/**
 * Odoo REST client with transparent access-token rotation.
 *
 * Tokens live in ``localStorage`` under three keys:
 *   - ``encoach_token``         — short-lived access JWT (1h)
 *   - ``encoach_refresh_token`` — long-lived refresh JWT  (7d)
 *   - ``encoach_token_exp``     — epoch seconds for the access token
 *
 * When a request receives ``401`` *and* a refresh token is present, the client
 * silently rotates the pair via ``POST /api/auth/refresh`` and retries the
 * original request exactly once. Multiple concurrent 401s coalesce onto the
 * same refresh promise so we never fire more than one rotation in flight.
 *
 * Motivation: before this change, every expired access token forced a full
 * re-login, which interrupted long admin dashboards (stats, reports) multiple
 * times per hour. With the refresh loop, access tokens can be short-lived
 * (1h) without hurting UX, giving us the security benefit of short access
 * windows without an eager logout.
 */

export const API_BASE_URL = (import.meta.env.VITE_API_BASE_URL?.trim() || "/api").replace(/\/$/, "");
const BASE_URL = API_BASE_URL;

export function extractApiErrorMessage(data: unknown, status: number, statusText: string): string {
  if (data && typeof data === "object" && data !== null && "error" in data) {
    const msg = (data as { error: unknown }).error;
    if (msg != null && String(msg).trim()) return String(msg);
  }
  return `${status} ${statusText}`;
}

export class ApiError extends Error {
  constructor(
    public status: number,
    public statusText: string,
    public data: unknown,
  ) {
    super(extractApiErrorMessage(data, status, statusText));
    this.name = "ApiError";
  }
}

const ACCESS_KEY = "encoach_token";
const REFRESH_KEY = "encoach_refresh_token";
const EXP_KEY = "encoach_token_exp";

function getAccessToken(): string | null {
  return localStorage.getItem(ACCESS_KEY);
}

function getRefreshToken(): string | null {
  return localStorage.getItem(REFRESH_KEY);
}

export function setToken(token: string): void {
  localStorage.setItem(ACCESS_KEY, token);
}

export function setRefreshToken(token: string | null | undefined): void {
  if (token) {
    localStorage.setItem(REFRESH_KEY, token);
  } else {
    localStorage.removeItem(REFRESH_KEY);
  }
}

export function setTokenExpiry(epochSeconds: number | null | undefined): void {
  if (epochSeconds && Number.isFinite(epochSeconds)) {
    localStorage.setItem(EXP_KEY, String(Math.floor(epochSeconds)));
  } else {
    localStorage.removeItem(EXP_KEY);
  }
}

/** Persist the full token bundle returned by /api/login or /api/auth/refresh. */
export function persistTokenBundle(bundle: {
  access_token?: string;
  token?: string;
  refresh_token?: string;
  expires_in?: number;
}): void {
  const access = bundle.access_token || bundle.token;
  if (access) setToken(access);
  setRefreshToken(bundle.refresh_token || null);
  if (bundle.expires_in) {
    setTokenExpiry(Math.floor(Date.now() / 1000) + bundle.expires_in);
  }
}

export function clearToken(): void {
  localStorage.removeItem(ACCESS_KEY);
  localStorage.removeItem(REFRESH_KEY);
  localStorage.removeItem(EXP_KEY);
}

// Shared refresh promise — any 401 that arrives while a refresh is in flight
// waits on the existing request instead of firing a duplicate.
let refreshPromise: Promise<boolean> | null = null;

async function performRefresh(): Promise<boolean> {
  const refreshToken = getRefreshToken();
  if (!refreshToken) return false;
  try {
    const res = await fetch(`${BASE_URL}/auth/refresh`, {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({ refresh_token: refreshToken }),
    });
    if (!res.ok) return false;
    const data: {
      access_token?: string;
      token?: string;
      refresh_token?: string;
      expires_in?: number;
    } = await res.json().catch(() => ({} as never));
    if (!data.access_token && !data.token) return false;
    persistTokenBundle(data);
    return true;
  } catch {
    return false;
  }
}

function refreshOnce(): Promise<boolean> {
  if (!refreshPromise) {
    refreshPromise = performRefresh().finally(() => {
      refreshPromise = null;
    });
  }
  return refreshPromise;
}

function buildHeaders(extra?: Record<string, string>, withJson = true): Record<string, string> {
  const headers: Record<string, string> = { ...extra };
  if (withJson) headers["Content-Type"] = headers["Content-Type"] || "application/json";

  const token = getAccessToken();
  if (token) headers["Authorization"] = `Bearer ${token}`;
  return headers;
}

