"""Utilities for parsing PDF, EPUB, MOBI files and extracting/generating covers.

Content is returned as a list of segments. Each segment is either:
  {"type": "text", "content": "..."} or
  {"type": "image", "src": "/book_images/abc123_0.png"}
This allows the frontend to render images inline between text blocks.
"""

import os
import base64
import fitz  # PyMuPDF
import ebooklib
from ebooklib import epub
from PIL import Image, ImageDraw, ImageFont
from bs4 import BeautifulSoup
import mobi
import shutil

import settings

IMG_COUNTER = 0


def ensure_dirs():
    os.makedirs(settings.UPLOAD_DIR, exist_ok=True)
    os.makedirs(settings.COVERS_DIR, exist_ok=True)
    os.makedirs(settings.IMAGES_DIR, exist_ok=True)


def _save_image_bytes(img_bytes: bytes, book_id: str, ext: str = "png") -> str:
    """Save image bytes to disk and return the URL path."""
    global IMG_COUNTER
    IMG_COUNTER += 1
    fname = f"{book_id}_{IMG_COUNTER}.{ext}"
    fpath = os.path.join(settings.IMAGES_DIR, fname)
    with open(fpath, "wb") as f:
        f.write(img_bytes)
    return f"/book_images/{fname}"


def _clean_pdf_text(raw: str) -> str:
    """Clean PDF text: join mid-sentence line breaks, keep paragraph breaks."""
    import re
    lines = raw.split("\n")
    result = []
    for line in lines:
        line = line.rstrip()
        if not line:
            # Empty line = paragraph break
            if result and result[-1] != "\n":
                result.append("\n")
            continue
        if result and result[-1] != "\n":
            prev = result[-1]
            # If previous line ends with sentence-ending punctuation, start new paragraph
            if prev and prev[-1] in '.!?:;»""\u201d\u2019':
                result.append("\n")
                result.append(line)
            elif prev and prev[-1] == '-':
                # Hyphenated word across lines: join without space, remove hyphen
                result[-1] = prev[:-1] + line
            else:
                # Mid-sentence break: join with space
                result[-1] = prev + " " + line
        else:
            result.append(line)
    # Collapse multiple newlines
    text = "\n".join(result)
    text = re.sub(r'\n{3,}', '\n\n', text)
    return text.strip()


def extract_pdf_content(filepath: str, book_id: str) -> list[dict]:
    """Extract text and images from PDF, returning ordered segments."""
    doc = fitz.open(filepath)
    segments = []
    for page in doc:
        blocks = page.get_text("dict", flags=fitz.TEXT_PRESERVE_WHITESPACE)["blocks"]
        # Collect raw text blocks and images sorted by position
        page_text_parts = []
        for block in sorted(blocks, key=lambda b: (b["bbox"][1], b["bbox"][0])):
            if block["type"] == 0:  # text block
                text = ""
                for line in block.get("lines", []):
                    for span in line.get("spans", []):
                        text += span.get("text", "")
                    text += "\n"
                text = text.strip()
                if text:
                    page_text_parts.append(text)
            elif block["type"] == 1:  # image block
                # Flush accumulated text before the image
                if page_text_parts:
                    merged = _clean_pdf_text("\n".join(page_text_parts))
                    if merged:
                        # Split into paragraphs
                        for para in merged.split("\n"):
                            para = para.strip()
                            if para:
                                segments.append({"type": "text", "content": para})
                    page_text_parts = []
                try:
                    img_bytes = block.get("image")
                    if img_bytes and len(img_bytes) > 500:
                        ext = block.get("ext", "png") or "png"
                        src = _save_image_bytes(img_bytes, book_id, ext)
                        segments.append({"type": "image", "src": src})
                except Exception:
                    pass
        # Flush remaining text from this page
        if page_text_parts:
            merged = _clean_pdf_text("\n".join(page_text_parts))
            if merged:
                for para in merged.split("\n"):
                    para = para.strip()
                    if para:
                        segments.append({"type": "text", "content": para})
    doc.close()
    return segments


def extract_pdf_cover(filepath: str, book_id: str) -> str | None:
    doc = fitz.open(filepath)
    if len(doc) == 0:
        doc.close()
        return None
    page = doc[0]
    images = page.get_images(full=True)
    if images:
        xref = images[0][0]
        base_image = doc.extract_image(xref)
        img_bytes = base_image["image"]
        ext = base_image["ext"]
        cover_path = os.path.join(settings.COVERS_DIR, f"{book_id}.{ext}")
        with open(cover_path, "wb") as f:
            f.write(img_bytes)
        doc.close()
        return cover_path
    doc.close()
    return None


def extract_epub_content(filepath: str, book_id: str) -> list[dict]:
    """Extract text and images from EPUB, returning ordered segments."""
    book = epub.read_epub(filepath, options={'ignore_ncx': True})

    # Build a map of image items by their file name for lookup
    image_map = {}
    for item in book.get_items_of_type(ebooklib.ITEM_IMAGE):
        image_map[item.get_name()] = item
        # Also map by basename for relative references
        image_map[os.path.basename(item.get_name())] = item

    segments = []
    for item in book.get_items_of_type(ebooklib.ITEM_DOCUMENT):
        soup = BeautifulSoup(item.get_content(), "html.parser")

        for elem in soup.descendants:
            if elem.name == 'img' or elem.name == 'image':
                src_attr = elem.get('src') or elem.get('xlink:href') or elem.get('href', '')
                # Resolve the image
                img_name = src_attr.split('/')[-1] if src_attr else ''
                img_item = image_map.get(src_attr) or image_map.get(img_name)
                if img_item:
                    try:
                        img_bytes = img_item.get_content()
                        if len(img_bytes) > 500:
                            ext = img_name.rsplit('.', 1)[-1] if '.' in img_name else 'png'
                            s = _save_image_bytes(img_bytes, book_id, ext)
                            segments.append({"type": "image", "src": s})
                    except Exception:
                        pass
            elif elem.name in ('p', 'div', 'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'li', 'blockquote'):
                text = elem.get_text(separator=" ", strip=True)
                if text:
                    seg = {"type": "text", "content": text}
                    if elem.name in ('h1', 'h2', 'h3'):
                        seg["heading"] = True
                    segments.append(seg)

