"""存档读写。

存档是纯 JSON，方便人工检查，也方便外部工具/AI 直接读取分析。
写入采用"临时文件 + 原子替换"，避免中途崩溃导致存档损坏。
"""

from __future__ import annotations

import json
import os
import time
from typing import Any, Dict, Optional, Tuple

from .models import GameState

SAVE_VERSION = 1


def default_save_path() -> str:
    """默认存档位置：项目根目录下的 saves/save.json。"""
    root = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
    return os.path.join(root, "saves", "save.json")


def save_state(state: GameState, path: Optional[str] = None) -> str:
    """把状态写入磁盘，返回实际写入路径。"""
    path = path or default_save_path()
    directory = os.path.dirname(os.path.abspath(path))
    os.makedirs(directory, exist_ok=True)

    payload = {
        "version": SAVE_VERSION,
        "saved_at": time.strftime("%Y-%m-%d %H:%M:%S"),
        "state": state.to_dict(),
    }
    # 注意：to_dict() 里的派生字段在读取时会被忽略，这里只取原始字段
    payload["state"] = _raw_state(state)

    tmp_path = path + ".tmp"
    with open(tmp_path, "w", encoding="utf-8") as handle:
        json.dump(payload, handle, ensure_ascii=False, indent=2)
        handle.flush()
        os.fsync(handle.fileno())
    os.replace(tmp_path, path)
    return path


def _raw_state(state: GameState) -> Dict[str, Any]:
    """导出可完整还原的原始字段（与 to_dict 的展示字段不同）。"""
    return {
        "day": state.day,
        "gold": state.gold,
        "level": state.level,
        "exp": state.exp,
        "ap": state.ap,
        "feed": state.feed,
        "plots": [
            {
                "index": p.index,
                "crop": p.crop,
                "growth": p.growth,
                "moisture": p.moisture,
                "planted_day": p.planted_day,
            }
            for p in state.plots
        ],
        "animals": [
            {
                "id": a.aid,
                "kind": a.kind,
                "fed": a.fed,
                "progress": a.progress,
                "starve": a.starve,
                "pending": a.pending,
            }
            for a in state.animals
        ],
        "market": state.market,
        "stats": {
            "harvested": state.total_harvested,
            "collected": state.total_collected,
            "earned": state.total_earned,
            "spent": state.total_spent,
        },
    }


def load_state(path: Optional[str] = None) -> Tuple[Optional[GameState], str]:
    """读取存档。

    返回 ``(state, message)``；失败时 ``state`` 为 None 并给出原因，
    调用方应当降级为"开新档"而不是崩溃。
    """
    path = path or default_save_path()
    if not os.path.exists(path):
        return None, f"未找到存档 {path}"

    try:
        with open(path, "r", encoding="utf-8") as handle:
            payload = json.load(handle)
    except (OSError, json.JSONDecodeError) as exc:
        return None, f"存档无法解析：{exc}"

    if not isinstance(payload, dict):
        return None, "存档格式错误：根节点不是对象"

    version = payload.get("version", 0)
    if version != SAVE_VERSION:
        return None, f"存档版本不兼容（文件 v{version}，当前 v{SAVE_VERSION}）"

    raw = payload.get("state")
    if not isinstance(raw, dict):
        return None, "存档缺少 state 字段"

    try:
        state = GameState.from_dict(raw)
    except (TypeError, ValueError, KeyError) as exc:
        return None, f"存档内容异常：{exc}"

    return state, f"已载入存档（第 {state.day} 天）"


def delete_save(path: Optional[str] = None) -> bool:
    path = path or default_save_path()
    try:
        os.remove(path)
        return True
    except OSError:
        return False