from IPython.lib.backgroundjobs import BackgroundJobManager
from IPython.core.magic         import register_line_magic
from IPython.display            import display
from IPython                    import get_ipython
from itertools                  import islice, chain
from ipywidgets                 import IntProgress, HTML, VBox

# Iterate through a generator without peaking, yeilding a list of elements
#
def chunks(iterable, size):
    iterator = iter(iterable)
    for first in iterator:
        yield list(chain([first], islice(iterator, (len(iterable)//size) - 1)))

# Magics for interacting with jobs
#
def jobs_manager():
    jobs = BackgroundJobManager()

    @register_line_magic
    def job(line):
        ip = get_ipython()
        jobs.new(line, ip.user_global_ns)

    return jobs

# Pretty progress bars for for jupyter notebook
#
def log_progress(sequence, every=None, size=None, name='Jobs'):
    is_iterator = False
    if size is None:
        try:
            size = len(sequence)
        except TypeError:
            is_iterator = True
    if size is not None:
        if every is None:
            if size <= 200:
                every = 1
            else:
                every = int(size / 200)     # every 0.5%
    else:
        assert every is not None, 'sequence is iterator, set every'

    if is_iterator:
        progress = IntProgress(min=0, max=1, value=1)
        progress.bar_style = 'info'
    else:
        progress = IntProgress(min=0, max=size, value=0)
    label = HTML()
    box = VBox(children=[label, progress])
    display(box)

    index = 0
    try:
        for index, record in enumerate(sequence, 1):
            if index == 1 or index % every == 0:
                if is_iterator:
                    label.value = '{name}: {index} / ?'.format(
                        name=name,
                        index=index
                    )
                else:
                    progress.value = index
                    label.value = u'{name}: {index} / {size}'.format(
                        name=name,
                        index=index,
                        size=size
                    )
            yield record
    except:
        progress.bar_style = 'danger'
        raise
    else:
        progress.bar_style = 'success'
        progress.value = index
        label.value = "{name}: {index}".format(
            name=name,
            index=str(index or '?')
        )