#!/usr/bin/env python3
"""
Extract and clean articles from Vietnamese Wikipedia dump.

UVW 2026: Underthesea Vietnamese Wikipedia Dataset
https://github.com/undertheseanlp/underthesea/issues/896
"""

import bz2
import json
import re
import unicodedata
from pathlib import Path
from typing import Iterator, Optional
from xml.etree import ElementTree as ET

from tqdm import tqdm


RAW_DIR = Path(__file__).parent.parent / "data" / "raw"
OUTPUT_DIR = Path(__file__).parent.parent / "data" / "processed"

# Wikipedia namespace (0.11 as of 2026)
NAMESPACE = "{http://www.mediawiki.org/xml/export-0.11/}"

# Patterns to remove from Wikipedia markup
WIKI_PATTERNS = [
    (r"\{\{[^}]+\}\}", ""),  # Templates
    (r"\[\[Category:[^\]]+\]\]", ""),  # Categories
    (r"\[\[Thể loại:[^\]]+\]\]", ""),  # Vietnamese categories
    (r"\[\[File:[^\]]+\]\]", ""),  # Files
    (r"\[\[Tập tin:[^\]]+\]\]", ""),  # Vietnamese files
    (r"\[\[Image:[^\]]+\]\]", ""),  # Images
    (r"\[\[Hình:[^\]]+\]\]", ""),  # Vietnamese images
    (r"<ref[^>]*>.*?</ref>", ""),  # References
    (r"<ref[^/]*/>", ""),  # Self-closing refs
    (r"<!--.*?-->", ""),  # Comments
    (r"\{\|.*?\|\}", ""),  # Tables
    (r"<[^>]+>", ""),  # HTML tags
    (r"\[https?://[^\s\]]+\s*([^\]]*)\]", r"\1"),  # External links
    (r"\[\[([^|\]]+)\|([^\]]+)\]\]", r"\2"),  # Internal links with display text
    (r"\[\[([^\]]+)\]\]", r"\1"),  # Simple internal links
    (r"'''?", ""),  # Bold/italic
    (r"={2,}([^=]+)={2,}", r"\1"),  # Headers
    (r"\*+", ""),  # List markers
    (r"#+", ""),  # Numbered list markers
]


def normalize_text(text: str) -> str:
    """Normalize Unicode text (NFC normalization)."""
    return unicodedata.normalize("NFC", text)


def clean_wiki_markup(text: str) -> str:
    """Remove Wikipedia markup and clean text."""
    # Apply regex patterns
    for pattern, replacement in WIKI_PATTERNS:
        text = re.sub(pattern, replacement, text, flags=re.DOTALL | re.MULTILINE)

    # Clean up whitespace
    text = re.sub(r"\n{3,}", "\n\n", text)
    text = re.sub(r"[ \t]+", " ", text)
    text = "\n".join(line.strip() for line in text.split("\n"))
    text = text.strip()

    return text


def is_valid_article(title: str, text: str) -> bool:
    """Check if an article should be included."""
    # Skip special pages
    skip_prefixes = [
        "Wikipedia:", "Thảo luận:", "Thành viên:", "Bản mẫu:",
        "Module:", "MediaWiki:", "Trợ giúp:", "Cổng thông tin:",
        "Chủ đề:", "TimedText:", "Gadget:", "Gadget definition:",
    ]
    for prefix in skip_prefixes:
        if title.startswith(prefix):
            return False

    # Skip redirects
    if text.strip().lower().startswith("#redirect") or text.strip().lower().startswith("#đổi"):
        return False

    # Skip disambiguation pages
    if "{{trang định hướng}}" in text.lower() or "{{disambiguation}}" in text.lower():
        return False

    return True


def parse_wikipedia_dump(dump_path: Path) -> Iterator[dict]:
    """Parse Wikipedia XML dump and yield articles."""
    with bz2.open(dump_path, "rt", encoding="utf-8") as f:
        context = ET.iterparse(f, events=("end",))

        for event, elem in context:
            if elem.tag == f"{NAMESPACE}page":
                title_elem = elem.find(f"{NAMESPACE}title")
                text_elem = elem.find(f".//{NAMESPACE}text")

                if title_elem is not None and text_elem is not None:
                    title = title_elem.text or ""
                    text = text_elem.text or ""

                    if is_valid_article(title, text):
                        yield {
                            "title": title,
                            "text": text,
                        }

