const IMAGE_PROXY_PATH = "/api/image-proxy";

type ImageProxyFormat = "webp" | "avif" | "jpeg" | "png";

export type ImageProxyOptions = {
  width?: number;
  quality?: number;
  format?: ImageProxyFormat;
  delivery?: "display" | "proxy";
};

function clamp(value: number, min: number, max: number): number {
  return Math.max(min, Math.min(max, value));
}

function normalizeWidth(width?: number): number | undefined {
  if (!Number.isFinite(width) || !width) return undefined;
  return clamp(Math.round(width), 64, 4096);
}

function normalizeQuality(quality?: number): number | undefined {
  if (!Number.isFinite(quality) || !quality) return undefined;
  return clamp(Math.round(quality), 40, 100);
}

function isAbsoluteHttpUrl(url: string): boolean {
  return /^https?:\/\//i.test(url);
}

function isBypassUrl(url: string): boolean {
  return (
    !url ||
    url.startsWith("data:") ||
    url.startsWith("blob:") ||
    url.startsWith(IMAGE_PROXY_PATH) ||
    !isAbsoluteHttpUrl(url)
  );
}

function isAliyunOssImageHost(hostname: string): boolean {
  const normalized = hostname.trim().toLowerCase();
  return normalized.endsWith(".aliyuncs.com") && normalized.includes(".oss-");
}

function isTrustedDirectStorageImageHost(hostname: string): boolean {
  const normalized = hostname.trim().toLowerCase();
  return (
    normalized === "yybb.top" ||
    normalized.endsWith(".qiniucs.com") ||
    normalized.endsWith(".qiniudn.com") ||
    normalized.endsWith(".clouddn.com") ||
    normalized.endsWith(".qbox.me")
  );
}

function resolveTrustedDirectStorageDisplayUrl(url: string): string | null {
  try {
    const target = new URL(url);
    return isTrustedDirectStorageImageHost(target.hostname)
      ? target.toString()
      : null;
  } catch {
    return null;
  }
}

function resolveAliyunOssDisplayUrl(
  url: string,
  options: Pick<ImageProxyOptions, "width" | "quality" | "format">
): string | null {
  let target: URL;
  try {
    target = new URL(url);
  } catch {
    return null;
  }

  if (!isAliyunOssImageHost(target.hostname)) {
    return null;
  }

  if (target.searchParams.has("x-oss-process")) {
    return target.toString();
  }

  const width = normalizeWidth(options.width);
  const quality = normalizeQuality(options.quality);
  const format = options.format;

  if (!width && !quality && !format) {
    return target.toString();
  }

  const processSteps = ["image"];
  if (width) {
    processSteps.push(`resize,w_${width}`);
  }
  if (quality) {
    processSteps.push(`quality,q_${quality}`);
  }
  if (format) {
    const ossFormat = format === "jpeg" ? "jpg" : format;
    if (ossFormat !== "webp" && ossFormat !== "jpg" && ossFormat !== "png") {
      return null;
    }
    processSteps.push(`format,${ossFormat}`);
  }

  target.searchParams.set("x-oss-process", processSteps.join("/"));
  return target.toString();
}

export function buildImageProxyUrl(url: string, options: ImageProxyOptions = {}): string {
  const source = String(url || "").trim();
  if (isBypassUrl(source)) {
    return source;
  }

  const trustedDirectStorageUrl = resolveTrustedDirectStorageDisplayUrl(source);
  if (trustedDirectStorageUrl) {
    return trustedDirectStorageUrl;
  }

  if (options.delivery !== "proxy") {
    const directDisplayUrl = resolveAliyunOssDisplayUrl(source, options);
    if (directDisplayUrl) {
      return directDisplayUrl;
    }
    return source;
  }

  const width = normalizeWidth(options.width);
  const quality = normalizeQuality(options.quality);
  const format = options.format;

  const params = new URLSearchParams();
  params.set("url", source);
  if (options.delivery === "proxy") params.set("proxy", "1");
  if (width) params.set("w", String(width));
  if (quality) params.set("q", String(quality));
  if (format) params.set("f", format);

  return `${IMAGE_PROXY_PATH}?${params.toString()}`;
}