import type { Acc, User } from "./types";

const API_BASE_URL = process.env.API_BASE_URL ?? "http://api-server:3000";

// Tab-switch responses come from the Next.js data cache for this many
// seconds before re-fetching. Mutations call revalidateTag() to evict
// the cached entry and force the next read to hit MySQL.
const CACHE_REVALIDATE_SECONDS = 30;

export const ACCOUNTS_TAG = "accounts";
export const USERS_TAG = "users";

// Page size used for both initial server-side fetch and infinite scroll
// on the client. 200 keeps each cached payload under ~50KB and renders
// in well under one frame even on phones.
export const PAGE_SIZE = 200;

export type Page<T> = { rows: T[]; hasMore: boolean; total: number };

export type AccountsPageOpts = {
  offset?: number;
  prefix?: string;
  sort?: "username" | "status";
  dir?: "asc" | "desc";
  q?: string;
};

export type UsersPageOpts = {
  offset?: number;
  prefix?: string;
  sort?: "f_username" | "t_username" | "last_update_time";
  dir?: "asc" | "desc";
  q?: string;
};

type FetchInit = {
  method?: "GET" | "POST";
  body?: unknown;
  cache?: RequestCache;
  next?: { revalidate?: number; tags?: string[] };
};

export async function fetchApi(path: string, options: FetchInit = {}): Promise<unknown> {
  const url = `${API_BASE_URL}${path}`;
  const init: RequestInit & { next?: FetchInit["next"] } = {
    method: options.method ?? "GET",
    headers: options.body ? { "content-type": "application/json" } : undefined,
    body: options.body ? JSON.stringify(options.body) : undefined,
  };
  if (options.next) {
    init.next = options.next;
  } else {
    init.cache = options.cache ?? "no-store";
  }
  const res = await fetch(url, init);
  if (!res.ok) {
    throw new Error(`API ${options.method ?? "GET"} ${path} failed: ${res.status}`);
  }
  return res.json();
}

function buildAccountsUrl(opts: AccountsPageOpts): string {
  const { offset = 0, prefix = "", sort = "username", dir = "desc", q = "" } = opts;
  const params = new URLSearchParams({
    limit: String(PAGE_SIZE),
    offset: String(offset),
    sort,
    dir,
  });
  if (prefix) params.set("prefix", prefix);
  if (q) params.set("q", q);
  return `/acc/?${params.toString()}`;
}

function buildUsersUrl(opts: UsersPageOpts): string {
  const { offset = 0, prefix = "", sort = "last_update_time", dir = "desc", q = "" } = opts;
  const params = new URLSearchParams({
    limit: String(PAGE_SIZE),
    offset: String(offset),
    sort,
    dir,
  });
  if (prefix) params.set("prefix", prefix);
  if (q) params.set("q", q);
  return `/user/?${params.toString()}`;
}

export async function getAccountsPage(opts: AccountsPageOpts = {}): Promise<Page<Acc>> {
  const data = (await fetchApi(buildAccountsUrl(opts), {
    next: { revalidate: CACHE_REVALIDATE_SECONDS, tags: [ACCOUNTS_TAG] },
  })) as { rows: Acc[]; total: number };
  return {
    rows: data.rows,
    hasMore: data.rows.length === PAGE_SIZE,
    total: data.total,
  };
}

export async function getUsersPage(opts: UsersPageOpts = {}): Promise<Page<User>> {
  const data = (await fetchApi(buildUsersUrl(opts), {
    next: { revalidate: CACHE_REVALIDATE_SECONDS, tags: [USERS_TAG] },
  })) as { rows: User[]; total: number };
  return {
    rows: data.rows,
    hasMore: data.rows.length === PAGE_SIZE,
    total: data.total,
  };
}