"""Text block extraction from analyzed layout."""

from __future__ import annotations

import re

from rag_cut.models import Block, BlockType
from rag_cut.parsers.pdf.layout import LayoutRegion, PageLayout

_UI_LABEL_RE = re.compile(r"^[\d\s\W]{0,6}[\u4e00-\u9fff]{1,6}$")
# "10.上升三角形態" / "1.2 ACCOUNT STATUS" (space after number optional)
_NUMBERED_HEADING_RE = re.compile(
    r"^\s*(\d+(?:\.\d+)*)(?:\.|．)?\s*([A-Za-z0-9\u4e00-\u9fff][A-Za-z0-9\u4e00-\u9fff&/ \-_:：]{2,})\s*$"
)

# Title+body merges must not become headings; real section titles stay shorter.
MAX_HEADING_CHARS = 100


def _numbered_heading_level(text: str) -> int | None:
    match = _NUMBERED_HEADING_RE.match(text.strip())
    if not match or len(match.group(2).strip()) < 3:
        return None
    return match.group(1).count(".") + 1


def _looks_like_ui_label(text: str) -> bool:
    """True for short UI chips; exclude numbered / CJK section titles."""
    stripped = text.strip()
    if _numbered_heading_level(stripped) is not None:
        return False
    if re.match(r"^\d+(?:\.\d+)*(?:\.|．)", stripped):
        return False
    # Short Chinese section banners like 「形態指標」are not toolbar labels.
    if re.fullmatch(r"[\u4e00-\u9fff]{2,12}", stripped):
        return False
    return bool(_UI_LABEL_RE.match(stripped))


def _font_heading_level(size: float, body_size: float, text: str) -> int | None:
    stripped = text.strip()
    numbered = _numbered_heading_level(stripped)
    if numbered and len(stripped) <= MAX_HEADING_CHARS:
        return numbered
    if len(stripped) < 4 or len(stripped) > MAX_HEADING_CHARS:
        return None
    if _looks_like_ui_label(stripped):
        return None

    # Compact CJK section titles such as 「形態指標」.
    if (
        size >= body_size + 3
        and re.fullmatch(r"[\u4e00-\u9fff]{2,12}", stripped)
        and not _numbered_heading_level(stripped)
    ):
        return 1

    if size >= body_size + 6:
        return 1 if len(stripped) >= 10 else 2
    if size >= body_size + 3:
        return 2 if len(stripped) >= 8 else 3
    if size >= body_size + 1.5:
        return 3
    return None


def extract_text_blocks(layout: PageLayout, chapter_title: str | None = None) -> tuple[list[Block], str | None]:
    """Extract heading/paragraph blocks; update chapter title when headings appear."""
    blocks: list[Block] = []
    current_chapter = chapter_title

    for region in layout.regions:
        if region.kind != "text":
            continue

        text = region.data.get("text", "").strip()
        if not text:
            continue

        font_size = float(region.data.get("font_size", layout.body_font_size))
        level = _font_heading_level(font_size, layout.body_font_size, text)
        page_no = layout.page_index + 1
        meta = {
            "page": page_no,
            "bbox": [region.x0, region.y0, region.x1, region.y1],
            "font_size": font_size,
            "body_font_size": layout.body_font_size,
            "page_height": layout.page_height,
        }
        if current_chapter:
            meta["chapter"] = current_chapter

        if level:
            if level <= 2:
                current_chapter = text
            if current_chapter:
                meta["chapter"] = current_chapter
            blk = Block(type=BlockType.HEADING, text=text, level=level, meta=meta)
        else:
            blk = Block(type=BlockType.PARAGRAPH, text=text, meta=meta)

        blocks.append(blk)

    return blocks, current_chapter