"""
从 Lite NL 会话消息构造 Text2SQL 可用的上文摘要，并判断上一轮是否为数据查询（用于续问意图分类）。
"""

from __future__ import annotations

import json
import logging
from typing import Any, Dict, List, Tuple

logger = logging.getLogger(__name__)

_MAX_ASSISTANT_SQL_CHARS = 1400
_MAX_ASSISTANT_TEXT_CHARS = 900
_MAX_BLOCK_CHARS = 7500


def _truncate(s: str, max_len: int) -> str:
    s = (s or "").strip()
    if len(s) <= max_len:
        return s
    return s[: max_len - 1].rstrip() + "…"


def summarize_assistant_nl_payload(content: str) -> str:
    """将落库的 assistant JSON 转为一小段可读摘要。"""
    raw = (content or "").strip()
    if not raw:
        return ""
    try:
        data: Dict[str, Any] = json.loads(raw)
    except json.JSONDecodeError:
        return _truncate(raw, _MAX_ASSISTANT_TEXT_CHARS)

    br = data.get("branch_result") or {}
    if isinstance(br.get("answer"), str) and br["answer"].strip():
        return "[助手] " + _truncate(br["answer"].strip(), _MAX_ASSISTANT_TEXT_CHARS)

    sql = (br.get("sql") or "").strip() if isinstance(br.get("sql"), str) else ""
    if sql:
        parts = ["[上轮 SQL] " + _truncate(sql, _MAX_ASSISTANT_SQL_CHARS)]
        if br.get("follow_up_required"):
            parts.append("[状态] 上轮为库探针0行，需补充条件后重问")
        for key in ("db_empty_feedback", "sql_explain"):
            v = br.get(key)
            if isinstance(v, str) and v.strip():
                parts.append("[说明] " + _truncate(v.strip(), 500))
                break
        return "\n".join(parts)

    intent = (data.get("intent") or {}).get("intent")
    return _truncate(f"[助手] intent={intent}", _MAX_ASSISTANT_TEXT_CHARS)


def last_assistant_was_data_query(items: List[Dict[str, Any]]) -> bool:
    """最后一条 assistant 消息是否为数据查询分支（含 SQL 或 DATA_QUERY intent）。"""
    for m in reversed(items or []):
        if m.get("role") != "assistant":
            continue
        raw = (m.get("content") or "").strip()
        if not raw:
            return False
        try:
            data = json.loads(raw)
        except json.JSONDecodeError:
            return False
        intent = (data.get("intent") or {}).get("intent")
        if intent == "DATA_QUERY":
            return True
        br = data.get("branch_result") or {}
        sql = (br.get("sql") or "").strip() if isinstance(br.get("sql"), str) else ""
        return bool(sql)
    return False


def messages_to_text2sql_context(
    items: List[Dict[str, Any]],
    *,
    max_chars: int = _MAX_BLOCK_CHARS,
    max_pairs: int = 8,
) -> Tuple[str, int]:
    """
    将会话消息列表转为供模型阅读的「上文」文本（不含本轮用户输入）。

    Returns:
        (context_text, num_user_turns_included)
    """
    if not items:
        return "", 0

    pairs: List[Tuple[str, str]] = []
    i = 0
    n = len(items)
    while i < n:
        u = items[i]
        if u.get("role") != "user":
            i += 1
            continue
        user_text = (u.get("content") or "").strip()
        asst_text = ""
        if i + 1 < n and items[i + 1].get("role") == "assistant":
            asst_text = summarize_assistant_nl_payload(str(items[i + 1].get("content") or ""))
            i += 2
        else:
            i += 1
        if user_text or asst_text:
            pairs.append((user_text, asst_text))

    if not pairs:
        return "", 0

    pairs = pairs[-max_pairs:]
    lines: List[str] = []
    total = 0
    user_count = 0
    for idx, (uq, aq) in enumerate(pairs, start=1):
        chunk_parts = [f"--- 第{idx}轮 ---"]
        if uq:
            chunk_parts.append(f"用户：{uq}")
        if aq:
            chunk_parts.append(f"{aq}")
        chunk = "\n".join(chunk_parts)
        if total + len(chunk) + 2 > max_chars:
            break
        lines.append(chunk)
        total += len(chunk) + 2
        if uq:
            user_count += 1

    return "\n\n".join(lines).strip(), user_count