import { Buffer } from "node:buffer";
import { register } from "../engine/registry";
import { RuntimeError, type CapabilityHandler } from "../engine/types";

const SM4_KEY = "INPUT_PARAM_KEY4";
const SM4_KEY_HEX = Buffer.from(SM4_KEY, "utf8").toString("hex");

function looksLikeBase64(value: string): boolean {
  const text = value.trim().replace(/\s+/g, "");
  if (!text || text.length % 4 !== 0 || !/^[A-Za-z0-9+/]+={0,2}$/.test(text)) return false;
  return Buffer.from(text, "base64").toString("base64").replace(/=+$/, "") === text.replace(/=+$/, "");
}

function readableUtf8(value: string): boolean {
  if (!value) return false;
  let controls = 0;
  for (const char of value) {
    const code = char.codePointAt(0)!;
    if (code < 32 && !["\n", "\r", "\t"].includes(char)) controls += 1;
    if (code === 0xfffd) controls += 10;
  }
  return controls === 0;
}

async function sm4Decrypt(value: string): Promise<string> {
  const { sm4 } = await import("sm-crypto");
  const errors: string[] = [];
  for (const padding of ["pkcs#7", "none"] as const) {
    try {
      const output = sm4.decrypt(value.toLowerCase(), SM4_KEY_HEX, { padding });
      if (output && readableUtf8(output)) return output;
      errors.push(`${padding}: empty or non-text output`);
    } catch (error) {
      errors.push(`${padding}: ${error instanceof Error ? error.message : String(error)}`);
    }
  }
  throw new RuntimeError("decryption_failed", "SM4 密文解密失败", { detail: errors.join("; ") });
}

const dodecryption: CapabilityHandler = async (_ctx, node, args) => {
  const words = String(args.words ?? args.value ?? args.text ?? "");
  if (!words.trim()) throw new RuntimeError("validation_error", "密文内容为空", { nodeId: node.id, componentId: node.componentId });
  if (looksLikeBase64(words)) {
    const decoded = Buffer.from(words, "base64").toString("utf8");
    if (readableUtf8(decoded)) return decoded;
  }
  return sm4Decrypt(words.trim());
};

register("Basic_Dodecryption", dodecryption);