fabfile.py

import string
import random
import time

from fabric import state
from fabric.api import run, sudo, cd, prompt, task, settings
from fabric.contrib import files
from fabric.colors import green, red
from fabric.context_managers import hide
from fabric.tasks import Task
from fabric.task_utils import crawl

from fabtools import require, python, supervisor, deb, system, nodejs, service


'''
Script to set up a cozy cloud environnement from a fresh system
Validated on a Debian squeeze 64 bits up to date.

Once your system is updated, launch
$ fab -H user@Ip.Ip.Ip.Ip:Port install
to install the full Cozy stack.
'''


''' Helpers '''


def id_generator(
        size=32,
        chars=string.ascii_uppercase + string.digits + string.ascii_lowercase):
    return ''.join(random.choice(chars) for x in range(size))


def simple_id_generator(size=40, chars=string.ascii_uppercase + string.digits):
    return ''.join(random.choice(chars) for x in range(size))


USERNAME = id_generator()
PASSWORD = id_generator()
TOKEN = simple_id_generator()


def is_pi():
    result = run('lscpu', quiet=True)
    return 'armv6l' in result


def is_arm():
    result = run('lscpu', quiet=True)
    return 'armv' in result


def print_failed(module):
    print(red('Installation of %s failed.\n' +
              'You can join us on our IRC channel: '
              + '#cozycloud on freenode.net to ask for assistance.') % module)
    exit()


def cozydo(cmd):
    '''Run a command as a cozy user'''
    sudo(cmd, user='cozy')


def su_delete(filename):
    '''Delete given file with root permission'''
    sudo('rm -rf %s' % filename)


def delete_if_exists(filename):
    '''Delete given file if it already exists'''
    if files.exists(filename):
        su_delete(filename)


def try_delayed_run(program, comparator, max_attempts=60, wait=1):
    '''
    Runs the given program and matches the resulting string by applying the
    comparator function (which should return something truthy or falsy). If the
    comparator returns false, wait for 'wait' seconds and retries, with
    a maximum of max_attempts attempts.
    Returns true if the comparator has returned true once, false otherwise.
    '''
    num_attempts = 0
    result = ''

    with hide('running', 'stdout'):
        result = run(program, warn_only=True)

    while not comparator(result) and num_attempts < max_attempts:
        time.sleep(wait)

        with hide('running', 'stdout'):
            result = run(program, warn_only=True)

        num_attempts += 1

    return comparator(result)


def get_couchdb_version():
    '''
    Return proper CouchDB version depending on distribution.
    '''
    version = '1.6.0'
    if system.distrib_id() == 'Debian' \
       and (system.distrib_release().startswith('6') or
            system.distrib_release().startswith('7')):
        version = '1.5.0'

    return version


def ask_for_confirmation(module):
    '''
    Simple function to ask for confirmation before uninstalling a module
    installed by this fabfile.
    '''
    confirm = prompt('Are you sure you want to definitely remove %s from your'
                     ' computer? ' % module, default="no")
    return confirm == "yes"


# Tasks


@task
def install():
    '''
    Install the full cozy stack.
    '''
    install_tools()
    install_node10()
    install_couchdb()
    install_postfix()
    create_cozy_user()
    config_couchdb()
    install_monitor()
    install_controller()
    install_indexer()
    install_data_system()
    install_home()
    install_proxy()
    create_cert()
    install_nginx()
    restart_cozy()
    print(green('Cozy installation finished. Now, enjoy!'))


@task
def install_dev():
    '''
    Install stuff to prepare a virtual machine dedicated to development.
    '''
    install_tools()
    install_node10()
    install_couchdb()
    install_postfix()
    create_cozy_user()
    install_monitor()
    install_controller_dev()
    install_indexer()
    install_data_system()
    install_home()
    install_proxy()
    print(green('The Cozy development environment has been installed.'))


