"use client";

import { useCallback, useEffect, useRef, useState } from "react";
import { usePathname, useRouter } from "next/navigation";
import { api, ApiClientError } from "./api";
import { useSession } from "./store";

export interface ApiState<T> {
  data: T | null;
  error: ApiClientError | null;
  loading: boolean;
  reload: () => Promise<void>;
  setData: React.Dispatch<React.SetStateAction<T | null>>;
}

/**
 * Client-side data hook. Handles the shared failure modes:
 * 401 → session expired → redirect to /login?next=…
 * 503 MAINTENANCE / network → surfaced as `error` for <ApiErrorState/>.
 */
export function useApi<T>(path: string | null): ApiState<T> {
  const [data, setData] = useState<T | null>(null);
  const [error, setError] = useState<ApiClientError | null>(null);
  const [loading, setLoading] = useState<boolean>(path !== null);
  const [tick, setTick] = useState(0);
  const router = useRouter();
  const pathname = usePathname();
  const hydrate = useSession((s) => s.hydrate);
  const seq = useRef(0);

  // When the path changes, flip back to loading during render (adjust-state-from-props).
  const [prevPath, setPrevPath] = useState(path);
  if (path !== prevPath) {
    setPrevPath(path);
    setLoading(path !== null);
  }

  useEffect(() => {
    if (!path) return;
    const my = ++seq.current;
    api<T>(path)
      .then((res) => {
        if (my !== seq.current) return;
        setData(res);
        setError(null);
        setLoading(false);
      })
      .catch((e: unknown) => {
        if (my !== seq.current) return;
        const err = e instanceof ApiClientError ? e : new ApiClientError(0, "UNKNOWN", "Something went wrong.");
        if (err.status === 401) {
          hydrate(null);
          router.replace(`/login?next=${encodeURIComponent(pathname)}&reason=expired`);
          return;
        }
        setError(err);
        setLoading(false);
      });
  }, [path, tick, router, pathname, hydrate]);

  const reload = useCallback(async () => {
    setLoading(true);
    setTick((t) => t + 1);
  }, []);

  return { data, error, loading, reload, setData };
}

/** Human copy for an API failure. */
export function describeError(e: unknown): { title: string; description: string; kind: "network" | "maintenance" | "server" | "other" } {
  if (e instanceof ApiClientError) {
    if (e.status === 0) return { kind: "network", title: "Connection lost", description: "Check your network and try again. Your credits and progress are safe." };
    if (e.status === 503 && e.code === "MAINTENANCE") return { kind: "maintenance", title: "Spinza is getting an upgrade.", description: "Your credits and progress are safe. Check back in a few minutes." };
    if (e.status >= 500) return { kind: "server", title: "Server unavailable", description: "Spinza is temporarily unreachable. Please try again shortly." };
    return { kind: "other", title: "Something went wrong", description: e.message };
  }
  return { kind: "other", title: "Something went wrong", description: "Please try again." };
}