import os

import torch
import torch.nn as nn
import numpy as np
import torch.nn.functional as F
import torchvision.transforms as T
from PIL import Image
from decord import VideoReader
from decord import cpu
from uniformerv2 import uniformerv2_b16
from mitv1_class_index import mitv1_classnames
from transforms import (
    GroupNormalize, GroupScale, GroupCenterCrop, 
    Stack, ToTorchFormatTensor
)

import gradio as gr
from huggingface_hub import hf_hub_download

class Uniformerv2(nn.Module):
    def __init__(self, model):
        super().__init__()
        self.backbone = model
    
    def forward(self, x):
        return self.backbone(x)

# Device on which to run the model
# Set to cuda to load on GPU
device = "cpu"
model_path = hf_hub_download(repo_id="Andy1621/uniformerv2", filename="mit_uniformerv2_b16_8x224.pyth")
# Pick a pretrained model 
model = Uniformerv2(uniformerv2_b16(pretrained=False, t_size=8, no_lmhra=True, temporal_downsample=False, num_classes=339))
state_dict = torch.load(model_path, map_location='cpu')
model.load_state_dict(state_dict)

# Set to eval mode and move to desired device
model = model.to(device)
model = model.eval()

# Create an id to label name mapping
mitv1_id_to_classname = {}
for k, v in mitv1_classnames.items():
    mitv1_id_to_classname[k] = v


def get_index(num_frames, num_segments=8):
    seg_size = float(num_frames - 1) / num_segments
    start = int(seg_size / 2)
    offsets = np.array([
        start + int(np.round(seg_size * idx)) for idx in range(num_segments)
    ])
    return offsets


def load_video(video_path):
    vr = VideoReader(video_path, ctx=cpu(0))
    num_frames = len(vr)
    frame_indices = get_index(num_frames, 8)

    # transform
    crop_size = 224
    scale_size = 256
    input_mean = [0.485, 0.456, 0.406]
    input_std = [0.229, 0.224, 0.225]

    transform = T.Compose([
        GroupScale(int(scale_size)),
        GroupCenterCrop(crop_size),
        Stack(),
        ToTorchFormatTensor(),
        GroupNormalize(input_mean, input_std) 
    ])

    images_group = list()
    for frame_index in frame_indices:
        img = Image.fromarray(vr[frame_index].asnumpy())
        images_group.append(img)
    torch_imgs = transform(images_group)
    return torch_imgs
    

def inference(video):
    vid = load_video(video)
    
    # The model expects inputs of shape: B x C x H x W
    TC, H, W = vid.shape
    inputs = vid.reshape(1, TC//3, 3, H, W).permute(0, 2, 1, 3, 4)
    
    prediction = model(inputs)
    prediction = F.softmax(prediction, dim=1).flatten()

    return {mitv1_id_to_classname[str(i)]: float(prediction[i]) for i in range(339)}
    

def set_example_video(example: list) -> dict:
    return gr.Video.update(value=example[0])


demo = gr.Blocks()
with demo:
    gr.Markdown(
        """
        # UniFormerV2-B
        Gradio demo for <a href='https://github.com/OpenGVLab/UniFormerV2' target='_blank'>UniFormerV2</a>: To use it, simply upload your video, or click one of the examples to load them. Read more at the links below.
        """
    )

    with gr.Box():
        with gr.Row():
                with gr.Column():
                    with gr.Row():
                        input_video = gr.Video(label='Input Video')
                    with gr.Row():
                        submit_button = gr.Button('Submit')
                with gr.Column():
                    label = gr.Label(num_top_classes=5)
        with gr.Row():
            example_videos = gr.Dataset(components=[input_video], samples=[['clapping.mp4'], ['jumping.mp4'], ['swimming.mp4']])

    gr.Markdown(
        """
        <p style='text-align: center'><a href='https://arxiv.org/abs/2211.09552' target='_blank'>[Arxiv] UniFormerV2: Spatiotemporal Learning by Arming Image ViTs with Video UniFormer</a> | <a href='https://github.com/OpenGVLab/UniFormerV2' target='_blank'>Github Repo</a></p>
        """
    )

    submit_button.click(fn=inference, inputs=input_video, outputs=label)
    example_videos.click(fn=set_example_video, inputs=example_videos, outputs=example_videos.components)

demo.launch(enable_queue=True)