"""知识域状态机与"从事项生成草稿"的纯函数（M3）。

为什么单独放一个模块：这两件事都是纯逻辑，不该缠在 HTTP 层或 ORM 里。
状态机能被 5 行测试覆盖；草稿拼装能被快照测试比对。放进 API 模块就只能靠 e2e 兜。

两个刻意的设计：

1. **草稿默认落 `draft`，不自动发布**（用户拍板）。自动生成的东西一定会有"看着像那么回事、
   其实漏了关键前提"的情况，人扫一眼的成本远低于让团队按错的结论办事。
2. **草稿正文如实转述来源**，不写"建议""应该"这类推断。LLM 阶段（M4）接进来时，
   `generated_by` 会从 `rule` 变成 `llm`，但"只转述、不改写结论"这条不变。
"""

from __future__ import annotations

from datetime import datetime
from typing import Any

from ..errors import AppError, ErrorCode

KNOWLEDGE_TRANSITIONS: dict[str, tuple[str, ...]] = {
    "draft": ("in_review", "published", "archived"),
    "in_review": ("draft", "published", "archived"),
    "published": ("archived",),
    "archived": ("draft",),
}

KNOWLEDGE_ACTIONS: dict[str, tuple[tuple[str, ...], str]] = {
    # action: (允许的前置状态, 目标状态)
    "submit_review": (("draft",), "in_review"),
    "withdraw": (("in_review",), "draft"),
    "publish": (("draft", "in_review"), "published"),
    "archive": (("draft", "in_review", "published"), "archived"),
    "restore": (("archived",), "draft"),
}

# 生成草稿时给读者的一句提示，防止有人把草稿当已确认的结论转发
DRAFT_BANNER = "> 这份草稿由系统根据来源自动整理，**请先核对再发布**；发布后才会进入团队检索。"

ACTION_LABEL: dict[str, str] = {
    "created": "创建",
    "status_changed": "状态变更",
    "promoted_to_ticket": "升级成工单",
    "ticket_created": "工单创建",
    "ticket_accept": "受理",
    "ticket_start": "开始办理",
    "ticket_submit": "提交验收",
    "ticket_approve": "验收通过",
    "ticket_reject": "验收驳回",
    "ticket_reassign": "改派",
    "ticket_cancel": "取消",
    "comment_added": "评论",
    "knowledge_created": "沉淀为知识",
}

# 状态流转在时间线里要写成人话：「待办 → 进行中」，光写"状态变更"等于没写
STATUS_LABEL: dict[str, str] = {
    "inbox": "收件箱",
    "todo": "待办",
    "doing": "进行中",
    "blocked": "被阻塞",
    "done": "已完成",
    "canceled": "已取消",
    "open": "待接收",
    "accepted": "已接受",
    "in_progress": "办理中",
    "pending_verify": "待验收",
}


def _describe(row: dict[str, Any]) -> str:
    """一条活动怎么念给读者听。"""
    action = str(row.get("action") or "")
    label = ACTION_LABEL[action]
    payload = row.get("payload") or {}
    if action == "status_changed" and isinstance(payload, dict):
        src, dst = payload.get("from"), payload.get("to")
        if src and dst:
            from_label = STATUS_LABEL.get(str(src), str(src))
            to_label = STATUS_LABEL.get(str(dst), str(dst))
            return f"{from_label} → {to_label}"
    if action == "knowledge_created" and isinstance(payload, dict) and payload.get("doc_type"):
        return f"{label}（{payload.get('doc_type')}）"
    return label


def target_status(action: str, current: str) -> str:
    """动作 → 目标状态。非法组合抛 7003，并把"现在还能做什么"带回去。"""
    rule = KNOWLEDGE_ACTIONS.get(action)
    if rule is None:
        raise AppError(
            ErrorCode.KNOWLEDGE_STATUS_INVALID,
            message=f"未知动作 {action}",
            details={"action": action, "allowed_actions": sorted(KNOWLEDGE_ACTIONS)},
        )
    allowed_from, to_status = rule
    if current not in allowed_from:
        allowed_actions = [a for a, (src, _) in KNOWLEDGE_ACTIONS.items() if current in src]
        raise AppError(
            ErrorCode.KNOWLEDGE_STATUS_INVALID,
            message=f"当前状态（{current}）不能{_label(action)}",
            details={
                "action": action,
                "from": current,
                "allowed_from": list(allowed_from),
                "allowed_actions": allowed_actions,
            },
        )
    return to_status


def ensure_transition(current: str, target: str) -> None:
    """直接改状态（不经过动作）时的校验。"""
    if target not in KNOWLEDGE_TRANSITIONS.get(current, ()):
        raise AppError(
            ErrorCode.KNOWLEDGE_STATUS_INVALID,
            message=f"不能从 {current} 直接变成 {target}",
            details={
                "from": current,
                "to": target,
                "allowed": list(KNOWLEDGE_TRANSITIONS.get(current, ())),
            },
        )


def sidebar_fields(target_status: str, now: datetime) -> dict[str, Any]:
    """状态跃迁时要顺手维护的时间戳。"""
    if target_status == "published":
        return {"published_at": now, "archived_at": None}
    if target_status == "archived":
        return {"archived_at": now}
    return {}


def can_publish_role(role: str) -> bool:
    """发布是"团队背书"，guest/member 只能提交审议。"""
    return role in ("owner", "admin")


def _label(action: str) -> str:
    return {
        "submit_review": "提交审议",
        "withdraw": "撤回审议",
        "publish": "发布",
        "archive": "归档",
        "restore": "恢复",
    }.get(action, action)


def render_draft(
    *,
    source_kind: str,
    title: str,
    body_md: str = "",
    resolution_md: str = "",
    created_at: datetime | None = None,
    closed_at: datetime | None = None,
    people: dict[str, str] | None = None,
    timeline: list[dict[str, Any]] | None = None,
    comments: list[dict[str, Any]] | None = None,
) -> str:
    """把一件事（任务或工单）整理成知识草稿的正文。

    只做"结构化的转述"：来源里有什么就写什么，没有的段落直接省略，
    不补写"经验教训"这类需要人判断的话。
    """
    people = people or {}
    out: list[str] = [DRAFT_BANNER, ""]

    when = _fmt(closed_at or created_at)
    origin = "工单" if source_kind == "ticket" else "任务"
    out.append(f"自动沉淀自{origin}「{title}」{('，' + when + ' 结束') if when else ''}。")
    out.append("")

    if people:
        line = "、".join(f"{k}：{v}" for k, v in people.items() if v)
        if line:
            out.append(f"- {line}")
            out.append("")

    out.append("## 背景")
    out.append("")
    out.append(
        body_md.strip() if body_md.strip() else "（来源里没有正文，补充一句这件事要解决什么。）"
    )
    out.append("")

    rows = [r for r in (timeline or []) if r.get("action") in ACTION_LABEL]
    if rows:
        out.append("## 过程")
        out.append("")
        for r in rows:
            out.append(f"- {_fmt(r.get('at'))} {_describe(r)}")
        out.append("")

    if resolution_md.strip():
        out.append("## 结论")
        out.append("")
        out.append(resolution_md.strip())
        out.append("")

    said = [c for c in (comments or []) if (c.get("body") or "").strip()]
    if said:
        out.append("## 讨论")
        out.append("")
        for c in said:
            who = c.get("author") or "某人"
            out.append(f"- **{who}**：{c['body'].strip()}")
        out.append("")

    return "\n".join(out).rstrip() + "\n"


def _fmt(value: Any) -> str:
    if isinstance(value, datetime):
        return value.strftime("%Y-%m-%d %H:%M")
    return ""