#!/usr/bin/env python3
"""
extractor.py — Text-Extraktion aus verschiedenen Dateiformaten.

Unterstützte Formate:
    .txt .md            → direkt lesen
    .docx               → python-docx
    .pdf                → pypdf (mit OCR-Fallback bei Scans)
    .png .jpg .jpeg     → OCR via Tesseract
    .tif .tiff .bmp     → OCR via Tesseract
    .webp               → OCR via Tesseract

Tesseract muss systemweit installiert sein:
    brew install tesseract tesseract-lang
"""

import re
from pathlib import Path

try:
    from pypdf import PdfReader
    _PDF_SUPPORT = True
except ImportError:
    _PDF_SUPPORT = False

try:
    from docx import Document as DocxDocument
    _DOCX_SUPPORT = True
except ImportError:
    _DOCX_SUPPORT = False

try:
    from PIL import Image
    import pytesseract
    _OCR_SUPPORT = True
except ImportError:
    _OCR_SUPPORT = False

try:
    from pdf2image import convert_from_path
    _PDF2IMAGE_SUPPORT = True
except ImportError:
    _PDF2IMAGE_SUPPORT = False


SUPPORTED_EXTENSIONS = {
    ".txt", ".md",
    ".pdf",
    ".docx",
    ".png", ".jpg", ".jpeg", ".tif", ".tiff", ".bmp", ".webp",
}

_PDF_MIN_TEXT_LENGTH = 150
_OCR_LANG = "deu+eng"


def extract(path: Path) -> str:
    if not path.exists():
        raise FileNotFoundError(f"Datei nicht gefunden: {path}")

    suffix = path.suffix.lower()

    if suffix not in SUPPORTED_EXTENSIONS:
        raise ValueError(
            f"Nicht unterstütztes Format '{suffix}'. "
            f"Unterstützt: {', '.join(sorted(SUPPORTED_EXTENSIONS))}"
        )

    if suffix in (".txt", ".md"):
        return _read_text(path)
    elif suffix == ".docx":
        return _read_docx(path)
    elif suffix == ".pdf":
        return _read_pdf(path)
    else:
        return _ocr_image(path)


def is_supported(path: Path) -> bool:
    return path.suffix.lower() in SUPPORTED_EXTENSIONS


def _read_text(path: Path) -> str:
    return path.read_text(encoding="utf-8")


def _read_docx(path: Path) -> str:
    if not _DOCX_SUPPORT:
        raise ImportError("python-docx nicht installiert: pip install python-docx")

    doc = DocxDocument(str(path))
    parts = []

    for element in doc.element.body:
        tag = element.tag.split("}")[-1]
        if tag == "p":
            runs = "".join(
                r.text for r in element.iter()
                if r.tag.endswith("}t") and r.text
            )
            text = runs.strip()
            if text:
                parts.append(text)
        elif tag == "tbl":
            for row in element.iter():
                if row.tag.endswith("}tr"):
                    cells = [
                        "".join(
                            t.text or "" for t in cell.iter()
                            if t.tag.endswith("}t")
                        ).strip()
                        for cell in row
                        if cell.tag.endswith("}tc")
                    ]
                    if any(cells):
                        parts.append(" | ".join(cells))

    return "\n\n".join(parts)


def _read_pdf(path: Path) -> str:
    if not _PDF_SUPPORT:
        raise ImportError("pypdf nicht installiert: pip install pypdf")

    reader = PdfReader(str(path))
    pages = [page.extract_text() or "" for page in reader.pages]
    text = "\n\n".join(pages).strip()

    if len(text) < _PDF_MIN_TEXT_LENGTH:
        if not _PDF2IMAGE_SUPPORT or not _OCR_SUPPORT:
            raise ImportError(
                "PDF scheint ein Scan zu sein, aber pdf2image oder pytesseract fehlen. "
                "Installieren: pip install pdf2image pytesseract && brew install tesseract"
            )
        print("    ℹ️  PDF scheint ein Scan – verwende OCR-Fallback...")
        text = _ocr_pdf(path)

    return text


def _ocr_pdf(path: Path) -> str:
    images = convert_from_path(str(path), dpi=300)
    pages = []
    for i, img in enumerate(images, 1):
        page_text = pytesseract.image_to_string(img, lang=_OCR_LANG)
        pages.append(page_text)
        print(f"    📄 OCR Seite {i}/{len(images)} abgeschlossen")
    return _clean_ocr("\n\n".join(pages))


def _ocr_image(path: Path) -> str:
    if not _OCR_SUPPORT:
        raise ImportError(
            "pytesseract oder Pillow nicht installiert. "
            "Installieren: pip install pytesseract Pillow && brew install tesseract tesseract-lang"
        )
    img = Image.open(str(path))
    raw = pytesseract.image_to_string(img, lang=_OCR_LANG)
    return _clean_ocr(raw)


def _clean_ocr(text: str) -> str:
    text = re.sub(r"[^\S\n]+", " ", text)
    text = re.sub(r"\n{3,}", "\n\n", text)
    text = re.sub(r"[|}{~`\\^]", "", text)
    text = re.sub(r"(\w)-\n(\w)", r"\1\2", text)
    return text.strip()