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import cStringIO as StringIO
import logging
import sys
import re
import tempfile

from webkitpy.tool.steps.abstractstep import AbstractStep
from webkitpy.common.system.executive import Executive, ScriptError
from webkitpy.common.checkout import diff_parser

from webkitpy.tool.steps import confirmdiff

_log = logging.getLogger(__name__)


class HasLanded(confirmdiff.ConfirmDiff):

    @classmethod
    def convert_to_svn(cls, diff):
        lines = StringIO.StringIO(diff).readlines()
        convert = diff_parser.get_diff_converter(lines)
        return "".join(convert(x) for x in lines)

    @classmethod
    def strip_change_log(cls, diff):
        output = []
        skipping = False
        for line in StringIO.StringIO(diff).readlines():
            indexline = re.match("^Index: ([^\\n]*/)?([^/\\n]*)$", line)
            if skipping and indexline:
                skipping = False
            if indexline and indexline.group(2) == "ChangeLog":
                skipping = True
            if not skipping:
                output.append(line)
        return "".join(output)

    @classmethod
    def diff_diff(cls, diff1, diff2, diff1_suffix, diff2_suffix, executive=None):
        # Now this is where it gets complicated, we need to compare our diff to the diff at landed_revision.
        diff1_patch = tempfile.NamedTemporaryFile(suffix=diff1_suffix + '.patch')
        diff1_patch.write(diff1)
        diff1_patch.flush()

        # Check if there are any differences in the patch that don't happen
        diff2_patch = tempfile.NamedTemporaryFile(suffix=diff2_suffix + '.patch')
        diff2_patch.write(diff2)
        diff2_patch.flush()

        # Diff the two diff's together...
        if not executive:
            executive = Executive()

        try:
            return executive.run_command(
                ["interdiff", diff1_patch.name, diff2_patch.name], decode_output=False)
        except ScriptError as e:
            _log.warning("Unable to find interdiff util (part of GNU difftools package) which is required.")
            raise

    def run(self, state):
        # Check if there are changes first
        if not self._tool.scm().local_changes_exist():
            _log.warn("No local changes found, exiting.")
            return True

        # Check if there is a SVN revision in the bug from the commit queue
        landed_revision = self.cached_lookup(state, "bug").commit_revision()
        if not landed_revision:
            raise ScriptError("Unable to find landed message in associated bug.")

        # Now this is there it gets complicated, we need to compare our diff to the diff at landed_revision.
        landed_diff_bin = self._tool.scm().diff_for_revision(landed_revision)
        landed_diff_trimmed = self.strip_change_log(self.convert_to_svn(landed_diff_bin))

        # Check if there are any differences in the patch that don't happen
        local_diff_bin = self._tool.scm().create_patch()
        local_diff_trimmed = self.strip_change_log(self.convert_to_svn(local_diff_bin))

        # Diff the two diff's together...
        diff_diff = self.diff_diff(landed_diff_trimmed, local_diff_trimmed,
                                   '-landed', '-local',
                                   executive=self._tool.executive)

        with self._show_pretty_diff(diff_diff) as pretty_diff_file:
            if not pretty_diff_file:
                self._tool.user.page(diff_diff)

            if self._tool.user.confirm("May I discard local changes?"):
                # Discard changes if the user confirmed we should
                _log.warn("Discarding changes as requested.")
                self._tool.scm().discard_local_changes()