import { NextRequest, NextResponse } from 'next/server';
import sharp from 'sharp';
import path from 'node:path';
import { readFile } from 'node:fs/promises';
import { configManager } from '@/lib/admin/config-manager';
import { getConfigDir } from '@/lib/admin/paths';
import {
  matchDomainBranding,
  parseDomainBranding,
  pickRequestHost,
} from '@/lib/admin/domain-branding';

/**
 * Variant → target output size + admin config key.
 * Matches the sizes declared in app/manifest.ts so the rendered PNG fits
 * the slot the manifest tells the browser about.
 */
const VARIANTS = {
  mobile: { width: 540, height: 720, configKey: 'pwaScreenshotMobileUrl' as const },
  desktop: { width: 1280, height: 720, configKey: 'pwaScreenshotDesktopUrl' as const },
} as const;

type Variant = keyof typeof VARIANTS;

// Cache resized images keyed by (variant, source URL).
const cache = new Map<string, Blob>();

async function fetchSourceImage(iconUrl: string): Promise<Buffer> {
  if (iconUrl.startsWith('http://') || iconUrl.startsWith('https://')) {
    const res = await fetch(iconUrl);
    if (!res.ok) throw new Error(`Failed to fetch PWA screenshot: ${res.status}`);
    return Buffer.from(await res.arrayBuffer());
  }

  // Admin-uploaded branding asset: served from /api/admin/branding/<file>
  // but stored on disk under getConfigDir()/branding/.
  const ADMIN_BRANDING_PREFIX = '/api/admin/branding/';
  if (iconUrl.startsWith(ADMIN_BRANDING_PREFIX)) {
    const filename = path.basename(iconUrl.slice(ADMIN_BRANDING_PREFIX.length));
    return readFile(path.join(getConfigDir(), 'branding', filename));
  }

  // Path relative to public/ directory
  const publicPath = path.join(process.cwd(), 'public', iconUrl.replace(/^\//, ''));
  return readFile(publicPath);
}

export async function GET(
  req: NextRequest,
  { params }: { params: Promise<{ variant: string }> },
) {
  const { variant: variantParam } = await params;
  if (!(variantParam in VARIANTS)) {
    return new NextResponse('Invalid variant. Allowed: mobile, desktop', { status: 400 });
  }
  const { width, height, configKey } = VARIANTS[variantParam as Variant];

  await configManager.ensureLoaded();
  const host = pickRequestHost(req);
  const domainOverrides = matchDomainBranding(
    host,
    parseDomainBranding(configManager.get<unknown>('domainBranding', [])),
  );
  const sources = configManager.getAllWithSources();
  const sourceEntry = sources[configKey];
  const screenshotUrl =
    domainOverrides[configKey] ||
    (sourceEntry?.source !== 'default' ? (sourceEntry?.value as string | undefined) : undefined);
  if (!screenshotUrl) {
    return new NextResponse('No PWA screenshot configured', { status: 404 });
  }

  const pngHeaders = {
    'Content-Type': 'image/png',
    'Cache-Control': 'public, max-age=86400',
    Vary: 'Host, X-Forwarded-Host',
  };
  const cacheKey = `${variantParam}|${screenshotUrl}`;

  try {
    if (cache.has(cacheKey)) {
      return new NextResponse(cache.get(cacheKey)!, { headers: pngHeaders });
    }

    const sourceBuffer = await fetchSourceImage(screenshotUrl);
    // 'cover' fills the target box without letterboxing - screenshots benefit
    // more from cropping than from a transparent frame around them. Users get
    // a hint about the recommended aspect ratio in the admin UI.
    const resized = await sharp(sourceBuffer)
      .resize(width, height, { fit: 'cover', position: 'center' })
      .png()
      .toBuffer();

    const ab = new ArrayBuffer(resized.byteLength);
    new Uint8Array(ab).set(resized);
    const blob = new Blob([ab], { type: 'image/png' });
    cache.set(cacheKey, blob);

    return new NextResponse(blob, { headers: pngHeaders });
  } catch (err) {
    console.error('Failed to generate PWA screenshot:', err);
    return new NextResponse('Failed to generate screenshot', { status: 500 });
  }
}