export function createHash(algorithm) {
  const alg = algorithm.toUpperCase().replace("-", "");

  const subtleAlg =
    alg === "SHA256"
      ? "SHA-256"
      : alg === "SHA1"
        ? "SHA-1"
        : alg === "SHA512"
          ? "SHA-512"
          : alg;

  let inputData = new Uint8Array(0);

  return {
    update(data) {
      if (typeof data === "string") {
        data = new TextEncoder().encode(data);
      }

      const merged = new Uint8Array(inputData.length + data.length);

      merged.set(inputData);
      merged.set(data, inputData.length);

      inputData = merged;

      return this;
    },

    digest(encoding) {
      console.warn("[shim:crypto] createHash.digest - using placeholder");

      const hash = simpleHash(inputData);

      if (encoding === "hex") {
        return hash;
      }

      if (encoding === "base64") {
        return btoa(hash);
      }

      return hash;
    },

    async digestAsync(encoding) {
      const hashBuffer = await crypto.subtle.digest(subtleAlg, inputData);
      const hashArray = new Uint8Array(hashBuffer);

      if (encoding === "hex") {
        return Array.from(hashArray)
          .map((b) => b.toString(16).padStart(2, "0"))
          .join("");
      }

      if (encoding === "base64") {
        return btoa(String.fromCharCode(...hashArray));
      }

      return hashArray;
    },
  };
}

function simpleHash(data) {
  let hash = 0;

  for (let i = 0; i < data.length; i++) {
    hash = ((hash << 5) - hash + data[i]) | 0;
  }

  return Math.abs(hash).toString(16).padStart(8, "0");
}