chain_example_03.py

# Prerequisites:
#
# - Using Python 3.5+
# - Install manhattan-chains (`pip install manhattan-chains`)
#

from manhattan.chains import Chain


# Define the chains

# Show the list

show = Chain([
    'get_list',
    'render_list'
])

@show.link
def get_list(state):
    if state.args[0] not in state.lists:
        return 'List not found: ' + state.args[0]

    state.list_name = state.args[0]
    state.list = state.lists[state.list_name]

@show.link
def render_list(state):
    lines = [state.list_name, '-' * len(state.list_name)]
    lines += ['- ' + item for item in state.list]
    return '\n' + '\n'.join(lines) + '\n'


# Add an item to the list

add = Chain([
    'get_list',
    'add_item',
    'render_list'
])

add.set_link(get_list)
add.set_link(render_list)

@add.link
def add_item(state):
    state.list.append(state.args[1])


# Add a new list

new = Chain([
    'is_name_unique',
    [
        [
            'add_list',
            'render_list'
        ],
        [
            'make_name_unique',
            'add_list',
            'render_list'
        ]
    ]
])

new.set_link(render_list)

@new.link
def is_name_unique(state):
    state.list_name = state.args[0]
    return state.list_name not in state.lists

@new.link
def add_list(state):
    state.lists[state.list_name] = []
    state.list = state.lists[state.list_name]

@new.link
def make_name_unique(state):
    i = 1
    while state.list_name in state.lists:
        state.list_name = '{0}-{1}'.format(state.list_name, i)


# Define a table of lists

lists = {
    'shopping': ['milk', 'eggs'],
    'todo': ['take dog to groomers']
}


# Define a table of actions the user can perform

actions = {
    'add': add,
    'new': new,
    'show': show
}


# Parse the users commands

while True:
    user_input = input('? ')
    [action, *args] = user_input.split(' ')

    if action == 'quit':
        break

    elif action in actions:
        output = actions[action](lists=lists, args=args)
        print(output)