"""distutils.dep_util

Utility functions for simple, timestamp-based dependency of files
and groups of files; also, function based entirely on such
timestamp dependency analysis."""

import os
from distutils.errors import DistutilsFileError


def newer (source, target):
 """Return true if 'source' exists and is more recently modified than
 'target', or if 'source' exists and 'target' doesn't. Return false if
 both exist and 'target' is the same age or younger than 'source'.
 Raise DistutilsFileError if 'source' does not exist.
 """
 if not os.path.exists(source):
 raise DistutilsFileError("file '%s' does not exist" %
 os.path.abspath(source))
 if not os.path.exists(target):
 return 1

 from stat import ST_MTIME
 mtime1 = os.stat(source)[ST_MTIME]
 mtime2 = os.stat(target)[ST_MTIME]

 return mtime1 > mtime2

# newer ()


def newer_pairwise (sources, targets):
 """Walk two filename lists in parallel, testing if each source is newer
 than its corresponding target. Return a pair of lists (sources,
 targets) where source is newer than target, according to the semantics
 of 'newer()'.
 """
 if len(sources) != len(targets):
 raise ValueError("'sources' and 'targets' must be same length")

 # build a pair of lists (sources, targets) where source is newer
 n_sources = []
 n_targets = []
 for i in range(len(sources)):
 if newer(sources[i], targets[i]):
 n_sources.append(sources[i])
 n_targets.append(targets[i])

 return (n_sources, n_targets)

# newer_pairwise ()


def newer_group (sources, target, missing='error'):
 """Return true if 'target' is out-of-date with respect to any file
 listed in 'sources'. In other words, if 'target' exists and is newer
 than every file in 'sources', return false; otherwise return true.
 'missing' controls what we do when a source file is missing; the
 default ("error") is to blow up with an OSError from inside 'stat()';
 if it is "ignore", we silently drop any missing source files; if it is
 "newer", any missing source files make us assume that 'target' is
 out-of-date (this is handy in "dry-run" mode: it'll make you pretend to
 carry out commands that wouldn't work because inputs are missing, but
 that doesn't matter because you're not actually going to run the
 commands).
 """
 # If the target doesn't even exist, then it's definitely out-of-date.
 if not os.path.exists(target):
 return 1

 # Otherwise we have to find out the hard way: if *any* source file
 # is more recent than 'target', then 'target' is out-of-date and
 # we can immediately return true. If we fall through to the end
 # of the loop, then 'target' is up-to-date and we return false.
 from stat import ST_MTIME
 target_mtime = os.stat(target)[ST_MTIME]
 for source in sources:
 if not os.path.exists(source):
 if missing == 'error': # blow up when we stat() the file
 pass
 elif missing == 'ignore': # missing source dropped from
 continue # target's dependency list
 elif missing == 'newer': # missing source means target is
 return 1 # out-of-date

 source_mtime = os.stat(source)[ST_MTIME]
 if source_mtime > target_mtime:
 return 1
 else:
 return 0

# newer_group ()