import datetime

import mercurial.context
import mercurial.node

from kallithea.lib.vcs.backends.base import BaseInMemoryChangeset
from kallithea.lib.vcs.exceptions import RepositoryError
from kallithea.lib.vcs.utils import ascii_str, safe_bytes


class MercurialInMemoryChangeset(BaseInMemoryChangeset):

    def commit(self, message, author, parents=None, branch=None, date=None,
               **kwargs):
        """
        Performs in-memory commit (doesn't check workdir in any way) and
        returns newly created ``Changeset``. Updates repository's
        ``revisions``.

        :param message: message of the commit
        :param author: full username, i.e. "Joe Doe <joe.doe@example.com>"
        :param parents: single parent or sequence of parents from which commit
          would be derived
        :param date: ``datetime.datetime`` instance. Defaults to
          ``datetime.datetime.now()``.
        :param branch: branch name, as string. If none given, default backend's
          branch would be used.

        :raises ``CommitError``: if any error occurs while committing
        """
        self.check_integrity(parents)

        from .repository import MercurialRepository
        if not isinstance(message, unicode) or not isinstance(author, unicode):
            raise RepositoryError('Given message and author needs to be '
                                  'an <unicode> instance got %r & %r instead'
                                  % (type(message), type(author)))

        if branch is None:
            branch = MercurialRepository.DEFAULT_BRANCH_NAME
        kwargs[b'branch'] = safe_bytes(branch)

        def filectxfn(_repo, memctx, bytes_path):
            """
            Callback from Mercurial, returning ctx to commit for the given
            path.
            """
            path = bytes_path  # will be different for py3

            # check if this path is removed
            if path in (node.path for node in self.removed):
                return None

            # check if this path is added
            for node in self.added:
                if node.path == path:
                    return mercurial.context.memfilectx(_repo, memctx, path=bytes_path,
                        data=node.content,
                        islink=False,
                        isexec=node.is_executable,
                        copysource=False)

            # or changed
            for node in self.changed:
                if node.path == path:
                    return mercurial.context.memfilectx(_repo, memctx, path=bytes_path,
                        data=node.content,
                        islink=False,
                        isexec=node.is_executable,
                        copysource=False)

            raise RepositoryError("Given path haven't been marked as added, "
                                  "changed or removed (%s)" % path)

        parents = [None, None]
        for i, parent in enumerate(self.parents):
            if parent is not None:
                parents[i] = parent._ctx.node()

        if date and isinstance(date, datetime.datetime):
            date = safe_bytes(date.strftime('%a, %d %b %Y %H:%M:%S'))

        commit_ctx = mercurial.context.memctx(
            repo=self.repository._repo,
            parents=parents,
            text=b'',
            files=[safe_bytes(x) for x in self.get_paths()],
            filectxfn=filectxfn,
            user=safe_bytes(author),
            date=date,
            extra=kwargs)

        # injecting given _repo params
        commit_ctx._text = safe_bytes(message)
        commit_ctx._user = safe_bytes(author)
        commit_ctx._date = date

        # TODO: Catch exceptions!
        n = self.repository._repo.commitctx(commit_ctx)
        # Returns mercurial node
        self._commit_ctx = commit_ctx  # For reference
        # Update vcs repository object & recreate mercurial _repo
        # new_ctx = self.repository._repo[node]
        # new_tip = ascii_str(self.repository.get_changeset(new_ctx.hex()))
        self.repository.revisions.append(ascii_str(mercurial.node.hex(n)))
        self._repo = self.repository._get_repo(create=False)
        self.repository.branches = self.repository._get_branches()
        tip = self.repository.get_changeset()
        self.reset()
        return tip