@task
def install_tools():
    '''
    Install build tools
    '''
    packages = ['python',
                'python-dev',
                'python-setuptools',
                'python-pip',
                'openssl',
                'libssl-dev',
                'libxml2-dev',
                'libxslt1-dev',
                'build-essential',
                'git',
                'sudo',
                'lsb-release',
                'imagemagick',
                'curl',
                'sqlite3',
                'wget']

    if system.distrib_id() == 'Ubuntu':
        packages.append('software-properties-common')

    deb.update_index()
    deb.upgrade()
    require.deb.packages(packages)

    # Dirty hack because of fabtools that don't install pip properly
    sudo('curl -o - https://bootstrap.pypa.io/ez_setup.py -O - | python')
    sudo('curl -o - https://bootstrap.pypa.io/get-pip.py | python -')

    print(green('Tools successfully installed'))


@task
def install_node10():
    '''
    install node 0.10.26
    '''

    if is_arm():
        with settings(warn_only=True):
            result = run('node -v')
            is_installed = result.find('v0.10.26')
            if is_installed != -1:
                print(green("Node.js is already installed"))
                return True

        version = '0.10.26'
        node_url = 'http://nodejs.org/dist/v{0}/node-v{0}-linux-arm-pi.tar.gz'
        require.file(url=node_url.format(version))
        run('tar -xzvf node-v%s-linux-arm-pi.tar.gz' % version)
        delete_if_exists('/opt/node')
        require.directory('/opt/node', use_sudo=True, owner='root')
        sudo('mv node-v%s-linux-arm-pi/* /opt/node' % version)
        sudo('ln -s /opt/node/bin/node /usr/local/bin/node')
        sudo('ln -s /opt/node/bin/node /usr/bin/node')
        sudo('ln -s /opt/node/bin/npm /usr/local/bin/npm')
        sudo('ln -s /opt/node/bin/npm /usr/bin/npm')

    else:
        require.nodejs.installed_from_source('0.10.26')

    print(green('node 0.10.26 successfully installed'))


@task
def install_couchdb():
    '''
    Install CouchDB 1.3.0 or 1.5.0 depending on the target distribution.
    '''

    # Check if controller is already installed, .
    with settings(warn_only=True):
        result = run('curl -X GET http://127.0.0.1:5984/')
        is_installed = result.find('Welcome')
        if is_installed != -1:
            print(green("CouchDB is already installed"))
            return True

    packages = [
        'erlang',
        'libicu-dev',
        'libcurl4-openssl-dev',
        'curl'
    ]

    if system.distrib_id() == 'Debian' \
            and system.distrib_release().startswith('6'):
        packages.append('libmozjs-dev')
    else:
        packages.append('libmozjs185-dev')
    require.deb.packages(packages)

    version = get_couchdb_version()

    require.file(
        url='http://apache.crihan.fr/dist/couchdb/source/' +
        '%s/apache-couchdb-%s.tar.gz' % (version, version))
    run('tar -xzvf apache-couchdb-%s.tar.gz' % version)
    with cd('apache-couchdb-%s' % version):
        run('./configure; make')
        result = sudo('make install')
        installed = result.find('You have installed Apache CouchDB,' +
                                ' time to relax.')
        if installed == -1:
            print_failed('couchdb')
    su_delete('apache-couchdb-%s' % version)
    su_delete('apache-couchdb-%s.tar.gz' % version)

    require.users.user('couchdb', home='/usr/local/var/lib/couchdb')
    sudo('chown -R couchdb:couchdb /usr/local/etc/couchdb')
    sudo('chown -R couchdb:couchdb /usr/local/var/lib/couchdb')
    sudo('chown -R couchdb:couchdb /usr/local/var/log/couchdb')
    sudo('chown -R couchdb:couchdb /usr/local/var/run/couchdb')
    sudo('chmod 0770 /usr/local/etc/couchdb')
    sudo('chmod 0770 /usr/local/var/lib/couchdb')
    sudo('chmod 0770 /usr/local/var/log/couchdb')
    sudo('chmod 0770 /usr/local/var/run/couchdb')

    require.supervisor.process(
        'couchdb', user='couchdb',
        command='couchdb', autostart='true',
        environment='HOME=/usr/local/var/lib/couchdb')
    print(green('CouchDB %s successfully installed' % version))