                # Clear element to save memory
                elem.clear()


def process_article(article: dict) -> Optional[dict]:
    """Process a single article."""
    title = normalize_text(article["title"])
    text = clean_wiki_markup(article["text"])
    text = normalize_text(text)

    # Skip articles with too little content
    if len(text) < 100:
        return None

    # Count sentences (simple heuristic)
    sentences = [s.strip() for s in re.split(r"[.!?]", text) if s.strip()]

    return {
        "id": title.replace(" ", "_"),
        "title": title,
        "content": text,
        "num_chars": len(text),
        "num_sentences": len(sentences),
    }


def save_plaintext(articles: list, output_dir: Path) -> None:
    """Save articles in plaintext format (one file per article)."""
    plaintext_dir = output_dir / "plaintext"
    plaintext_dir.mkdir(parents=True, exist_ok=True)

    for article in tqdm(articles, desc="Saving plaintext"):
        # Sanitize filename
        filename = re.sub(r'[<>:"/\\|?*]', "_", article["id"])[:200]
        filepath = plaintext_dir / f"{filename}.txt"

        with open(filepath, "w", encoding="utf-8") as f:
            f.write(f"{article['title']}\n\n")
            f.write(article["content"])


def save_jsonl(articles: list, output_path: Path) -> None:
    """Save articles in JSONL format."""
    output_path.parent.mkdir(parents=True, exist_ok=True)

    with open(output_path, "w", encoding="utf-8") as f:
        for article in articles:
            f.write(json.dumps(article, ensure_ascii=False) + "\n")


def save_metadata(articles: list, output_path: Path) -> None:
    """Save dataset metadata."""
    total_chars = sum(a["num_chars"] for a in articles)
    total_sentences = sum(a["num_sentences"] for a in articles)

    metadata = {
        "name": "UVW 2026",
        "full_name": "Underthesea Vietnamese Wikipedia Dataset",
        "version": "1.0.0",
        "year": 2026,
        "language": "vi",
        "license": "CC BY-SA 4.0",
        "source": "Vietnamese Wikipedia",
        "url": "https://vi.wikipedia.org",
        "statistics": {
            "num_articles": len(articles),
            "num_characters": total_chars,
            "num_sentences": total_sentences,
            "avg_chars_per_article": total_chars // len(articles) if articles else 0,
        },
    }

    with open(output_path, "w", encoding="utf-8") as f:
        json.dump(metadata, f, ensure_ascii=False, indent=2)


def main():
    """Extract and process Vietnamese Wikipedia articles."""
    dump_path = RAW_DIR / "viwiki-latest-pages-articles.xml.bz2"

    if not dump_path.exists():
        print(f"Wikipedia dump not found: {dump_path}")
        print("Please run download_wikipedia.py first.")
        return

    OUTPUT_DIR.mkdir(parents=True, exist_ok=True)

    print("Parsing and processing Wikipedia dump...")
    print(f"Input: {dump_path}")

    articles = []
    for raw_article in tqdm(parse_wikipedia_dump(dump_path), desc="Processing"):
        processed = process_article(raw_article)
        if processed:
            articles.append(processed)

    print(f"\nTotal articles extracted: {len(articles)}")

    # Save in multiple formats
    print("\nSaving datasets...")

    # JSONL format (HuggingFace compatible)
    save_jsonl(articles, OUTPUT_DIR / "uvw_2026.jsonl")
    print(f"  - JSONL: {OUTPUT_DIR / 'uvw_2026.jsonl'}")

    # Plaintext format (underthesea compatible)
    save_plaintext(articles, OUTPUT_DIR)
    print(f"  - Plaintext: {OUTPUT_DIR / 'plaintext/'}")

    # Metadata
    save_metadata(articles, OUTPUT_DIR / "metadata.json")
    print(f"  - Metadata: {OUTPUT_DIR / 'metadata.json'}")

    print("\nDataset creation complete!")


if __name__ == "__main__":
    main()