"""Split extracted book text into TTS-sized chunks."""

import re
from typing import List

from . import config


def split_into_chunks(text: str, max_words: int = config.CHUNK_SIZE_WORDS) -> List[str]:
    """Split text into chunks of at most ``max_words`` words.

    Splits on sentence boundaries. Sentences longer than the limit are split
    further at clause punctuation (which is kept attached for TTS prosody).
    A single sentence with no clause punctuation longer than the limit is
    kept intact as one oversized chunk.
    """
    if not text.strip():
        return []

    sentences = re.split(r"(?<=[.!?])\s+", text)
    chunks = []
    current_chunk = ""
    current_words = 0

    for sentence in sentences:
        sentence_words = len(sentence.split())

        if sentence_words > max_words:
            if current_chunk:
                chunks.append(current_chunk.strip())
                current_chunk = ""
                current_words = 0

            # Split long sentences at clause boundaries, keeping punctuation.
            parts = re.split(r"(?<=[,;:])\s*", sentence)
            for part in parts:
                part_words = len(part.split())
                if current_words + part_words <= max_words:
                    current_chunk += part + " "
                    current_words += part_words
                else:
                    if current_chunk:
                        chunks.append(current_chunk.strip())
                    current_chunk = part + " "
                    current_words = part_words
        else:
            if current_words + sentence_words <= max_words:
                current_chunk += sentence + " "
                current_words += sentence_words
            else:
                if current_chunk:
                    chunks.append(current_chunk.strip())
                current_chunk = sentence + " "
                current_words = sentence_words

    if current_chunk.strip():
        chunks.append(current_chunk.strip())

    return [chunk for chunk in chunks if chunk.strip()]