"""
utils/dataset_loader.py - Load Natural Questions + Wikipedia Dataset
======================================================================

Clean implementation for loading:
- Natural Questions: Q&A dataset with answers extracted from Wikipedia
- Wikipedia: Standard Wikipedia dataset chunked into ~100 word passages
"""

from typing import List, Dict, Optional
from dataclasses import dataclass
from pathlib import Path
import json

from datasets import load_dataset
from tqdm import tqdm


@dataclass
class Question:
    """Question with answers and context"""
    id: str
    question: str
    answers: List[str]
    context: str = ""
    has_answer: bool = True


# =============================================================================
# NATURAL QUESTIONS DATASET
# =============================================================================

class NaturalQuestionsDataset:
    """Load Natural Questions dataset"""
    
    def __init__(self, cache_dir: str = "./data/datasets"):
        self.cache_dir = Path(cache_dir)
        self.cache_dir.mkdir(parents=True, exist_ok=True)
        self.dataset = None
        self.questions = []
    
    def load(self, max_samples: int = 100, show_progress: bool = True):
        """Load Natural Questions validation set"""
        if show_progress:
            print(f"\n📥 Loading Natural Questions...")
            print("=" * 80)
        
        # Load from HuggingFace
        self.dataset = load_dataset(
            "google-research-datasets/natural_questions",
            split="validation",
            cache_dir=str(self.cache_dir),
        )
        
        if show_progress:
            print(f"✅ Loaded {len(self.dataset)} questions from dataset")
        
        # Extract questions
        self._extract_questions(max_samples, show_progress)
    
    def _extract_questions(self, max_samples: int, show_progress: bool):
        """Extract questions from dataset"""
        if show_progress:
            print(f"\n🔄 Extracting questions...")
        
        # Debug first item
        if show_progress:
            print(f"\n🔍 Inspecting first item structure:")
            self._debug_first_item()
        
        num_to_process = min(max_samples, len(self.dataset))
        questions = []
        
        for idx in tqdm(range(num_to_process), desc="Processing", disable=not show_progress):
            item = self.dataset[idx]
            
            # Get question
            question_text = self._extract_question(item)
            if not question_text:
                continue
            
            # Get answers
            answers = self._extract_answers(item)
            if not answers:  # Skip questions without answers
                continue
            
            # Get context
            context = self._extract_context(item)
            
            questions.append(Question(
                id=str(item.get('id', f'nq_{idx}')),
                question=question_text,
                answers=answers,
                context=context,
                has_answer=True
            ))
        
        self.questions = questions
        
        if show_progress:
            print(f"\n✅ Successfully extracted {len(questions)} questions with answers")
            if len(questions) == 0:
                print(f"❌ ERROR: Extracted 0 questions from {num_to_process} items")
                print(f"   This means the answer extraction is failing.")
                print(f"   Check the debug output above to see the data structure.")
    
    def _debug_first_item(self):
        """Debug first item to understand structure"""
        if len(self.dataset) == 0:
            print("   ❌ Dataset is empty!")
            return
        
        item = self.dataset[0]
        
        # Question
        print(f"\n   📝 Question:")
        if 'question' in item:
            q = item['question']
            print(f"      Type: {type(q)}")
            if isinstance(q, dict):
                print(f"      Keys: {list(q.keys())}")
                print(f"      Text: {q.get('text', 'N/A')[:100]}")
            else:
                print(f"      Value: {str(q)[:100]}")
        
        # Annotations
        print(f"\n   📋 Annotations:")
        if 'annotations' in item:
            anns = item['annotations']
            print(f"      Type: {type(anns)}")
            
            if isinstance(anns, list):
                print(f"      Count: {len(anns)}")
                if len(anns) > 0:
                    ann = anns[0]
                    print(f"      First annotation keys: {list(ann.keys())}")
                    
                    if 'short_answers' in ann:
                        short_ans = ann['short_answers']
                        print(f"      Short answers count: {len(short_ans) if isinstance(short_ans, list) else 'Not a list'}")
                        if isinstance(short_ans, list) and len(short_ans) > 0:
                            print(f"      First short answer: {short_ans[0]}")
            elif isinstance(anns, dict):
                print(f"      It's a dict with keys: {list(anns.keys())}")
                # If it's a dict, check if it has the fields we need
                if 'short_answers' in anns:
                    short_ans = anns['short_answers']
                    print(f"      Short answers type: {type(short_ans)}")
                    print(f"      Short answers: {short_ans}")
            else:
                print(f"      Unexpected type: {type(anns)}")
                print(f"      Value: {anns}")
        else:
            print(f"      ❌ No 'annotations' field found")
        
