import io
import re
import html
import zipfile
import posixpath
import urllib.parse
import xml.etree.ElementTree as ET
from html.parser import HTMLParser
from typing import Tuple, List, Dict


def count_words(text: str) -> int:
    """
    Counts words in text across multiple languages, ignoring isolated punctuation.
    """
    if not text:
        return 0
    return len(re.findall(r"\b[\w]+(?:['’][\w]+)?\b", text))


class HTMLTextExtractor(HTMLParser):
    """
    Strips HTML tags cleanly while preserving paragraph and heading breaks with newlines.
    Also extracts the first heading and/or <title> tag for chapter naming.
    """
    def __init__(self):
        super().__init__()
        self.text_parts: List[str] = []
        self.ignore_tags = {"style", "script", "noscript"}
        self.ignore_depth = 0
        self.heading: str | None = None
        self.in_heading = False
        self.heading_parts: List[str] = []
        self.title: str | None = None
        self.in_title = False
        self.title_parts: List[str] = []

    def handle_starttag(self, tag: str, attrs):
        t = tag.lower()
        if t in self.ignore_tags:
            self.ignore_depth += 1
        elif t == "title":
            self.in_title = True
            self.title_parts = []
        elif t in {"h1", "h2", "h3", "h4", "h5", "h6"}:
            self.text_parts.append("\n\n")
            if not self.heading:
                self.in_heading = True
                self.heading_parts = []
        elif t in {"p", "div", "section", "article", "blockquote", "header", "footer"}:
            self.text_parts.append("\n\n")
        elif t in {"br", "hr", "li", "tr"}:
            self.text_parts.append("\n")

    def handle_endtag(self, tag: str):
        t = tag.lower()
        if t in self.ignore_tags:
            self.ignore_depth = max(0, self.ignore_depth - 1)
        elif t == "title":
            self.in_title = False
            self.title = "".join(self.title_parts).strip()
        elif t in {"h1", "h2", "h3", "h4", "h5", "h6"}:
            self.text_parts.append("\n\n")
            if self.in_heading:
                self.in_heading = False
                if not self.heading:
                    self.heading = "".join(self.heading_parts).strip()
        elif t in {"p", "div", "section", "article", "blockquote", "header", "footer"}:
            self.text_parts.append("\n\n")
        elif t in {"li", "tr"}:
            self.text_parts.append("\n")

    def handle_data(self, data: str):
        if self.in_title:
            self.title_parts.append(data)
        if self.ignore_depth == 0 and not self.in_title:
            # Replace non-breaking spaces with standard space
            cleaned_data = data.replace("\xa0", " ")
            self.text_parts.append(cleaned_data)
            if self.in_heading:
                self.heading_parts.append(cleaned_data)

    def get_text(self) -> str:
        raw = "".join(self.text_parts)
        lines = [line.strip() for line in raw.split("\n")]
        clean = "\n".join(lines)
        return re.sub(r"\n{3,}", "\n\n", clean).strip()


def parse_epub(file_bytes: bytes) -> Tuple[str, str, List[Dict[str, str]]]:
    """
    Parses an EPUB file archive and extracts:
      - title: book title
      - author: creator/author
      - chapters: list of {"title": str, "content": str}
    """
    try:
        z = zipfile.ZipFile(io.BytesIO(file_bytes))
    except Exception as e:
        raise ValueError(f"Invalid EPUB archive: {e}")

    # 1. Locate root OPF file from META-INF/container.xml
    opf_path = None
    try:
        container_data = z.read("META-INF/container.xml")
        root = ET.fromstring(container_data)
        rootfile = root.find(".//{*}rootfile")
        if rootfile is not None:
            opf_path = rootfile.attrib.get("full-path")
    except Exception:
        pass

    if not opf_path:
        for name in z.namelist():
            if name.lower().endswith(".opf"):
                opf_path = name
                break

    if not opf_path:
        raise ValueError("Invalid EPUB: no OPF file found")

    opf_path = opf_path.replace("\\", "/").lstrip("/")
    opf_dir = posixpath.dirname(opf_path)

    try:
        opf_content = z.read(opf_path)
    except KeyError:
        # Try lowercase matching
        name_map = {n.lower(): n for n in z.namelist()}
        if opf_path.lower() in name_map:
            opf_content = z.read(name_map[opf_path.lower()])
        else:
            raise ValueError(f"OPF file not found in archive: {opf_path}")

