"""Loopback-only, empty-data UI preview. Never used by the production runtime."""

from __future__ import annotations

import argparse
from dataclasses import replace
from typing import Mapping
from urllib.parse import urlsplit

from arr_web.app import PortalApplication, SessionLedger
from arr_web.contracts import PortalError, Response, failure
from arr_web.repository import UnavailablePortalRepository
from arr_web.server import serve


class EmptyPreviewRepository(UnavailablePortalRepository):
    def list_jobs(self, month_key, limit=50, offset=0):
        return [], 0

    def list_monthly_runs(self, month_key, limit=50, offset=0):
        return [], 0

    def list_history_month_counts(self):
        return []

    def list_months(self):
        return []


class ReadOnlyPreview:
    """Render the actual portal with unavailable services and no external state."""

    def __init__(self) -> None:
        self._sessions = SessionLedger()
        self._app = PortalApplication(
            repository=EmptyPreviewRepository(), sessions=self._sessions
        )

    def handle(
        self, method: str, target: str, headers: Mapping[str, str],
        body: bytes = b"", client_id: str = "direct",
    ) -> Response:
        if method != "GET":
            return Response.json(405, failure(PortalError(
                "PREVIEW_READ_ONLY", "本地预览仅供查看，不能提交业务操作。", 405
            )), headers={"Allow": "GET"})

        path = urlsplit(target).path
        if path == "/assets/preview.css":
            return Response(200, (
                ".local-preview-banner{margin:0 0 20px;padding:12px 16px;"
                "border:1px solid var(--line);border-radius:12px;"
                "background:var(--blue-soft);color:var(--ink);font-size:13px}"
            ).encode(), "text/css; charset=utf-8", {"Cache-Control": "no-store"})

        # Internal, transient identity belongs only to this empty preview instance.
        # No browser cookie, credentials, runtime configuration or real service is used.
        session_id, _ = self._sessions.issue("")
        request_headers = {k: v for k, v in headers.items() if k.lower() != "cookie"}
        request_headers["Cookie"] = f"arr_session={session_id}"
        try:
            response = self._app.handle(method, target, request_headers, body, client_id)
        finally:
            self._sessions.revoke(session_id)

        if path in {"/", "/index.html"} and response.status == 200:
            html = response.body.decode("utf-8").replace(
                "<title>ARR Report</title>", "<title>ARR Report · 本地只读预览</title>"
            ).replace(
                "</head>", '<link rel="stylesheet" href="/assets/preview.css" /></head>'
            ).replace(
                '<main class="shell page" id="main-content">',
                '<main class="shell page" id="main-content">'
                '<aside class="local-preview-banner" role="note">'
                '<strong>本地只读预览</strong> · 仅展示页面，未连接业务数据；'
                '上传和自动下载均未启用。</aside>',
            )
            response = replace(response, body=html.encode("utf-8"))
        return response


def main() -> None:
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("--port", type=int, default=8872)
    args = parser.parse_args()
    print(f"Read-only preview: http://127.0.0.1:{args.port}/", flush=True)
    serve(ReadOnlyPreview(), "127.0.0.1", args.port)


if __name__ == "__main__":
    main()