"""在大屏 JSON 副本上按路径更新组件属性，用于后端校验动作能否执行"""

from copy import deepcopy

from app.actions.base import BaseActionHandler
from app.schemas.actions import UpdateAction
from app.schemas.screen import Screen


class UpdateHandler(BaseActionHandler[UpdateAction]):
    def apply(self, screen: Screen, action: UpdateAction) -> Screen:
        # 确认目标存在，后续路径访问和赋值均在大屏副本中进行
        result, target = self.copy_target(screen, action.target_id)

        # 未设置的 style 视为空对象，只允许直接添加末级字段
        if action.section == "style" and target.style is None:
            target.style = {}

        # 获取动作指定的属性区域，作为路径遍历的起点
        current = getattr(target, action.section)
        # 逐段访问路径，只有到达末级时才写入新值
        for index, segment in enumerate(action.path):
            # 标记当前是否为末级，用于区分继续访问和最终赋值
            last = index == len(action.path) - 1
            # 保存走到当前段的路径，异常时指出具体失败位置
            location = f"{action.section} {action.path[: index + 1]!r}"
            # 如果当前容器是字典，路径段必须是字符串键
            if isinstance(current, dict):
                if not isinstance(segment, str):
                    raise ValueError(f"对象路径必须使用字符串键: {location}")
                # 中间层必须已存在，只允许在末级新增键，避免凭空构造嵌套结构
                if not last and segment not in current:
                    raise ValueError(f"中间路径不存在: {location}")
            elif isinstance(current, list):
                # 数组只接受整数下标，使用精确类型判断排除 bool
                if type(segment) is not int:
                    raise ValueError(f"数组路径必须使用整数下标: {location}")
                # 只允许访问已有元素，不接受负下标，也不通过赋值扩展数组
                if not 0 <= segment < len(current):
                    raise ValueError(f"数组下标越界: {location}")
            else:
                # 标量或 None 不能继续按路径访问，停止执行并返回明确错误
                raise ValueError(f"路径无法继续访问，当前值不是对象或数组: {location}")

            if last:
                # 新值也复制，避免后续修改结果时影响 Action
                current[segment] = deepcopy(action.value)
            else:
                # 尚未到达末级，进入已校验存在的下一层容器
                current = current[segment]

        # 返回属性更新后的大屏副本，原始大屏和动作值均未被修改
        return result


if __name__ == "__main__":
    screen = Screen.model_validate(
        {
            "canvas": {"width": 1920, "height": 1080},
            "nodes": [
                {
                    "id": "sales-chart",
                    "type": "chart",
                    "layout": {"x": 100, "y": 200, "width": 400, "height": 300},
                    "props": {"option": {"title": {"text": "销售额", "show": True}}},
                }
            ],
        }
    )
    action = UpdateAction(
        target_id="sales-chart",
        section="props",
        path=["option", "title", "text"],
        value="月度销售额",
    )
    handler = UpdateHandler()
    final_screen = handler.apply(screen, action)
    print(final_screen.model_dump_json(indent=2))
    print("原始标题:", screen.nodes[0].props["option"]["title"]["text"])

    try:
        handler.apply(
            screen,
            UpdateAction(
                target_id="sales-chart",
                section="props",
                path=["missing", "text"],
                value="新标题",
            ),
        )
    except ValueError as error:
        print("无效路径:", error)