    # 2. Extract metadata (title, author)
    title = "Untitled"
    author = ""
    opf_tree = None
    try:
        opf_tree = ET.fromstring(opf_content)
        title_el = opf_tree.find(".//{*}title")
        if title_el is not None and title_el.text:
            title = title_el.text.strip()
        creator_el = opf_tree.find(".//{*}creator")
        if creator_el is not None and creator_el.text:
            author = creator_el.text.strip()
    except Exception:
        opf_str = opf_content.decode("utf-8", errors="ignore")
        tm = re.search(r"<[^:]*:?title[^>]*>(.*?)</[^:]*:?title>", opf_str, re.I | re.S)
        if tm:
            title = re.sub(r"<[^>]+>", "", tm.group(1)).strip()
        cm = re.search(r"<[^:]*:?creator[^>]*>(.*?)</[^:]*:?creator>", opf_str, re.I | re.S)
        if cm:
            author = re.sub(r"<[^>]+>", "", cm.group(1)).strip()

    # 3. Parse Manifest (id -> href, media-type)
    manifest: Dict[str, Dict[str, str]] = {}
    if opf_tree is not None:
        for item in opf_tree.findall(".//{*}item"):
            iid = item.attrib.get("id")
            href = item.attrib.get("href")
            media_type = item.attrib.get("media-type", "").lower()
            if iid and href:
                manifest[iid] = {"href": href, "media_type": media_type}
    else:
        opf_str = opf_content.decode("utf-8", errors="ignore")
        for m in re.finditer(r'<item\s+[^>]*id=["\']([^"\']+)["\'][^>]*href=["\']([^"\']+)["\']', opf_str, re.I):
            manifest[m.group(1)] = {"href": m.group(2), "media_type": ""}

    # 4. Spine items in reading order
    spine_ids: List[str] = []
    if opf_tree is not None:
        for itemref in opf_tree.findall(".//{*}itemref"):
            idref = itemref.attrib.get("idref")
            if idref:
                spine_ids.append(idref)
    else:
        opf_str = opf_content.decode("utf-8", errors="ignore")
        for m in re.finditer(r'<itemref\s+[^>]*idref=["\']([^"\']+)["\']', opf_str, re.I):
            spine_ids.append(m.group(1))

    # Fallback if spine is empty: find all html/xhtml files in manifest
    candidate_paths: List[str] = []
    if spine_ids:
        for idref in spine_ids:
            item = manifest.get(idref)
            if item:
                candidate_paths.append(item["href"])
    else:
        for item in manifest.values():
            href = item["href"]
            if href.lower().endswith((".xhtml", ".html", ".htm")):
                candidate_paths.append(href)

    namelist_map = {name.lower(): name for name in z.namelist()}
    chapters: List[Dict[str, str]] = []
    chapter_num = 1

    for href in candidate_paths:
        unquoted = urllib.parse.unquote(href)
        rel_path = posixpath.normpath(posixpath.join(opf_dir, unquoted)) if opf_dir else unquoted
        rel_path = rel_path.replace("\\", "/").lstrip("/")

        actual_path = None
        if rel_path in z.namelist():
            actual_path = rel_path
        elif rel_path.lower() in namelist_map:
            actual_path = namelist_map[rel_path.lower()]

        if not actual_path:
            continue

        try:
            raw_bytes = z.read(actual_path)
            try:
                html_str = raw_bytes.decode("utf-8")
            except UnicodeDecodeError:
                html_str = raw_bytes.decode("latin-1", errors="replace")
        except Exception:
            continue

        parser = HTMLTextExtractor()
        parser.feed(html_str)
        text = parser.get_text()

