"""
Test script to inspect dataset loading pipeline.

Usage:
    python test_dataset.py config/pretrain.yaml
    python test_dataset.py config/sft.yaml --num-samples 10
    python test_dataset.py config/sft.yaml --sft --num-samples 5  # Show SFT-specific info
"""

import sys
import argparse
from pathlib import Path
from typing import Optional, Dict
import torch
from tqdm import tqdm

# Add src to path for imports
sys.path.insert(0, str(Path(__file__).parent.parent / "src"))

from taoTrain.config import load_config, TrainingModeEnum, PretrainConfig
from taoTrain.core import create_datasets
from taoTrain.data import TokenizationQueue, AsyncBatchIterator
from taoTrain.data import BaseJSONLDataset, SFTJSONLDataset, parse_sft_record
from taoTrain.utils import set_seed, get_device


def print_separator(title: str = "", char: str = "=", width: int = 80):
    """Print a formatted separator line."""
    if title:
        print(f"\n{char} {title} {char * (width - len(title) - 3)}")
    else:
        print(f"\n{char * width}")


def format_tensor_info(tensor: torch.Tensor) -> str:
    """Format tensor information for display."""
    return f"shape={tuple(tensor.shape)}, dtype={tensor.dtype}, device={tensor.device}"


def get_special_token_ids(tokenizer) -> Dict[str, Optional[int]]:
    """
    Extract special token IDs from tokenizer.
    
    Returns dict with keys: bos, eos, pad, unk
    """
    special_tokens = {
        "bos": None,
        "eos": None,
        "pad": None,
        "unk": None,
    }
    
    if tokenizer is None:
        return special_tokens
    
    # Try different ways to access special token IDs based on tokenizer type
    try:
        # For SentencePieceTokenizerWrapper
        if hasattr(tokenizer, 'bos_id'):
            special_tokens["bos"] = tokenizer.bos_id()
        if hasattr(tokenizer, 'eos_id'):
            special_tokens["eos"] = tokenizer.eos_id()
        if hasattr(tokenizer, 'pad_id'):
            special_tokens["pad"] = tokenizer.pad_id()
        if hasattr(tokenizer, 'unk_id'):
            special_tokens["unk"] = tokenizer.unk_id()
        
        # For HuggingFace tokenizers
        if hasattr(tokenizer, 'bos_token_id'):
            special_tokens["bos"] = tokenizer.bos_token_id
        if hasattr(tokenizer, 'eos_token_id'):
            special_tokens["eos"] = tokenizer.eos_token_id
        if hasattr(tokenizer, 'pad_token_id'):
            special_tokens["pad"] = tokenizer.pad_token_id
        if hasattr(tokenizer, 'unk_token_id'):
            special_tokens["unk"] = tokenizer.unk_token_id
    except Exception as e:
        pass  # If extraction fails, keep defaults
    
    return special_tokens


def count_special_tokens(token_ids: torch.Tensor, special_token_ids: Dict[str, Optional[int]]) -> Dict[str, int]:
    """
    Count occurrences of special tokens in token IDs.
    
    Args:
        token_ids: 1D tensor of token IDs
        special_token_ids: Dict mapping special token names to IDs
    
    Returns:
        Dict with counts of each special token
    """
    counts = {}
    
    # Convert to CPU numpy for efficient counting
    if isinstance(token_ids, torch.Tensor):
        ids_numpy = token_ids.cpu().numpy()
    else:
        ids_numpy = token_ids
    
    for token_name, token_id in special_token_ids.items():
        if token_id is not None:
            count = (ids_numpy == token_id).sum()
            counts[token_name] = int(count)
        else:
            counts[token_name] = 0
    
    return counts


def print_sample(sample_idx: int, sample: Dict[str, torch.Tensor], tokenizer=None, 
                 special_token_ids: Optional[Dict[str, Optional[int]]] = None, max_display: int = 20):
    """Print a single sample with formatted information."""
    print(f"\n  Sample {sample_idx}:")
    
    # Input IDs
    if "input_ids" in sample:
        input_ids = sample["input_ids"]
        print(f"    input_ids: {format_tensor_info(input_ids)}")
        print(f"      Values: {input_ids[:max_display].tolist()}{'...' if len(input_ids) > max_display else ''}")

        
        labels = sample["labels"]
        print(f"    labels: {format_tensor_info(labels)}")
        print(f"      Values: {labels[:max_display].tolist()}{'...' if len(labels) > max_display else ''}")
        
