#!/usr/bin/env python3
"""
ACL-LKNet Training CLI
======================
Standalone command-line entrypoint for training ACL-LKNet models.
Supports single-fold training, full 5-fold stratified cross-validation,
and Phase 1 self-supervised pretraining (Masked Slice Modeling).

Usage Examples:
    # Train Fold 1 with default configuration:
    python train_cv.py --data_dir /path/to/mrnet --fold 1

    # Train all 5 folds sequentially for cross-validation:
    python train_cv.py --data_dir /path/to/mrnet --cv

    # Run Phase 1 Masked Slice Modeling (SSL) pretraining:
    python train_cv.py --data_dir /path/to/mrnet --ssl_pretrain
"""

import os
import sys
import argparse
import logging
import torch

# Ensure local package imports work seamlessly
sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))

from src.config import Config
from src.train import train_supervised, train_ssl, train_5fold_cross_validation
from src.utils import set_seed, setup_logging


def parse_args():
    parser = argparse.ArgumentParser(
        description="Train ACL-LKNet (Phase 1 SSL Pretraining or Phase 2 Supervised Fine-Tuning)."
    )
    parser.add_argument(
        "--data_dir", type=str, default="./data/mrnet",
        help="Path to Stanford MRNet dataset root directory (containing train, valid, and test folders)."
    )
    parser.add_argument(
        "--output_dir", type=str, default="./checkpoints",
        help="Directory where model checkpoints and logs will be saved."
    )
    parser.add_argument(
        "--backbone", type=str, default="convnext_tiny",
        choices=["convnext_tiny", "resnet18", "replknet"],
        help="Backbone architecture (ConvNeXt-Tiny recommended for large receptive field)."
    )
    parser.add_argument(
        "--fold", type=int, default=1, choices=[1, 2, 3, 4, 5],
        help="Fold index to train (1-5) when not running full cross-validation."
    )
    parser.add_argument(
        "--cv", action="store_true",
        help="Run complete 5-fold stratified cross-validation."
    )
    parser.add_argument(
        "--ssl_pretrain", action="store_true",
        help="Run Phase 1 Masked Slice Modeling (MSM) self-supervised pretraining."
    )
    parser.add_argument(
        "--ssl_checkpoint", type=str, default=None,
        help="Optional path to SSL-pretrained backbone checkpoint to initialize Phase 2 training."
    )
    parser.add_argument(
        "--epochs", type=int, default=30,
        help="Maximum training epochs (monitored by early stopping patience=20)."
    )
    parser.add_argument(
        "--lr_backbone", type=float, default=1.0e-5,
        help="Differential learning rate for pretrained backbone."
    )
    parser.add_argument(
        "--lr_head", type=float, default=3.0e-4,
        help="Learning rate for newly initialized attention and classification heads."
    )
    parser.add_argument(
        "--batch_size", type=int, default=1,
        help="Physical batch size (keep = 1 on 15-16 GB GPUs to prevent OOM)."
    )
    parser.add_argument(
        "--accum_steps", type=int, default=8,
        help="Gradient accumulation steps to achieve effective batch size = 8."
    )
    parser.add_argument(
        "--device", type=str, default="cuda" if torch.cuda.is_available() else "cpu",
        help="Compute device ('cuda' or 'cpu')."
    )
    parser.add_argument(
        "--seed", type=int, default=42,
        help="Random seed for reproducibility across PyTorch, NumPy, and Python."
    )
    return parser.parse_args()


def main():
    args = parse_args()
    
    # Initialize master configuration
    config = Config(
        data_dir=args.data_dir,
        checkpoint_dir=args.output_dir,
        log_dir=os.path.join(args.output_dir, "logs"),
        backbone_name=args.backbone,
        epochs=args.epochs,
        backbone_lr=args.lr_backbone,
        lr=args.lr_head,
        batch_size=args.batch_size,
        accumulation_steps=args.accum_steps,
        device=args.device,
        seed=args.seed,
    )
    
    os.makedirs(config.checkpoint_dir, exist_ok=True)
    os.makedirs(config.log_dir, exist_ok=True)
    setup_logging(config.log_dir)
    set_seed(config.seed)
    
    logging.info(f"Initialized ACL-LKNet with Backbone: {config.backbone_name} on {config.device}")
    
    if args.ssl_pretrain:
        logging.info("Starting Phase 1: Masked Slice Modeling (MSM) SSL Pretraining...")
        train_ssl(config)
    elif args.cv:
        logging.info(f"Starting 5-Fold Stratified Cross-Validation on MRNet...")
        results = train_5fold_cross_validation(config, ssl_checkpoint=args.ssl_checkpoint)
        print("\n" + "=" * 60)
        print("Cross-Validation Complete! Summary:")
        print(f"Mean Val AUROC: {results.get('mean_val_auc', 'N/A')}")
        print("=" * 60)
    else:
        logging.info(f"Starting Single Fold Training: Fold {args.fold}...")
        config.experiment_name = f"acl_lknet_fold{args.fold}"
        train_supervised(config, fold_idx=args.fold - 1, ssl_checkpoint=args.ssl_checkpoint)


if __name__ == "__main__":
    main()