"""office_proxy - 把 /office/* 请求转发到本机 univer-office Node 服务(9091)。

univer-office 承担 markdown<->IDocumentData 转换与 docx/xlsx/ppt 导出，
这些能力是 Node 生态(Univer + docx/exceljs/pptxgenjs)，Python 侧无法直接实现，
故通过 ahserver 的 startswiths 机制做反向代理。

路由映射：
  /office/render        -> http://127.0.0.1:9091/render      (markdown -> IDocumentData)
  /office/extract       -> http://127.0.0.1:9091/extract     (IDocumentData -> 纯文本)
  /office/export/docx   -> http://127.0.0.1:9091/export/docx (markdown -> docx 二进制)
"""
import aiohttp
from aiohttp import web
from appPublic.registerfunction import registerFunction
from appPublic.log import error, debug

OFFICE_BACKEND = 'http://127.0.0.1:9091'

# hop-by-hop 头，转发时需剔除
_HOP_BY_HOP = {
    'host', 'content-length', 'transfer-encoding', 'connection',
    'keep-alive', 'upgrade', 'proxy-authenticate', 'proxy-authorization',
    'te', 'trailers',
}


async def office_proxy(request, params_kw, *args, **env):
    """把 /office/* 转发到 9091。args = leading 之后的路径段，如 ('render',) 或 ('export','docx')。"""
    path = '/'.join(args)
    url = f'{OFFICE_BACKEND}/{path}'
    debug(f'office_proxy: {request.method} {url}')

    body = await request.read()
    headers = {k: v for k, v in request.headers.items() if k.lower() not in _HOP_BY_HOP}

    try:
        timeout = aiohttp.ClientTimeout(total=180)
        async with aiohttp.ClientSession(timeout=timeout) as session:
            async with session.request(request.method, url, headers=headers, data=body) as resp:
                resp_body = await resp.read()
                resp_headers = {
                    k: v for k, v in resp.headers.items()
                    if k.lower() not in _HOP_BY_HOP and k.lower() != 'content-encoding'
                }
                return web.Response(body=resp_body, status=resp.status, headers=resp_headers)
    except Exception as e:
        error(f'office_proxy failed: {e}')
        return web.Response(body=f'office backend error: {e}'.encode(), status=502)


registerFunction('office_proxy', office_proxy)