        # Count special tokens
        if special_token_ids is not None:
            special_counts = count_special_tokens(input_ids, special_token_ids)
            special_summary = ", ".join([f"{name}={count}" for name, count in special_counts.items()])
            print(f"      Special tokens: {special_summary}")
        
        # Try to decode if tokenizer available
        if tokenizer is not None:
            try:
                decoded = tokenizer.decode(input_ids.tolist()[:max_display], skip_special_tokens=False)
                preview = decoded.replace('\n', '\\n')
                print(f"      Decoded: {preview}...")
            except Exception as e:
                print(f"      [Decode error: {e}]")
    
    # Attention mask
    if "attention_mask" in sample:
        attention_mask = sample["attention_mask"]
        print(f"    attention_mask: {format_tensor_info(attention_mask)}")
        non_pad_count = attention_mask.sum().item()
        print(f"      Non-padding tokens: {non_pad_count}/{len(attention_mask)}")
    
    # Labels
    if "labels" in sample:
        labels = sample["labels"]
        print(f"    labels: {format_tensor_info(labels)}")
        valid_labels = labels[labels != -100]
        print(f"      Valid labels (not -100): {len(valid_labels)}/{len(labels)}")


def print_sample_sft(sample_idx: int, sample: Dict[str, torch.Tensor], mask: Optional[list] = None,
                     tokenizer=None, special_token_ids: Optional[Dict[str, Optional[int]]] = None, 
                     max_display: int = 20):
    """
    Print a single SFT sample with detailed masking information.
    
    Shows:
    - Which tokens are user input (mask=0, labeled -100)
    - Which tokens are assistant output (mask=1, labeled with token id)
    - Token decoding and special token information
    """
    print(f"\n  SFT Sample {sample_idx}:")
    
    if "input_ids" in sample:
        input_ids = sample["input_ids"]
        print(f"    input_ids: {format_tensor_info(input_ids)}")
        
        labels = sample["labels"]
        print(f"    labels: {format_tensor_info(labels)}")
        
        # Show mask breakdown
        if mask is not None:
            mask_array = mask
            user_count = sum(1 for m in mask_array if m == 0)
            assistant_count = sum(1 for m in mask_array if m == 1)
            print(f"    Mask breakdown:")
            print(f"      - User input tokens (mask=0, ignored): {user_count}")
            print(f"      - Assistant output tokens (mask=1, trained): {assistant_count}")
            
            # Show which regions are which
            print(f"    Token regions (first {max_display} tokens):")
            for i in range(min(max_display, len(input_ids))):
                token_id = input_ids[i].item()
                label = labels[i].item()
                mask_val = mask_array[i] if i < len(mask_array) else 0
                region_type = "USER  " if mask_val == 0 else "ASST  "
                label_str = "IGNORE" if label == -100 else f"{label:5d}"
                
                # Try to decode token
                token_str = "?"
                if tokenizer is not None:
                    try:
                        token_str = tokenizer.decode([token_id], skip_special_tokens=False).replace('\n', '\\n')[:15]
                    except:
                        token_str = f"ID:{token_id}"
                
                print(f"      [{i:3d}] {region_type} | label={label_str} | token={token_str}")
            
            if len(input_ids) > max_display:
                print(f"      ... and {len(input_ids) - max_display} more tokens")
        else:
            # Fallback: just show labels
            masked_count = (labels == -100).sum().item()
            valid_count = (labels != -100).sum().item()
            print(f"    Token labels breakdown:")
            print(f"      - Masked tokens (label=-100): {masked_count}")
            print(f"      - Training tokens: {valid_count}")


def inspect_dataset(config_path: str, num_samples: int = 10, max_display: int = 20, show_sft: bool = False):
    """
    Main inspection function.
    
