"""Choose a PDF chunking strategy from parsed document signals."""

from __future__ import annotations

import re
from pathlib import Path

from rag_cut.models import Block, BlockType

FEATURE_TITLE_RE = re.compile(r"^\s*\d{1,2}[.．、]\s*[A-Za-z0-9\u4e00-\u9fff&/ -]{2,24}")
OPERATION_TERMS = (
    "点击",
    "點擊",
    "选择",
    "選擇",
    "输入",
    "輸入",
    "打开",
    "打開",
    "登入",
    "用戶可",
    "用户可",
    "按<",
    "點撃",
)
REPORT_TERMS = (
    "年度报告",
    "年报",
    "財務報表",
    "财务报表",
    "公司治理",
    "董事会",
    "董事會",
    "审计报告",
    "審計報告",
    "合并资产负债表",
    "合併資產負債表",
    "经营情况",
    "經營情況",
    "营业收入",
    "營業收入",
    "现金流量",
    "現金流量",
    "股东",
    "股東",
)
REPORT_NAME_TERMS = ("annual", "report", "年度", "年报", "年報", "研报", "研報")

PDF_STRATEGY_FEATURE_STEPS = "pdf_feature_step_screenshot"
PDF_STRATEGY_OUTLINE_REPORT = "pdf_outline_report"


def _text(block: Block) -> str:
    return (block.text or block.markdown or "").strip()


def _term_count(text: str, terms: tuple[str, ...]) -> int:
    return sum(text.count(term) for term in terms)


def choose_pdf_chunk_strategy(path: Path, blocks: list[Block]) -> str:
    """Classify PDFs as operation manuals or report-like documents."""
    text_blocks = [block for block in blocks if block.type != BlockType.IMAGE and _text(block)]
    image_count = sum(1 for block in blocks if block.type == BlockType.IMAGE)
    sample = "\n".join(_text(block) for block in text_blocks[:240])
    filename = path.name.lower()

    report_score = _term_count(sample, REPORT_TERMS)
    if any(term in filename for term in REPORT_NAME_TERMS):
        report_score += 3

    feature_title_count = sum(1 for block in text_blocks if FEATURE_TITLE_RE.match(_text(block)))
    operation_score = _term_count(sample, OPERATION_TERMS)
    screenshot_density = image_count / max(len(text_blocks), 1)

    if report_score >= 3 and operation_score < 18:
        return PDF_STRATEGY_OUTLINE_REPORT

    if feature_title_count >= 3 and operation_score >= 6 and image_count >= 3 and screenshot_density >= 0.12:
        return PDF_STRATEGY_FEATURE_STEPS

    return PDF_STRATEGY_OUTLINE_REPORT