// The ads-network abstraction (D28). VK is the only network now; a future network for another
// platform implements the same rewardedReady/showRewarded surface without touching the callers. On
// the contour a build flag (VITE_ADS_STUB) substitutes a toast stub for the real ad, so the reward
// flow is testable without waiting for a real ad — production never sets the flag, so a real ad that
// fails to load there must not credit (no stub fallback in prod).
import { executionContext } from './wallet';
import { vkRewardedReady, vkShowRewarded, vkShowInterstitial } from './vk';
import { showToast } from './app.svelte';
import type { AdsConfig } from './model';

/**
 * adsStubEnabled reports the contour test stub (VITE_ADS_STUB=1). Production never sets it, so it
 * always shows real ads. The mock e2e forces it on so the reward flow is exercisable without a VK
 * bridge. To capture the real VK ad result on the contour (the diagnostic), deploy with the flag
 * off first; flip it on afterwards for routine stub testing.
 */
export function adsStubEnabled(): boolean {
  if (import.meta.env.MODE === 'mock') return true;
  return (import.meta.env as Record<string, string | undefined>).VITE_ADS_STUB === '1';
}

/** RewardedResult is one rewarded-ad view: whether it was watched, and whether it was the test stub
 *  (so the caller can show the "ad fired" marker toast). */
export interface RewardedResult {
  watched: boolean;
  stub: boolean;
}

/**
 * rewardedReady reports whether a rewarded ad is ready to show, gating the "watch for chips" button.
 * The stub is always ready; a real ad is ready only inside VK with preloaded material. Rewarded is
 * VK-only (D28).
 */
export async function rewardedReady(): Promise<boolean> {
  if (adsStubEnabled()) return true;
  if (executionContext() !== 'vk') return false;
  return vkRewardedReady();
}

/**
 * showRewarded shows a rewarded ad and reports whether it was watched, the raw provider result, and
 * whether it was the stub. On the stub it resolves watched immediately (the caller shows the "ad
 * fired" toast).
 */
export async function showRewarded(): Promise<RewardedResult> {
  if (adsStubEnabled()) {
    return { watched: true, stub: true };
  }
  return { watched: await vkShowRewarded(), stub: false };
}

// The post-move interstitial gate is client-mirrored: the server sends the cooldowns + suppressed in
// the profile (Profile.ads); the client tracks the last-shown time in localStorage and self-gates.
// Last-shown is per-device (cleared with storage) — acceptable for a frequency gate.
//
// It is a SINGLE shared timestamp across kinds, not one per kind: the kind only selects the required
// gap (hint's short cooldown vs the move / vs_ai one), while the wait is always measured from the
// last interstitial of ANY kind. A per-kind timer let a hint ad and a move ad stack — after a
// hint-move ad the move timer was still zero, so the next plain move fired an ad immediately.
const INTERSTITIAL_LAST_KEY = 'ads.interstitial.last';

// interstitialLast reads the last-shown epoch millis of any interstitial (0 when absent/corrupt, or
// when a pre-shared-timer value — an object — is still stored: it decodes to 0 and self-heals).
function interstitialLast(): number {
  try {
    const raw = localStorage.getItem(INTERSTITIAL_LAST_KEY);
    if (raw) {
      const n = Number(raw);
      return Number.isFinite(n) ? n : 0;
    }
  } catch {
    /* a corrupt or unavailable store simply resets the gate */
  }
  return 0;
}

function recordInterstitial(now: number): void {
  try {
    localStorage.setItem(INTERSTITIAL_LAST_KEY, String(now));
  } catch {
    /* ignore a write failure — the worst case is one extra ad next time */
  }
}

/**
 * maybeShowInterstitial shows a post-move (`kind='move'`, global / vs_ai cooldown) or post-hint
 * (`kind='hint'`, its own short cooldown) interstitial when the client-mirrored gate allows: not
 * suppressed (no-ads), online, inside VK (the stub bypasses VK), and the required gap has elapsed
 * since the last interstitial of any kind. The kind picks the gap; the timer is shared, so a hint ad
 * and a move ad never fire within a cooldown of each other. The stub (contour test) shows an "ad
 * fired" toast. Returns whether an ad was shown. Fire-and-forget — the caller does not await it.
 */
export async function maybeShowInterstitial(
  ads: AdsConfig | undefined,
  kind: 'move' | 'hint',
  opts: { vsAi: boolean; online: boolean },
): Promise<boolean> {
  if (!ads || ads.suppressed || !opts.online) return false;
  const stub = adsStubEnabled();
  if (!stub && executionContext() !== 'vk') return false;
  const cooldownS = kind === 'hint' ? ads.cooldownHintS : opts.vsAi ? ads.cooldownVsAiS : ads.cooldownGlobalS;
  const now = Date.now();
  if (now - interstitialLast() < cooldownS * 1000) return false;
  const shown = stub ? (showToast('ad fired'), true) : await vkShowInterstitial();
  if (shown) recordInterstitial(now);
  return shown;
}