@task
def config_couchdb():
    if files.exists('/etc/cozy/couchdb.login'):
        # CouchDB has an old admin
        with hide('running', 'stdout'):
            # Recover old password
            logins = sudo('cat /etc/cozy/couchdb.login')
            logsCouchDB = logins.split('\r\n')
            # Add new admin
            couch_admin_path = '@127.0.0.1:5984/_config/admins/'
            run('curl -X PUT http://%s:%s%s%s -d \'\"%s\"\'' %
                (
                    logsCouchDB[0],
                    logsCouchDB[1],
                    couch_admin_path,
                    USERNAME,
                    PASSWORD,
                ))
            # Delete old admin
            run('curl -X DELETE ' +
                'http://%s:%s@127.0.0.1:5984/_config/admins/%s' %
                (USERNAME, PASSWORD, logsCouchDB[0]))
            sudo('rm -rf /etc/cozy/couchdb.login')
    else:
        # CouchDB has not an admin
        # Create admin
        with hide('running', 'stdout'):
            couch_admin_path = '127.0.0.1:5984/_config/admins/'
            run('curl -X PUT http://%s%s -d \'\"%s\"\'' %
                (couch_admin_path, USERNAME, PASSWORD))
        sudo('mkdir -p /etc/cozy')

    # Create file to keep admin's password
    require.files.file(
        path='/etc/cozy/couchdb.login',
        contents=USERNAME + '\n' + PASSWORD,
        use_sudo=True,
        owner='cozy-data-system',
        mode='700'
    )
    version = get_couchdb_version()
    print(green('CouchDB %s successfully configured' % version))


@task
def install_postfix():
    '''
    Install a postfix instance (required for mail sending).
    '''
    require.postfix.server('mydomain.net')
    print(green('Postfix successfully installed'))


@task
def create_cozy_user():
    '''
    Add Cozy user with no home directory.
    '''
    require.user('cozy', home=False, create_home=False)
    require.user('cozy-data-system', create_home=True)
    require.user('cozy-home', create_home=True)
    print(green('Cozy users successfully added'))


@task
def install_monitor():
    '''
    Install Coffeescript, Compound and Cozy Monitor.
    '''
    with settings(warn_only=True):
        if sudo('npm install -g coffee-script cozy-monitor').succeeded:
            print(green('Monitor and coffee script successfully installed'))
        else:
            print('Warning: Retry to install coffee-script and monitor')
            if sudo('npm install -g coffee-script cozy-monitor').succeeded:
                print(green('Monitor and coffee script successfully installed'))
            else:
                print(red('Error: Monitor and coffee script have not been installed'))
                print_failed('cozy-monitor')


@task
def install_controller():
    '''
    Install Cozy Controller Application Manager. Daemonize with supervisor.
    '''
    # Check if controller is already installed, .
    with settings(warn_only=True):
        result = run('curl -X GET http://127.0.0.1:9002/drones/running')
        is_installed = result.find('Application is not authenticated')
        if is_installed != -1:
            print(green("Cozy Controller already installed"))
            return True
    sudo('npm install -g cozy-controller')
    require.directory('/etc/cozy', owner='root', use_sudo=True)
    require.supervisor.process(
        'cozy-controller',
        command='cozy-controller',
        environment='NODE_ENV="production",BIND_IP_PROXY="127.0.0.1"',
        user='root'
    )

    print('Waiting for cozy-controller to be launched...')
    program = 'curl -X GET http://127.0.0.1:9002/drones/running'

    def comparator(result):
        return result == 'Application is not authenticated'

    # Run curl until we get the MATCH_STR or a timeout
    if not try_delayed_run(program, comparator):
        print_failed('cozy-controller')

    print(green('Cozy Controller successfully started'))


@task
def install_controller_dev():
    '''
    Install Cozy Controller Application Manager. Daemonize with supervisor.
    '''
    sudo('npm install -g cozy-controller')
    require.supervisor.process(
        'cozy-controller',
        command='cozy-controller',
        environment='NODE_ENV="development"',
        user='root'
    )
    supervisor.restart_process('cozy-controller')

    time.sleep(5)
    with hide('running', 'stdout'):
        result = run('curl -X GET http://127.0.0.1:9002/')
    if result != '{"message":"No drones specified"}':
        print_failed("cozy-controller")

    print(green('Cozy Controller successfully started'))


@task
def install_indexer():
    '''
    Install Cozy Data Indexer. Use supervisord to daemonize it.
    '''
    home = '/usr/local/cozy-indexer'
    indexer_dir = '%s/cozy-data-indexer' % home
    indexer_env_dir = '%s/virtualenv' % indexer_dir
    python_exe = indexer_dir + '/virtualenv/bin/python'
    indexer_exe = 'server.py'
    process_name = 'cozy-indexer'

