from io import BytesIO
import os
import struct
from itertools import chain

from pytouhou.utils.interpolator import Interpolator
from pytouhou.game.sprite import Sprite


class Background(object):
    def __init__(self, stage, anim):
        self.stage = stage
        self.anim = anim
        self.objects = []
        self.object_instances = []
        self._uvs = b''
        self._vertices = b''
        self.nb_vertices = 0

        self.build_objects()
        self.build_object_instances()


    def build_object_instances(self):
        self.object_instances = []
        for obj, ox, oy, oz in self.stage.object_instances:
            obj_id = self.stage.objects.index(obj)

            obj_instance = []
            for face_vertices, face_uvs in self.objects[obj_id]:
                obj_instance.append((tuple((x + ox, y + oy, z + oz)
                                        for x, y, z in face_vertices),
                                    face_uvs))
            self.object_instances.append(obj_instance)
        # Z-sorting
        def keyfunc(obj):
            return min(z for face in obj for x, y, z in face[0])
        self.object_instances.sort(key=keyfunc, reverse=True)


    def object_instances_to_vertices_uvs(self):
        vertices = tuple(vertex for obj in self.object_instances
                            for face in obj for vertex in face[0])
        uvs = tuple(uv for obj in self.object_instances
                            for face in obj for uv in face[1])
        return vertices, uvs


    def build_objects(self):
        self.objects = []
        for i, obj in enumerate(self.stage.objects):
            faces = []
            for script_index, ox, oy, oz, width_override, height_override in obj.quads:
                sprite = Sprite(self.anim, script_index)
                sprite.update(0, width_override, height_override)
                uvs, vertices = sprite._uvs, tuple((x + ox, y + oy, z + oz) for x, y, z in sprite._vertices)
                faces.append((vertices, uvs))
            self.objects.append(faces)


    def update(self, frame):
        if not self._uvs or not self._vertices:
            vertices, uvs = self.object_instances_to_vertices_uvs()
            self.nb_vertices = len(vertices)
            vertices_format = 'f' * (3 * self.nb_vertices)
            uvs_format = 'f' * (2 * self.nb_vertices)
            self._vertices = struct.pack(vertices_format, *chain(*vertices))
            self._uvs = struct.pack(uvs_format, *chain(*uvs))

            self.position_interpolator = Interpolator((0, 0, 0))
            self.fog_interpolator = Interpolator((0, 0, 0, 0, 0))
            self.position2_interpolator = Interpolator((0, 0, 0))

        for frame_num, message_type, args in self.stage.script:
            if frame_num == frame:
                if message_type == 0:
                    self.position_interpolator.set_interpolation_start(frame_num, args)
                elif message_type == 1:
                    self.fog_interpolator.set_interpolation_end_values(args)
                elif message_type == 2:
                    self.position2_interpolator.set_interpolation_end_values(args)
                elif message_type == 3:
                    duration, = args
                    self.position2_interpolator.set_interpolation_end_frame(frame_num + duration)
                elif message_type == 4:
                    duration, = args
                    self.fog_interpolator.set_interpolation_end_frame(frame_num + duration)
            if frame_num > frame and message_type == 0:
                self.position_interpolator.set_interpolation_end(frame_num, args)
                break

        self.position2_interpolator.update(frame)
        self.fog_interpolator.update(frame)
        self.position_interpolator.update(frame)