# Copyright 2014 Pants project contributors (see CONTRIBUTORS.md).
# Licensed under the Apache License, Version 2.0 (see LICENSE).

from abc import ABC, abstractmethod

from pants.base.build_environment import get_buildroot
from pants.scm.scm import Scm


class Workspace(ABC):
    """Tracks the state of the current workspace."""

    class WorkspaceError(Exception):
        """Indicates a problem reading the local workspace."""

    @abstractmethod
    def touched_files(self, parent):
        """Returns the paths modified between the parent state and the current workspace state."""

    @abstractmethod
    def changes_in(self, rev_or_range):
        """Returns the paths modified by some revision, revision range or other identifier."""


class ScmWorkspace(Workspace):
    """A workspace that uses an Scm to determine the touched files.

    :API: public
    """

    def __init__(self, scm):
        """
        :API: public
        """
        super().__init__()

        if scm is None:
            raise self.WorkspaceError(
                "Cannot figure out what changed without a configured " "source-control system."
            )
        self._scm = scm

    def touched_files(self, parent):
        """
        :API: public
        """
        try:
            return self._scm.changed_files(
                from_commit=parent, include_untracked=True, relative_to=get_buildroot()
            )
        except Scm.ScmException as e:
            raise self.WorkspaceError("Problem detecting changed files.", e)

    def changes_in(self, rev_or_range):
        """
        :API: public
        """
        try:
            return self._scm.changes_in(rev_or_range, relative_to=get_buildroot())
        except Scm.ScmException as e:
            raise self.WorkspaceError("Problem detecting changes in {}.".format(rev_or_range), e)