# Copyright 2019 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Class to manage a git repository via python.

This class is to be used to implement git commands over
a python API and manage the current state of the git repo.

  Typical usage example:

    r_man =  RepoManager('https://github.com/google/oss-fuzz.git')
    r_man.checkout('5668cc422c2c92d38a370545d3591039fb5bb8d4')
"""
import datetime
import logging
import os
import shutil

import utils


class RepoManager:
  """Repo manager."""

  def __init__(self, repo_dir):
    self.repo_dir = repo_dir

  def _is_git_repo(self):
    """Test if the current repo dir is a git repo or not.

    Returns:
      True if the current repo_dir is a valid git repo.
    """
    git_path = os.path.join(self.repo_dir, '.git')
    return os.path.isdir(git_path)

  def git(self, cmd, check_result=False):
    """Run a git command.

    Args:
      command: The git command as a list to be run.
      check_result: Should an exception be thrown on failed command.

    Returns:
      stdout, stderr, error code.
    """
    return utils.execute(['git'] + cmd,
                         location=self.repo_dir,
                         check_result=check_result)

  def commit_exists(self, commit):
    """Checks to see if a commit exists in the project repo.

    Args:
      commit: The commit SHA you are checking.

    Returns:
      True if the commit exits in the project.
    """
    if not commit.rstrip():
      return False

    _, _, err_code = self.git(['cat-file', '-e', commit])
    return not err_code

  def commit_date(self, commit):
    """Get the date of a commit.

    Args:
      commit: The commit hash.

    Returns:
      A datetime representing the date of the commit.
    """
    out, _, _ = self.git(['show', '-s', '--format=%ct', commit],
                         check_result=True)
    return datetime.datetime.fromtimestamp(int(out), tz=datetime.timezone.utc)

  def get_git_diff(self, base='origin...'):
    """Gets a list of files that have changed from the repo head.

    Returns:
      A list of changed file paths or None on Error.
    """
    self.fetch_unshallow()
    # Add '--' so that git knows we aren't talking about files.
    command = ['diff', '--name-only', base, '--']
    out, err_msg, err_code = self.git(command)
    if err_code:
      logging.error('Git diff failed with error message %s.', err_msg)
      return None
    if not out:
      logging.error('No diff was found.')
      return None
    return [line for line in out.splitlines() if line]

  def get_current_commit(self):
    """Gets the current commit SHA of the repo.

    Returns:
      The current active commit SHA.
    """
    out, _, _ = self.git(['rev-parse', 'HEAD'], check_result=True)
    return out.strip()

  def get_parent(self, commit, count):
    """Gets the count'th parent of the given commit.

    Returns:
      The parent commit SHA.
    """
    self.fetch_unshallow()
    out, _, err_code = self.git(['rev-parse', commit + '~' + str(count)],
                                check_result=False)
    if err_code:
      return None

    return out.strip()

  def fetch_all_remotes(self):
    """Fetch all remotes for checkouts that track a single branch."""
    self.git([
        'config', 'remote.origin.fetch', '+refs/heads/*:refs/remotes/origin/*'
    ],
             check_result=True)
    self.git(['remote', 'update'], check_result=True)

  def get_commit_list(self, newest_commit, oldest_commit=None):
    """Gets the list of commits(inclusive) between the old and new commits.

    Args:
      newest_commit: The newest commit to be in the list.
      oldest_commit: The (optional) oldest commit to be in the list.

    Returns:
      The list of commit SHAs from newest to oldest.

    Raises:
      ValueError: When either the oldest or newest commit does not exist.
      RuntimeError: When there is an error getting the commit list.
    """
    self.fetch_unshallow()
    if oldest_commit and not self.commit_exists(oldest_commit):
      raise ValueError('The oldest commit %s does not exist' % oldest_commit)
    if not self.commit_exists(newest_commit):
      raise ValueError('The newest commit %s does not exist' % newest_commit)
    if oldest_commit == newest_commit:
      return [oldest_commit]

    if oldest_commit:
      commit_range = oldest_commit + '..' + newest_commit
    else:
      commit_range = newest_commit

    out, _, err_code = self.git(['rev-list', commit_range])
    commits = out.split('\n')
    commits = [commit for commit in commits if commit]
    if err_code or not commits:
      raise RuntimeError('Error getting commit list between %s and %s ' %
                         (oldest_commit, newest_commit))

    # Make sure result is inclusive
    if oldest_commit:
      commits.append(oldest_commit)
    return commits

  def fetch_branch(self, branch):
    """Fetches a remote branch from origin."""
    return self.git(
        ['fetch', 'origin', '{branch}:{branch}'.format(branch=branch)])

  def fetch_unshallow(self):
    """Gets the current git repository history."""
    shallow_file = os.path.join(self.repo_dir, '.git', 'shallow')
    if os.path.exists(shallow_file):
      _, err, err_code = self.git(['fetch', '--unshallow'], check_result=False)
      if err_code:
        logging.error('Unshallow returned non-zero code: %s', err)

  def checkout_pr(self, pr_ref):
    """Checks out a remote pull request.

    Args:
      pr_ref: The pull request reference to be checked out.
    """
    self.fetch_unshallow()
    self.git(['fetch', 'origin', pr_ref], check_result=True)
    self.git(['checkout', '-f', 'FETCH_HEAD'], check_result=True)

  def checkout_commit(self, commit, clean=True):
    """Checks out a specific commit from the repo.

    Args:
      commit: The commit SHA to be checked out.

    Raises:
      RuntimeError: when checkout is not successful.
      ValueError: when commit does not exist.
    """
    self.fetch_unshallow()
    if not self.commit_exists(commit):
      raise ValueError('Commit %s does not exist in current branch' % commit)
    self.git(['checkout', '-f', commit], check_result=True)
    if clean:
      self.git(['clean', '-fxd'], check_result=True)
    if self.get_current_commit() != commit:
      raise RuntimeError('Error checking out commit %s' % commit)

  def remove_repo(self):
    """Removes the git repo from disk."""
    if os.path.isdir(self.repo_dir):
      shutil.rmtree(self.repo_dir)


def clone_repo_and_get_manager(repo_url, base_dir, repo_name=None):
  """Clones a repo and constructs a repo manager class.

    Args:
      repo_url: The github url needed to clone.
      base_dir: The full file-path where the git repo is located.
      repo_name: The name of the directory the repo is cloned to.
    """
  if repo_name is None:
    repo_name = os.path.basename(repo_url).replace('.git', '')
  repo_dir = os.path.join(base_dir, repo_name)
  manager = RepoManager(repo_dir)

  if not os.path.exists(repo_dir):
    _clone(repo_url, base_dir, repo_name)

  return manager


def _clone(repo_url, base_dir, repo_name):
  """Creates a clone of the repo in the specified directory.

     Raises:
       ValueError: when the repo is not able to be cloned.
  """
  utils.execute(['git', 'clone', repo_url, repo_name],
                location=base_dir,
                check_result=True)