"""
VicAI Utilities
Helper functions for training and evaluation.
"""

import json
import logging
import math
import os
import sys
from pathlib import Path
from typing import Dict, Optional

import torch
import torch.distributed as dist
from torch.optim import AdamW


def get_logger(name: str, log_file: Optional[Path] = None) -> logging.Logger:
    """Create a logger with file and console handlers."""
    logger = logging.getLogger(name)
    logger.setLevel(logging.INFO)
    
    # Clear existing handlers
    logger.handlers = []
    
    # Formatter
    formatter = logging.Formatter(
        '%(asctime)s - %(name)s - %(levelname)s - %(message)s',
        datefmt='%Y-%m-%d %H:%M:%S'
    )
    
    # Console handler
    console_handler = logging.StreamHandler(sys.stdout)
    console_handler.setLevel(logging.INFO)
    console_handler.setFormatter(formatter)
    logger.addHandler(console_handler)
    
    # File handler
    if log_file:
        log_file.parent.mkdir(parents=True, exist_ok=True)
        file_handler = logging.FileHandler(log_file)
        file_handler.setLevel(logging.INFO)
        file_handler.setFormatter(formatter)
        logger.addHandler(file_handler)
    
    return logger


def save_checkpoint(
    model,
    optimizer,
    scaler,
    step: int,
    loss: float,
    path: Path,
):
    """Save model checkpoint."""
    path.parent.mkdir(parents=True, exist_ok=True)
    
    # Unwrap model if using DDP/FSDP
    state_dict = model.state_dict()
    if hasattr(model, 'module'):
        state_dict = model.module.state_dict()
    
    checkpoint = {
        'model': state_dict,
        'optimizer': optimizer.state_dict(),
        'scaler': scaler.state_dict() if scaler else None,
        'step': step,
        'loss': loss,
    }
    
    torch.save(checkpoint, path)


def load_checkpoint(
    model,
    optimizer,
    scaler,
    path: str,
    device,
):
    """Load model checkpoint."""
    checkpoint = torch.load(path, map_location=device)
    
    # Handle both wrapped and unwrapped models
    state_dict = checkpoint['model']
    if hasattr(model, 'module'):
        model.module.load_state_dict(state_dict)
    else:
        model.load_state_dict(state_dict)
    
    optimizer.load_state_dict(checkpoint['optimizer'])
    
    if scaler and checkpoint.get('scaler'):
        scaler.load_state_dict(checkpoint['scaler'])
    
    return checkpoint.get('step', 0)


def get_lr_scheduler(optimizer, args):
    """Create learning rate scheduler with warmup and cosine decay."""
    
    def lr_lambda(current_step):
        if current_step < args.warmup_steps:
            # Linear warmup
            return current_step / args.warmup_steps
        else:
            # Cosine decay
            progress = (current_step - args.warmup_steps) / (args.max_steps - args.warmup_steps)
            progress = min(1.0, progress)
            cosine_decay = 0.5 * (1 + math.cos(math.pi * progress))
            return args.min_lr / args.learning_rate + (1 - args.min_lr / args.learning_rate) * cosine_decay
    
    from torch.optim.lr_scheduler import LambdaLR
    return LambdaLR(optimizer, lr_lambda)


def configure_optimizers(model, args):
    """Configure optimizer with weight decay."""
    # Separate parameters that should and shouldn't have weight decay
    decay_params = []
    no_decay_params = []
    
    for name, param in model.named_parameters():
        if not param.requires_grad:
            continue
        
        # Don't apply weight decay to bias and normalization parameters
        if 'bias' in name or 'norm' in name or 'embedding' in name:
            no_decay_params.append(param)
        else:
            decay_params.append(param)
    
    param_groups = [
        {'params': decay_params, 'weight_decay': args.weight_decay},
        {'params': no_decay_params, 'weight_decay': 0.0},
    ]
    
    optimizer = AdamW(
        param_groups,
        lr=args.learning_rate,
        betas=(args.beta1, args.beta2),
        eps=1e-8,
    )
    
    return optimizer


def estimate_loss(model, data_loader, device, num_batches=10):
    """Estimate loss on a data loader."""
    model.eval()
    total_loss = 0
    
    with torch.no_grad():
        for i, batch in enumerate(data_loader):
            if i >= num_batches:
                break
            
            input_ids = batch['input_ids'].to(device)
            labels = batch['labels'].to(device)
            
            outputs = model(input_ids, targets=labels)
            total_loss += outputs['loss'].item()
    
    model.train()
    return total_loss / num_batches


def get_grad_norm(model):
    """Calculate gradient norm."""
    total_norm = 0.0
    for p in model.parameters():
        if p.grad is not None:
            total_norm += p.grad.data.norm(2).item() ** 2
    return total_norm ** 0.5


def clip_gradients(model, max_norm):
    """Clip gradients by norm."""
    torch.nn.utils.clip_grad_norm_(model.parameters(), max_norm)


class AverageMeter:
    """Track running average of metrics."""
    
