"""Functions and classes related to generating regions.
"""
from . import Utl, Node, Ifc, g

def makelink(newnode, oldnode, direction):
    """Make reciprocal links between two nodes.
    
    This function takes two nodes and builds a link between them in the
    specified direction.
    
    @param newnode: The node the link is to.
    @type newnode: L{th.Node.Node}
    @param oldnode: The node the link is from.
    @type oldnode: L{th.Node.Node}
    @param direction: The direction the link is in. See L{th.Map} for possible
        directions.
    @type direction: L{int}
    """
    if direction == 0:
        if oldnode: oldnode.north = newnode
        if newnode: newnode.south = oldnode
    elif direction == 1:
        if oldnode: oldnode.east = newnode
        if newnode: newnode.west = oldnode
    elif direction == 2:
        if oldnode: oldnode.south = newnode
        if newnode: newnode.north = oldnode
    elif direction == 3:
        if oldnode: oldnode.west = newnode
        if newnode: newnode.east = oldnode

def gen_region(start, region_num, region_func):
    """Generate a region.
    
    This function is called by L{th.Map.genregions} with functions imported
    from the L{th.regions} modules.
    
    L{region_func} is called with L{start} as the first parameter,
    L{region_num} as the second parameter, and the initial direction of the
    region from the starting node as the third parameter. See L{th.Map} for 
    possible directions.
    
    @type start: L{th.Node.Node}
    @type region_num: L{int}
    """
    initdr, stop = Utl.rn(4), 0
    while stop < 4:
        initdr = (initdr + 1) % 4
        if (initdr == 0 and start.north) or (initdr == 1 and start.east) or \
           (initdr == 2 and start.south) or (initdr == 3 and start.west):
            stop += 1
        else:
            region_func(start, region_num, initdr)
            break

class RegionBridge(Node.Node):
    """A node representing the bridge between the main grid and a region.
    """
    def xinit(self):
        self.special_symbol = '&'
        self.description = """You are at a staircase in the steam tunnels. One way leads
back out into the winding maze and one way leads deeper in."""
        self.name = "Stairs Down"
        self.unique = True
        self.tunnel = False
        self.color = Ifc.BRIGHT_RED
        self.bridge = True
        self.north, self.south, self.east, self.west = (
            self.src.north, self.src.south, self.src.east, self.src.west)
        if self.north: self.north.south = self
        if self.south: self.south.north = self
        if self.east: self.east.west = self
        if self.west: self.west.east = self
        self.mons, self.items = self.src.mons, self.src.items
        for o in self.mons + self.items:
            o.here = self
        self.x, self.y = self.pos = self.src.pos
        if self.src in g.nodes:
            g.nodes.remove(self.src)
        del self.src