#!/usr/bin/env python3
"""
extract_text.py — Text Extraction: Extract plain text from all content files in CatholicCorpus.

Walks Tasks 01–17 and extracts plain text from PDF, EPUB, HTML, HTM, XML,
and TXT files. Output is written to a parallel directory structure under
text_extraction/extracted/ so the extracted text ships alongside the
raw source files as part of the corpus.

Each source file produces one .txt file with the same relative path.

Usage:
    python3 extract_text.py                  # Process all tasks
    python3 extract_text.py --task 05_ccel   # Process a single task
    python3 extract_text.py --resume         # Skip files already extracted
    python3 extract_text.py --dry-run        # Show what would be processed

Requirements:
    pip install pdfplumber lxml beautifulsoup4 ebooklib
"""
from __future__ import annotations

import argparse
import html
import json
import logging
import os
import re
import sys
import time
import zipfile
from pathlib import Path
from typing import Optional

# Corpus root is one level up from this task folder
TASK_DIR = Path(__file__).resolve().parent
CORPUS_ROOT = TASK_DIR.parent
OUTPUT_DIR = TASK_DIR / "extracted"
MANIFEST = CORPUS_ROOT / "master_manifest.json"

# Configure logging
logging.basicConfig(
    level=logging.INFO,
    format="%(asctime)s [%(levelname)s] %(message)s",
    handlers=[
        logging.FileHandler(TASK_DIR / "extract_text.log"),
        logging.StreamHandler(),
    ],
)
log = logging.getLogger(__name__)

# Tasks to skip (this task folder, and task 17 which is copyrighted)
SKIP_TASKS = {"text_extraction"}

# ── Extractors ────────────────────────────────────────────────────────

def extract_pdf(path: Path) -> Optional[str]:
    """Extract text from PDF using pdfplumber, with page-at-a-time processing."""
    import pdfplumber

    # Skip very large scanned PDFs that would OOM (>200 MB)
    file_size_mb = path.stat().st_size / (1024 * 1024)
    if file_size_mb > 200:
        log.warning("  Skipping oversized PDF (%.0f MB): %s", file_size_mb, path.name)
        return None

    pages = []
    try:
        with pdfplumber.open(path) as pdf:
            for i, page in enumerate(pdf.pages):
                try:
                    text = page.extract_text()
                    if text:
                        pages.append(text)
                except Exception as e:
                    log.warning("  Page %d failed in %s: %s", i, path.name, e)
                    continue
    except Exception as e:
        log.warning("  Could not open PDF %s: %s", path.name, e)
        return None

    return "\n\n".join(pages) if pages else None


def extract_epub(path: Path) -> Optional[str]:
    """Extract text from EPUB using ebooklib + BeautifulSoup."""
    try:
        import ebooklib
        from ebooklib import epub
    except ImportError:
        log.warning("ebooklib not installed — skipping EPUB: %s", path)
        return None

    from bs4 import BeautifulSoup

    try:
        book = epub.read_epub(str(path), options={"ignore_ncx": True})
    except Exception as e:
        log.warning("  Could not open EPUB %s: %s", path.name, e)
        return None

    texts = []
    for item in book.get_items():
        if item.get_type() == ebooklib.ITEM_DOCUMENT:
            soup = BeautifulSoup(item.get_content(), "html.parser")
            text = soup.get_text(separator="\n", strip=True)
            if text:
                texts.append(text)
    return "\n\n".join(texts) if texts else None


def extract_html(path: Path) -> Optional[str]:
    """Extract text from HTML/HTM using BeautifulSoup."""
    from bs4 import BeautifulSoup

    try:
        content = path.read_text(encoding="utf-8", errors="replace")
    except Exception:
        content = path.read_bytes().decode("latin-1", errors="replace")

    soup = BeautifulSoup(content, "html.parser")

    # Remove script and style elements
    for tag in soup(["script", "style", "nav", "header", "footer"]):
        tag.decompose()

    text = soup.get_text(separator="\n", strip=True)
    return text if text.strip() else None


def extract_tei_xml(path: Path) -> Optional[str]:
    """Extract text from TEI XML, stripping all tags."""
    from lxml import etree

    try:
        tree = etree.parse(str(path))
    except etree.XMLSyntaxError:
        # Try as plain XML / strip tags with regex fallback
        try:
            content = path.read_text(encoding="utf-8", errors="replace")
            text = re.sub(r"<[^>]+>", " ", content)
            text = html.unescape(text)
            text = re.sub(r"\s+", " ", text).strip()
            return text if text else None
        except Exception:
            return None

    # Try TEI namespace first
    ns = {"tei": "http://www.tei-c.org/ns/1.0"}
    body = tree.find(".//tei:body", ns)
    if body is None:
        body = tree.find(".//body")
    if body is None:
        body = tree.getroot()

    # Extract all text content
    text = etree.tostring(body, method="text", encoding="unicode")
    text = re.sub(r"\s+", " ", text).strip()
    return text if text else None


def extract_pos_xml(path: Path) -> Optional[str]:
    """Extract text from .pos.xml files (ZIP-compressed POS-tagged XML)."""
    try:
        with zipfile.ZipFile(path, "r") as zf:
            for name in zf.namelist():
                if name.endswith(".xml") or name.endswith(".POS.xml"):
                    content = zf.read(name).decode("utf-8", errors="replace")
                    text = re.sub(r"<[^>]+>", " ", content)
                    text = html.unescape(text)
                    text = re.sub(r"\s+", " ", text).strip()
                    if text:
                        return text
    except (zipfile.BadZipFile, Exception) as e:
        log.warning("Could not extract .pos.xml %s: %s", path, e)
    return None


def extract_txt(path: Path) -> Optional[str]:
    """Read plain text file."""
    try:
        text = path.read_text(encoding="utf-8", errors="replace")
        return text if text.strip() else None
    except Exception:
        return None


