"""
Arcs
====

This example showcases the ability of `iplotx` to curve edges into arcs, using tension to define the angular span of the arc.
"""

import igraph as ig
import matplotlib.pyplot as plt
import iplotx as ipx


g = ig.Graph.Full(4)
layout = [[0, 0], [1, 0], [2, 0], [3, 0]]

fig, ax = plt.subplots()
ipx.plot(
    g,
    layout=layout,
    ax=ax,
    edge_arc=True,
    edge_tension=-1,
)

# %%
#
# Other values of tension can be used to create different arc shapes:

fig, axs = plt.subplots(2, 2, figsize=(8, 8))
for tension, ax in zip([0.5, 2.5, -0.5, -2.5], axs.ravel()):
    ipx.plot(
        g,
        layout=layout,
        ax=ax,
        edge_arc=True,
        edge_tension=tension,
        margins=0.15,
        title=f"Edge tension = {tension:.2f}",
    )

# %%
# .. tip::
#  Tension is defined as the tangent of the quarter of the angle spanned by the arc. A tension of 0 gives
#  a straight line, a tension of 1 gives a semicircle, and higher tensions give increasingly larger arcs. A tension of
#  infinity would give you a straight line away from the target vertex, but is not accepted by the library. Negative
#  tensions result in arcs curving in the opposite direction.
#