import os
import shutil
import dotbot
import dotbot.util


class Link(dotbot.Plugin):
    '''
    Symbolically links dotfiles.
    '''

    _directive = 'link'

    def handle(self, directive, links, dry_run):
        success = True
        defaults = self._context.defaults().get('link', {})
        for destination, source in links.items():
            destination = os.path.expandvars(destination)
            relative = defaults.get('relative', False)
            canonical_path = defaults.get('canonicalize-path', True)
            force = defaults.get('force', False)
            relink = defaults.get('relink', False)
            test = defaults.get('if', None)
            ignore_missing = defaults.get('ignore-missing', False)
            if isinstance(source, dict):
                # extended config
                test = source.get('if', test)
                relative = source.get('relative', relative)
                canonical_path = source.get('canonicalize-path', canonical_path)
                force = source.get('force', force)
                relink = source.get('relink', relink)
                ignore_missing = source.get('ignore-missing', ignore_missing)
                path = self._default_source(destination, source.get('path'))
            else:
                path = self._default_source(destination, source)
            if test is not None and not self._test_success(test):
                self._log.verbose('Skipping %s' % destination)
                continue
            path = os.path.expandvars(os.path.expanduser(path))
            if not ignore_missing and not self._exists(os.path.join(self._context.base_directory(), path)):
                # we seemingly check this twice (here and in _link) because
                # if the file doesn't exist and force is True, we don't
                # want to remove the original (this is tested by
                # link-force-leaves-when-nonexistent.bash)
                success = False
                self._log.warning('Nonexistent source %s -> %s' %
                    (destination, path))
                continue
            if force or relink:
                success &= self._delete(path, destination, relative, canonical_path, force, dry_run)
            success &= self._link(path, destination, relative, canonical_path, ignore_missing, dry_run)

        if dry_run:
            if success:
                self._log.verbose('link/dry run: nothing to do')
            else:
                self._log.verbose('link/dry run: some targets are missing')
        else:
            if success:
                self._log.verbose('All links have been set up')
            else:
                self._log.error('Some links were not successfully set up')

        return success

    def _test_success(self, command):
        ret = dotbot.util.shell_command(command, cwd=self._context.base_directory())
        if ret != 0:
            self._log.debug('Test \'%s\' returned false' % command)
        return ret == 0

    def _default_source(self, destination, source):
        if source is None:
            basename = os.path.basename(destination)
            if basename.startswith('.'):
                return basename[1:]
            else:
                return basename
        else:
            return source

    def _is_link(self, path):
        '''
        Returns true if the path is a symbolic link.
        '''
        return os.path.islink(os.path.expanduser(path))

    def _link_destination(self, path):
        '''
        Returns the destination of the symbolic link.
        '''
        path = os.path.expanduser(path)
        return os.readlink(path)

    def _exists(self, path):
        '''
        Returns true if the path exists.
        '''
        path = os.path.expanduser(path)
        return os.path.exists(path)

    def _delete(self, source, path, relative, canonical_path, force, dry_run):
        success = True
        source = os.path.join(self._context.base_directory(canonical_path=canonical_path), source)
        fullpath = os.path.expanduser(path)
        if relative:
            source = self._relative_path(source, fullpath)
        if ((self._is_link(path) and self._link_destination(path) != source) or
                (self._exists(path) and not self._is_link(path))):
            self._log.info('Removing %s' % path)

            if dry_run:
                return False

            try:
                if os.path.islink(fullpath):
                    os.unlink(fullpath)
                    removed = True
                elif force:
                    if os.path.isdir(fullpath):
                        shutil.rmtree(fullpath)
                    else:
                        os.remove(fullpath)
            except OSError:
                self._log.warning('Failed to remove %s' % path)
                success = False

        return success

    def _relative_path(self, source, destination):
        '''
        Returns the relative path to get to the source file from the
        destination file.
        '''
        destination_dir = os.path.dirname(destination)
        return os.path.relpath(source, destination_dir)

    def _link(self, source, link_name, relative, canonical_path, ignore_missing, dry_run):
        '''
        Links link_name to source.

        Returns true if successfully linked files.
        '''
        success = False
        destination = os.path.expanduser(link_name)
        base_directory = self._context.base_directory(canonical_path=canonical_path)
        absolute_source = os.path.join(base_directory, source)
        if relative:
            source = self._relative_path(absolute_source, destination)
        else:
            source = absolute_source
        if (not self._exists(link_name) and self._is_link(link_name) and
                self._link_destination(link_name) != source):
            self._log.warning('Invalid link %s -> %s' %
                (link_name, self._link_destination(link_name)))
        # we need to use absolute_source below because our cwd is the dotfiles
        # directory, and if source is relative, it will be relative to the
        # destination directory
        elif not self._exists(link_name) and (ignore_missing or self._exists(absolute_source)):
            self._log.verbose('Creating link %s -> %s' % (link_name, source))
            if not dry_run:
                try:
                    os.symlink(source, destination)
                    success = True
                except OSError:
                    self._log.warning('Linking failed %s -> %s' % (link_name, source))
        elif self._exists(link_name) and not self._is_link(link_name):
            self._log.warning(
                '%s already exists but is a regular file or directory' %
                link_name)
        elif self._is_link(link_name) and self._link_destination(link_name) != source:
            self._log.warning('Incorrect link %s -> %s' %
                (link_name, self._link_destination(link_name)))
        # again, we use absolute_source to check for existence
        elif not self._exists(absolute_source):
            if self._is_link(link_name):
                self._log.warning('Nonexistent source %s -> %s' %
                    (link_name, source))
            else:
                self._log.warning('Nonexistent source for %s : %s' %
                    (link_name, source))
        else:
            self._log.verbose('Link exists %s -> %s' % (link_name, source))
            success = True
        return success