        # Document tokens
        print(f"\n   📄 Document:")
        if 'document' in item:
            doc = item['document']
            print(f"      Type: {type(doc)}")
            if isinstance(doc, dict):
                print(f"      Keys: {list(doc.keys())}")
                
                if 'tokens' in doc:
                    tokens = doc['tokens']
                    print(f"      Tokens type: {type(tokens)}")
                    
                    if isinstance(tokens, dict):
                        print(f"      Tokens keys: {list(tokens.keys())}")
                        if 'token' in tokens:
                            token_list = tokens['token']
                            print(f"      Token list length: {len(token_list) if isinstance(token_list, list) else 'Not a list'}")
                            if isinstance(token_list, list) and len(token_list) > 0:
                                print(f"      First 10 tokens: {token_list[:10]}")
                    elif isinstance(tokens, list):
                        print(f"      Tokens list length: {len(tokens)}")
                        print(f"      First 10 tokens: {tokens[:10]}")
        
        # Try extraction
        print(f"\n   🧪 Testing extraction methods:")
        question = self._extract_question(item)
        print(f"      Question extracted: '{question[:50]}...' " if question else "      ❌ Failed to extract question")
        
        answers = self._extract_answers(item)
        print(f"      Answers extracted: {answers}" if answers else "      ❌ Failed to extract answers")
        
        if not answers and 'annotations' in item:
            print(f"\n      🔍 Deep dive into annotations:")
            anns = item['annotations']
            
            # Convert to list format for uniform processing
            ann_list = [anns] if isinstance(anns, dict) else (anns if isinstance(anns, list) else [])
            
            for i, ann in enumerate(ann_list[:2]):  # Check first 2 annotations
                print(f"\n      Annotation {i}:")
                if isinstance(ann, dict):
                    print(f"         Keys: {list(ann.keys())}")
                    
                    if 'short_answers' in ann:
                        sa = ann['short_answers']
                        print(f"         Short answers type: {type(sa)}")
                        
                        if isinstance(sa, list):
                            print(f"         Short answers count: {len(sa)}")
                            if len(sa) > 0:
                                first_sa = sa[0]
                                print(f"         First short answer: {first_sa}")
                                
                                if isinstance(first_sa, dict):
                                    start = first_sa.get('start_token')
                                    end = first_sa.get('end_token')
                                    print(f"         Start: {start}, End: {end}")
                                    
                                    if start is not None and end is not None:
                                        reconstructed = self._get_text_from_tokens(item, start, end)
                                        print(f"         Reconstructed: '{reconstructed}'")
    
    def _extract_question(self, item: dict) -> str:
        """Extract question text"""
        if 'question' not in item:
            return ""
        
        q = item['question']
        if isinstance(q, dict):
            return q.get('text', '')
        elif isinstance(q, str):
            return q
        return ""
    
    def _extract_answers(self, item: dict) -> List[str]:
        """Extract answers from annotations"""
        answers = []
        
        if 'annotations' not in item:
            return answers
        
        annotations = item['annotations']
        
        # Handle both list and dict formats
        annotation_list = []
        if isinstance(annotations, list):
            annotation_list = annotations
        elif isinstance(annotations, dict):
            # If it's a single dict, treat it as a list of one
            annotation_list = [annotations]
        else:
            return answers
        
        for ann in annotation_list:
            if not isinstance(ann, dict):
                continue
            
            # Get short answers
            short_answers = ann.get('short_answers', [])
            if not isinstance(short_answers, list) or len(short_answers) == 0:
                continue
            
            # Extract each answer
            for ans_span in short_answers:
                if not isinstance(ans_span, dict):
                    continue
                
                # Method 1: Try to get text directly (if available)
                text_field = ans_span.get('text', [])
                if isinstance(text_field, list) and len(text_field) > 0:
                    # Text is provided directly
                    for text in text_field:
                        if text and str(text).strip():
                            answers.append(str(text).strip())
                    continue
                
                # Method 2: Reconstruct from tokens
                start = ans_span.get('start_token')
                end = ans_span.get('end_token')
                
                # Handle list format for start/end tokens
                if isinstance(start, list):
                    start = start[0] if len(start) > 0 else None
                if isinstance(end, list):
                    end = end[0] if len(end) > 0 else None
                
                if start is None or end is None:
                    continue
                
                # Reconstruct from tokens
                answer_text = self._get_text_from_tokens(item, start, end)
                if answer_text:
                    answers.append(answer_text)
        
