emmental/trackdb/stack.py

# Copyright 2021 (c) Anna Schumaker.
from . import tags

class TagStack:
    def __init__(self):
        self.tags = [ ]

    def __do_next__(self, tag):
        if track := tag.next():
            track.add_to_playlist("Previous")
        return track

    def next(self):
        if len(self.tags) == 0:
            return self.__do_next__(tags.User["Collection"])
        if track := self.__do_next__(self.tags[0]):
            return track
        self.pop()
        return self.next()

    def pop(self):
        self.tags.pop(0)

    def previous(self):
        return tags.User["Previous"].next()

    def push(self, tag):
        if tag == tags.User["Previous"]:
            return
        if tag == tags.User["Collection"]:
            self.tags.clear()
            return
        if tag in self.tags:
            self.tags.remove(tag)
        self.tags.insert(0, tag)
        tag.stacked()

    def queue(self, track):
        track.add_to_playlist("Up Next")
        self.push(tags.User["Up Next"])