#!/usr/bin/env python3

import os
import subprocess
import sys
from concurrent.futures import ThreadPoolExecutor

SAFEBRANCHES = ['master', 'develop', 'rc']
DEBUG = False

# TODO: local changes, branch updated. Is there a way to know, whether rebase would be successful? If yes: do so

def dPrint(*args, **kwargs):
    if DEBUG:
        print(' '.join(map(str, args)), **kwargs)

def getStdout(command):
    process = None
    process = subprocess.run(command,
                             stdout=subprocess.PIPE,
                             stderr=subprocess.PIPE)
    if process.returncode != 0:
        print('Failed to execute command:', command)
        if process.stdout:
            print('  Stdout:')
            print(process.stdout.decode('UTF-8'))
        if process.stderr:
            print('  Stderr:')
            print(process.stderr.decode('UTF-8'))
        return ''
    if process.stdout:
        return process.stdout.decode('UTF-8').strip()
    return ''

def getGitStdout(path, command):
    dPrint('[ running', command, 'on', path, ']')
    if isinstance(command, str):
        cmd = 'git -C %s %s' % (path, command)
        return getStdout(cmd.split())
    if isinstance(command, list):
        cmd = ['git', '-C', path]
        cmd.extend(command)
        return getStdout(cmd)

def findChanges(statusoutput):
    dPrint('Parsing for changes:')
    for line in statusoutput.split('\n'):
        dPrint('      Status Line:', line)
        if line.startswith('A ') or line.startswith('D ') or line.startswith('M '):
            return True
    return False

def updatePath(path):
    friendly_path = os.path.basename(path)
    dPrint('Repository:', path)
    head = getGitStdout(path, 'rev-parse --abbrev-ref HEAD')
    changed = findChanges(getGitStdout(path, 'status --porcelain'))
    cur_branch = getGitStdout(path, 'rev-parse --abbrev-ref HEAD')

    # Fetch changes, delete removed repositories
    getGitStdout(path, 'fetch --all --prune')

    # Go through branches and merge with upstream
    branches = getGitStdout(path, [
        'for-each-ref',
        '--format=%(refname:short)#%(upstream)#%(upstream:track,nobracket)',
        'refs/heads'
    ])
    for branch in branches.split('\n'):
        local_branch, upstream_branch, tracking = branch.split('#')
        if not upstream_branch or tracking == 'gone':
            print('[%s]' % friendly_path, local_branch, 'has no upstream branch.')
            continue
        if local_branch == cur_branch and changed:
            print('[%s]' % friendly_path, 'has a working branch with changes, skipped.')
            continue
        dPrint('Update for', friendly_path, local_branch, upstream_branch)
        local = getGitStdout(path, ['rev-parse', '--quiet', '--verify', local_branch])
        remote = getGitStdout(path, ['rev-parse', '--quiet', '--verify', upstream_branch])
        base = getGitStdout(path, ['merge-base', local_branch, upstream_branch])
        dPrint('    Branch:', local_branch)
        dPrint('  Upstream:', upstream_branch)
        dPrint('      Local', local)
        dPrint('     Remote', remote)
        dPrint('       Base', base)
        if local == remote:
            continue
        if local == base:
            if local_branch == cur_branch:
                getGitStdout(path, ['merge', remote])
                local_short = getGitStdout(path, ['rev-parse', '--short', local])
                remote_short = getGitStdout(path, ['rev-parse', '--short', remote])
                shortstat = getGitStdout(path, ['diff', '--shortstat', local, remote])
                print('[%s]' % friendly_path, 'Updated branch', cur_branch, '{}..{}'.format(local_short, remote_short), "\n", shortstat)
            else:
                getGitStdout(path, ['branch', '-f', local_branch, remote])
                shortstat = getGitStdout(path, ['diff', '--shortstat', local, remote])
                print('[%s] Updated branch %s:' % (friendly_path, cur_branch), '{}..{}'.format(local, remote), "\n", shortstat)
        if remote == base:
            print('[%s] %s is ahead. Consider pushing your changes.' % (friendly_path, local_branch))

    # Find safe branch (master/development/rc)
    branches = getGitStdout(path, [
        'for-each-ref',
        '--format=%(refname:short)',
        'refs/heads'
    ]).split('\n')
    for branch in SAFEBRANCHES:
        if branch in branches:
            safe_branch = branch
            break

    # No safe branch found. What is this?
    if not safe_branch:
        print('Does the repository', friendly_path, 'not have any safe branch?')
        return

    # print('Safe branch:', safe_branch)

    # Checkout master, if detached HEAD and not proceeded
    if head == 'HEAD':
        if changed:
            print('[%s] Head detached, but changes found. Stash them to checkout %s.' % (
                friendly_path,
                safe_branch
            ))
        else:
            headrev = getGitStdout(path, 'rev-parse --quiet --verify HEAD')
            mergerev = getGitStdout(path, ['merge-base', 'HEAD', safe_branch])
            if headrev == mergerev:
                print('[%s] Head detached, checking %s out.' % (friendly_path, safe_branch),
                      getGitStdout(path, 'checkout ' + safe_branch))
            else:
                print('[%s] Head detached, but not part of safe branch!' % friendly_path)

    # Delete branches, that were already merged to master
    merged_branches = getGitStdout(path, [
        'branch',
        '--format=%(refname:short)',
        '--merged=%s' % safe_branch
    ]).split('\n')
    # print('[%s]' % friendly_path, 'Deletion of branches', merged_branches, SAFEBRANCHES, cur_branch)
    for merged_branch in merged_branches:
        if merged_branch in SAFEBRANCHES:
            continue
        if merged_branch == cur_branch:
            continue
        get_tracking_status = getGitStdout(path, [
            'for-each-ref',
            '--format=%(upstream:track,nobracket)',
            'refs/heads/%s' % merged_branch
            ])
        if get_tracking_status.strip() == 'gone':
            print('[%s]' % friendly_path, 'Removing branch by force, upstream is gone.')
            print('[%s]' % friendly_path,
                getGitStdout(path, ['branch', '-D', merged_branch]))
        else:
            print('[%s]' % friendly_path,
                getGitStdout(path, ['branch', '-d', merged_branch]))

def main():
    paths = []
    if len(sys.argv) == 1:
        paths.append('.')
    else:
        for path in sys.argv[1:]:
            paths.append(path)

    repos = []
    for path in paths:
        for subdir, dirs, _ in os.walk(path):
            # dPrint(subdir, dir, files)
            if '.git' in dirs:
                repos.append(subdir)

    if len(repos) == 0:
        print('No repositories found.')
        return

    print('Updating', len(repos), 'repositories.')
    # executor = ThreadPoolExecutor(max_workers=len(repos))
    executor = ThreadPoolExecutor(max_workers=8)
    for repo in repos:
        # updatePath(subdir)
        executor.submit(updatePath, repo)
    executor.shutdown()


if __name__ == "__main__":
    main()