"""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."""

# created 2000/04/03, Greg Ward (extracted from util.py)

__revision__ = "$Id$"

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" % 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    """Return true if 'target' is out-of-date with respect to any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       assume that 'target' is out-of-date (this is handy in "dry-run"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 ()


# XXX this isn't used anywhere, and worse, it has the same name as a method
# in Command with subtly different semantics.  (This one just has one
# source -> one dest; that one has many sources -> one dest.)  Nuke it?
def make_file (src, dst, func, args,
               verbose=0, update_message=None, noupdate_message=None):
    """Makes 'dst' from 'src' (both filenames) by calling 'func' with
       'args', but only if it needs to: i.e. if 'dst' does not exist or
       'src' is newer than 'dst'."""

    if newer (src, dst):
        if verbose and update_message:
            print update_message
        apply (func, args)
    else:
        if verbose and noupdate_message:
            print noupdate_message

# make_file ()