from __future__ import annotations
from r6_guided import Graph, S, T, Gen1, Gen2, Generic, Optional
from queue import PriorityQueue
from typing import Tuple, TYPE_CHECKING

def a_star( graph: Graph[ T ], start: T ) -> Gen2[ T, int ]:
    q : PriorityQueue[ Tuple[ int, T ] ] = PriorityQueue()
    q.put( ( 0, start ) )
    while not q.empty():
        prio, item = q.get()
        for succ in graph[ item ]:
            nprio = yield succ
            q.put( ( nprio, succ ) )

class cor_iter( Generic[ T, S ] ):
    def __init__( self, cor: Gen2[ T, S ] ) -> None:
        self.to_send : Optional[ S ] = None
        self.cor = cor

    def __iter__( self ) -> cor_iter[ T, S ]:
        return self

    def __next__( self ) -> T:
        if self.to_send is not None:
            return self.cor.send( self.to_send )
        else:
            return next( self.cor )

    def reply( self, v: S ) -> None:
        self.to_send = v

if TYPE_CHECKING:
    def bfs( graph: Graph[ T ], start : T ) -> Gen1[ T ]:
        pass