    # Check if indexer is already installed, .
    with settings(warn_only=True):
        result = run('curl -X GET http://127.0.0.1:9102/')
        is_installed = result.find("Cozy Data Indexer")
        if is_installed != -1:
            print(green("Data Indexer already installed"))
            return True

    require.files.directory(home, use_sudo=True)

    with cd(home):
        if files.exists('cozy-data-indexer'):
            su_delete('cozy-data-indexer')
        sudo('git clone https://github.com/cozy/cozy-data-indexer.git')

    require.python.virtualenv(indexer_env_dir, use_sudo=True)
    with python.virtualenv(indexer_env_dir):
        python.install_requirements(
            indexer_dir + '/requirements/common.txt', use_sudo=True)

    sudo('chown -R cozy:cozy %s' % home)

    require.supervisor.process(
        process_name,
        command='%s %s' % (python_exe, indexer_exe),
        directory=indexer_dir,
        user='cozy'
    )
    supervisor.restart_process(process_name)

    time.sleep(10)
    result = run('curl -X GET http://127.0.0.1:9102/')
    is_installed = result.find("Cozy Data Indexer")

    if is_installed == -1:
        print_failed("cozy-data-indexer")

    print(green("Data Indexer successfully started"))


@task
def install_data_system():
    '''
    Install Cozy Data System. Daemonize with Haibu.
    '''
    result = sudo('cozy-monitor install data-system')
    installedApp = result.find('successfully installed')
    if installedApp == -1:
        print_failed('data-system')
    else:
        print(green('Data-system successfully installed'))


@task
def install_home():
    '''
    Install Cozy Home
    '''
    result = sudo('cozy-monitor install home')
    installedApp = result.find('successfully installed')
    if installedApp == -1:
        print_failed('home')
    else:
        print(green('Home successfully installed'))


@task
def install_proxy():
    '''
    Install Cozy Proxy
    '''
    result = sudo('cozy-monitor install proxy')
    installedApp = result.find('successfully installed')
    if installedApp == -1:
        print_failed('proxy')
    else:
        print(green('Proxy successfully installed'))


@task
def create_cert():
    '''
    Create SSL certificates.
    '''

    etc_dir = '/etc/cozy'
    require.files.directory(etc_dir, use_sudo=True, owner='cozy')
    with cd(etc_dir):
        sudo('openssl dhparam -out ./dh2048.pem -outform PEM -2 2048')
        sudo('openssl genrsa -out ./server.key 2048')
        sudo(
            'openssl req -new -x509 -days 3650 -key ' +
            './server.key -out ./server.crt  -batch')
        sudo('chmod 640 server.key')
        require.group('ssl-cert')
        sudo('chown cozy:ssl-cert ./server.key')
    print(green('Certificates successfully created.'))


def reset_cert():
    '''
    Reset SSL certificates
    '''

    delete_if_exists('/etc/cozy/dh2048.pem')
    delete_if_exists('/etc/cozy/server.crt')
    delete_if_exists('/etc/cozy/server.key')
    print(green('Previous certificates successfully deleted.'))
    create_cert()


PROXIED_SITE_TEMPLATE = '''
server {
    listen %(port)s;

    ssl_certificate /etc/cozy/server.crt;
    ssl_certificate_key /etc/cozy/server.key;
    ssl_dhparam /etc/cozy/dh2048.pem;
    ssl_session_cache shared:SSL:10m;
    ssl_session_timeout  10m;
    ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
    ssl_ciphers ALL:!aNULL:!eNULL:!LOW:!EXP:!RC4:!3DES:+HIGH:+MEDIUM;
    ssl_prefer_server_ciphers   on;
    ssl on;

    gzip_vary on;
    client_max_body_size 1024M;

    add_header Strict-Transport-Security max-age=2678400;

    location / {
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $http_host;
        proxy_redirect http:// https://;
        proxy_pass %(proxy_url)s;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
    }

    access_log /var/log/nginx/%(server_name)s.log;
}

# Always redirect http:// to https://
server {
    listen 80;
    return 301 https://$host$request_uri;
}

'''