/**
 * Query param values we know how to serialise into a URL. Arrays are joined
 * with commas because that's what our Odoo controllers expect for multi-value
 * filters (e.g. `?state=draft,confirmed`).
 */
export type QueryParamValue =
  | string
  | number
  | boolean
  | null
  | undefined
  | Array<string | number | boolean>;

/**
 * Accept any object-shaped bag of query params. We intentionally use `object`
 * here rather than `Record<string, QueryParamValue>` because typed interfaces
 * (e.g. `PaginationParams`) don't satisfy a `Record<...>` index signature by
 * default, which would force every call-site to cast.
 */
export type QueryParams = object;

function buildUrl(path: string, params?: QueryParams): string {
  const url = new URL(`${BASE_URL}${path}`, window.location.origin);
  if (params) {
    for (const [key, rawValue] of Object.entries(params as Record<string, unknown>)) {
      if (rawValue === undefined || rawValue === null) continue;
      if (Array.isArray(rawValue)) {
        if (rawValue.length === 0) continue;
        url.searchParams.set(key, rawValue.map(v => String(v)).join(","));
        continue;
      }
      url.searchParams.set(key, String(rawValue));
    }
  }
  return url.toString();
}

async function parseResponse<T>(response: Response): Promise<T> {
  const data = await response.json().catch(() => null);
  if (!response.ok) throw new ApiError(response.status, response.statusText, data);
  return data as T;
}

type RequestInitWithSkip = RequestInit & { _skipRetry?: boolean };

async function performRequest<T>(url: string, init: RequestInitWithSkip): Promise<T> {
  const response = await fetch(url, init);

  // Auth/refresh endpoints opt out of the retry loop — otherwise a bad
  // refresh token would recurse forever.
  const isAuthEndpoint = url.includes("/auth/refresh") || url.includes("/login");

  if (response.status === 401 && !init._skipRetry && !isAuthEndpoint) {
    const hadRefresh = !!getRefreshToken();
    if (hadRefresh) {
      const rotated = await refreshOnce();
      if (rotated) {
        // Rebuild headers so the new access token is attached.
        const newInit: RequestInitWithSkip = {
          ...init,
          _skipRetry: true,
          headers: {
            ...(init.headers as Record<string, string>),
            Authorization: `Bearer ${getAccessToken()}`,
          },
        };
        return performRequest<T>(url, newInit);
      }
    }
    const hadAccess = !!getAccessToken();
    clearToken();
    if (hadAccess || hadRefresh) {
      window.location.href = "/login";
    }
    throw new ApiError(401, response.statusText, await response.json().catch(() => null));
  }

  return parseResponse<T>(response);
}

export const api = {
  async get<T>(path: string, params?: QueryParams): Promise<T> {
    return performRequest<T>(buildUrl(path, params), {
      method: "GET",
      headers: buildHeaders(),
    });
  },

  async post<T>(path: string, body?: unknown): Promise<T> {
    return performRequest<T>(buildUrl(path), {
      method: "POST",
      headers: buildHeaders(),
      body: body ? JSON.stringify(body) : undefined,
    });
  },

  async patch<T>(path: string, body?: unknown): Promise<T> {
    return performRequest<T>(buildUrl(path), {
      method: "PATCH",
      headers: buildHeaders(),
      body: body ? JSON.stringify(body) : undefined,
    });
  },

  async put<T>(path: string, body?: unknown): Promise<T> {
    return performRequest<T>(buildUrl(path), {
      method: "PUT",
      headers: buildHeaders(),
      body: body ? JSON.stringify(body) : undefined,
    });
  },

  async delete<T>(path: string): Promise<T> {
    return performRequest<T>(buildUrl(path), {
      method: "DELETE",
      headers: buildHeaders(),
    });
  },

  async upload<T>(path: string, formData: FormData): Promise<T> {
    return performRequest<T>(buildUrl(path), {
      method: "POST",
      headers: buildHeaders(undefined, false),
      body: formData,
    });
  },
};