import os

from django.apps import apps
from django.contrib.staticfiles.finders import get_finders
from django.contrib.staticfiles.storage import staticfiles_storage
from django.core.checks import Tags
from django.core.files.storage import FileSystemStorage
from django.core.management.base import BaseCommand, CommandError
from django.core.management.color import no_style
from django.utils.functional import cached_property


class Command(BaseCommand):
    """
    Copies or symlinks static files from different locations to the
    settings.STATIC_ROOT.
    """
    help = "Collect static files in a single location."
    requires_system_checks = [Tags.staticfiles]

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.copied_files = []
        self.symlinked_files = []
        self.unmodified_files = []
        self.post_processed_files = []
        self.storage = staticfiles_storage
        self.style = no_style()

    @cached_property
    def local(self):
        try:
            self.storage.path('')
        except NotImplementedError:
            return False
        return True

    def add_arguments(self, parser):
        parser.add_argument(
            '--noinput', '--no-input', action='store_false', dest='interactive',
            help="Do NOT prompt the user for input of any kind.",
        )
        parser.add_argument(
            '--no-post-process', action='store_false', dest='post_process',
            help="Do NOT post process collected files.",
        )
        parser.add_argument(
            '-i', '--ignore', action='append', default=[],
            dest='ignore_patterns', metavar='PATTERN',
            help="Ignore files or directories matching this glob-style "
                 "pattern. Use multiple times to ignore more.",
        )
        parser.add_argument(
            '-n', '--dry-run', action='store_true',
            help="Do everything except modify the filesystem.",
        )
        parser.add_argument(
            '-c', '--clear', action='store_true',
            help="Clear the existing files using the storage "
                 "before trying to copy or link the original file.",
        )
        parser.add_argument(
            '-l', '--link', action='store_true',
            help="Create a symbolic link to each file instead of copying.",
        )
        parser.add_argument(
            '--no-default-ignore', action='store_false', dest='use_default_ignore_patterns',
            help="Don't ignore the common private glob-style patterns (defaults to 'CVS', '.*' and '*~').",
        )

    def set_options(self, **options):
        """
        Set instance variables based on an options dict
        """
        self.interactive = options['interactive']
        self.verbosity = options['verbosity']
        self.symlink = options['link']
        self.clear = options['clear']
        self.dry_run = options['dry_run']
        ignore_patterns = options['ignore_patterns']
        if options['use_default_ignore_patterns']:
            ignore_patterns += apps.get_app_config('staticfiles').ignore_patterns
        self.ignore_patterns = list({os.path.normpath(p) for p in ignore_patterns})
        self.post_process = options['post_process']

    def collect(self):
        """
        Perform the bulk of the work of collectstatic.

        Split off from handle() to facilitate testing.
        """
        if self.symlink and not self.local:
            raise CommandError("Can't symlink to a remote destination.")

        if self.clear:
            self.clear_dir('')

        if self.symlink:
            handler = self.link_file
        else:
            handler = self.copy_file

        found_files = {}
        for finder in get_finders():
            for path, storage in finder.list(self.ignore_patterns):
                # Prefix the relative path if the source storage contains it
                if getattr(storage, 'prefix', None):
                    prefixed_path = os.path.join(storage.prefix, path)
                else:
                    prefixed_path = path

                if prefixed_path not in found_files:
                    found_files[prefixed_path] = (storage, path)
                    handler(path, prefixed_path, storage)
                else:
                    self.log(
                        "Found another file with the destination path '%s'. It "
                        "will be ignored since only the first encountered file "
                        "is collected. If this is not what you want, make sure "
                        "every static file has a unique path." % prefixed_path,
                        level=1,
                    )

        # Storage backends may define a post_process() method.
        if self.post_process and hasattr(self.storage, 'post_process'):
            processor = self.storage.post_process(found_files,
                                                  dry_run=self.dry_run)
            for original_path, processed_path, processed in processor:
                if isinstance(processed, Exception):
                    self.stderr.write("Post-processing '%s' failed!" % original_path)
                    # Add a blank line before the traceback, otherwise it's
                    # too easy to miss the relevant part of the error message.
                    self.stderr.write()
                    raise processed
                if processed:
                    self.log("Post-processed '%s' as '%s'" %
                             (original_path, processed_path), level=2)
                    self.post_processed_files.append(original_path)
                else:
                    self.log("Skipped post-processing '%s'" % original_path)

        return {
            'modified': self.copied_files + self.symlinked_files,
            'unmodified': self.unmodified_files,
            'post_processed': self.post_processed_files,
        }

    def handle(self, **options):
        self.set_options(**options)
        message = ['\n']
        if self.dry_run:
            message.append(
                'You have activated the --dry-run option so no files will be modified.\n\n'
            )

        message.append(
            'You have requested to collect static files at the destination\n'
            'location as specified in your settings'
        )

        if self.is_local_storage() and self.storage.location:
            destination_path = self.storage.location
            message.append(':\n\n    %s\n\n' % destination_path)
            should_warn_user = (
                self.storage.exists(destination_path) and
                any(self.storage.listdir(destination_path))
            )
        else:
            destination_path = None
            message.append('.\n\n')
            # Destination files existence not checked; play it safe and warn.
            should_warn_user = True

        if self.interactive and should_warn_user:
            if self.clear:
                message.append('This will DELETE ALL FILES in this location!\n')
            else:
                message.append('This will overwrite existing files!\n')

            message.append(
                'Are you sure you want to do this?\n\n'
                "Type 'yes' to continue, or 'no' to cancel: "
            )
            if input(''.join(message)) != 'yes':
                raise CommandError("Collecting static files cancelled.")

