# SPDX-License-Identifier: CC0-1.0

import sys

from subprocess import Popen, PIPE
import warnings

from matplotlib import interactive, is_interactive
from matplotlib._pylab_helpers import Gcf
from matplotlib.backend_bases import (_Backend, FigureManagerBase)
from matplotlib.backends.backend_agg import FigureCanvasAgg


# XXX heuristic for interactive repl
if sys.flags.interactive:
    interactive(True)


class FigureManagerSixel(FigureManagerBase):

    def show(self):

        try:
            print()
            p = Popen(["convert", 'png:-', 'sixel:-'], stdin=PIPE)
            self.canvas.figure.savefig(p.stdin, bbox_inches="tight", format='png') 
            p.stdin.close()
            p.wait()
        except FileNotFoundError:
            warnings.warn("Unable to convert plot to sixel format: Imagemagick not found.")


class FigureCanvasSixel(FigureCanvasAgg):
    manager_class = FigureManagerSixel


@_Backend.export
class _BackendSixelAgg(_Backend):

    FigureCanvas = FigureCanvasSixel
    FigureManager = FigureManagerSixel

    # Noop function instead of None signals that
    # this is an "interactive" backend
    mainloop = lambda: None

    # XXX: `draw_if_interactive` isn't really intended for
    # on-shot rendering. We run the risk of being called
    # on a figure that isn't completely rendered yet, so
    # we skip draw calls for figures that we detect as
    # not being fully initialized yet. Our heuristic for
    # that is the presence of axes on the figure.
    @classmethod
    def draw_if_interactive(cls):
        manager = Gcf.get_active()
        if is_interactive() and manager.canvas.figure.get_axes():
            cls.show()

    @classmethod
    def show(cls, *args, **kwargs):
        _Backend.show(*args, **kwargs)
        Gcf.destroy_all()