import { config } from "../config.js";
import type { components } from "../generated/server-api.js";

export type ProductCredential = {
  authorization: string;
  projectId: string;
  expiresAt?: string | null;
};

export type AgentAuthContext = components["schemas"]["AgentAuthContextResponse"];

export class ProductServerClient {
  constructor(private readonly baseUrl = config.TJWATER_SERVER_BASE_URL) {}

  async authenticateUser(authorization: string): Promise<{ user_id: string }> {
    let response: Response;
    try {
      response = await fetch(new URL("/api/v1/access-context", this.baseUrl), {
        headers: { Accept: "application/json", Authorization: authorization },
      });
    } catch { throw new ProductServerClientError(503, "TJWater Server unavailable"); }
    const parsed = parseJson(await response.text());
    if (!response.ok) throw new ProductServerClientError(response.status, "TJWater Server rejected identity verification");
    if (!parsed || typeof parsed !== "object" || !("user_id" in parsed) || typeof parsed.user_id !== "string" || !parsed.user_id.trim()) {
      throw new ProductServerClientError(502, "TJWater Server returned invalid identity");
    }
    return { user_id: parsed.user_id };
  }

  async authenticate(credential: ProductCredential): Promise<AgentAuthContext> {
    const url = new URL("/api/v1/agent-auth-context", this.baseUrl);
    let response: Response;
    try {
      response = await fetch(url, {
        headers: {
          Accept: "application/json",
          Authorization: credential.authorization,
          "X-Project-Id": credential.projectId,
        },
      });
    } catch {
      throw new ProductServerClientError(503, "TJWater Server unavailable");
    }

    const text = await response.text();
    const parsed = parseJson(text);
    if (!response.ok) {
      throw new ProductServerClientError(
        response.status,
        readErrorMessage(parsed, "TJWater Server rejected identity verification"),
      );
    }
    if (!parsed || typeof parsed !== "object") {
      throw new ProductServerClientError(502, "TJWater Server returned invalid JSON");
    }
    return parsed as AgentAuthContext;
  }
}

export class ProductServerClientError extends Error {
  constructor(readonly status: number, message: string) {
    super(message);
  }
}

const parseJson = (text: string): unknown => {
  if (!text.trim()) return null;
  try {
    return JSON.parse(text);
  } catch {
    return null;
  }
};

const readErrorMessage = (value: unknown, fallback: string) => {
  if (!value || typeof value !== "object") return fallback;
  const record = value as Record<string, unknown>;
  if (typeof record.detail === "string") return record.detail;
  if (typeof record.message === "string") return record.message;
  return fallback;
};