    def __init__(self):
        self.reset()
    
    def reset(self):
        self.val = 0
        self.avg = 0
        self.sum = 0
        self.count = 0
    
    def update(self, val, n=1):
        self.val = val
        self.sum += val * n
        self.count += n
        self.avg = self.sum / self.count


class EarlyStopping:
    """Early stopping to prevent overfitting."""
    
    def __init__(self, patience=5, min_delta=0.0):
        self.patience = patience
        self.min_delta = min_delta
        self.counter = 0
        self.best_loss = None
        self.early_stop = False
    
    def __call__(self, val_loss):
        if self.best_loss is None:
            self.best_loss = val_loss
        elif val_loss > self.best_loss - self.min_delta:
            self.counter += 1
            if self.counter >= self.patience:
                self.early_stop = True
        else:
            self.best_loss = val_loss
            self.counter = 0
        
        return self.early_stop


def count_parameters(model):
    """Count trainable parameters."""
    return sum(p.numel() for p in model.parameters() if p.requires_grad)


def format_num_parameters(num_params):
    """Format parameter count for display."""
    if num_params >= 1e9:
        return f"{num_params / 1e9:.2f}B"
    elif num_params >= 1e6:
        return f"{num_params / 1e6:.2f}M"
    elif num_params >= 1e3:
        return f"{num_params / 1e3:.2f}K"
    else:
        return str(num_params)


def get_device_info():
    """Get information about available GPUs."""
    if not torch.cuda.is_available():
        return "No CUDA available"
    
    info = []
    for i in range(torch.cuda.device_count()):
        props = torch.cuda.get_device_properties(i)
        info.append(
            f"GPU {i}: {props.name} ({props.total_memory / 1e9:.1f} GB)"
        )
    
    return "\n".join(info)


def print_model_summary(model):
    """Print a summary of the model architecture."""
    print("\n" + "=" * 60)
    print("MODEL SUMMARY")
    print("=" * 60)
    
    total_params = 0
    trainable_params = 0
    
    print(f"\n{'Layer':<40} {'Parameters':>15} {'Trainable':>10}")
    print("-" * 70)
    
    for name, param in model.named_parameters():
        num_params = param.numel()
        total_params += num_params
        if param.requires_grad:
            trainable_params += num_params
            trainable = "Yes"
        else:
            trainable = "No"
        
        print(f"{name:<40} {num_params:>15,} {trainable:>10}")
    
    print("-" * 70)
    print(f"{'Total':<40} {total_params:>15,}")
    print(f"{'Trainable':<40} {trainable_params:>15,}")
    print(f"{'Non-trainable':<40} {total_params - trainable_params:>15,}")
    print("=" * 60 + "\n")


def save_training_config(args, output_path: Path):
    """Save training configuration to JSON."""
    config = vars(args)
    with open(output_path, 'w') as f:
        json.dump(config, f, indent=2)


def load_training_config(config_path: Path):
    """Load training configuration from JSON."""
    with open(config_path, 'r') as f:
        return json.load(f)


def all_reduce_dict(data: Dict, device):
    """All reduce dictionary values across processes."""
    if not dist.is_initialized():
        return data
    
    reduced_data = {}
    for key, value in data.items():
        if isinstance(value, (int, float)):
            tensor = torch.tensor([value], device=device)
            dist.all_reduce(tensor, op=dist.ReduceOp.AVG)
            reduced_data[key] = tensor.item()
        else:
            reduced_data[key] = value
    
    return reduced_data


def set_seed(seed: int):
    """Set random seed for reproducibility."""
    import random
    import numpy as np
    
    random.seed(seed)
    np.random.seed(seed)
    torch.manual_seed(seed)
    torch.cuda.manual_seed_all(seed)
    
    # For deterministic operations (may be slower)
    torch.backends.cudnn.deterministic = True
    torch.backends.cudnn.benchmark = False


def get_memory_usage():
    """Get current memory usage."""
    if torch.cuda.is_available():
        allocated = torch.cuda.memory_allocated() / 1e9
        reserved = torch.cuda.memory_reserved() / 1e9
        max_allocated = torch.cuda.max_memory_allocated() / 1e9
        return {
            'allocated_gb': allocated,
            'reserved_gb': reserved,
            'max_allocated_gb': max_allocated,
        }
    return {'allocated_gb': 0, 'reserved_gb': 0, 'max_allocated_gb': 0}


if __name__ == "__main__":
    # Test utilities
    logger = get_logger("test")
    logger.info("Testing logger")
    
    print(get_device_info())
    
    meter = AverageMeter()
    for i in range(10):
        meter.update(i)
    print(f"Average: {meter.avg}")