"""
services/declaration_service.py
为每个目录（章节）生成一个"声明"。

声明：一段说明该章节应写什么、结构与约束的撰写指引，存入
report_template_sections.section_prompt。

优先用 LLM（结合章节标题 + 该章节正文）生成；未配置或失败时
回退到确定性模板，保证流程稳定可用。
"""

from __future__ import annotations

import logging
import re
from concurrent.futures import ThreadPoolExecutor, as_completed

from config import settings
from services.llm_client import chat_completions_json, llm_configured

logger = logging.getLogger(__name__)

_SYSTEM_PROMPT = (
    "你是报告模板专家。任务：阅读给定章节的范文（参考正文），总结这一章应该怎么写，"
    "作为后续报告撰写该章节的写作指引。需提炼：①内容要点（写哪些事项）；"
    "②组织结构（应有的小节/条目顺序）；③数据与口径要求（需引用的对比/指标/表格等）；"
    "④写作约束（先事实后评价、缺失写「待补充」、不得编造）。"
    "严格要求：不要输出任何思考过程或解释；只输出 JSON 对象 {\"guide\": \"...\"}；"
    "guide 为 300 字以内的写作指引纯文本（不含 markdown 标题）；"
    "范文缺失或过短时，按章节标题给出通用写作指引。"
)


def _strip_number_prefix(title: str) -> str:
    t = str(title or "").strip()
    t = re.sub(r"^(?:\d+(?:\.\d+)*|[一二三四五六七八九十]+[、.．])\s*", "", t).strip()
    return t


def _fallback_declaration(section_title: str) -> str:
    label = _strip_number_prefix(section_title) or "本章节"
    return (
        f"本章节为「{label}」。撰写时应紧扣标题主题，先陈述事实与数据，再给出分析与评价；"
        f"结构需与标题保持一致，条理清晰、用语规范；"
        f"所有结论须有依据，缺失信息写「待补充」，禁止编造。"
    )


def _build_user_prompt(section_title: str, content: str) -> str:
    body = (content or "").strip()
    if len(body) > 2500:
        body = body[:2500]
    body_block = f"\n\n该章节范文（参考正文，节选）：\n```\n{body}\n```" if body else ""
    return (
        f"章节标题：{section_title}{body_block}\n\n"
        f"请根据上述范文，总结该章节应该怎么写，并只返回 JSON：{{\"guide\": \"300字以内的写作指引\"}}。"
    )


def generate_declaration(section_title: str, content: str = "") -> str:
    """根据范文为单个章节生成"怎么写"的写作指引（JSON 取 guide，自动剔除思考过程）。"""
    use_llm = bool(getattr(settings, "DECLARATION_USE_LLM", True)) and llm_configured()
    if not use_llm:
        return _fallback_declaration(section_title)
    try:
        data = chat_completions_json(
            system_prompt=_SYSTEM_PROMPT,
            user_prompt=_build_user_prompt(section_title, content),
            temperature=0.2,
            max_tokens=2048,
        )
        guide = str((data or {}).get("guide") or "").strip()
        if guide:
            return guide
    except Exception as e:  # noqa: BLE001 - 兜底，保证主流程不被 LLM 影响
        logger.warning("生成章节声明失败，使用兜底模板 | title=%s | err=%s", section_title, e)
    return _fallback_declaration(section_title)


def _content_for_section(s: dict, content_by_key: dict[str, str]) -> str:
    """目录键可能是 canonical 形式，优先用标题中的编号前缀去匹配正文。"""
    title = str(s.get("sectionTitle") or "")
    m = re.match(r"^(\d+(?:\.\d+)*)", title.strip())
    num = m.group(1) if m else ""
    return content_by_key.get(num, "") or content_by_key.get(str(s.get("sectionKey") or ""), "")


def generate_declarations(sections: list[dict], content_by_key: dict[str, str] | None = None) -> list[str]:
    """
    为目录中每个章节并发生成"怎么写"的写作指引（基于范文）。
    sections: [{sectionKey, sectionTitle}, ...]
    content_by_key: 章节编号/键 -> 范文正文，用于为指引提供上下文（可选）。

    每章一次 LLM 调用，多线程并发以打满 GPU（LLM 为网络 I/O，线程下真正并行）。
    """
    content_by_key = content_by_key or {}
    tasks = [(str(s.get("sectionTitle") or ""), _content_for_section(s, content_by_key)) for s in sections]
    if not tasks:
        return []

    use_llm = bool(getattr(settings, "DECLARATION_USE_LLM", True)) and llm_configured()
    if not use_llm:
        return [_fallback_declaration(title) for title, _ in tasks]

    max_workers = max(int(getattr(settings, "TEMPLATE_UPLOAD_LLM_MAX_WORKERS", 8) or 8), 1)
    results: list[str] = [""] * len(tasks)

    if len(tasks) == 1:
        results[0] = generate_declaration(*tasks[0])
        return results

    workers = min(max_workers, len(tasks))
    with ThreadPoolExecutor(max_workers=workers) as executor:
        future_to_idx = {
            executor.submit(generate_declaration, title, content): i
            for i, (title, content) in enumerate(tasks)
        }
        for fut in as_completed(future_to_idx):
            idx = future_to_idx[fut]
            try:
                results[idx] = fut.result()
            except Exception as e:  # noqa: BLE001
                logger.warning("章节声明并发生成失败，使用兜底 | idx=%s | err=%s", idx, e)
                results[idx] = _fallback_declaration(tasks[idx][0])
    logger.info("章节声明生成 | 章节=%s | 线程=%s", len(tasks), workers)
    return results