import type { OptimizerDataCache } from "./cache";

export function createRequestHandler(cache: OptimizerDataCache) {
  return (request: Request): Response => {
    if (request.method !== "GET") {
      return jsonResponse({ error: "Method not allowed" }, 405, {
        Allow: "GET",
      });
    }

    const path = new URL(request.url).pathname.replace(/\/+$/, "") || "/";
    if (path === "/health") {
      const payload = cache.getPayload();
      return jsonResponse(
        payload
          ? {
              status: payload.status,
              fetchedAt: payload.fetchedAt,
              nextRefreshAt: payload.nextRefreshAt,
              optimizerCount: payload.optimizerCount,
              failedOptimizerCount: payload.failedOptimizerCount,
              ...(payload.lastError ? { lastError: payload.lastError } : {}),
            }
          : {
              status: cache.getLastError() ? "error" : "starting",
              ...(cache.getLastError()
                ? { lastError: cache.getLastError() }
                : {}),
            },
        payload ? 200 : 503,
      );
    }

    if (path === "/" || path === "/api/optimizers") {
      const payload = cache.getPayload();
      return payload
        ? jsonResponse(payload)
        : jsonResponse(
            {
              status: cache.getLastError() ? "error" : "starting",
              message: "No optimizer data is available yet",
              ...(cache.getLastError()
                ? { lastError: cache.getLastError() }
                : {}),
            },
            503,
          );
    }

    return jsonResponse({ error: "Not found" }, 404);
  };
}

function jsonResponse(
  value: unknown,
  status = 200,
  additionalHeaders: Record<string, string> = {},
): Response {
  return Response.json(value, {
    status,
    headers: {
      "Cache-Control": "no-store",
      ...additionalHeaders,
    },
  });
}