import re
import os.path

from dbt.clients.system import run_cmd, rmdir
from dbt.logger import GLOBAL_LOGGER as logger
import dbt.exceptions


def clone(repo, cwd, dirname=None, remove_git_dir=False, branch=None):
    clone_cmd = ['git', 'clone', '--depth', '1']

    if branch is not None:
        clone_cmd.extend(['--branch', branch])

    clone_cmd.append(repo)

    if dirname is not None:
        clone_cmd.append(dirname)

    result = run_cmd(cwd, clone_cmd, env={'LC_ALL': 'C'})

    if remove_git_dir:
        rmdir(os.path.join(dirname, '.git'))

    return result


def list_tags(cwd):
    out, err = run_cmd(cwd, ['git', 'tag', '--list'], env={'LC_ALL': 'C'})
    tags = out.decode('utf-8').strip().split("\n")
    return tags


def _checkout(cwd, repo, branch):
    logger.debug('  Checking out branch {}.'.format(branch))

    run_cmd(cwd, ['git', 'remote', 'set-branches', 'origin', branch])
    run_cmd(cwd, ['git', 'fetch', '--tags', '--depth', '1', 'origin', branch])

    tags = list_tags(cwd)

    # Prefer tags to branches if one exists
    if branch in tags:
        spec = 'tags/{}'.format(branch)
    else:
        spec = 'origin/{}'.format(branch)

    out, err = run_cmd(cwd, ['git', 'reset', '--hard', spec],
                       env={'LC_ALL': 'C'})
    return out, err


def checkout(cwd, repo, branch=None):
    if branch is None:
        branch = 'master'
    try:
        return _checkout(cwd, repo, branch)
    except dbt.exceptions.CommandResultError as exc:
        stderr = exc.stderr.decode('utf-8').strip()
    dbt.exceptions.bad_package_spec(repo, branch, stderr)


def get_current_sha(cwd):
    out, err = run_cmd(cwd, ['git', 'rev-parse', 'HEAD'], env={'LC_ALL': 'C'})

    return out.decode('utf-8')


def remove_remote(cwd):
    return run_cmd(cwd, ['git', 'remote', 'rm', 'origin'], env={'LC_ALL': 'C'})


def clone_and_checkout(repo, cwd, dirname=None, remove_git_dir=False,
                       branch=None):
    exists = None
    try:
        _, err = clone(repo, cwd, dirname=dirname,
                       remove_git_dir=remove_git_dir)
    except dbt.exceptions.CommandResultError as exc:
        err = exc.stderr.decode('utf-8')
        exists = re.match("fatal: destination path '(.+)' already exists", err)
        if not exists:  # something else is wrong, raise it
            raise

    directory = None
    start_sha = None
    if exists:
        directory = exists.group(1)
        logger.debug('Updating existing dependency {}.', directory)
    else:
        matches = re.match("Cloning into '(.+)'", err.decode('utf-8'))
        if matches is None:
            raise dbt.exceptions.RuntimeException(
                f'Error cloning {repo} - never saw "Cloning into ..." from git'
            )
        directory = matches.group(1)
        logger.debug('Pulling new dependency {}.', directory)
    full_path = os.path.join(cwd, directory)
    start_sha = get_current_sha(full_path)
    checkout(full_path, repo, branch)
    end_sha = get_current_sha(full_path)
    if exists:
        if start_sha == end_sha:
            logger.debug('  Already at {}, nothing to do.', start_sha[:7])
        else:
            logger.debug('  Updated checkout from {} to {}.',
                         start_sha[:7], end_sha[:7])
    else:
        logger.debug('  Checked out at {}.', end_sha[:7])
    return directory