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import os
import tempfile


class PrettyPatch(object):

    def __init__(self, executive):
        self._executive = executive

    def pretty_diff_file(self, diff):
        # Diffs can contain multiple text files of different encodings
        # so we always deal with them as byte arrays, not unicode strings.
        assert isinstance(diff, str)
        pretty_diff = self.pretty_diff(diff)
        diff_file = tempfile.NamedTemporaryFile(suffix='.html')
        diff_file.write(pretty_diff)
        diff_file.flush()
        return diff_file

    def pretty_diff(self, diff):
        # prettify.rb will hang forever if given no input.
        # Avoid the hang by returning an empty string.
        if not diff:
            return ''

        pretty_patch_path = os.path.join(os.path.dirname(__file__), '..', '..',
                                         'webkitruby', 'PrettyPatch')
        prettify_path = os.path.join(pretty_patch_path, 'prettify.rb')
        args = [
            'ruby',
            '-I',
            pretty_patch_path,
            prettify_path,
        ]
        # PrettyPatch does not modify the encoding of the diff output
        # so we can't expect it to be utf-8.
        return self._executive.run_command(args, input=diff, decode_output=False)