        # Remove duplicates
        return list(set(a.strip() for a in answers if a and a.strip()))
    
    def _get_text_from_tokens(self, item: dict, start_token: int, end_token: int) -> str:
        """Get text from document tokens using start/end indices"""
        if 'document' not in item:
            return ""
        
        doc = item['document']
        if not isinstance(doc, dict) or 'tokens' not in doc:
            return ""
        
        tokens = doc['tokens']
        
        # Get token list
        token_list = None
        if isinstance(tokens, dict) and 'token' in tokens:
            token_list = tokens['token']
        elif isinstance(tokens, list):
            token_list = tokens
        
        if not token_list or not isinstance(token_list, list):
            return ""
        
        # Check bounds
        if start_token < 0 or end_token >= len(token_list) or start_token > end_token:
            return ""
        
        # Extract and join tokens
        answer_tokens = token_list[start_token:end_token+1]
        return " ".join(str(t) for t in answer_tokens).strip()
    
    def _extract_context(self, item: dict) -> str:
        """Extract context from document"""
        if 'document' not in item:
            return ""
        
        doc = item['document']
        if not isinstance(doc, dict) or 'tokens' not in doc:
            return ""
        
        tokens = doc['tokens']
        
        # Get token list
        token_list = None
        if isinstance(tokens, dict) and 'token' in tokens:
            token_list = tokens['token']
        elif isinstance(tokens, list):
            token_list = tokens
        
        if not token_list or not isinstance(token_list, list):
            return ""
        
        # Take first 100 tokens as context
        context_tokens = token_list[:100]
        return " ".join(str(t) for t in context_tokens)
    
    def get_questions(self) -> List[Question]:
        """Get loaded questions"""
        return self.questions
    
    def save_json(self, filepath: str):
        """Save questions to JSON"""
        if not self.questions:
            print(f"⚠️  No questions to save")
            return
        
        filepath = Path(filepath)
        filepath.parent.mkdir(parents=True, exist_ok=True)
        
        data = [
            {
                'id': q.id,
                'question': q.question,
                'answers': q.answers,
                'context': q.context,
            }
            for q in self.questions
        ]
        
        with open(filepath, 'w', encoding='utf-8') as f:
            json.dump(data, f, indent=2, ensure_ascii=False)
        
        print(f"✅ Saved {len(data)} questions to {filepath}")
    
    def get_stats(self) -> Dict:
        """Get dataset statistics"""
        if not self.questions:
            return {
                'total': 0,
                'with_answers': 0,
                'avg_question_len': 0,
                'avg_answers': 0
            }
        
        return {
            'total': len(self.questions),
            'with_answers': sum(1 for q in self.questions if q.answers),
            'avg_question_len': sum(len(q.question.split()) for q in self.questions) / len(self.questions),
            'avg_answers': sum(len(q.answers) for q in self.questions) / len(self.questions)
        }


# =============================================================================
# WIKIPEDIA CORPUS (Full Dataset from HuggingFace)
# =============================================================================

@dataclass
class WikiPassage:
    """Wikipedia passage"""
    id: str
    title: str
    text: str
    url: str = ""


class WikiDPRCorpus:
    """Load full Wikipedia corpus from HuggingFace wikimedia/wikipedia"""
    
    def __init__(self, cache_dir: str = "./data/datasets"):
        self.cache_dir = Path(cache_dir)
        self.cache_dir.mkdir(parents=True, exist_ok=True)
        self.corpus = None
        self.passages = []
    
    def load(
        self,
        language: str = "20231101.simple",  # or "20231101.en" for full English
        max_passages: int = 10000,
        show_progress: bool = True
    ):
        """
        Load full Wikipedia corpus from HuggingFace
        
        Args:
            language: Wikipedia dump date.language (e.g., "20231101.simple", "20231101.en")
            max_passages: Maximum number of passages to extract
            show_progress: Show progress
        """
        if show_progress:
            print(f"\n📥 Loading Wikipedia corpus ({language})...")
            print("=" * 80)
            print(f"⚠️  Note: Full English Wikipedia is ~20GB, Simple is ~200MB")
        
        # Load full Wikipedia dataset
        self.corpus = load_dataset(
            "wikimedia/wikipedia",
            language,
            split="train",
            cache_dir=str(self.cache_dir),
        )
        
        if show_progress:
            print(f"✅ Loaded {len(self.corpus)} Wikipedia articles")
        
