"""Solution to 2020/23"""

from collections import deque

EXAMPLE = '389125467'
INPUT = '952316487'

# INPUT = EXAMPLE

MOVES = 10_000_000

INPUT = list(map(int, INPUT))
INPUT = INPUT + list(range(max(INPUT) + 1, 1_000_000 + 1))


def main():
    cups = CrabCups(INPUT)
    print(cups)

    for move in range(MOVES):
        if move % 1_000_000 == 0:
            print(f'-- MOVE {move} --')
        cups.move()

    print()
    print('finished')
    print(cups._nodes[1].next.value * cups._nodes[1].next.next.value)

    exit()


class CrabCups:
    def __init__(self, cups):
        nodes = dict()
        i = 0
        prev = None
        while i < len(cups):
            node = Node(cups[i])
            if prev:
                node.prev = prev
                prev.next = node
            prev = node
            nodes[cups[i]] = node
            i += 1
        nodes[cups[0]].prev = nodes[cups[-1]]
        nodes[cups[-1]].next = nodes[cups[0]]
        self._nodes = nodes
        self.cur = nodes[cups[0]]
        self.cup_count = len(cups)
        self.last_cur = None
        self.last_pick_up = None
        self.last_destination = None

    def move(self):
        pick_up = set()
        link = self.cur
        self.last_cur = self.cur
        self.last_pick_up = link.next
        for _ in range(3):
            link = link.next
            pick_up.add(link.value)

        # wire cur with cup after pickups
        link.next.prev = self.cur
        self.cur.next = link.next

        # find dest
        dest = self.cur.value - 1
        dest = dest if dest != 0 else self.cup_count
        while dest in pick_up:
            dest -= 1
            dest = dest if dest != 0 else self.cup_count
        dest = self._nodes[dest]
        self.last_dest = dest

        dest.next.prev = link
        link.next = dest.next

        link = link.prev.prev
        dest.next = link
        link.prev = dest

        self.cur = self.cur.next

    def as_list(self, start):
        cups = [start.value]
        cur = start.next
        while not cur is start:
            cups.append(cur.value)
            cur = cur.next
        return cups


class Node:
    next = None
    prev = None

    def __init__(self, val):
        self.value = val


main()