import calendar
from datetime import datetime, timedelta
import time

try:
    from bzrlib import bzrdir, revisionspec
except ImportError:
    pass

from reviewboard.scmtools.core import SCMTool, PRE_CREATION
from reviewboard.scmtools.errors import SCMError


# BZRTool: An interface to Bazaar SCM Tool (http://bazaar-vcs.org/)

class BZRTool(SCMTool):
    name = "Bazaar"

    # Timestamp format in bzr diffs.
    # This isn't totally accurate: there should be a %z at the end.
    # Unfortunately, strptime() doesn't support %z.
    DIFF_TIMESTAMP_FORMAT = '%Y-%m-%d %H:%M:%S'

    # "bzr diff" indicates that a file is new by setting the old
    # timestamp to the epoch time.
    PRE_CREATION_TIMESTAMP = '1970-01-01 00:00:00 +0000'

    def __init__(self, repository):
        SCMTool.__init__(self, repository)

    def get_file(self, path, revision):
        if revision == BZRTool.PRE_CREATION_TIMESTAMP:
            return ''

        revspec = self._revspec_from_revision(revision)
        filepath = self._get_full_path(path)

        branch = None
        try:
            try:
                tree, branch, relpath = bzrdir.BzrDir.open_containing_tree_or_branch(filepath)
                branch.lock_read()
                revtree = revisionspec.RevisionSpec.from_string(revspec).as_tree(branch)
                fileid = revtree.path2id(relpath)
                contents = revtree.get_file_text(fileid)
            except Exception, e:
                raise SCMError(e)
        finally:
            if branch:
                branch.unlock()

        return contents

    def parse_diff_revision(self, file_str, revision_str):
        if revision_str == BZRTool.PRE_CREATION_TIMESTAMP:
            return (file_str, PRE_CREATION)

        return file_str, revision_str

    def get_fields(self):
        return ['basedir', 'diff_path']

    def get_diffs_use_absolute_paths(self):
        return False

    def _get_full_path(self, path, basedir=None):
        """Returns the full path to a file."""
        parts = [self.repository.path.strip("/")]

        if basedir:
            parts.append(basedir.strip("/"))

        parts.append(path.strip("/"))

        return "/".join(parts)

    def _revspec_from_revision(self, revision):
        """Returns a revspec based on the revision found in the diff.
        
        In addition to the standard date format from "bzr diff", this
        function supports the revid: syntax provided by the bzr diff-revid plugin.
        """

        if revision.startswith('revid:'):
            revspec = revision
        else:
            revspec = 'date:' + str(self._revision_timestamp_to_local(revision))

        return revspec

    def _revision_timestamp_to_local(self, timestamp_str):
        """When using a date to ask bzr for a file revision, it expects
        the date to be in local time. So, this function converts a
        timestamp from a bzr diff file to local time.
        """

        timestamp = datetime(*time.strptime(timestamp_str[0:19], BZRTool.DIFF_TIMESTAMP_FORMAT)[0:6])

        # Now, parse the difference to GMT time (such as +0200)
        # If only strptime() supported %z, we wouldn't have to do this manually.
        delta = timedelta(hours=int(timestamp_str[21:23]), minutes=int(timestamp_str[23:25]))
        if timestamp_str[20] == '+':
            timestamp -= delta
        else:
            timestamp += delta

        # convert to local time
        return datetime.fromtimestamp(calendar.timegm(timestamp.timetuple()))