from git import Repo
import os
import sys

class FormulaRepo():

    # class variables
    repo_url = ''
    repo_path = ''
    repo = None

    # class constructor
    def __init__(self, formula):
        self.repo_url = formula.git_url
        self.repo_path = formula.local_path

    # retrieves repo from remote location
    def retrieve(self):
        # check if the destination directory exists
        if not os.path.exists(self.repo_path):
            # clone git repo
            print('Downloading ' + self.repo_url + ' into ' + self.repo_path)
            self.repo = Repo.clone_from(self.repo_url, self.repo_path)
        else:
            # let the user know it's already downloaded so we'll update it later
            print(self.repo_path + ' already exists, so we\'re not downloading it again.')
            self.repo = Repo(self.repo_path)

    # check if the repo is up to date
    def check_tracking_info(self, tracking_key, tracking_value):
        if tracking_key == 0:
            # tracking a specific branch on the repo
            if tracking_value != False:
                # check to make sure that the given branch name actually exists first
                if not tracking_value in self.repo.branches:
                    print('%s is not an existing branch name for %s - please fix this.' % (tracking_value, self.repo_path))
                    sys.exit(1)

                repo_branch = self.repo.head.reference
                # check to make sure that the current tracked branch is, in fact, what we want
                if repo_branch != tracking_value:
                    self.repo.head.reference = repo_branch

            # let the user know which branch we're using
            print('For %s, we\'re using the %s branch.' % (self.repo_path, self.repo.head.reference))
        elif tracking_key == 1:
            # tracking a specific tag on the repo
            print('Tracking a tag')
        elif tracking_key == 2:
            # tracking a specific commit on the repo
            print('Tracking a commit')
        else:
            # we shouldn't get here...
            print('So... somehow %s got a tracking key of %d, but that is not a valid tracking key!' % (self.repo_path, tracking_key))
            sys.exit(1)


    # pull any new updates for the repo
    def pull_updates(self):
        print('Pulling updates for %s.' % self.repo_path)
        # git pull
        self.repo.remotes.origin.pull()