"""任务状态: DESIGN.md §7.1 规约,落 `<task_dir>/state.json`。

Task 是 Session 的上层概念 —— Session 只管对话消息,Task 还管 mode/description/
status/tokens/cost/timestamps,这些是跨轮次共享、和文件系统状态对齐的元数据。

文件路径约定(workspace/ 下):
    tasks/<task_id>/state.json     ← 此模块负责
    tasks/<task_id>/messages.json  ← Session 落
"""
from __future__ import annotations

import json
from dataclasses import asdict, dataclass, fields
from datetime import datetime
from pathlib import Path
from typing import Optional


@dataclass
class TaskState:
    task_id: str
    mode: str = ""               # 自由形式: coding / ppt / proposal / general / 自定
    description: str = ""        # 一句话描述,便于列表识别
    status: str = "active"       # active / completed / abandoned
    model: str = ""              # caps.model_id
    model_profile: str = ""      # 档案名,如 deepseek_v4.flash
    reasoning_effort: str = ""
    cwd: str = ""                # 任务的工作基目录
    created_at: str = ""         # ISO 时间戳
    updated_at: str = ""
    tokens_prompt: int = 0
    tokens_completion: int = 0
    cost_usd: float = 0.0        # 暂不算,留位

    @property
    def tokens_total(self) -> int:
        return self.tokens_prompt + self.tokens_completion

    def save(self, task_dir: Path) -> None:
        task_dir.mkdir(parents=True, exist_ok=True)
        self.updated_at = datetime.now().isoformat(timespec="seconds")
        (task_dir / "state.json").write_text(
            json.dumps(asdict(self), ensure_ascii=False, indent=2),
            encoding="utf-8",
        )

    @classmethod
    def load(cls, task_dir: Path) -> Optional["TaskState"]:
        p = task_dir / "state.json"
        if not p.exists():
            return None
        try:
            data = json.loads(p.read_text(encoding="utf-8"))
        except Exception:
            return None
        if not isinstance(data, dict):
            return None
        # 容忍 schema 演化:只取已知字段,缺失字段用 dataclass 默认
        known = {f.name for f in fields(cls)}
        kwargs = {k: v for k, v in data.items() if k in known}
        if "task_id" not in kwargs:
            kwargs["task_id"] = task_dir.name
        return cls(**kwargs)