import {
  buildCodexHeaders,
  isJsonObject,
  isOpenAICodexModel,
  mergeFeatureHeader,
  resolveCodexResponsesUrl,
  type Model,
} from "./native-compaction.js";

export function isNativeCompactionModel(model: unknown): model is Model<any> {
  return isOpenAICodexModel(model) || (
    isJsonObject(model) && model.provider === "sub-api" && model.api === "openai-responses"
  );
}

export function buildNativeCompactionTransport(params: {
  model: Pick<Model<any>, "provider" | "api" | "baseUrl">;
  apiKey?: string;
  headers?: Record<string, string>;
  sessionId: string;
}): { url: string; headers: Headers } {
  if (isOpenAICodexModel(params.model)) {
    if (!params.apiKey) throw new Error("Codex native compaction authentication requires an API key.");
    return {
      url: resolveCodexResponsesUrl(params.model.baseUrl),
      headers: buildCodexHeaders({ ...params, apiKey: params.apiKey }),
    };
  }
  if (!isNativeCompactionModel(params.model)) {
    throw new Error("Native compaction is not supported for this provider and API.");
  }
  if (!params.model.baseUrl?.trim()) {
    throw new Error("SubAPI native compaction requires an explicit baseUrl.");
  }
  let url: URL;
  try {
    url = new URL(params.model.baseUrl.trim());
  } catch {
    throw new Error("SubAPI native compaction requires a valid HTTP(S) baseUrl.");
  }
  if (!["https:", "http:"].includes(url.protocol) || url.username || url.password || url.hash) {
    throw new Error("SubAPI native compaction requires an HTTP(S) baseUrl without credentials or a fragment.");
  }
  const path = url.pathname.replace(/\/+$/, "");
  url.pathname = path.endsWith("/responses") ? path : `${path}/responses`;

  // Sub2API accepts native compaction v2 through its public Responses endpoint.
  // The gateway owns upstream Codex credentials; honor the client's resolved authentication.
  const headers = new Headers(params.headers);
  if (!headers.get("authorization")?.trim()) {
    if (params.apiKey?.trim()) {
      headers.set("authorization", `Bearer ${params.apiKey}`);
    } else if (!headers.get("cf-aig-authorization")?.trim()) {
      throw new Error("SubAPI native compaction authentication requires an API key or a non-empty Authorization or cf-aig-authorization header.");
    }
  }
  headers.set("content-type", "application/json");
  headers.set("accept", "text/event-stream");
  headers.set("OpenAI-Beta", "responses=experimental");
  headers.set("originator", "pi");
  headers.set("user-agent", "pi-compaction");
  headers.set("session-id", params.sessionId);
  headers.set("x-client-request-id", params.sessionId);
  headers.set("x-codex-beta-features", mergeFeatureHeader(headers.get("x-codex-beta-features")));
  return { url: url.toString(), headers };
}