/**
 * Day 5 — controlled beta access gate.
 *
 * This is a SOFT, frontend-only gate so the builder can share DocDoe with a
 * small, selected group of SSLC beta students. It is intentionally NOT strong
 * security: it is a shared access code checked entirely in the browser, with
 * no backend, no account system, and no payment. Do not describe this as
 * "secure authentication" anywhere in the UI or docs.
 *
 * Privacy: only a beta code, an optional nickname, class, board and language
 * preference are stored — all on this device. No email, phone, full name,
 * exact school, location, or parent contact is ever asked for or stored.
 */

export type BetaAccessState = {
  hasAccess: boolean;
  accessCodeLabel?: string;
  grantedAt?: string;
  studentNickname?: string;
  classLevel?: string;
  board?: string;
  languagePreference?: string;
};

export type BetaAccessProfile = {
  studentNickname?: string;
  classLevel?: string;
  board?: string;
  languagePreference?: string;
};

export type BetaAccessGrantResult =
  | { ok: true; state: BetaAccessState }
  | { ok: false; error: "invalid_code" | "storage_unavailable" };

export const BETA_ACCESS_STORAGE_KEY = "docdoe:beta-access";

/**
 * Small local allowlist for this beta. Easy to update: add/remove strings.
 * Codes are matched case-insensitively after trimming.
 */
export const BETA_ACCESS_CODES = ["DOCDOE-BETA", "SSLC-PHYSICS", "ASSESS-CLASS10"];

export const BETA_ACCESS_DEFAULTS = {
  classLevel: "Class 10",
  board: "Kerala SSLC",
  languagePreference: "English",
};

function hasStorage(): boolean {
  return typeof window !== "undefined" && typeof window.localStorage !== "undefined";
}

function normalizeCode(code: string): string {
  return code.trim().toUpperCase();
}

/** True if the code matches an active beta allowlist entry (case-insensitive). */
export function validateBetaAccessCode(code: string): boolean {
  const normalized = normalizeCode(code ?? "");
  if (!normalized) return false;
  return BETA_ACCESS_CODES.some((allowed) => normalizeCode(allowed) === normalized);
}

function isAccessStateLike(value: unknown): value is BetaAccessState {
  return Boolean(value) && typeof value === "object" && typeof (value as Record<string, unknown>).hasAccess === "boolean";
}

/** Load access state. Corrupt/absent storage yields "no access", never throws. */
export function loadBetaAccess(): BetaAccessState {
  if (!hasStorage()) return { hasAccess: false };
  try {
    const raw = window.localStorage.getItem(BETA_ACCESS_STORAGE_KEY);
    if (!raw) return { hasAccess: false };
    const parsed = JSON.parse(raw);
    if (!isAccessStateLike(parsed)) return { hasAccess: false };
    return parsed;
  } catch {
    return { hasAccess: false };
  }
}

export function saveBetaAccess(state: BetaAccessState): void {
  if (!hasStorage()) return;
  try {
    window.localStorage.setItem(BETA_ACCESS_STORAGE_KEY, JSON.stringify(state));
  } catch {
    // Best-effort only; the gate simply re-prompts on the next load.
  }
}

export function clearBetaAccess(): void {
  if (!hasStorage()) return;
  try {
    window.localStorage.removeItem(BETA_ACCESS_STORAGE_KEY);
  } catch {
    // ignore
  }
}

export function hasBetaAccess(): boolean {
  return loadBetaAccess().hasAccess;
}

/**
 * Validate a code and, if active, grant + persist access with the given
 * (fully optional, non-identifying) profile fields. Returns a friendly error
 * on failure without explaining exactly why the code was rejected.
 */
export function grantBetaAccess(code: string, profile: BetaAccessProfile = {}): BetaAccessGrantResult {
  if (!validateBetaAccessCode(code)) {
    return { ok: false, error: "invalid_code" };
  }
  if (!hasStorage()) {
    return { ok: false, error: "storage_unavailable" };
  }

  const state: BetaAccessState = {
    hasAccess: true,
    accessCodeLabel: normalizeCode(code),
    grantedAt: new Date().toISOString(),
    studentNickname: profile.studentNickname?.trim() || undefined,
    classLevel: profile.classLevel?.trim() || BETA_ACCESS_DEFAULTS.classLevel,
    board: profile.board?.trim() || BETA_ACCESS_DEFAULTS.board,
    languagePreference: profile.languagePreference?.trim() || BETA_ACCESS_DEFAULTS.languagePreference,
  };
  saveBetaAccess(state);
  return { ok: true, state };
}