"""运行中改 goal 的纯函数与信号文件格式。

信号文件格式（与 host.py 内联读侧同款契约，改一处必须同步
另一处，跨模块测试钉住它）：
    <state_dir>/goal-updates/<safe_host_name>.json
    {"version": int, "goal": str, "task_id": str | None}
其中 safe_host_name 与 host.py 的 _interrupt_request_path 同款：
只留 [A-Za-z0-9_.-]，其余字符换成 "-"。

本模块不 import cloud.server / cloud.worker，只用标准库，
host.py 不直接 import 它（host.py 是可独立部署的脚本，只用
标准库），host.py 里有一份同格式的内联读侧。

语义：
- version 单调递增，服务端每次成功改 goal 就 +1；循环只应用
  version > 已应用版本的信号，过期版本直接丢弃。
- 信号文件只由 worker 侧写（镜像线程每 30 秒把库里更新的
  goal_version 写成信号；断点续跑认领时钩子先写一次），
  host 循环在轮次边界读、应用后由检查点落盘 + 清理。
- 信号本身不含签名：它只在 host-state 目录（worker 与 host
  循环共享的同一目录）里流转，调用方是受信的 worker 进程；
  不要把信号文件路径暴露成公开接口。
"""

import json
import os
import re
import uuid

GOAL_UPDATE_DIRNAME = "goal-updates"


def safe_host_name(host_name):
    """与 host.py _interrupt_request_path 同款的安全化。"""
    return re.sub(r"[^A-Za-z0-9_.-]", "-", str(host_name))


def signal_path(state_path, host_name):
    """信号文件绝对路径：state 文件同目录下的 goal-updates 子目录。"""
    return os.path.join(
        os.path.dirname(os.path.abspath(state_path)),
        GOAL_UPDATE_DIRNAME,
        safe_host_name(host_name) + ".json",
    )


def write_goal_update_signal(state_path, host_name, version, goal,
                             task_id=None):
    """原子写信号文件（写临时文件再 os.replace）。

    version 必须为正整数，goal 必须为非空字符串，否则
    ValueError；调用方（worker 镜像/认领钩子）负责吞异常，
    信号写失败绝不能炸掉任务执行本身。
    """
    if not isinstance(version, int) or isinstance(version, bool) \
            or version < 1:
        raise ValueError("goal update version must be a positive int")
    if not isinstance(goal, str) or not goal.strip():
        raise ValueError("goal update goal must be a non-empty string")
    path = signal_path(state_path, host_name)
    os.makedirs(os.path.dirname(path), exist_ok=True)
    tmp = "%s.tmp.%s" % (path, os.getpid())
    payload = {"version": version, "goal": goal, "task_id": task_id}
    with open(tmp, "w", encoding="utf-8") as fh:
        json.dump(payload, fh, ensure_ascii=False)
    os.replace(tmp, path)
    return path


def read_goal_update_signal(state_path, host_name, applied_version):
    """读信号，返回 (version, goal) 或 None。

    以下情况一律返回 None，绝不抛：文件不存在、JSON 坏、
    version 不是正整数、goal 不是非空字符串、version <=
    已应用版本（过期信号）。调用方按 None 处理即可。
    """
    try:
        applied = int(applied_version or 0)
    except (TypeError, ValueError):
        applied = 0
    try:
        with open(signal_path(state_path, host_name),
                  encoding="utf-8") as fh:
            data = json.load(fh)
    except Exception:
        return None
    if not isinstance(data, dict):
        return None
    version = data.get("version")
    goal = data.get("goal")
    if not isinstance(version, int) or isinstance(version, bool) \
            or version < 1:
        return None
    if not isinstance(goal, str) or not goal.strip():
        return None
    if version <= applied:
        return None
    return (version, goal)


def consume_goal_update_signal(state_path, host_name, applied_version):
    """已应用版本的信号文件尽力删掉（删失败静默）。

    只删 version <= 已应用版本的信号；更新的信号（写于应用
    之后、尚未应用）绝不能被误删。返回是否删掉了文件。
    """
    try:
        applied = int(applied_version or 0)
    except (TypeError, ValueError):
        applied = 0
    path = signal_path(state_path, host_name)
    try:
        with open(path, encoding="utf-8") as fh:
            data = json.load(fh)
    except Exception:
        return False
    if not isinstance(data, dict):
        return False
    version = data.get("version")
    if not isinstance(version, int) or isinstance(version, bool):
        return False
    if version > applied:
        return False
    try:
        os.remove(path)
    except Exception:
        return False
    return True


def build_goal_update_notice(old_goal, new_goal):
    """轮次边界应用新 goal 时，喂给 agent 的显式通知块。"""
    return (
        "目标已更新（运行中改 goal）：\n"
        "旧目标：%s\n"
        "新目标：%s\n"
        "请继续完成新目标，不要重复已完成的部分；完成与否只按"
        "新目标判断；此前如已输出过“目标已达成”，该宣告对新"
        "目标作废——新目标满足时请重新宣告，否则继续工作。"
        % (old_goal, new_goal)
    )


def ensure_goal_history_table(conn):
    """幂等建 task_goal_history 表（改 goal 的审计历史）。

    id 为随机 hex；(task_id, version) 上的索引供按任务查
    历史时用。调用方负责 commit。
    """
    conn.execute(
        "CREATE TABLE IF NOT EXISTS task_goal_history("
        "id TEXT PRIMARY KEY, task_id TEXT NOT NULL, "
        "old_goal TEXT, new_goal TEXT NOT NULL, "
        "version INTEGER NOT NULL, created_by TEXT, "
        "created_at REAL NOT NULL)"
    )
    conn.execute(
        "CREATE INDEX IF NOT EXISTS idx_task_goal_history_task "
        "ON task_goal_history(task_id, version)"
    )


def apply_goal_update(conn, task_id, old_goal, old_version, new_goal,
                      user_id, now):
    """在同一连接里做一次改 goal 写库（不 commit，调用方提交）。

    CAS 在 version 上：只有 version 仍是 old_version（老行
    NULL 按 0 计）时才更新，否则返回 None（调用方回 409 请
    刷新后重试，绝不静默覆盖并发改动）。成功时同时写
    goal_history 一行，返回新 version。
    """
    old_v = int(old_version or 0)
    if old_v == 0:
        cur = conn.execute(
            "UPDATE tasks SET goal = ?, goal_version = ?, "
            "updated_at = ? WHERE id = ? AND "
            "(goal_version IS NULL OR goal_version = 0)",
            (new_goal, old_v + 1, now, task_id),
        )
    else:
        cur = conn.execute(
            "UPDATE tasks SET goal = ?, goal_version = ?, "
            "updated_at = ? WHERE id = ? AND goal_version = ?",
            (new_goal, old_v + 1, now, task_id, old_v),
        )
    if cur.rowcount != 1:
        return None
    conn.execute(
        "INSERT INTO task_goal_history(id, task_id, old_goal, "
        "new_goal, version, created_by, created_at) "
        "VALUES(?, ?, ?, ?, ?, ?, ?)",
        (uuid.uuid4().hex, task_id, old_goal, new_goal,
         old_v + 1, user_id, now),
    )
    return old_v + 1