"""
Zoom-level dependent labels
===========================
"""

# %%
# If there are many data points, their labels may be difficult to read. To selectively display
# labels depending on the zoom level, use the :class:`plotly.graph_objects.FigureWidget` class and
# register a callback.
#
# .. hint::
#
#    You will need to install the |anywidget| package to use
#    the :class:`plotly.graph_objects.FigureWidget` class. See
#    the `Plotly documentation <https://plotly.com/python/figurewidget>`__ for details.

import functools

import plotly
import plotly.graph_objects as go
import scipy

from pdendro import attach_dendrogram

X = plotly.data.iris()[["sepal_length", "sepal_width", "petal_length", "petal_width"]]
Z = scipy.cluster.hierarchy.linkage(X)

fig = go.FigureWidget()
_ = attach_dendrogram(fig, Z)

# %%
# The following code registers a callback to change labels on zooming:

def update_ticks(axis, axis_range, all_ticktext, max_n_ticks):
    """Update ticks for limiting the number."""
    step = int(abs(axis_range[1]-axis_range[0])//max_n_ticks) + 1
    axis.update(tickvals=list(range(0, len(all_ticktext), step)), ticktext=all_ticktext[::step])

# axis for data point labels
axis = fig.layout.xaxis

# get all labels
all_ticks = zip(axis.tickvals, axis.ticktext, strict=True)
all_ticks = sorted(all_ticks, key=lambda item: item[0])
_, all_ticktext = zip(*all_ticks, strict=True)

# register a callback
callback = functools.partial(update_ticks, all_ticktext=all_ticktext, max_n_ticks=5)
axis.on_change(callback, "range")

# initialize
callback(axis, axis.range)

# %%
# The figure can be shown as follows:

fig

# sphinx_gallery_start_ignore

fig.update_layout(margin={"l": 5, "r": 5, "t": 5, "b": 5}, width=550, height=330)

# generate a zoomed-out image
fig.write_image("zoomed_out_figure.svg")

# generate a zoomed-in image
fig.update_xaxes(range=[-0.5, 7.5])
fig.write_image("zoomed_in_figure.svg")

# sphinx_gallery_end_ignore

# %%
# .. note::
#
#    The figure is not displayed in the documentation because
#    the :class:`plotly.graph_objects.FigureWidget` object can only be displayed in |jupyter|.
#    The following images illustrate the appearance at various zoom levels:
#
#    .. image:: /_galleries/examples/data_point_label/zoomed_out_figure.svg
#       :alt: zoomed-out figure
#       :align: center
#
#    .. image :: /_galleries/examples/data_point_label/zoomed_in_figure.svg
#       :alt: zoomed-in figure
#       :align: center

# sphinx_gallery_start_ignore

import plotly.io as pio

# generate a thumbnail
fig.update_layout(margin=None, width=None, height=None)
pio.show(fig)

# sphinx_gallery_end_ignore