    Args:
        config_path: Path to YAML config file
        num_samples: Number of samples to display (batches or individual samples)
        max_display: Max tokens to display in preview
        show_sft: If True, show SFT-specific masking information (requires SFT dataset)
    """
    # ========================================================================
    # Step 1: Load and validate config
    # ========================================================================
    print_separator("STEP 1: LOAD CONFIGURATION")
    
    config_path = Path(config_path)
    if not config_path.exists():
        print(f"✗ Config file not found: {config_path}")
        sys.exit(1)
    
    print(f"✓ Loading config from: {config_path}")
    
    # Try to load config - auto-detect mode or use default
    try:
        # Try to infer mode from filename or use default
        if "pretrain" in str(config_path).lower():
            mode = TrainingModeEnum.PRETRAIN
        elif "sft" in str(config_path).lower():
            mode = TrainingModeEnum.SFT
        elif "rl" in str(config_path).lower() or "dpo" in str(config_path).lower():
            mode = TrainingModeEnum.RL
        else:
            mode = TrainingModeEnum.PRETRAIN  # Default
        
        config = load_config(config_path, mode)
        print(f"✓ Config loaded (mode: {config.mode.value})")
    except Exception as e:
        print(f"✗ Failed to load config: {e}")
        sys.exit(1)
    
    # Print config summary
    print(f"\nConfiguration Summary:")
    print(f"  - Mode: {config.mode.value}")
    print(f"  - Model: {config.model.architecture_type.value}")
    print(f"  - Vocab size: {config.model.vocab_size}")
    print(f"  - Max seq length: {config.model.max_seq_length}")
    print(f"  - Batch size: {config.batch_size}")
    print(f"  - Dataset source: {'Local JSONL' if config.dataset.local else 'HuggingFace'}")
    
    if config.dataset.local:
        print(f"  - JSONL path: {config.dataset.jsonl_path}")
        print(f"  - Tokenizer: {config.dataset.tokenizer_type or 'auto-detect'}")
        if config.dataset.tokenizer_path:
            print(f"  - Tokenizer path: {config.dataset.tokenizer_path}")
        print(f"  - Samples per chunk: {config.dataset.samples_per_chunk}")
        print(f"  - Tokenizer threads: {config.dataset.tokenizer_threads}")
    else:
        print(f"  - Dataset name: {config.dataset.dataset_name}")
        print(f"  - Dataset config: {config.dataset.config or 'default'}")
        print(f"  - Split: {config.dataset.split}")
    
    if config.dataset.max_samples:
        print(f"  - Max samples (limit): {config.dataset.max_samples}")
    
    # Print SFT-specific config if applicable
    if show_sft and hasattr(config, 'response_loss_only'):
        print(f"\n  SFT Configuration:")
        print(f"  - Response loss only: {config.response_loss_only}")
        user_token = getattr(config, 'user_token', '<user>')
        assistant_token = getattr(config, 'assistant_token', '<assistant>')
        print(f"  - User token: {user_token}")
        print(f"  - Assistant token: {assistant_token}")
        checkpoint_path = getattr(config, 'checkpoint_path', None)
        if checkpoint_path:
            print(f"  - Checkpoint path: {checkpoint_path}")
    
    # ========================================================================
    # Step 2: Setup device and random seed
    # ========================================================================
    print_separator("STEP 2: SETUP DEVICE AND SEED")
    
    device = get_device(config.device)
    print(f"✓ Device: {device}")
    print(f"✓ CUDA available: {torch.cuda.is_available()}")
    if torch.cuda.is_available():
        print(f"  - GPU: {torch.cuda.get_device_name(0)}")
        print(f"  - CUDA version: {torch.version.cuda}")
    
    set_seed(config.seed)
    print(f"✓ Random seed set: {config.seed}")
    
    # ========================================================================
    # Step 3: Create datasets
    # ========================================================================
    print_separator("STEP 3: CREATE DATASETS")
    
    try:
        train_dataset, val_dataset = create_datasets(config)
        print(f"✓ Train dataset created: {type(train_dataset).__name__}")
        if val_dataset:
            print(f"✓ Validation dataset created: {type(val_dataset).__name__}")
        else:
            print(f"✓ No validation dataset (JSONL or not configured)")
    except Exception as e:
        print(f"✗ Failed to create datasets: {e}")
        import traceback
        traceback.print_exc()
        sys.exit(1)
    
    print(f"  - Train dataset length: {len(train_dataset)}")
    
    # ========================================================================
    # Step 4: Setup async pipeline (for JSONL datasets)
    # ========================================================================
    async_loader = None
    tokenizer = None
    special_token_ids = None
    
    if isinstance(train_dataset, BaseJSONLDataset):
        print_separator("STEP 4: SETUP ASYNC PIPELINE")
        