        # Extract passages
        self._extract_passages(max_passages, show_progress)
    
    def _extract_passages(self, max_passages: int, show_progress: bool):
        """
        Extract passages by chunking Wikipedia articles into ~100 word chunks
        (matching wiki_dpr format)
        """
        if show_progress:
            print(f"\n🔄 Chunking articles into ~100 word passages...")
        
        passages = []
        article_idx = 0
        
        iterator = tqdm(
            total=max_passages,
            desc="Extracting passages",
            disable=not show_progress
        )
        
        while len(passages) < max_passages and article_idx < len(self.corpus):
            item = self.corpus[article_idx]
            article_idx += 1
            
            # Get article data
            article_id = item.get('id', f'wiki_{article_idx}')
            title = item.get('title', '')
            text = item.get('text', '')
            url = item.get('url', '')
            
            # Skip empty or very short articles
            if not text or len(text.strip()) < 100:
                continue
            
            # Split into ~100 word chunks (wiki_dpr format)
            words = text.split()
            chunk_size = 100
            
            for chunk_idx in range(0, len(words), chunk_size):
                if len(passages) >= max_passages:
                    break
                
                chunk_words = words[chunk_idx:chunk_idx + chunk_size]
                
                # Skip very short chunks
                if len(chunk_words) < 20:
                    continue
                
                chunk_text = ' '.join(chunk_words)
                
                passages.append(WikiPassage(
                    id=f'{article_id}_chunk_{chunk_idx // chunk_size}',
                    title=title,
                    text=chunk_text,
                    url=url
                ))
                
                iterator.update(1)
        
        iterator.close()
        self.passages = passages
        
        if show_progress:
            print(f"✅ Extracted {len(passages)} passages from {article_idx} articles")
            print(f"   Each passage is ~100 words (wiki_dpr format)")
    
    def get_passages(self) -> List[WikiPassage]:
        """Get loaded passages"""
        return self.passages
    
    def save_json(self, filepath: str):
        """Save passages to JSON"""
        if not self.passages:
            print(f"⚠️ No passages to save")
            return
        
        filepath = Path(filepath)
        filepath.parent.mkdir(parents=True, exist_ok=True)
        
        data = [
            {
                'id': p.id,
                'title': p.title,
                'text': p.text,
                'url': p.url,
            }
            for p in self.passages
        ]
        
        with open(filepath, 'w', encoding='utf-8') as f:
            json.dump(data, f, indent=2, ensure_ascii=False)
        
        print(f"✅ Saved {len(data)} passages to {filepath}")
    
    def get_stats(self) -> Dict:
        """Get corpus statistics"""
        if not self.passages:
            return {}
        
        return {
            "total_passages": len(self.passages),
            "avg_passage_length": sum(len(p.text.split()) for p in self.passages) / len(self.passages),
            "unique_titles": len(set(p.title for p in self.passages)),
        }


if __name__ == "__main__":
    print("📚 Dataset Loader Test")
    print("=" * 80)
    
    # Test 1: Natural Questions
    print("\n[Test 1] Natural Questions")
    nq = NaturalQuestionsDataset()
    nq.load(max_samples=50, show_progress=True)
    
    questions = nq.get_questions()
    if len(questions) > 0:
        print(f"\n📋 Sample Questions (first 3):")
        for i, q in enumerate(questions[:3], 1):
            print(f"\n{i}. Q: {q.question}")
            print(f"   A: {q.answers}")
        
        stats = nq.get_stats()
        print(f"\n📊 Stats: {stats['total']} questions")
        
        nq.save_json("./data/datasets/nq_sample.json")
    
    # Test 2: Wikipedia Corpus
    print("\n" + "=" * 80)
    print("\n[Test 2] Wikipedia Corpus")
    
    wiki = WikiDPRCorpus()
    wiki.load(
        language="20231101.en",  # Full English Wikipedia, change to "20231101.simple" for Simple English
        max_passages=10000,
        show_progress=True
    )
    
    passages = wiki.get_passages()
    print(f"\n📋 Sample Passages (first 3):")
    for i, p in enumerate(passages[:3], 1):
        print(f"\n{i}. Title: {p.title}")
        print(f"   Text: {p.text[:100]}...")
        print(f"   URL: {p.url}")
    
    stats = wiki.get_stats()
    print(f"\n📊 Stats:")
    for key, value in stats.items():
        print(f"   {key}: {value}")
    
    wiki.save_json("./data/datasets/wiki_passages_1000.json")
    
    print("\n" + "=" * 80)
    print("✅ Test complete!")