"""运行时只读配置接口。

向前端暴露由后端 ``.env`` / 启动器决定的非敏感配置项，
让前端可以根据后端策略切换实现（如 PDF 预览引擎），
而不必把每个环境变量都硬编码进打包产物。
"""

from __future__ import annotations

from flask import current_app

from dms.api.v1.blueprint import api_v1
from dms.common.response import success_response


@api_v1.get("/config/runtime")
def get_runtime_config():
    pdf_viewer_engine = current_app.config.get(
        "DMS_PDF_VIEWER_ENGINE", "iframe"
    )
    if pdf_viewer_engine not in {"iframe", "pdfjs"}:
        pdf_viewer_engine = "iframe"
    response, status = success_response(
        {"pdfViewerEngine": pdf_viewer_engine}
    )
    # 该接口仅暴露非敏感开关，允许浏览器缓存以减少首屏请求。
    response.headers["Cache-Control"] = "public, max-age=60"
    return response, status