# train_model.py

"""
TODO:
- Add more different videos with different parateters into the training set.
- Add different scenes with the same parameters
"""

import argparse
import json
import os

from featureExtraction import psnr

os.environ['TF_CPP_MIN_LOG_LEVEL'] = '1'

import gc
import tensorflow as tf
from tensorflow.keras.callbacks import EarlyStopping, ModelCheckpoint, Callback

gpus = tf.config.experimental.list_physical_devices('GPU')
if gpus:
    try:
        for gpu in gpus:
            tf.config.experimental.set_memory_growth(gpu, True)
    except RuntimeError as e:
        print(e)


from video_compression_model import VideoCompressionModel, data_generator

from globalVars import HEIGHT, WIDTH, MAX_FRAMES, LOGGER

# Constants
BATCH_SIZE = 16
EPOCHS = 100
LEARNING_RATE = 0.001
DECAY_STEPS = 40
DECAY_RATE = 0.9
MODEL_SAVE_FILE = "models/model.tf"
MODEL_CHECKPOINT_DIR = "checkpoints"
EARLY_STOP = 5
    
def save_model(model):
    try:
        LOGGER.debug("Attempting to save the model.")
        os.makedirs("models", exist_ok=True)
        model.save(MODEL_SAVE_FILE, save_format='tf')
        LOGGER.info("Model saved successfully!")
    except Exception as e:
        LOGGER.error(f"Error saving the model: {e}")
        raise

    
def load_video_metadata(list_path):
    """
    Load video metadata from a JSON file.

    Args:
    - json_path (str): Path to the JSON file containing video metadata.

    Returns:
    - list: List of dictionaries, each containing video details.
    """
    
    LOGGER.trace(f"Entering: load_video_metadata({list_path})")
    try:
        with open(list_path, "r") as json_file:
            file = json.load(json_file)
            LOGGER.trace(f"load_video_metadata returning: {file}")
            return file
    except FileNotFoundError:
        LOGGER.error(f"Metadata file {list_path} not found.")
        raise
    except json.JSONDecodeError:
        LOGGER.error(f"Error decoding JSON from {list_path}.")
        raise


def main():
    global BATCH_SIZE, EPOCHS, LEARNING_RATE, MODEL_SAVE_FILE, MAX_FRAMES, DECAY_STEPS, DECAY_RATE
    # Argument parsing
    parser = argparse.ArgumentParser(description="Train the video compression model.")
    parser.add_argument('-b', '--batch_size', type=int, default=BATCH_SIZE, help='Batch size for training.')
    parser.add_argument('-e', '--epochs', type=int, default=EPOCHS, help='Number of epochs for training.')
    parser.add_argument('-l', '--learning_rate', type=float, default=LEARNING_RATE, help='Learning rate for training.')
    parser.add_argument('-c', '--continue_training', type=str, nargs='?', const=MODEL_SAVE_FILE, default=None, help='Path to the saved model to continue training. If used without a value, defaults to the MODEL_SAVE_FILE.')
    parser.add_argument('-m', '--max_frames', type=int, default=MAX_FRAMES, help='Batch size for training.')
    parser.add_argument('-ds', '--decay_steps', type=int, default=DECAY_STEPS, help='Decay size for training.')
    parser.add_argument('-dr', '--decay_rate', type=float, default=DECAY_RATE, help='Decay rate for training.')
    args = parser.parse_args()
    
    BATCH_SIZE = args.batch_size
    EPOCHS = args.epochs
    LEARNING_RATE = args.learning_rate
    MAX_FRAMES = args.max_frames
    DECAY_RATE = args.decay_rate
    DECAY_STEPS = args.decay_steps

    # Display training configuration
    LOGGER.info("Starting the training with the given configuration.")
    LOGGER.info("Training configuration:")
    LOGGER.info(f"Batch size: {BATCH_SIZE}")
    LOGGER.info(f"Epochs: {EPOCHS}")
    LOGGER.info(f"Learning rate: {LEARNING_RATE}")
    LOGGER.info(f"Max Frames: {MAX_FRAMES}")
    LOGGER.info(f"Continue training from: {MODEL_SAVE_FILE}")
    
    LOGGER.debug(f"Max video resolution: {WIDTH}x{HEIGHT}")

    # Load all video metadata
    all_videos = load_video_metadata("test_data/validation/validation.json")

    # Split into training and validation
    split_index = int(0.8 * len(all_videos))
    training_videos = all_videos[:split_index]
    validation_videos = all_videos[split_index:]

    if args.continue_training:
        model = tf.keras.models.load_model(args.continue_training)
    else:
        model = VideoCompressionModel()
        
        
    # Define exponential decay schedule
    lr_schedule = tf.keras.optimizers.schedules.ExponentialDecay(
        initial_learning_rate=LEARNING_RATE,
        decay_steps=DECAY_STEPS,
        decay_rate=DECAY_RATE,
        staircase=False
    )


    # Set optimizer and compile the model
    optimizer = tf.keras.optimizers.Adam(learning_rate=lr_schedule)
    model.compile(loss='mse', optimizer=optimizer, metrics=[psnr])
    
    # Define checkpoints and early stopping
    checkpoint_callback = ModelCheckpoint(
        filepath=os.path.join(MODEL_CHECKPOINT_DIR, "epoch-{epoch:02d}.tf"),
        save_weights_only=False,
        save_best_only=False,
        verbose=1,
        save_format="tf"
    )
    early_stop = EarlyStopping(monitor='val_loss', patience=EARLY_STOP, verbose=1, restore_best_weights=True)

    # Calculate steps per epoch for training and validation
    if MAX_FRAMES <= 0:
        average_frames_per_video = 2880  # Given 2 minutes @ 24 fps
    else:
        average_frames_per_video = max(MAX_FRAMES, 0)
        
    total_frames_train = average_frames_per_video * len(training_videos)
    total_frames_validation = average_frames_per_video * len(validation_videos)
    steps_per_epoch_train = total_frames_train // BATCH_SIZE
    steps_per_epoch_validation = total_frames_validation // BATCH_SIZE

    # Train the model
    LOGGER.info("Starting model training.")
    model.fit(
        data_generator(training_videos, BATCH_SIZE), 
        epochs=EPOCHS, 
        steps_per_epoch=steps_per_epoch_train,
        validation_data=data_generator(validation_videos, BATCH_SIZE),  # Add validation data here
        validation_steps=steps_per_epoch_validation,  # Add validation steps here
        callbacks=[early_stop, checkpoint_callback]
    )
    LOGGER.info("Model training completed.")
    
    save_model(model)


if __name__ == "__main__":
    try:
        main()
    except Exception as e:
        LOGGER.error(f"Unexpected error during training: {e}")
        raise