"""Various utility functions."""

from collections import namedtuple, Counter
from os.path import commonprefix

__unittest = True

_MAX_LENGTH = 80
_PLACEHOLDER_LEN = 12
_MIN_BEGIN_LEN = 5
_MIN_END_LEN = 5
_MIN_COMMON_LEN = 5
_MIN_DIFF_LEN = _MAX_LENGTH - \
 (_MIN_BEGIN_LEN + _PLACEHOLDER_LEN + _MIN_COMMON_LEN +
 _PLACEHOLDER_LEN + _MIN_END_LEN)
assert _MIN_DIFF_LEN >= 0

def _shorten(s, prefixlen, suffixlen):
 skip = len(s) - prefixlen - suffixlen
 if skip > _PLACEHOLDER_LEN:
 s = '%s[%d chars]%s' % (s[:prefixlen], skip, s[len(s) - suffixlen:])
 return s

def _common_shorten_repr(*args):
 args = tuple(map(safe_repr, args))
 maxlen = max(map(len, args))
 if maxlen <= _MAX_LENGTH:
 return args

 prefix = commonprefix(args)
 prefixlen = len(prefix)

 common_len = _MAX_LENGTH - \
 (maxlen - prefixlen + _MIN_BEGIN_LEN + _PLACEHOLDER_LEN)
 if common_len > _MIN_COMMON_LEN:
 assert _MIN_BEGIN_LEN + _PLACEHOLDER_LEN + _MIN_COMMON_LEN + \
 (maxlen - prefixlen) < _MAX_LENGTH
 prefix = _shorten(prefix, _MIN_BEGIN_LEN, common_len)
 return tuple(prefix + s[prefixlen:] for s in args)

 prefix = _shorten(prefix, _MIN_BEGIN_LEN, _MIN_COMMON_LEN)
 return tuple(prefix + _shorten(s[prefixlen:], _MIN_DIFF_LEN, _MIN_END_LEN)
 for s in args)

def safe_repr(obj, short=False):
 try:
 result = repr(obj)
 except Exception:
 result = object.__repr__(obj)
 if not short or len(result) < _MAX_LENGTH:
 return result
 return result[:_MAX_LENGTH] + ' [truncated]...'

def strclass(cls):
 return "%s.%s" % (cls.__module__, cls.__qualname__)

def sorted_list_difference(expected, actual):
 """Finds elements in only one or the other of two, sorted input lists.

 Returns a two-element tuple of lists. The first list contains those
 elements in the "expected" list but not in the "actual" list, and the
 second contains those elements in the "actual" list but not in the
 "expected" list. Duplicate elements in either input list are ignored.
 """
 i = j = 0
 missing = []
 unexpected = []
 while True:
 try:
 e = expected[i]
 a = actual[j]
 if e < a:
 missing.append(e)
 i += 1
 while expected[i] == e:
 i += 1
 elif e > a:
 unexpected.append(a)
 j += 1
 while actual[j] == a:
 j += 1
 else:
 i += 1
 try:
 while expected[i] == e:
 i += 1
 finally:
 j += 1
 while actual[j] == a:
 j += 1
 except IndexError:
 missing.extend(expected[i:])
 unexpected.extend(actual[j:])
 break
 return missing, unexpected


def unorderable_list_difference(expected, actual):
 """Same behavior as sorted_list_difference but
 for lists of unorderable items (like dicts).

 As it does a linear search per item (remove) it
 has O(n*n) performance."""
 missing = []
 while expected:
 item = expected.pop()
 try:
 actual.remove(item)
 except ValueError:
 missing.append(item)

 # anything left in actual is unexpected
 return missing, actual

def three_way_cmp(x, y):
 """Return -1 if x < y, 0 if x == y and 1 if x > y"""
 return (x > y) - (x < y)

_Mismatch = namedtuple('Mismatch', 'actual expected value')

def _count_diff_all_purpose(actual, expected):
 'Returns list of (cnt_act, cnt_exp, elem) triples where the counts differ'
 # elements need not be hashable
 s, t = list(actual), list(expected)
 m, n = len(s), len(t)
 NULL = object()
 result = []
 for i, elem in enumerate(s):
 if elem is NULL:
 continue
 cnt_s = cnt_t = 0
 for j in range(i, m):
 if s[j] == elem:
 cnt_s += 1
 s[j] = NULL
 for j, other_elem in enumerate(t):
 if other_elem == elem:
 cnt_t += 1
 t[j] = NULL
 if cnt_s != cnt_t:
 diff = _Mismatch(cnt_s, cnt_t, elem)
 result.append(diff)

 for i, elem in enumerate(t):
 if elem is NULL:
 continue
 cnt_t = 0
 for j in range(i, n):
 if t[j] == elem:
 cnt_t += 1
 t[j] = NULL
 diff = _Mismatch(0, cnt_t, elem)
 result.append(diff)
 return result

def _count_diff_hashable(actual, expected):
 'Returns list of (cnt_act, cnt_exp, elem) triples where the counts differ'
 # elements must be hashable
 s, t = Counter(actual), Counter(expected)
 result = []
 for elem, cnt_s in s.items():
 cnt_t = t.get(elem, 0)
 if cnt_s != cnt_t:
 diff = _Mismatch(cnt_s, cnt_t, elem)
 result.append(diff)
 for elem, cnt_t in t.items():
 if elem not in s:
 diff = _Mismatch(0, cnt_t, elem)
 result.append(diff)
 return result