# ── Dispatcher ────────────────────────────────────────────────────────

EXTRACTORS = {
    ".pdf": extract_pdf,
    ".epub": extract_epub,
    ".html": extract_html,
    ".htm": extract_html,
    ".xml": extract_tei_xml,
    ".txt": extract_txt,
}


def extract_file(source: Path) -> Optional[str]:
    """Route a file to the appropriate extractor."""
    ext = source.suffix.lower()

    # Special case: .pos.xml files are zipped
    if source.name.endswith(".pos.xml"):
        return extract_pos_xml(source)

    extractor = EXTRACTORS.get(ext)
    if extractor is None:
        return None
    return extractor(source)


# ── Main processing ──────────────────────────────────────────────────

def process_task(task_name: str, task_dir: Path, resume: bool, dry_run: bool) -> dict:
    """Process all content files in a task directory."""
    stats = {"processed": 0, "skipped": 0, "failed": 0, "empty": 0, "already_done": 0}
    out_task = OUTPUT_DIR / task_name

    # Extensions we extract from
    target_exts = {".pdf", ".epub", ".html", ".htm", ".xml", ".txt"}

    for source in sorted(task_dir.rglob("*")):
        if not source.is_file():
            continue
        if source.suffix.lower() not in target_exts:
            continue
        # Skip _source.json sidecars and download scripts
        if source.name.startswith("_source") or source.name == "download_script.py":
            continue
        # Skip .pos.xml duplicates (prefer the regular .xml for text extraction)
        if source.name.endswith(".pos.xml"):
            stats["skipped"] += 1
            continue

        rel = source.relative_to(task_dir)
        out_path = out_task / rel.with_suffix(".txt")

        if resume and out_path.exists() and out_path.stat().st_size > 0:
            stats["already_done"] += 1
            continue

        if dry_run:
            log.info("  [DRY-RUN] Would extract: %s", rel)
            stats["processed"] += 1
            continue

        try:
            text = extract_file(source)
            if text and len(text.strip()) > 10:
                out_path.parent.mkdir(parents=True, exist_ok=True)
                out_path.write_text(text, encoding="utf-8")
                stats["processed"] += 1
            else:
                stats["empty"] += 1
        except Exception as e:
            log.warning("  FAILED: %s — %s", rel, e)
            stats["failed"] += 1

    return stats


def discover_tasks() -> list:
    """Find all task directories (NN_*) in the corpus root, excluding this one."""
    import re as _re
    pattern = _re.compile(r"^\d{2}_")
    found = [p.name for p in CORPUS_ROOT.iterdir()
             if p.is_dir() and pattern.match(p.name) and p.name not in SKIP_TASKS]
    return sorted(found)


def main():
    parser = argparse.ArgumentParser(
        description="Task 18: Extract plain text from all CatholicCorpus content files"
    )
    parser.add_argument("--task", help="Process only this task folder (e.g., 05_ccel)")
    parser.add_argument("--resume", action="store_true", help="Skip files already extracted")
    parser.add_argument("--dry-run", action="store_true", help="Show what would be processed")
    args = parser.parse_args()

    OUTPUT_DIR.mkdir(exist_ok=True)

    task_names = [args.task] if args.task else discover_tasks()

    log.info("=" * 60)
    log.info("CatholicCorpus — Text Extraction")
    log.info("Corpus root: %s", CORPUS_ROOT)
    log.info("Output: %s", OUTPUT_DIR)
    log.info("Tasks to process: %s", ", ".join(task_names))
    if args.resume:
        log.info("Mode: RESUME (skipping existing)")
    if args.dry_run:
        log.info("Mode: DRY-RUN")
    log.info("=" * 60)

    grand_stats = {"processed": 0, "skipped": 0, "failed": 0, "empty": 0, "already_done": 0}
    start = time.time()

    for task_name in task_names:
        task_dir = CORPUS_ROOT / task_name
        if not task_dir.exists():
            log.warning("Skipping %s — directory not found", task_name)
            continue

        log.info("")
        log.info("TASK: %s", task_name)
        log.info("-" * 40)

        stats = process_task(task_name, task_dir, args.resume, args.dry_run)

        for k in grand_stats:
            grand_stats[k] += stats[k]

        log.info("  Extracted: %d | Empty: %d | Failed: %d | Skipped: %d | Already done: %d",
                 stats["processed"], stats["empty"], stats["failed"],
                 stats["skipped"], stats["already_done"])

    elapsed = time.time() - start
    log.info("")
    log.info("=" * 60)
    log.info("EXTRACTION COMPLETE")
    log.info("  Total extracted: %d", grand_stats["processed"])
    log.info("  Empty/no-text:   %d", grand_stats["empty"])
    log.info("  Failed:          %d", grand_stats["failed"])
    log.info("  Skipped (.pos):  %d", grand_stats["skipped"])
    log.info("  Already done:    %d", grand_stats["already_done"])
    log.info("  Time: %.1f minutes", elapsed / 60)
    log.info("=" * 60)

    # Write extraction summary
    summary = {
        "generated_at": int(time.time()),
        "generated_at_iso": time.strftime("%Y-%m-%d %H:%M:%S %Z", time.localtime()),
        "stats": grand_stats,
        "elapsed_seconds": round(elapsed, 1),
    }
    (OUTPUT_DIR / "_extraction_summary.json").write_text(
        json.dumps(summary, indent=2)
    )
    log.info("Wrote %s", OUTPUT_DIR / "_extraction_summary.json")


if __name__ == "__main__":
    main()