    # Deduplicate consecutive identical text segments
    deduped = []
    for seg in segments:
        if deduped and seg["type"] == "text" and deduped[-1]["type"] == "text" and deduped[-1]["content"] == seg["content"]:
            continue
        deduped.append(seg)
    return deduped


def extract_epub_cover(filepath: str, book_id: str) -> str | None:
    book = epub.read_epub(filepath, options={'ignore_ncx': True})
    for item in book.get_items():
        if 'cover' in (item.get_name() or '').lower() and item.get_type() in (
            ebooklib.ITEM_IMAGE, ebooklib.ITEM_COVER
        ):
            ext = item.get_name().rsplit('.', 1)[-1] if '.' in item.get_name() else 'jpg'
            cover_path = os.path.join(settings.COVERS_DIR, f"{book_id}.{ext}")
            with open(cover_path, "wb") as f:
                f.write(item.get_content())
            return cover_path
    for item in book.get_items_of_type(ebooklib.ITEM_IMAGE):
        ext = item.get_name().rsplit('.', 1)[-1] if '.' in item.get_name() else 'jpg'
        cover_path = os.path.join(settings.COVERS_DIR, f"{book_id}.{ext}")
        with open(cover_path, "wb") as f:
            f.write(item.get_content())
        return cover_path
    return None


def extract_mobi_content(filepath: str, book_id: str) -> list[dict]:
    """Extract text from MOBI as segments."""
    tempdir, extracted_path = mobi.extract(filepath)
    try:
        if extracted_path and os.path.isfile(extracted_path):
            with open(extracted_path, "r", encoding="utf-8", errors="ignore") as f:
                content = f.read()
            soup = BeautifulSoup(content, "html.parser")
            segments = []
            for elem in soup.find_all(['p', 'div', 'h1', 'h2', 'h3', 'h4', 'h5', 'h6']):
                text = elem.get_text(separator=" ", strip=True)
                if text:
                    segments.append({"type": "text", "content": text})
            return segments if segments else [{"type": "text", "content": "[Empty book]"}]
        return [{"type": "text", "content": "[Could not extract MOBI content]"}]
    finally:
        if tempdir and os.path.isdir(tempdir):
            shutil.rmtree(tempdir, ignore_errors=True)


def extract_mobi_cover(filepath: str, book_id: str) -> str | None:
    return None


def generate_cover(title: str, book_id: str) -> str:
    img = Image.new("RGB", (400, 600), color=(45, 55, 72))
    draw = ImageDraw.Draw(img)
    try:
        font = ImageFont.truetype("arial.ttf", 28)
    except (OSError, IOError):
        font = ImageFont.load_default()
    words = title.split()
    lines, current = [], ""
    for w in words:
        test = f"{current} {w}".strip()
        bbox = draw.textbbox((0, 0), test, font=font)
        if bbox[2] - bbox[0] > 360:
            if current: lines.append(current)
            current = w
        else:
            current = test
    if current: lines.append(current)
    y = 200
    for line in lines:
        bbox = draw.textbbox((0, 0), line, font=font)
        w = bbox[2] - bbox[0]
        draw.text(((400 - w) / 2, y), line, fill="white", font=font)
        y += 40
    cover_path = os.path.join(settings.COVERS_DIR, f"{book_id}.png")
    img.save(cover_path)
    return cover_path


def parse_book(filepath: str, book_id: str, title: str) -> dict:
    """Parse a book file and return content segments + cover path + chapters."""
    import re
    ext = os.path.splitext(filepath)[1].lower()
    segments = []
    cover = None

    if ext == ".pdf":
        segments = extract_pdf_content(filepath, book_id)
        cover = extract_pdf_cover(filepath, book_id)
    elif ext == ".epub":
        segments = extract_epub_content(filepath, book_id)
        cover = extract_epub_cover(filepath, book_id)
    elif ext == ".mobi":
        segments = extract_mobi_content(filepath, book_id)
        cover = extract_mobi_cover(filepath, book_id)
    else:
        raise ValueError(f"Unsupported format: {ext}")

    if not cover:
        cover = generate_cover(title, book_id)

    # Build chapter index from headings or chapter-like patterns
    chapters = []
    chapter_pattern = re.compile(
        r'^(chapter|chapitre|capitolo|capítulo|kapitel|hoofdstuk|kapittel|rozdział)\s+\w+',
        re.IGNORECASE
    )
    for i, seg in enumerate(segments):
        if seg.get("heading"):
            chapters.append({"title": seg["content"][:80], "segment": i})
        elif seg["type"] == "text" and chapter_pattern.match(seg["content"].strip()):
            chapters.append({"title": seg["content"].strip()[:80], "segment": i})

    # Flat page text for DB
    current_text = [seg["content"] for seg in segments if seg["type"] == "text"]
    pages = ["\n\n".join(current_text)] if current_text else ["[Empty]"]

    return {"pages": pages, "segments": segments, "cover": cover, "chapters": chapters}