### 1. Imports and class names setup ###
import gradio as gr
import os 
import torch

from model import create_vit_model
from timeit import default_timer as timer
from typing import Tuple, Dict

# Setup class names
with open("class_names.txt", "r") as f:
  class_names = [food_name.strip() for food_name in f.readlines()]

### 2. Model and transforms perparation ###
vit, vit_transforms = create_vit_model(
    num_classes=325)

# Load save weights
vit.load_state_dict(
    torch.load(
        f="bird_classification_vit.pth",
        map_location=torch.device("cpu") # load the model to the CPU
    )
)

### 3. Predict function ### 

def predict(img) -> Tuple[Dict, float]:
  # Start a timer
  start_time = timer()

  # Transform the input image for use with EffNetB2
  img = vit_transforms(img).unsqueeze(0) # unsqueeze = add batch dimension on 0th index

  # Put model into eval mode, make prediction
  vit.eval()
  with torch.inference_mode():
    # Pass transformed image through the model and turn the prediction logits into probaiblities
    pred_probs = torch.softmax(vit(img), dim=1)

  # Create a prediction label and prediction probability dictionary
  pred_labels_and_probs = {class_names[i]: float(pred_probs[0][i]) for i in range(len(class_names))}

  # Calculate pred time
  end_time = timer()
  pred_time = round(end_time - start_time, 4)

  # Return pred dict and pred time
  return pred_labels_and_probs, pred_time

### 4. Gradio app ### 

# Create title, description and article
title = "Bird Species Classification"
description = "A [Transformer] computer vision model to classify Bird species.."
article = "Created by Chidera Stanley [Transformer using PyTorch]"

# Create example list
example_list = [["examples/" + example] for example in os.listdir("examples")]

# Create the Gradio demo
app = gr.Interface(fn=predict, # maps inputs to outputs
                    inputs=gr.Image(type="pil"),
                    outputs=[gr.Label(num_top_classes=3, label="Predictions"),
                             gr.Number(label="Prediction time (s)")],
                    examples=example_list,
                    title=title,
                    description=description,
                    article=article)

# Launch the demo!
app.launch()