        collected = self.collect()

        if self.verbosity >= 1:
            modified_count = len(collected['modified'])
            unmodified_count = len(collected['unmodified'])
            post_processed_count = len(collected['post_processed'])
            return (
                "\n%(modified_count)s %(identifier)s %(action)s"
                "%(destination)s%(unmodified)s%(post_processed)s."
            ) % {
                'modified_count': modified_count,
                'identifier': 'static file' + ('' if modified_count == 1 else 's'),
                'action': 'symlinked' if self.symlink else 'copied',
                'destination': (" to '%s'" % destination_path if destination_path else ''),
                'unmodified': (', %s unmodified' % unmodified_count if collected['unmodified'] else ''),
                'post_processed': (collected['post_processed'] and
                                   ', %s post-processed'
                                   % post_processed_count or ''),
            }

    def log(self, msg, level=2):
        """
        Small log helper
        """
        if self.verbosity >= level:
            self.stdout.write(msg)

    def is_local_storage(self):
        return isinstance(self.storage, FileSystemStorage)

    def clear_dir(self, path):
        """
        Delete the given relative path using the destination storage backend.
        """
        if not self.storage.exists(path):
            return

        dirs, files = self.storage.listdir(path)
        for f in files:
            fpath = os.path.join(path, f)
            if self.dry_run:
                self.log("Pretending to delete '%s'" % fpath, level=1)
            else:
                self.log("Deleting '%s'" % fpath, level=1)
                try:
                    full_path = self.storage.path(fpath)
                except NotImplementedError:
                    self.storage.delete(fpath)
                else:
                    if not os.path.exists(full_path) and os.path.lexists(full_path):
                        # Delete broken symlinks
                        os.unlink(full_path)
                    else:
                        self.storage.delete(fpath)
        for d in dirs:
            self.clear_dir(os.path.join(path, d))

    def delete_file(self, path, prefixed_path, source_storage):
        """
        Check if the target file should be deleted if it already exists.
        """
        if self.storage.exists(prefixed_path):
            try:
                # When was the target file modified last time?
                target_last_modified = self.storage.get_modified_time(prefixed_path)
            except (OSError, NotImplementedError, AttributeError):
                # The storage doesn't support get_modified_time() or failed
                pass
            else:
                try:
                    # When was the source file modified last time?
                    source_last_modified = source_storage.get_modified_time(path)
                except (OSError, NotImplementedError, AttributeError):
                    pass
                else:
                    # The full path of the target file
                    if self.local:
                        full_path = self.storage.path(prefixed_path)
                        # If it's --link mode and the path isn't a link (i.e.
                        # the previous collectstatic wasn't with --link) or if
                        # it's non-link mode and the path is a link (i.e. the
                        # previous collectstatic was with --link), the old
                        # links/files must be deleted so it's not safe to skip
                        # unmodified files.
                        can_skip_unmodified_files = not (self.symlink ^ os.path.islink(full_path))
                    else:
                        # In remote storages, skipping is only based on the
                        # modified times since symlinks aren't relevant.
                        can_skip_unmodified_files = True
                    # Avoid sub-second precision (see #14665, #19540)
                    file_is_unmodified = (
                        target_last_modified.replace(microsecond=0) >=
                        source_last_modified.replace(microsecond=0)
                    )
                    if file_is_unmodified and can_skip_unmodified_files:
                        if prefixed_path not in self.unmodified_files:
                            self.unmodified_files.append(prefixed_path)
                        self.log("Skipping '%s' (not modified)" % path)
                        return False
            # Then delete the existing file if really needed
            if self.dry_run:
                self.log("Pretending to delete '%s'" % path)
            else:
                self.log("Deleting '%s'" % path)
                self.storage.delete(prefixed_path)
        return True

    def link_file(self, path, prefixed_path, source_storage):
        """
        Attempt to link ``path``
        """
        # Skip this file if it was already copied earlier
        if prefixed_path in self.symlinked_files:
            return self.log("Skipping '%s' (already linked earlier)" % path)
        # Delete the target file if needed or break
        if not self.delete_file(path, prefixed_path, source_storage):
            return
        # The full path of the source file
        source_path = source_storage.path(path)
        # Finally link the file
        if self.dry_run:
            self.log("Pretending to link '%s'" % source_path, level=1)
        else:
            self.log("Linking '%s'" % source_path, level=2)
            full_path = self.storage.path(prefixed_path)
            os.makedirs(os.path.dirname(full_path), exist_ok=True)
            try:
                if os.path.lexists(full_path):
                    os.unlink(full_path)
                os.symlink(source_path, full_path)
            except AttributeError:
                import platform
                raise CommandError("Symlinking is not supported by Python %s." %
                                   platform.python_version())
            except NotImplementedError:
                import platform
                raise CommandError("Symlinking is not supported in this "
                                   "platform (%s)." % platform.platform())
            except OSError as e:
                raise CommandError(e)
        if prefixed_path not in self.symlinked_files:
            self.symlinked_files.append(prefixed_path)

    def copy_file(self, path, prefixed_path, source_storage):
        """
        Attempt to copy ``path`` with storage
        """
        # Skip this file if it was already copied earlier
        if prefixed_path in self.copied_files:
            return self.log("Skipping '%s' (already copied earlier)" % path)
        # Delete the target file if needed or break
        if not self.delete_file(path, prefixed_path, source_storage):
            return
        # The full path of the source file
        source_path = source_storage.path(path)
        # Finally start copying
        if self.dry_run:
            self.log("Pretending to copy '%s'" % source_path, level=1)
        else:
            self.log("Copying '%s'" % source_path, level=2)
            with source_storage.open(path) as source_file:
                self.storage.save(prefixed_path, source_file)
        self.copied_files.append(prefixed_path)
