__license__ = "Public Domain"


SCREEN_SIZE = (800,600)

## Initialize Pygame library and create the screen.
import pygame
pygame.init()
screen = pygame.display.set_mode((SCREEN_SIZE))
from pygame.locals import * ## Convenient constants.

## Create a timer for framerate regulation.
clock = pygame.time.Clock()

import random ## For demo
import time ## For FPS counter.




class World:
    """A demo of a game world with constant "facts".

    These facts can be changed by the game's *Logic functions."""
    def __init__(self,**options):
        self.world_time = 0
        self.alignment = "Good"
        self.squirrels = True




class Game:
    """The main class of the game.

    Attempts to follow the MVC Architecture:
    -Model: class World
    -View: *Draw functions
    -Controller (and game logic): *Logic functions
    """
    def __init__(self,**options):
        self.logic_function = None
        self.draw_function = None
        self.states = []

        self.framerate = 20

        self.world = World()

    """ State Control """

    def GetStateFunctions(self,state_name):
        try:
            name = state_name + "Logic"
            logic_function = getattr(self,name)
            name = state_name + "Draw"
            draw_function = getattr(self,name)
        except:
            raise "Error: Couldn't find matching logic/draw functions for state \""+state_name+"\"."
        return logic_function, draw_function        

    def PushState(self,state_name):
        """Start a new game state, but revert when done."""
        logic_function, draw_function = self.GetStateFunctions(state_name)
        self.logic_function = logic_function
        self.draw_function = draw_function
        self.states.append(state_name)

    def PopState(self):
        """End the current game state."""
        try:
            self.states.pop()
            if self.states:
                self.logic_function, self.draw_function = self.GetStateFunctions(self.states[-1])
            else:
                self.logic_function, self.draw_function = None, None
        except:
            raise "Error: There are no game states to pop!"

    def JumpState(self,state_name):
        """Pop and push to end this state and switch to another."""
        self.PopState()
        self.PushState(state_name)

    """ Main Loop """

    def MainLoop(self):
        """Do basic event-handling until the program ends.

        The game logic and drawing are handled by a pair
        of functions that can be replaced on the fly to
        represent switching to different aspects of gameplay,
        such as a title screen, battle screen etc.."""
        cycles = 0
        starting_time = time.time()
        while self.states: ## Until there's nothing to do:
            self.draw_function()
            unhandled_events = self.logic_function()

            if unhandled_events:
                for event in unhandled_events:
                    if event.type == QUIT:
                        return
                    elif event.type == KEYDOWN and event.key == K_ESC:
                        return

            pygame.display.update()
            clock.tick(self.framerate)
            cycles += 1

        ## At program's end, display the overall framerate.
        if cycles:
            ending_time = time.time()
            fps = cycles/float(ending_time - starting_time)
            print "FPS: "+str(fps)

    """ Game States """

    def NevadaLogic(self):
        """Nonsense demo. Advance the world's time."""

        ## Specialized game logic. Increment the game world's timer.
        self.world.world_time += 1

        ## Specialized input handling.
        for event in pygame.event.get():
            if event.type == KEYDOWN:
                self.PopState()
                print "World timer: "+str(self.world.world_time)
                return

    def NevadaDraw(self):
        """Nonsense demo. Draw stuff."""
        color = random.randint(80,180)
        x = random.randint(0,700)
        y = random.randint(0,500)
        screen.fill((0,0,0))
        pygame.draw.rect(screen,(color),(x,y,100,100))

g = Game() ## Create the demo Game object.
g.MainLoop() ## Run. Nothing will happen; no states to run.
g.PushState("Nevada") ## Give it something to do.
g.MainLoop() ## Now go, displaying flashing blue squares till a key is pressed.