@task
def install_nginx():
    '''
    Install NGINX and make it use certs.
    '''
    if system.distrib_id() == 'Debian':
        if not is_arm():
            key_url = 'http://nginx.org/packages/keys/nginx_signing.key'
            require.file(url=key_url)
            deb.add_apt_key('nginx_signing.key')
            su_delete('nginx_signing.key')

            url = 'http://nginx.org/packages/debian/'
            distrib = 'squeeze'
            if system.distrib_release().startswith('7'):
                distrib = 'wheezy'
            require.deb.source('nginx', url, distrib, 'nginx')

        require.deb.package('nginx')
        contents = PROXIED_SITE_TEMPLATE % {
            'server_name': 'cozy',
            'port': 443,
            'proxy_url': 'http://127.0.0.1:9104'
        }
        require.files.file(
            '/etc/nginx/conf.d/cozy.conf',
            contents=contents,
            use_sudo=True)

    else:
        require.deb.ppa('ppa:nginx/stable')

        require.nginx.site(
            'cozy',
            template_contents=PROXIED_SITE_TEMPLATE,
            enabled=True,
            port=443,
            proxy_url='http://127.0.0.1:9104'
        )
    delete_if_exists('/etc/nginx/conf.d/default.conf')
    delete_if_exists('/etc/nginx/conf.d/example_ssl.conf')
    delete_if_exists('/etc/nginx/sites-enabled/default')
    service.restart('nginx')
    print(green('Nginx successfully installed.'))


@task
def restart_cozy():
    sudo('cozy-monitor restart data-system')
    sudo('cozy-monitor restart home')
    sudo('cozy-monitor restart proxy')
    print(green('Stack restarted successfully.'))


# No setup tasks

@task
def restart_controller():
    if is_pi():
        sudo('/etc/init.d/cozy-controller stop')
        with settings(warn_only=True):
            sudo('pkill node')
        sudo('/etc/init.d/cozy-controller start')
    else:
        supervisor.stop_process('cozy-controller')
        with settings(warn_only=True):
            sudo('pkill node')
        supervisor.start_process('cozy-controller')
    time.sleep(10)


@task
def update_stack():
    '''
    Update applications
    '''
    nodejs.update_package('cozy-controller')
    nodejs.update_package('cozy-monitor')

    restart_controller()
    sudo('cozy-monitor update data-system')
    # we force the home to start because the controller waits before starting
    # it.
    sudo('cozy-monitor start home')
    sudo('cozy-monitor update home')
    sudo('cozy-monitor update proxy')
    update_indexer()
    print(green('Stack updated successfully.'))


@task
def upgrade_to_node10():
    '''
    Upgrade the whole stack to node 0.10.26
    '''
    install_node10()

    nodejs.update_package('cozy-controller')
    nodejs.update_package('cozy-monitor')

    sudo('cozy-monitor uninstall data-system')
    sudo('cozy-monitor uninstall home')
    sudo('cozy-monitor uninstall proxy')
    restart_controller()

    sudo('cozy-monitor install data-system')
    sudo('cozy-monitor install home')
    sudo('cozy-monitor install proxy')
    sudo('rm -rf /usr/local/cozy/apps/*/*/*/node_modules')
    update_all_apps()
    restart_controller()
    print(green('Cozy successfully upgraded to node 0.10.26.'))


@task
def update_all_apps():
    sudo('cozy-monitor update-all')
    print(green('All apps successfully updated.'))


@task
def update_indexer():
    '''
    Update Cozy indexer module.
    '''
    home = '/usr/local/cozy-indexer'
    indexer_dir = '%s/cozy-data-indexer' % home
    indexer_env_dir = '%s/virtualenv' % indexer_dir

    with cd(indexer_dir):
        sudo('git pull origin master')

    with python.virtualenv(indexer_env_dir):
        python.install_requirements(indexer_dir + '/requirements/common.txt',
                                    upgrade=True, use_sudo=True)

    supervisor.restart_process('cozy-indexer')


@task
def reset_account():
    '''
    Delete current user account
    '''
    with cd('ls /usr/local/cozy/apps/home/home/cozy-home/'):
        sudo('coffee commands cleanuser')
    print(green('Current account deleted.'))


@task
def reset_controller_token():
    '''
    Reset controller token
    '''

    file_path = '/etc/cozy/controller.token'
    delete_if_exists(file_path)
    print(green('Controller token successfully deleted.'))

    require.files.file(
        path=file_path,
        mode='700',
        contents=TOKEN,
        use_sudo=True,
        owner='cozy-home'
    )
    print(green('Controller token successfully generated.'))


