:
 *
 * unsigned_type<16>::type a; // 16-bit unsigned if available (probably unsigned short)
 * signed_type<8>::type a; // 8-bit signed if available (probably char)
 */

// Empty class if everything failed
struct empty_base
{
};

// To allow inheritance from this and get the integer type out
template<typename T>
struct identity
{
  typedef T type;
};

/**
 * The following two templates are a compile-time if-statement.
 */
template<bool Cond, class Then, class Else>
struct If
{
  typedef Then ret;
};

template<class Then, class Else>
struct If<false, Then, Else>
{
  typedef Else ret;
};

// Looks whether the desired type exists
template<typename T, std::size_t bits, typename Else>
struct type_if_size
: If<sizeof (T) * CHAR_BIT >= bits, identity<T>, Else>::ret
{
};

template<std::size_t bits>
struct unsigned_type
: type_if_size<unsigned char, bits,
    type_if_size<unsigned short, bits,
      type_if_size<unsigned int, bits,
        type_if_size<unsigned long, bits,
          empty_base // No such type
        >
      >
    >
  >
{
};

template<std::size_t bits>
struct signed_type
: type_if_size<signed char, bits
  , type_if_size<signed short, bits
    , type_if_size<signed int, bits
      , type_if_size<signed long, bits
        , empty_base // No such type
        >
      >
    >
  >
{
};

// This is a vector that stores each element's index in the object.
// This only works for pointers to objects.
template<class T, unsigned T::*index = &T::index, class Alloc = std::allocator<T *> >
struct indexing_vector : std::vector<T *, Alloc>
{
  typedef typename indexing_vector::size_type size_type;
  typedef typename indexing_vector::iterator iterator;
  
  iterator find (const T *obj)
  {
    return obj->*index
      ? this->begin () + obj->*index - 1
      : this->end ();
  }

  void erase (T *obj)
  {
    unsigned pos = obj->*index;
    obj->*index = 0;

    if (pos < this->size ())
      {
        (*this)[pos - 1] = (*this)[this->size () - 1];
        (*this)[pos - 1]->*index = pos;
      }

    this->pop_back ();
  }

  void insert (T *obj)
  {
    this->push_back (obj);
    obj->*index = this->size ();
  }
};

struct str_hash
{
  std::size_t operator () (char const *s) const
  {
    unsigned long hash = 0;

    // use the one-at-a-time hash function.
    // see http://burtleburtle.net/bob/hash/doobs.html
    while (*s)
      {
        hash += *s++;
        hash += hash << 10;
        hash ^= hash >>  6;
      }

    hash += hash <<  3;
    hash ^= hash >> 11;
    hash += hash << 15;

    return hash;
  }
};

struct str_eq
{
  bool operator () (char const * const s1, char const * const s2) const
  {
    if (s1 == NULL || s2 == NULL)
      throw nullpointer_exception ();
    return !strcmp (s1, s2);
  }
};

struct str_lt
{
  bool operator () (char const * const s1, char const * const s2) const
  {
    if (s1 == NULL || s2 == NULL)
      throw nullpointer_exception ();
    return strcmp (s1, s2) < 0;
  }
};

E int irccasecmp (char const * const s1, char const * const s2);
E int ircncasecmp (char const * const s1, char const * const s2, int maxlen);

struct irccase_lt
{
  bool operator () (char const * const s1, char const * const s2) const
  {
    if (s1 == NULL || s2 == NULL)
      throw nullpointer_exception ();
    return irccasecmp (s1, s2) < 0;
  }
};

typedef double tstamp;

inline tstamp
now ()
{
#ifdef HAVE_GETTIMEOFDAY
  struct timeval tv;

  gettimeofday (&tv, 0);
  return tstamp (tv.tv_sec) + tstamp (tv.tv_usec) * tstamp (1e-6);
#else
  return tstamp (time (NULL));
#endif
}

#if 0
/**
 * Comma delimited output to std::cout
 */

namespace impl
{
  struct C
  {
    template<typename T>
    C operator << (T const &t) const
    {
      std::cout << ", " << t;
      return C();
    }
    
    C operator << (std::ostream &(* const f) (std::ostream &)) const
    {
      std::cout << f;
      return C();
    }
    
    C operator << (std::ios_base &(* const f) (std::ios_base &)) const
    {
      std::cout << f;
      return C();
    }
  };

  enum Del
  {
    del
  };
  
  template<typename T>
  C operator << (Del, T const &t)
  {
    std::cout << t;
    return C();
  }
  
  inline Del
  operator << (Del, std::ostream &(* const f) (std::ostream &))
  {
    std::cout << f;
    return del;
  }
  
  inline Del
  operator << (Del, std::ios_base &(* const f) (std::ios_base &))
  {
    std::cout << f;
    return del;
  }

  // The <<'s taking std::ios_base&(std::ios_base&)'s are for things like std::hex.
  // The <<'s taking std::ostream&(std::ostream&)'s are for things like std::endl.

  inline Del
  operator << (std::ostream &, Del)
  {
    return del;
  }
  // To allow: std::cout << del << 2 << 4
}

using impl::del;
#endif

// Allow pasting things, even if one of the arguments is a macro itself
#define PASTE(A, B)              DOPASTE (A, B)
#define DOPASTE(A, B)            DODOPASTE (A, B)
#define DODOPASTE(A, B)          A ## B

#define PASTE3(A, B, C)          PASTE (PASTE (A, B), C)
#define PASTE4(A, B, C, D)       PASTE (PASTE3 (A, B, C), D)
#define PASTE5(A, B, C, D, E)    PASTE (PASTE4 (A, B, C, D), E)
#define PASTE6(A, B, C, D, E, F) PASTE (PASTE5 (A, B, C, D, E), F)

namespace impl
{
  template<bool>
  struct static_assert;

  template<>
  struct static_assert<true>
  {
  };
}

#define static_assert(cond) ::impl::static_assert<(cond)> PASTE (static_assert_, __LINE__)

E int itoa (uint32_t n, char *buf, int buflen);
E int itoa (uint64_t n, char *buf, int buflen);

inline int
itoa (int32_t n, char *buf, int buflen)
{
  *buf = '-';
  buf += (n < 0);
  uint32_t u = n < 0 ? -n : n;
  return itoa (u, buf, buflen - 1);
}

inline int
itoa (int64_t n, char *buf, int buflen)
{
  *buf = '-';
  buf += (n < 0);
  uint64_t u = n < 0 ? -n : n;
  return itoa (u, buf, buflen - 1);
}

template<typename IntType, int N>
inline int
itoa (IntType n, char (&buf)[N])
{
  return itoa (n, buf, N);
}

#endif