import type {
  AuthResponse, BlogPost, BlogPostDetail, ChartData, CostResult, Destination, FAQ,
  ProfileStats, SearchResult, Stats, SyncedUserPlan, Testimonial, Tool, Visa,
} from "./types";

const API_BASE = process.env.NEXT_PUBLIC_API_URL || "http://localhost:8000/api/v1";

// Fallback data when API is unavailable (build time / offline)
const FALLBACK_STATS: Stats = { countries: 195, avg_cost: 42, satisfaction: 87, total_nomads: "35.6M", active_today: 127 };
const FALLBACK_TICKER = { messages: ["🌴 小林 刚刚抵达清迈", "💻 Marco 在里斯本完成了 Sprint", "✈️ 今日新增 127 位游民出发"] };

async function fetchAPI<T>(path: string, options?: RequestInit): Promise<T> {
  const isMutation = options?.method && options.method !== "GET";
  try {
    const res = await fetch(`${API_BASE}${path}`, {
      ...options,
      headers: { "Content-Type": "application/json", ...options?.headers },
      ...(isMutation ? { cache: "no-store" } : { next: { revalidate: 60 } }),
    });
    if (!res.ok) throw new Error(`API error: ${res.status}`);
    return res.json();
  } catch (err) {
    if (isMutation) throw err;
    throw err;
  }
}

async function fetchWithFallback<T>(path: string, fallback: T): Promise<T> {
  try {
    return await fetchAPI<T>(path);
  } catch {
    return fallback;
  }
}

export const api = {
  getStats: () => fetchWithFallback("/stats", FALLBACK_STATS),
  getTicker: () => fetchWithFallback("/ticker", FALLBACK_TICKER),
  getDestinations: (params?: { region?: string; search?: string; sort?: string }) => {
    const q = new URLSearchParams();
    if (params?.region) q.set("region", params.region);
    if (params?.search) q.set("search", params.search);
    if (params?.sort) q.set("sort", params.sort);
    const qs = q.toString();
    return fetchAPI<Destination[]>(`/destinations${qs ? `?${qs}` : ""}`);
  },
  getDestination: (slug: string) => fetchAPI<Destination>(`/destinations/${slug}`),
  compareDestinations: (slugs: string[]) =>
    fetchAPI<Destination[]>("/destinations/compare", {
      method: "POST",
      body: JSON.stringify({ slugs }),
    }),
  getVisas: () => fetchWithFallback<Visa[]>("/visas", []),
  getFaqs: () => fetchWithFallback<FAQ[]>("/faqs", []),
  getTestimonials: () => fetchWithFallback<Testimonial[]>("/testimonials", []),
  getTools: () => fetchWithFallback<Tool[]>("/tools", []),
  getBlog: () => fetchWithFallback<BlogPost[]>("/blog", []),
  getBlogPost: (slug: string) => fetchAPI<BlogPostDetail>(`/blog/${slug}`),
  subscribe: (email: string) =>
    fetchAPI<{ success: boolean; message: string }>("/subscribe", {
      method: "POST",
      body: JSON.stringify({ email }),
    }),
  calculateCost: (data: { destination_slug: string; housing: string; months: number }) =>
    fetchAPI<CostResult>("/calculator", { method: "POST", body: JSON.stringify(data) }),
  getChartCost: () => fetchWithFallback<ChartData>("/charts/cost", { labels: [], datasets: [{ data: [] }] }),
  getChartSpeed: () => fetchWithFallback<ChartData>("/charts/speed", { labels: [], datasets: [{ data: [] }] }),
  getChartGrowth: () => fetchWithFallback<ChartData>("/charts/growth", { labels: [], datasets: [{ data: [] }] }),
  getChartRadar: () => fetchWithFallback<ChartData>("/charts/radar", { labels: [], datasets: [] }),
  // Auth
  login: (email: string, password: string) =>
    fetchAPI<AuthResponse>("/auth/login", { method: "POST", body: JSON.stringify({ email, password }) }),
  register: (email: string, password: string, name: string) =>
    fetchAPI<AuthResponse>("/auth/register", { method: "POST", body: JSON.stringify({ email, password, name }) }),
  demoLogin: () => fetchAPI<AuthResponse>("/auth/demo"),
  getFavorites: (token: string) =>
    fetchAPI<{ slugs: string[] }>("/auth/favorites", { headers: { Authorization: `Bearer ${token}` } }),
  toggleFavorite: (slug: string, token: string) =>
    fetchAPI<{ slugs: string[] }>("/auth/favorites", {
      method: "POST",
      headers: { Authorization: `Bearer ${token}` },
      body: JSON.stringify({ destination_slug: slug }),
    }),
  getFavoriteDestinations: (token: string) =>
    fetchAPI<Destination[]>("/auth/favorites/detail", {
      headers: { Authorization: `Bearer ${token}` },
    }),
  getProfileStats: (token: string) =>
    fetchAPI<ProfileStats>("/auth/profile/stats", {
      headers: { Authorization: `Bearer ${token}` },
    }),
  getPlan: (token: string) =>
    fetchAPI<SyncedUserPlan>("/auth/plan", {
      headers: { Authorization: `Bearer ${token}` },
    }),
  savePlan: (token: string, plan: SyncedUserPlan) =>
    fetchAPI<SyncedUserPlan>("/auth/plan", {
      method: "PUT",
      headers: { Authorization: `Bearer ${token}` },
      body: JSON.stringify(plan),
    }),
  search: (q: string) => fetchAPI<SearchResult[]>(`/search?q=${encodeURIComponent(q)}`),
};