@task
def reset_security_tokens():
    '''
    Reset all the security tokens for the Cozy (SSL certificates,
    Controller token, CouchDB superuser)
    '''

    reset_cert()
    reset_controller_token()
    config_couchdb()
    print(green('All the tokens have been reset.'))
    restart_cozy()
    service.restart('nginx')


"""Uninstall tasks"""


@task
def uninstall_all():
    '''
    Uninstall the whole stack (work in progress)
    '''

    sudo('cozy-monitor uninstall-all')
    if ask_for_confirmation("Cozy"):
        uninstall_cozy()
    if ask_for_confirmation("Node.js"):
        uninstall_node10()
    if ask_for_confirmation("CouchDB"):
        uninstall_couchdb()
    if ask_for_confirmation("Postfix"):
        uninstall_postfix()
    if ask_for_confirmation("Cozy users"):
        sudo('userdel -r cozy')
        sudo('userdel -r cozy-data-system')
        sudo('userdel -r cozy-home')


@task
def uninstall_node10():
    '''
    Uninstall node 0.10.26
    '''

    sudo('npm uninstall npm')
    version = '0.10.26'
    folder = 'node-v%s' % version
    filename = folder + '.tar.gz'
    require.file(url='http://nodejs.org/dist/v%s/%s' % (version, filename))
    sudo('tar -xzf %s' % filename)

    with cd('%s' % folder):
        sudo('./configure')
        sudo('make uninstall')
        sudo('make distclean')
    su_delete('%s*' % folder)
    print(green('Node {0} successfully uninstalled'.format(version)))


@task
def uninstall_couchdb():
    '''
    Uninstall CouchDB 1.3.0 or 1.5.0
    '''
    version = get_couchdb_version()
    require.file(
        url='http://apache.crihan.fr/dist/couchdb/source/' +
        '%s/apache-couchdb-%s.tar.gz' % (version, version))
    run('tar -xzvf apache-couchdb-%s.tar.gz' % version)
    with cd('apache-couchdb-%s' % version):
        sudo('./configure')
        sudo('make uninstall')
        sudo('make distclean')
    su_delete('/usr/local/share/couchdb')
    su_delete('/usr/local/lib/couchdb')
    su_delete('/usr/local/var/lib/couchdb')
    su_delete('/usr/local/var/log/couchdb')
    su_delete('/usr/local/var/run/couchdb')
    su_delete('/usr/local/share/doc/couchdb')
    su_delete('/usr/local/bin/couchjs')
    su_delete('/usr/local/bin/couchdb')
    su_delete('apache-couchdb-%s' % version)
    su_delete('apache-couchdb-%s.tar.gz' % version)
    su_delete('/etc/supervisor/conf.d/couchdb.conf')
    su_delete('/etc/cozy/couchdb.login')
    # removes dependency of CouchDB
    require.deb.uninstall('erlang', False, ['--auto-remove'])
    supervisor.update_config()
    print(green('CouchDB %s successfully uninstalled' % version))


@task
def uninstall_postfix():
    '''
    Uninstall postfix.
    '''
    require.deb.uninstall('postfix')
    print(green('Postfix successfully uninstalled'))


@task
def uninstall_cozy():
    '''
    Uninstall postfix.
    '''
    supervisor.stop_process('cozy-controller')
    supervisor.stop_process('cozy-indexer')
    su_delete('/usr/local/var/cozy-indexer')
    su_delete('/usr/local/cozy-indexer')
    su_delete('/usr/local/cozy')
    su_delete('/home/cozy*')
    su_delete('/etc/cozy')
    su_delete('/etc/nginx/conf.d/cozy.conf')
    su_delete('/etc/supervisor/conf.d/cozy-controller.conf')
    su_delete('/etc/supervisor/conf.d/cozy-indexer.conf')
    supervisor.update_config()
    print(green('Cozy successfully uninstalled'))


"""Help tasks"""


@task
def help(name=None):
    """Display help for a given task

    Options:
        name    - The task to display help on.

    To display a list of available tasks type:

        $ fab -l

    To display help on a specific task type:

        $ fab help:<name>
    """

    if name is None:
        name = "help"

    task = crawl(name, state.commands)
    if isinstance(task, Task):
        doc = getattr(task, "__doc__", None)
        if doc is not None:
            print("Help on {0:s}:".format(name))
            print(doc)
        else:
            print("No help available for {0:s}".format(name))
    else:
        print("No such task {0:s}".format(name))
        print("For a list of tasks type: fab -l")