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# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.

from __future__ import absolute_import, print_function, unicode_literals

r'''This module contains code for managing clobbering of the tree.'''

import errno
import os
import subprocess
import sys

from mozfile.mozfile import remove as mozfileremove
from textwrap import TextWrapper


CLOBBER_MESSAGE = ''.join([TextWrapper().fill(line) + '\n' for line in
                           '''
The CLOBBER file has been updated, indicating that an incremental build since \
your last build will probably not work. A full/clobber build is required.

The reason for the clobber is:

{clobber_reason}

Clobbering can be performed automatically. However, we didn't automatically \
clobber this time because:

{no_reason}

The easiest and fastest way to clobber is to run:

 $ mach clobber

If you know this clobber doesn't apply to you or you're feeling lucky -- \
Well, are ya? -- you can ignore this clobber requirement by running:

 $ touch {clobber_file}
'''.splitlines()])


class Clobberer(object):
    def __init__(self, topsrcdir, topobjdir, substs=None):
        """Create a new object to manage clobbering the tree.

        It is bound to a top source directory and to a specific object
        directory.
        """
        assert os.path.isabs(topsrcdir)
        assert os.path.isabs(topobjdir)

        self.topsrcdir = os.path.normpath(topsrcdir)
        self.topobjdir = os.path.normpath(topobjdir)
        self.src_clobber = os.path.join(topsrcdir, 'CLOBBER')
        self.obj_clobber = os.path.join(topobjdir, 'CLOBBER')
        if substs:
            self.substs = substs
        else:
            self.substs = dict()

        # Try looking for mozilla/CLOBBER, for comm-central
        if not os.path.isfile(self.src_clobber):
            self.src_clobber = os.path.join(topsrcdir, 'mozilla', 'CLOBBER')

        assert os.path.isfile(self.src_clobber)

    def clobber_needed(self):
        """Returns a bool indicating whether a tree clobber is required."""

        # No object directory clobber file means we're good.
        if not os.path.exists(self.obj_clobber):
            return False

        # Object directory clobber older than current is fine.
        if os.path.getmtime(self.src_clobber) <= \
                os.path.getmtime(self.obj_clobber):

            return False

        return True

    def clobber_cause(self):
        """Obtain the cause why a clobber is required.

        This reads the cause from the CLOBBER file.

        This returns a list of lines describing why the clobber was required.
        Each line is stripped of leading and trailing whitespace.
        """
        with open(self.src_clobber, 'rt') as fh:
            lines = [l.strip() for l in fh.readlines()]
            return [l for l in lines if l and not l.startswith('#')]

    def have_winrm(self):
        # `winrm -h` should print 'winrm version ...' and exit 1
        try:
            p = subprocess.Popen(['winrm.exe', '-h'],
                                 stdout=subprocess.PIPE,
                                 stderr=subprocess.STDOUT)
            return p.wait() == 1 and p.stdout.read().startswith('winrm')
        except Exception:
            return False

    def collect_subdirs(self, root, exclude):
        """Gathers a list of subdirectories excluding specified items."""
        paths = []
        try:
            for p in os.listdir(root):
                if p not in exclude:
                    paths.append(os.path.join(root, p))
        except OSError as e:
            if e.errno != errno.ENOENT:
                raise

        return paths

    def delete_dirs(self, root, paths_to_delete):
        """Deletes the given subdirectories in an optimal way."""
        procs = []
        for p in sorted(paths_to_delete):
            path = os.path.join(root, p)
            if sys.platform.startswith('win') and self.have_winrm() and os.path.isdir(path):
                procs.append(subprocess.Popen(['winrm', '-rf', path]))
            else:
                # We use mozfile because it is faster than shutil.rmtree().
                mozfileremove(path)

        for p in procs:
            p.wait()

    def remove_objdir(self, full=True):
        """Remove the object directory.

        ``full`` controls whether to fully delete the objdir. If False,
        some directories (e.g. Visual Studio Project Files) will not be
        deleted.
        """
        # Determine where cargo build artifacts are stored
        RUST_TARGET_VARS = ('RUST_HOST_TARGET', 'RUST_TARGET')
        rust_targets = set([self.substs[x] for x in RUST_TARGET_VARS if x in self.substs])
        rust_build_kind = 'release'
        if self.substs.get('MOZ_DEBUG_RUST'):
            rust_build_kind = 'debug'

        # Top-level files and directories to not clobber by default.
        no_clobber = {
            '.mozbuild',
            'msvc',
        }

        # Hold off on clobbering cargo build artifacts
        no_clobber |= rust_targets

        if full:
            paths = [self.topobjdir]
        else:
            paths = self.collect_subdirs(self.topobjdir, no_clobber)

        self.delete_dirs(self.topobjdir, paths)

        # Now handle cargo's build artifacts and skip removing the incremental
        # compilation cache.
        for target in rust_targets:
            cargo_path = os.path.join(self.topobjdir, target, rust_build_kind)
            paths = self.collect_subdirs(cargo_path, {'incremental', })
            self.delete_dirs(cargo_path, paths)

    def maybe_do_clobber(self, cwd, allow_auto=False, fh=sys.stderr):
        """Perform a clobber if it is required. Maybe.

        This is the API the build system invokes to determine if a clobber
        is needed and to automatically perform that clobber if we can.

        This returns a tuple of (bool, bool, str). The elements are:

          - Whether a clobber was/is required.
          - Whether a clobber was performed.
          - The reason why the clobber failed or could not be performed. This
            will be None if no clobber is required or if we clobbered without
            error.
        """
        assert cwd
        cwd = os.path.normpath(cwd)

        if not self.clobber_needed():
            print('Clobber not needed.', file=fh)
            return False, False, None

        # So a clobber is needed. We only perform a clobber if we are
        # allowed to perform an automatic clobber (off by default) and if the
        # current directory is not under the object directory. The latter is
        # because operating systems, filesystems, and shell can throw fits
        # if the current working directory is deleted from under you. While it
        # can work in some scenarios, we take the conservative approach and
        # never try.
        if not allow_auto:
            return True, False, \
               self._message('Automatic clobbering is not enabled\n'
                             '  (add "mk_add_options AUTOCLOBBER=1" to your '
                             'mozconfig).')

        if cwd.startswith(self.topobjdir) and cwd != self.topobjdir:
            return True, False, self._message(
                'Cannot clobber while the shell is inside the object directory.')

        objdir = self.topobjdir.encode('utf-8', 'replace')
        print('Automatically clobbering %s' % objdir, file=fh)
        try:
            self.remove_objdir(False)
            print('Successfully completed auto clobber.', file=fh)
            return True, True, None
        except (IOError) as error:
            return True, False, self._message(
                'Error when automatically clobbering: ' + str(error))

    def _message(self, reason):
        lines = [' ' + line for line in self.clobber_cause()]

        return CLOBBER_MESSAGE.format(clobber_reason='\n'.join(lines),
                                      no_reason='  ' + reason, clobber_file=self.obj_clobber)