#!/usr/bin/env python

from __future__ import division

import string
import random
from collections import deque
from copy import deepcopy
import traceback

from common import *

import pygame
pygame.init()
from pygame.locals import *

def scale_aspect((source_width, source_height), (target_width, target_height)):
    source_aspect = source_width / source_height
    target_aspect = target_width / target_height
    if source_aspect > target_aspect:
        # restrict width
        width = target_width
        height = width / source_aspect
    else:
        # restrict height
        height = target_height
        width = height * source_aspect
    return (width, height)

class SnakeEngine(object):
    EDGE_COLOR = (255, 255, 255)
    EDGE_WIDTH = 1

    def __init__(self, rows, columns, n_apples, width=800, height=600, fullscreen=False):
        super(SnakeEngine, self).__init__()
        flags = 0
        if fullscreen:
            flags |= pygame.FULLSCREEN
        self.screen = pygame.display.set_mode((width, height), flags)

        self.width = width
        self.height = height

        self.letters = list(string.lowercase)
        self.letters.reverse()

        self.bots = {}

        self.new_game(rows, columns, n_apples)

    def get_random_position(self):
        x = random.randint(0, self.columns - 1)
        y = random.randint(0, self.rows - 1)
        return (x, y)

    def new_game(self, rows, columns, n_apples):
        self.rows = rows
        self.columns = columns

        # make board
        self.board = [[Squares.EMPTY for x in xrange(columns)] for y in xrange(rows)]
        for i in xrange(n_apples):
            x, y = self.get_random_position()
            self.board[y][x] = Squares.APPLE

        # make board surface
        self.board_width, self.board_height = scale_aspect(
            (columns, rows), (self.width, self.height)
        )
        self.surface = pygame.Surface((self.board_width, self.board_height))

        # load sprites
        xscale = self.board_width / self.columns
        yscale = self.board_height / self.rows

        def load_image(image):
            new_size = scale_aspect(image.get_size(), (xscale, yscale))
            return pygame.transform.smoothscale(image, new_size)

        self.apple = load_image(Sprites.APPLE)
        self.eyes = load_image(Sprites.EYES)

    def add_bot(self, bot):
        """
        A bot is a callable object, with this method signature:
            def bot_callable(
                board=[[cell for cell in row] for row in board],
                position=(snake_x, snake_y)
                ):
                return random.choice('RULD')
        """
        letter = self.letters.pop()

        for i in xrange(self.rows * self.columns):
            x, y = self.get_random_position()
            if self.board[y][x] == Squares.EMPTY:
                break
        else:
            raise KeyError, "Could not insert snake into the board."

        colour = (255, 0, 0)
        self.bots[letter] = [bot, colour, deque([(x, y)])]
        self.board[y][x] = letter.upper()
        return letter

    def remove_bot(self, letter):
        letter = letter.lower()

        for row in self.board:
            for x, cell in enumerate(row):
                if cell.lower() == letter:
                    row[x] = Squares.EMPTY

        del self.bots[letter]

    def draw_board(self):
        xscale = self.board_width / self.columns
        yscale = self.board_height / self.rows

        # Draw grid.
        for y, row in enumerate(self.board):
            for x, cell in enumerate(row):
                left = int(x * xscale)
                top = int(y * yscale)
                w = int((x + 1) * xscale) - left
                h = int((y + 1) * yscale) - top
                r = Rect(left, top, w, h)

                # Draw a square.
                pygame.draw.rect(self.surface, self.EDGE_COLOR, r,
                                 self.EDGE_WIDTH)

                # Draw the things on the square.
                if cell == Squares.APPLE:
                    self.surface.blit(self.apple, r.topleft)

                elif cell.isalpha(): # Snake...
                    colour = self.bots[cell.lower()][1]
                    self.surface.fill(colour, r)

                    if cell.isupper(): # Snake head
                        self.surface.blit(self.eyes, r.topleft)

    def update_snakes(self):
        directions = {
            'U': (0, -1),
            'D': (0, 1),
            'L': (-1, 0),
            'R': (1, 0),
        }

        for letter, (bot, colour, path) in self.bots.items():
            board = deepcopy(self.board)
            try:
                x, y = path[0]
                d = bot(board, (x, y))

                # Sanity checking...
                assert isinstance(d, basestring), \
                    "Return value should be a string."
                d = d.upper()
                assert d in directions, "Return value should be 'U', 'D', 'L' or 'R'."

                # Get new position.
                dx, dy = directions[d]
                nx = x + dx
                ny = y + dy

                oldcell = self.board[ny][nx]
                if oldcell in (Squares.EMPTY, Squares.APPLE):
                    # Move snake forward.
                    self.board[ny][nx] = letter.upper()
                    path.append((nx, ny))

                    # Make old head into body.
                    self.board[y][x] = letter.lower()

                    if oldcell != Squares.APPLE:
                        # Remove last part of snake.
                        ox, oy = path.popleft()
                        self.board[oy][ox] = Squares.EMPTY
                else:
                    self.remove_bot(letter)

            except:
                print "Exception in bot %s (%s):" % (letter.upper(), bot)
                print '-'*60
                traceback.print_exc()
                print '-'*60
                self.remove_bot(letter)

    def run(self):
        clock = pygame.time.Clock()

        running = True
        while running:
            for event in pygame.event.get():
                if event.type == pygame.QUIT or \
                   (event.type == pygame.KEYDOWN and event.key == K_ESCAPE):
                    running = False
                    break
            if not running: break

            # Clear the screen.
            self.screen.fill((0, 0, 0))
            self.surface.fill((0, 0, 0))

            # Draw the board.
            self.draw_board()

            # Center the board.
            x = (self.width - self.board_width) / 2
            y = (self.height - self.board_height) / 2
            self.screen.blit(self.surface, (x, y))

            # Update the display.
            pygame.display.flip()
            clock.tick(40)

            # Let the snakes move!
            self.update_snakes()

        # Early window close, late process cleanup.
        pygame.display.quit()

if __name__ == '__main__':
    from bots import random_bot

    game = SnakeEngine(25, 25, 10)
    game.add_bot(random_bot)
    game.run()