        # Extract components
        chunk_manager = train_dataset.chunk_manager
        tokenizer = train_dataset.tokenizer
        
        # Get special token IDs
        special_token_ids = get_special_token_ids(tokenizer)
        print(f"✓ Special token IDs extracted:")
        for token_name, token_id in special_token_ids.items():
            print(f"  - {token_name.upper()}: {token_id}")
        
        print(f"✓ ChunkManager found:")
        print(f"  - Total chunks: {chunk_manager.num_chunks}")
        print(f"  - Effective lines: {chunk_manager.effective_lines}")
        print(f"  - File size: {chunk_manager.file_size_bytes / (1024**2):.1f} MB")
        print(f"  - Chunk line ranges: {chunk_manager.chunk_line_ranges[:3]}..." if len(chunk_manager.chunk_line_ranges) > 3 else f"  - Chunk line ranges: {chunk_manager.chunk_line_ranges}")
        
        print(f"✓ Tokenizer found: {type(tokenizer).__name__}")
        
        # Create tokenization queue
        print(f"✓ Creating TokenizationQueue...")
        try:
            tokenization_queue = TokenizationQueue(
                chunk_manager=chunk_manager,
                tokenizer=tokenizer,
                config=config,
                max_queue_size=4,
                shuffle_chunks=True,
                num_threads=config.dataset.tokenizer_threads,
            )
            print(f"  - Max queue size: 4")
            print(f"  - Tokenizer threads: {config.dataset.tokenizer_threads}")
            print(f"  - Total items: {tokenization_queue.total_items}")
        except Exception as e:
            print(f"✗ Failed to create TokenizationQueue: {e}")
            import traceback
            traceback.print_exc()
            sys.exit(1)
        
        # Create async batch iterator
        print(f"✓ Creating AsyncBatchIterator...")
        try:
            async_loader = AsyncBatchIterator(
                tokenization_queue=tokenization_queue,
                batch_size=config.batch_size,
                device=device,
                drop_last=True,
                gradient_accumulation_steps=config.gradient_accumulation_steps,
            )
            print(f"  - Batch size: {config.batch_size}")
            print(f"  - Device: {device}")
            print(f"  - Gradient accumulation: {config.gradient_accumulation_steps}")
        except Exception as e:
            print(f"✗ Failed to create AsyncBatchIterator: {e}")
            import traceback
            traceback.print_exc()
            sys.exit(1)
    else:
        print_separator("STEP 4: USING STANDARD DATALOADER")
        
        from taoTrain.data.loaders import get_dataloader
        
        tokenizer = getattr(train_dataset, "tokenizer", None)
        
        # Get special token IDs
        special_token_ids = get_special_token_ids(tokenizer)
        if tokenizer is not None:
            print(f"✓ Special token IDs extracted:")
            for token_name, token_id in special_token_ids.items():
                print(f"  - {token_name.upper()}: {token_id}")
        
        print(f"✓ HuggingFace dataset detected")
        print(f"✓ Will use standard DataLoader (batch_size={config.batch_size})")
        
        # Create standard dataloader
        try:
            train_loader = get_dataloader(
                train_dataset,
                config,
                shuffle=False,
                drop_last=False,
            )
            async_loader = train_loader
            print(f"✓ DataLoader created")
        except Exception as e:
            print(f"✗ Failed to create DataLoader: {e}")
            import traceback
            traceback.print_exc()
            sys.exit(1)
    
    # ========================================================================
    # Step 5: Fetch and display samples
    # ========================================================================
    print_separator(f"STEP 5: FETCH FIRST {num_samples} BATCHES")
    
    if async_loader is None:
        print(f"✗ No data loader available")
        sys.exit(1)
    
    total_samples = 0
    total_tokens = 0
    batch_idx = -1  # Initialize to track if any batches were processed
    cumulative_special_counts = {"bos": 0, "eos": 0, "pad": 0, "unk": 0}
    
    try:
        for batch_idx, batch in enumerate(tqdm(async_loader, total=num_samples, desc="Fetching batches")):
            if batch_idx >= num_samples:
                break
            
            print_separator(f"BATCH {batch_idx}", char="-", width=60)
            print(f"Batch keys: {batch.keys()}")
            