        # Skip chapters with little or no readable text
        if count_words(text) < 1:
            continue

        ch_title = parser.heading or parser.title or f"Chapter {chapter_num}"
        # If ch_title is identical to book title or very long, format nicely
        if len(ch_title) > 120:
            ch_title = f"Chapter {chapter_num}"

        chapters.append({"title": ch_title, "content": text})
        chapter_num += 1

    if not chapters:
        chapters = [{"title": title if title != "Untitled" else "Chapter 1", "content": ""}]

    return title, author, chapters


def split_long_text(text: str, target_words: int = 3000) -> List[str]:
    """
    Splits text into chunks of approximately target_words on paragraph boundaries.
    """
    paragraphs = [p.strip() for p in re.split(r"\n{2,}", text) if p.strip()]
    if not paragraphs:
        return [text.strip()] if text.strip() else []

    chunks: List[str] = []
    current_paras: List[str] = []
    current_count = 0

    for p in paragraphs:
        w_count = count_words(p)
        # If single paragraph is massive (> target_words * 1.5), split by words
        if w_count > target_words * 1.5:
            if current_paras:
                chunks.append("\n\n".join(current_paras))
                current_paras = []
                current_count = 0
            words = p.split()
            for i in range(0, len(words), target_words):
                chunk = " ".join(words[i : i + target_words])
                if chunk.strip():
                    chunks.append(chunk)
            continue

        if current_count + w_count > target_words and current_count > 0:
            chunks.append("\n\n".join(current_paras))
            current_paras = [p]
            current_count = w_count
        else:
            current_paras.append(p)
            current_count += w_count

    if current_paras:
        chunks.append("\n\n".join(current_paras))

    return chunks


def parse_text(content: str, title: str = "Untitled", author: str = "") -> Tuple[str, str, List[Dict[str, str]]]:
    """
    Parses plain text or Markdown into readable chapters.
    Splits by explicit chapter markers (e.g. 'Chapter X', '# Chapter') or chunks of ~3000 words.
    """
    content = content.replace("\r\n", "\n").replace("\r", "\n").strip()
    if not content:
        return title, author, [{"title": title if title != "Untitled" else "Chapter 1", "content": ""}]

    lines = content.split("\n")
    first_line = lines[0].strip()

    # Extract title from first line or # Heading / <h1...> if default or generic README
    if title == "Untitled" or title.lower().startswith("readme"):
        if first_line.startswith("# "):
            title = first_line.lstrip("# ").strip()
            if len(lines) > 1:
                content = "\n".join(lines[1:]).strip()
        elif first_line.lower().startswith("title:"):
            title = first_line.split(":", 1)[1].strip()
            if len(lines) > 1:
                content = "\n".join(lines[1:]).strip()
        else:
            h1_match = re.search(r"<h1[^>]*>(.*?)</h1>", content[:1500], re.IGNORECASE)
            if h1_match:
                detected = re.sub(r"<[^>]+>", "", h1_match.group(1)).strip()
                if detected:
                    title = detected

    # Extract author from next line if missing
    if not author:
        lines = content.split("\n")
        if lines and lines[0].lower().startswith(("author:", "by:")):
            author = lines[0].split(":", 1)[1].strip()
            if len(lines) > 1:
                content = "\n".join(lines[1:]).strip()

    heading_pattern = re.compile(
        r"^[ \t]*(?:"
        r"#{1,3}[ \t]+(.+)|"
        r"((?:Chapter|CHAPTER|Глава|ГЛАВА|Part|PART|Section|SECTION|Act|ACT|Scene|SCENE)[ \t]+[0-9IVXLCDMivxlcdm\w\.\-]+(?:[ \t]*[:\-–—\.][ \t]*.*|[ \t]+[^\n\r]+)?)"
        r")[ \t]*$",
        re.MULTILINE,
    )

    matches = list(heading_pattern.finditer(content))
    chapters: List[Dict[str, str]] = []

    if len(matches) >= 1:
        # Pre-chapter intro text
        intro = content[: matches[0].start()].strip()
        if intro and count_words(intro) > 10:
            chapters.append({"title": "Introduction", "content": intro})

        for i, m in enumerate(matches):
            h_text = (m.group(1) or m.group(2)).strip()
            start = m.start()
            end = matches[i + 1].start() if i + 1 < len(matches) else len(content)
            body = content[start:end].strip()
            if body:
                chapters.append({"title": h_text, "content": body})

    if not chapters:
        # No headings detected: split by ~3000 words chunks
        chunks = split_long_text(content, target_words=3000)
        if len(chunks) == 1:
            chapters = [{"title": title if title != "Untitled" else "Chapter 1", "content": chunks[0]}]
        else:
            for idx, chunk in enumerate(chunks, start=1):
                chapters.append({"title": f"Chapter {idx}", "content": chunk})

    return title, author, chapters