"""
会话档案存储
============
按「会话指纹」持久化每个客户会话的对话档案（客户消息 + 我方回复 + 上次画面快照），
写入 conversations.json，机器人重启后上下文不丢失。

有了档案之后，机器人的提取策略从「每次翻屏复制大段历史」变为：
  - 首次遇到某会话：翻屏提取一次可见历史，建档；
  - 之后每次：只提取最新一屏，与档案中的上次画面快照做增量比对，
    只把【新增的消息】发给 AI，完整上下文由档案历史直接提供。
"""

import json
import os
import time
import threading

# 每个会话最多留存的消息条数（防止档案无限膨胀；AI 实际使用条数由 AI_CONTEXT_MAX_ROUNDS 决定）
MAX_MESSAGES_PER_SESSION = 200
# 画面快照最多留存的行数（用于增量比对）
MAX_SNAPSHOT_LINES = 80


class ConversationStore:
    def __init__(self, path: str):
        self.path  = path
        self._lock = threading.Lock()
        self._data = {}
        self._mtime = 0
        self._load()

    # ── 持久化 ────────────────────────────────────────────────────────────────
    def _load(self):
        try:
            if os.path.exists(self.path):
                with open(self.path, encoding="utf-8") as f:
                    self._data = json.load(f)
                try:
                    self._mtime = os.path.getmtime(self.path)
                except Exception:
                    self._mtime = 0
            else:
                self._data = {}
                self._mtime = 0
        except Exception:
            self._data = {}
            self._mtime = 0

    def _maybe_reload(self):
        """GUI 删除档案后，监听进程下次读写前自动同步磁盘。"""
        try:
            mt = os.path.getmtime(self.path) if os.path.exists(self.path) else 0
        except Exception:
            return
        if mt != self._mtime:
            self._load()

    def save(self):
        """原子写入磁盘（先写临时文件再替换，避免中途崩溃损坏档案）。"""
        with self._lock:
            tmp = self.path + ".tmp"
            try:
                with open(tmp, "w", encoding="utf-8") as f:
                    json.dump(self._data, f, ensure_ascii=False, indent=1)
                os.replace(tmp, self.path)
                try:
                    self._mtime = os.path.getmtime(self.path)
                except Exception:
                    pass
            except Exception:
                pass

    # ── 档案访问 ──────────────────────────────────────────────────────────────
    def _entry(self, fp_hex: str) -> dict:
        self._maybe_reload()
        return self._data.setdefault(fp_hex, {
            "history":    [],   # [{"role": "user"/"assistant", "content": str, "ts": float}]
            "last_lines": [],   # 上次提取时聊天框的画面快照（按行），用于增量比对
            "updated":    0,
        })

    def has_record(self, fp_hex: str) -> bool:
        self._maybe_reload()
        e = self._data.get(fp_hex)
        return bool(e and (e.get("history") or e.get("last_lines")))

    def history(self, fp_hex: str) -> list:
        """返回该会话的消息历史（列表为活引用，请勿直接修改，用 append）。"""
        return self._entry(fp_hex)["history"]

    def append(self, fp_hex: str, role: str, content: str):
        e = self._entry(fp_hex)
        e["history"].append({"role": role, "content": content, "ts": time.time()})
        if len(e["history"]) > MAX_MESSAGES_PER_SESSION:
            e["history"] = e["history"][-MAX_MESSAGES_PER_SESSION:]
        e["updated"] = time.time()

    def last_lines(self, fp_hex: str) -> list:
        return self._entry(fp_hex)["last_lines"]

    def set_last_lines(self, fp_hex: str, lines: list):
        e = self._entry(fp_hex)
        e["last_lines"] = list(lines)[-MAX_SNAPSHOT_LINES:]
        e["updated"]    = time.time()

    def list_sessions(self, limit: int = 200) -> list:
        """按最近更新排序，返回会话摘要列表。"""
        self._maybe_reload()
        items = []
        for sid, entry in (self._data or {}).items():
            if not isinstance(entry, dict):
                continue
            hist = entry.get("history") or []
            preview = ""
            for m in reversed(hist):
                c = (m.get("content") or "").strip()
                if c:
                    preview = c.replace("\n", " ")[:80]
                    break
            if not preview:
                lines = entry.get("last_lines") or []
                preview = " ".join(lines[-3:])[:80] if lines else ""
            items.append({
                "session_id": sid,
                "updated": entry.get("updated") or 0,
                "message_count": len(hist),
                "preview": preview,
            })
        items.sort(key=lambda x: x.get("updated") or 0, reverse=True)
        return items[: max(1, min(limit, 500))]

    def delete(self, fp_hex: str) -> bool:
        """删除指定会话档案。"""
        self._maybe_reload()
        with self._lock:
            if fp_hex not in self._data:
                return False
            del self._data[fp_hex]
        self.save()
        return True

    def clear_all(self) -> int:
        """清空全部会话档案，返回删除条数。"""
        self._maybe_reload()
        with self._lock:
            n = len(self._data)
            self._data = {}
        self.save()
        return n

    def count(self) -> int:
        self._maybe_reload()
        return len(self._data or {})