"""Display a game area."""

import pygame
import pymunk
import pymunk.pygame_util

from nagslang.constants import COLLISION_TYPE_PLAYER, CALLBACK_COLLIDERS
from nagslang.events import ScreenChange, DoorEvent, FireEvent
from nagslang.level import Level
from nagslang.protagonist import Protagonist
from nagslang.screens.base import Screen
from nagslang.game_object import Bullet


class ControlKeys(object):
    direction_keys = {
        (0, 1): set([pygame.locals.K_UP, pygame.locals.K_w]),
        (0, -1): set([pygame.locals.K_DOWN, pygame.locals.K_s]),
        (-1, 0): set([pygame.locals.K_LEFT, pygame.locals.K_a]),
        (1, 0): set([pygame.locals.K_RIGHT, pygame.locals.K_d]),
    }

    def __init__(self):
        self.keys_down = set()

    def key_down(self, key):
        self.keys_down.add(key)

    def key_up(self, key):
        self.keys_down.discard(key)

    def handle_event(self, ev):
        if ev.type == pygame.locals.KEYDOWN:
            self.key_down(ev.key)
        elif ev.type == pygame.locals.KEYUP:
            self.key_up(ev.key)

    def get_direction(self):
        dx, dy = 0, 0
        for (tx, ty), keys in self.direction_keys.iteritems():
            if self.keys_down & keys:
                dx += tx
                dy += ty
        return (dx, dy)


class Drawables(object):
    def __init__(self):
        self._drawables = {}

    def add(self, drawable):
        self._drawables.setdefault(drawable.zorder, []).append(drawable)

    def remove(self, drawable):
        self._drawables[drawable.zorder].remove(drawable)

    def get_drawables(self):
        for zorder in sorted(self._drawables):
            for drawable in self._drawables[zorder]:
                yield drawable

    __iter__ = get_drawables


class AreaScreen(Screen):

    def setup(self):
        self._disable_render = False  # Avoid redrawing on scene changes
        self.keys = ControlKeys()
        self._level = Level(self.name)
        self._level.load(self.space)
        self._drawables = Drawables()
        self.add_walls()
        self._add_collision_handlers()
        if self.protagonist is not None:
            # We do things this way to avoid extra pymunk
            # juggling to move objects between spaces
            old_protagonist = self.protagonist
            self.add_protagonist()
            self.protagonist.copy_state(old_protagonist)
        else:
            self.add_protagonist()
        self.add_game_objects()

    def _collision_pre_solve_handler(self, space, arbiter):
        gobj = arbiter.shapes[1].physicser.game_object
        result = gobj.collide_with_protagonist(self.protagonist)
        # The collision handler must return `True` or `False`. We don't want to
        # accidentally reject collisions from handlers that return `None`, so
        # we explicitly check for `False` and treate everything else as `True`.
        if result is False:
            return False
        return True

    def _add_collision_handlers(self):
        for collision_type in CALLBACK_COLLIDERS:
            self.space.add_collision_handler(
                COLLISION_TYPE_PLAYER, collision_type,
                pre_solve=self._collision_pre_solve_handler)

    def add_walls(self):
        self.walls = []
        body = pymunk.Body()
        body.position = (0, 0)
        walls = self._level.get_walls()
        for wall in walls:
            corners = wall
            corner = corners[-1]
            for next_corner in corners:
                wall = pymunk.Segment(body, corner, next_corner, 5)
                wall.elasticity = 1.0
                self.walls.append(wall)
                corner = next_corner
        self.space.add(*self.walls)

    def add_game_objects(self):
        for drawable in self._level.drawables:
            self._drawables.add(drawable)

    def add_protagonist(self):
        self.protagonist = Protagonist(self.space, (350, 300))
        self._drawables.add(self.protagonist)

    def handle_event(self, ev):
        if ev.type == pygame.locals.KEYDOWN:
            if ev.key == pygame.locals.K_ESCAPE:
                ScreenChange.post('menu')
            if ev.key == pygame.locals.K_c:
                self.protagonist.toggle_form()
                self.world.transformations += 1
            if ev.key == pygame.locals.K_SPACE:
                self.world.attacks += 1
                self.protagonist.attack()
        elif DoorEvent.matches(ev):
            self.protagonist.set_position(ev.dest_pos)
            if ev.destination != self.name:
                # Go to anther screen
                self._disable_render = True
                self.world.rooms += 1
                ScreenChange.post(ev.destination, self.protagonist)
                return
            # else we're teleporting within the screen, and just the
            # position change is enough
        elif FireEvent.matches(ev):
            bullet = Bullet(self.space, ev.source, ev.impulse)
            self._drawables.add(bullet)
        self.keys.handle_event(ev)

    def _calc_viewport(self, level_surface, display_surface):
        level_size = level_surface.get_size()
        display_size = display_surface.get_size()
        protagnist_pos = self.protagonist.physicser.get_render_position(
            level_surface)
        x_wide = display_size[0] // 2
        y_wide = display_size[1] // 2
        if display_size[0] > level_size[0]:
            x = -(display_size[0] - level_size[0]) // 2
        elif protagnist_pos[0] < x_wide:
            x = 0
        elif protagnist_pos[0] > level_size[0] - x_wide:
            x = level_size[0] - display_size[0]
        else:
            x = protagnist_pos[0] - x_wide
        if display_size[1] > level_size[1]:
            y = -(display_size[1] - level_size[1]) // 2
        elif protagnist_pos[1] < y_wide:
            y = 0
        elif protagnist_pos[1] > level_size[1] - y_wide:
            y = level_size[1] - display_size[1]
        else:
            y = protagnist_pos[1] - y_wide
        return pygame.rect.Rect(x, y, display_size[0], display_size[1])

    def render(self, surface):
        if self._disable_render:
            return
        background = self._level.get_background()
        mysurface = background.copy()
        for drawable in self._drawables:
            drawable.render(mysurface)
        render_rect = self._calc_viewport(mysurface, surface)
        surface.blit(mysurface, (0, 0), render_rect)
        for overlay in self._level.overlay_drawables:
            if overlay.is_visible():
                overlay.render(surface, render_rect.topleft)
        self.render_health_bar(surface)

    def tick_protagonist(self):
        dx, dy = self.keys.get_direction()
        self.protagonist.set_direction(dx, dy)

    def tick(self, seconds):
        self.tick_protagonist()
        for drawable in self._drawables:
            drawable.animate()

        super(AreaScreen, self).tick(seconds)

    def render_health_bar(self, surface, damage_experienced=None):
        rect = pygame.Rect(50, 500, 110, 50)
        if damage_experienced:
            health_box_colour = pygame.color.THECOLORS['red']
        else:
            health_box_colour = pygame.color.THECOLORS['white']
        pygame.draw.rect(surface,  health_box_colour, rect, 0)
        if self.protagonist.in_human_form():
            health_colour = pygame.color.THECOLORS['red']
        else:
            health_colour = pygame.color.THECOLORS['purple']
        rect = pygame.Rect(55, 505, self.protagonist.get_health_level(), 40)
        pygame.draw.rect(surface,  health_colour,
                         rect, 0)