            # Print batch shapes
            for key, tensor in batch.items():
                print(f"  {key}: {format_tensor_info(tensor)}")
            
            # Count tokens and special tokens
            if "input_ids" in batch:
                batch_token_count = batch["input_ids"].numel()
                total_tokens += batch_token_count
                print(f"  Total tokens in batch: {batch_token_count}")
                
                # Count special tokens in entire batch
                if special_token_ids is not None:
                    batch_input_ids = batch["input_ids"].view(-1)  # Flatten batch
                    batch_special_counts = count_special_tokens(batch_input_ids, special_token_ids)
                    special_str = ", ".join([f"{name}={count}" for name, count in batch_special_counts.items()])
                    print(f"  Batch special tokens: {special_str}")
                    # Accumulate counts
                    for token_name, count in batch_special_counts.items():
                        cumulative_special_counts[token_name] += count
            
            # Print individual samples in batch
            batch_size = next(iter(batch.values())).shape[0]
            total_samples += batch_size
            
            print(f"\nSamples in batch (showing first 3 of {batch_size}):")
            for sample_idx in range(min(3, batch_size)):
                sample = {key: tensor[sample_idx] for key, tensor in batch.items()}
                
                # For SFT datasets, try to get mask info
                mask = None
                if show_sft and isinstance(train_dataset, SFTJSONLDataset):
                    try:
                        # Access the mask from the dataset's current chunk
                        if (hasattr(train_dataset, '_current_chunk_data') and 
                            train_dataset._current_chunk_data is not None and
                            "mask" in train_dataset._current_chunk_data):
                            
                            # We need to map from batch sample index back to dataset index
                            # For simplicity, access the local chunk index
                            chunk_idx = batch_idx * batch_size + sample_idx
                            if chunk_idx < len(train_dataset._current_chunk_data["mask"]):
                                mask = train_dataset._current_chunk_data["mask"][sample_idx]
                    except Exception as e:
                        print(f"      [Could not access mask: {e}]")
                    
                    # Use SFT-specific print function
                    print_sample_sft(batch_idx * batch_size + sample_idx, sample, mask, tokenizer, special_token_ids, max_display)
                else:
                    # Use regular print function
                    print_sample(batch_idx * batch_size + sample_idx, sample, tokenizer, special_token_ids, max_display)
            
            if batch_size > 3:
                print(f"  ... and {batch_size - 3} more samples")
    
    except Exception as e:
        print(f"✗ Error during batch fetching: {e}")
        import traceback
        traceback.print_exc()
        sys.exit(1)
    
    # ========================================================================
    # Summary Statistics
    # ========================================================================
    print_separator("SUMMARY STATISTICS")
    
    print(f"Total batches fetched: {min(batch_idx + 1, num_samples)}")
    print(f"Total samples: {total_samples}")
    print(f"Total tokens: {total_tokens}")
    if total_samples > 0:
        print(f"Average tokens per sample: {total_tokens / total_samples:.1f}")
    
    # Print special token summary
    if special_token_ids is not None:
        print(f"\nSpecial token counts across all batches:")
        for token_name, token_id in special_token_ids.items():
            total_count = cumulative_special_counts[token_name]
            pct = (total_count / total_tokens * 100) if total_tokens > 0 else 0
            print(f"  - {token_name.upper()}: {total_count} tokens ({pct:.2f}%)")
    
    print_separator()
    print("✓ Inspection complete!")


def main():
    """Main entry point with argument parsing."""
    parser = argparse.ArgumentParser(
        description="Test dataset loading pipeline - inspect data shapes, tokenization, and samples"
    )
    parser.add_argument(
        "config_path",
        type=str,
        help="Path to YAML/JSON config file (e.g., config/pretrain.yaml)"
    )
    parser.add_argument(
        "--num-samples",
        type=int,
        default=10,
        help="Number of batches to display (default: 10)"
    )
    parser.add_argument(
        "--max-display",
        type=int,
        default=20,
        help="Maximum tokens to display in preview (default: 20)"
    )
    parser.add_argument(
        "--sft",
        action="store_true",
        help="If set, show SFT-specific masking information (user vs assistant tokens)"
    )
    
    args = parser.parse_args()
    
    inspect_dataset(
        args.config_path,
        num_samples=args.num_samples,
        max_display=args.max_display,
        show_sft=args.sft
    )


if __name__ == "__main__":
    main()